partb

Rules for the Classification of Charter Yachts Effective from 1 January 2006

Part BHull

RINA S.p.A.Via Corsica, 12 - 16128 Genova - ItalyTel. +39 01053851 - Fax: +39 0105351000E-MAIL [email protected] - WEB www.rina.orgC.F./P.Iva 03794120109Cap. Soc. EURO 30.192.800,00 i.v.R.I. Genova N. 03794120109

Editor: Marcello Lucentini

Editorial office: RINA S.p.A. Via Corsica, 12 - 16128 GENOVA Tel. +39 010 53851

Printed by: Graphic Sector SAS Genova - Italy

Publication registred under No. 25/73 of 11 April 1973

Court of Genova

© RINA S.p.A. - All rights reserved

PREAMBLE TO THE RULES: GENERAL CONDITIONS

Definitions:"Rules" means the Rules for the Classification of Yachtsengaged in Commercial Use for Sport or Pleasure, that donot carry Cargo and do not carry more than 12 Passengerswhether contained herein or in other documents issued bythe Society."Services" means the activities described in article 1 below,rendered by the Society upon request made by or on behalfof the Interested Party."Society" means RINA S.p.A. and any other Company per-taining to the RINA Group which provides the Services.“Surveyor” means technical staff acting on behalf of theSociety in the performance of the Services.“Interested Party” means a party, other than the Society,having responsibility for the classification of the yacht, suchas the Owner of the yacht and his representatives, or theyacht builder, or the engine builder, or the supplier of partsto be tested.“Owner” means the Registered Owner or the DisponentOwner or the Manager or any other party with the responsi-bility to keep the yacht seaworthy, having particular regardto the provisions relating to the maintenance of class laiddown in Part A, Chapter 2 of the Rules.“Administration” means the Government of the State whoseflag the yacht is entitled to fly or the State under whoseauthority the yacht is operating in the specific case.

Article 11.1. - The purpose of the Society is, among others, the clas-sification and certification of vessels, sea and river units, off-shore structures and craft of all kinds and the certification oftheir parts and components.The Society:- sets forth and develops Rules, Guidance Notes and otherdocuments;- issues Certificates, Statements and Reports based on itssur-vey activity.1.2. – The Society also takes part in the implementation ofNational Regulations as well as International Rules andStandards, by delegation from different Governments.1.3. – The Society carries out Technical Assistance onrequest and provides special services outside the scope ofclassification, which are regulated by these general condi-tions unless expressly derogated.

Article 22.1. - The Rules developed by the Society endeavor to meetthe state of currently available technology at the time theyare published. The Society is not responsible for any inade-quacy or failure of these Rules or any other relevant docu-ments as a result of future development of techniques,which could not have been reasonably foreseen at the timeof their publication.2.2. - The Society exercises due care and skill: - in the selection of its Surveyors- in the performance of its services, considering the state ofcurrently available technology at the time the services areperformed.2.3. - Surveys conducted by the Society include, but are notlimited to, visual inspection and non-destructive testing.Unless otherwise required, surveys are conducted throughsampling techniques and do not consist of comprehensiveverification or monitoring of the yacht or the good subjectto certification. The Society may also commission labora-tory testing, underwater inspection by divers and other

checks carried out by and under the responsibility of quali-fied service suppliers. Survey practices and procedures areselected by the Society at its sole discretion based on itsexperience and knowledge and according to generallyaccepted technical standards in the industry.

Article 33.1. - The class assigned to a yacht reflects the opinion ofthe Society that the yacht, given the intended use andwithin the relevant time frame, complies with the Rulesapplicable at the time the service is rendered. Entry intoforce and application of new Rules are dealt with in Part A,Chapter 1, Section 1, Article 2 of the Rules.3.2. - No report, statement, notation on a plan, review, Cer-tificate of Classification or any document or informationissued or given as part of the services provided by the Soci-ety shall have any legal effect or implication other than arepresentation that the yacht, structure, item of material,equipment or machinery or any other item covered by suchdocument or information meets the Rules. Any such repre-sentation is issued solely for the use ofthe Society, its com-mittees and clients or other duly authorized bodies and forno other purpose.The validity, application, meaning and interpretation of aCertificate of Classification, or any similar document orinformation issued by the Societyin connection with or infurtherance of the performance of its services, is governedby the Rules of the Society, which is the sole subject entitledto their interpretation.Any disagreement on technical matters between the Inter-ested Party and the Surveyor in the carrying out of his func-tions shall be raised in writing as soon as possible with theSociety , which will settle any divergence of opinion or dis-pute.3.3. - The classification of a yacht, or the issuance of a cer-tificate in relation to or in furtherance of the classification ofa yacht or the performance of services by the Society shallhave the validity conferred upon it by the Rules of the Soci-ety at the time of the assignment of class or issuance of thecertificate and in no case shall amount to a representation,statement or warranty of seaworthiness, structural integrity,quality or fitness for a particular purpose or service of anyyacht, structure, material, equipment or machinery sur-veyed by the Society.3.4. - Any document issued by the Society in relation to itsactivities reflects the condition of the yacht at the time ofthe survey, with reference to the applicable Rules. 3.5. - The Rules, surveys performed, reports, certificates andother documents issued by RINA are in no way intended toreplace the duties and responsibilities of other parties suchas Governments, designers, ship builders, manufacturers,repairers, suppliers, contractors or sub-contractors, Ownersor operators, underwriters, sellers or intended buyers of ayacht or other surveyed goods. They do not relieve suchparties from any warranty or responsibility or other contrac-tual obligations expressed or implied or from any liabilitywhatsoever against third parties, nor do they confer on suchother parties any right, claim or cause of action against theSociety.In particular, the above-mentioned activities of the Societydo not relieve the Owner of his duty to ensure the propermaintenance of the yacht at all times.In no case, therefore, the Society shall assume the obliga-tions incumbent upon the above-mentioned parties, evenwhen it is consulted in connection with inquiries concern-

ing matters not covered by its Rules or other documents.Insofar as they are not provided for in the Preamble theduties and responsibilities of the Owner and Interested Par-ties with respect to the services rendered by RINA are out-lined in Part A, Chapter 1, Section 1, Article 3.

Article 44.1. – Any request for any service of the Society shall besubmitted in writing and signed by or on behalf of the Inter-ested Party. Such request will be considered irrevocable assoon as received by the Society and shall entail acceptanceby the applicant of all relevant requirements of the Rules,including the Preamble. Upon acceptance of the written request by the Society , acontract between the latter and the Interested Party isentered into, which is regulated by the present GeneralConditions.4.2. - In consideration of the services rendered by the Soci-ety , the Interested Party and the person applying for the ser-vice shall jointly be liable for the payment of the relevantfees, even if the service is not concluded for any cause nonpertaining to the Society, upon receipt of the invoice andshall reimburse the expenses incurred. Interests at the legalcurrent rate increased by 2% may be demanded in theevent of late payment.4.3. - The contract and the validity of the relevant certifi-cates, if any, may be terminated at the request of either partysubject to 30 days’ notice to be given in writing. Failure topay the fees required for services carried out by the Societywhich fall within the scope of the above-mentioned con-tract will entitle the Society to terminate the contract and tosuspend the Services.Unless decided otherwise by the Society , termination of thecontract implies that the assignment of class to a yacht iswithheld or, if already assigned, that it is suspended or with-drawn.

Article 55.1. - In providing the services mentioned in Article 1above, as well as other information or advice, neither theSociety nor any of its servants or agents warrants the accu-racy of any information or advice supplied. Furthermore, allexpress and implied warranties are specifically disclaimed.Except as provided for in paragraph 5.2 below, and also inthe case of surveys carried out by delegation of Govern-ments, neither RINA nor any of its servants or agents will beliable for any loss, damage or expense of whatever naturesustained by any person, in tort or in contract, due to anyact or omission of whatever nature, whether or not negli-gent, and howsoever caused.5.2. – Notwithstanding the provisions in paragraph 5.1above, should any user of RINA 's services prove that he hassuffered a loss or damage due to any negligent act or omis-sion of RINA, its servants or agents, then RINA will paycompensation to such person for his proved loss, up to, butnot exceeding, five times the amount of the fee - if any -charged by RINA for the specific service, information oradvice or, if no fee is charged, a maximum of 10 thousandEuro.Where the fees are related to a number of services, theamount of fees will be apportioned for the purpose of thecalculation of the maximum compensation, by reference tothe estimated time involved in the performance of each ser-vice. Any liability for indirect or consequential loss, damage

or expenses is specifically excluded.In any case, irrespective of the amount of the fees, the max-imum damages payable by RINA will be not more than 1million Euro. Payment of compensation under this para-graph will not entail any admission of responsibility and/orliability by RINA and will be made without prejudice to thedisclaimer clause contained in paragraph 5.1 above.5.3. - Any claim for loss or damages of whatever nature byvirtue of the provisions set forth herein shall be made inwriting, and notice shall be provided to RINA within THREEMONTHS of the date on which the services were first sup-plied or the damages first discovered. Failure to providesuch notice within the time set forth herein will constitutean absolute bar to the pursuit of such claim against RINA.

Article 66.1. - Any dispute arising from or in connection with theRules or with the services of RINA, including any issuesconcerning responsibility, liability or limitations of liability,will be determined in accordance with Italian Law and pro-ceedings will be instituted in or transferred to the Court ofGenoa, Italy, which will have exclusive jurisdiction to hearand settle any such dispute.6.2. - As partial departure from point 6.1 above, the Societyshall have the faculty to submit any claim concerning thepayment of the fees for the Services to the Jurisdiction of theCourts of the place where the registered office of the Inter-ested Party or of the Applicant is located.

Article 77.1. - All plans, specifications, documents and informationprovided to, issued by, or made known to RINA, in connec-tion with the performance of its services, will be treated asconfidential and will not be made available to any otherparty without authorization of the Interested Party, except asprovided for or required by any applicable international,European or domestic legislation, IACS Code of Ethics,Charter or other IACS rules, enforceable Court order orinjunction.Information about the classification and statutory certifica-tion status, including transfer, changes, suspensions, with-drawals of class, recommendations/conditions of class,operating conditions or restrictions issued against classedyachts and other related information, as may be required,may be published on the website or released by othermeans, without the prior consent of the Interested Party.7.2. - In the event of transfer of class or addition of a secondclass or withdrawal from a double/dual class, the InterestedParty undertakes to provide or to permit RINA to provide theother Classification Society with all building plans anddrawings, certificates, documents and information relevantto the classed unit, including its history file, as the otherClassification Society may require for the purpose of classi-fication in compliance with IACS Procedure PR 1A, asamended, and applicable legislation. It is the Owner's dutyto ensure that, whenever required, the consent of thebuilder is obtained with regard to the provision of plans anddrawings to the new Society, either by way of appropriatestipulation in the building contract or by other agreement.

Article 88.1. – Should any part of this Preamble be declared invalid,this will not affect the validity of the remaining provisions.

EXPLANATORY NOTE TO PART B

1. Reference editionThe reference edition of these Rules is the edition effec-tive from 1 January 2006.

2. Effective date of the requirements2.1 All requirements in which new or amended provi-

sions with respect to those contained in the refer-ence edition have been introduced are followed by a date shown in brackets.

The date shown in brackets is the effective date of entry into force of the requirements as amended by the last updating. The effective date of all those requirements not followed by any date shown in brackets is that of the reference edition.

2.2 Item 4 below provides a summary of the technical changes from the preceding edition. In general, this list does not include those items to which only edi-torial changes have been made not affecting the effective date of the requirements contained therein.

3. Rule subdivision and cross-references3.1 Rule subdivision

The Rules are subdivided into six parts, from A to F.

Part A: Classification and Surveys

Part B: Hull

Part C: Machinery, Electrical Installations and Auto-mation

Part D: Materials and Welding

Part E: Safety Rules

Part F: Additional Class Notations

Each Part consists of:• Chapters• Sections and possible Appendices• Articles• Sub-articles• Requirements

Figures (abbr. Fig) and Tables (abbr. Tab) are numbered in ascending order within each Section or Appendix.

3.2 Cross-references

Examples: Pt A, Ch 3, Sec 1, [3.2.1] or Pt A, Ch 3, App 1, [3.2.1] • Pt A means Part A

The part is indicated when it is different from the part in which the cross-reference appears. Otherwise, it is not indicated.• Ch 3 means Chapter 3

The Chapter is indicated when it is different from the chapter in which the cross-reference appears. Other-wise, it is not indicated.• Sec 1 means Section 1 (or App 1 means

Appendix 1 )

The Section (or Appendix) is indicated when it is differ-ent from the Section (or Appendix) in which the cross-reference appears. Otherwise, it is not indicated.• [3.2.1] refers to requirement 1, within sub-article 2

of article 3.

Cross-references to an entire Part or Chapter are not abbreviated as indicated in the following examples:• Part A for a cross-reference to Part A• Part A, Chapter 1 for a cross-reference to Chapter 1

of Part A.

4. Summary of amendments introduced in the edi-tion effective from 1 January 2006

This edition of the Rules for the Classification of CharterYachts is considered as a “reference edition” for futureamendments. It annuls and replaces the 2005 editionissued with Rule Variation DIP/2005/01 effective from15 April 2005 which superseded the “Additional rulesapplicable to pleasure vessels for the assignment of theClass Notation CCL (Charter Class)”.

RULES FOR THE CLASSIFICATION OF

CHARTER YACHTS

Part BHull

Chapters 1 2 3 4 5

Chapter 1 GENERAL REQUIREMENTS

Chapter 2 STEEL HULLS

Chapter 3 ALUMINIUM HULLS

Chapter 4 REINFORCED PLASTIC HULLS

Chapter 5 WOOD HULLS

CHAPTER 1GENERAL REQUIREMENTS

Section 1 General Requirements

1 Rule application 29

1.1

2 Equivalents 29

2.1

3 Direct calculations for monohull and twin hull yacht 29

3.1 Direct calculations for monohull yachts3.2 Direct calculations for twin hull yachts

4 Definitiond and symbols 32

4.1 General4.2 Symbols4.3 Definitions

5 Subdivision, integrity of hull and superstructure 33

5.1 Number of watertight bulkheads5.2 Watertight bulkheads5.3 Sea connections and overboard discharge5.4 Stern and side doors below the weather deck5.5 Hatch on the weather deck5.6 Sidescuttles and windows5.7 Skylights5.8 Outer doors5.9 Drawings5.10 Ventilator5.11 Air pipes5.12 Bulwarks, railings

Section 2 Hull Outfittings

1 Rudders and steering gear 39

1.1 General1.2 Rudder stock1.3 Coupling between rudder stock and mainpiece1.4 Rudder mainpiece and blade1.5 Rudder bearings, pintles and stuffing boxes1.6 Steering gear and associated apparatus

2 Propeller shaft brackets 43

2.1 Double arm brackets2.2 Single arm brackets

3 Ballast 43

3.1

RINA Rules for Charter Yachts 2006 3

4 Stabiliser arrangements 44

4.1 General4.2 Stabiliser arrangements4.3 Stabilising tanks

5 Thruster tunnels 44

5.1 Tunnel wall thickness5.2 Tunnel arrangement details

6 Water-jet drive ducts 44

6.1

7 Crane support arrangements 45

7.1

Section 3 Equipments

1 General 46

1.1

2 Anchors 46

2.1

3 Chain cables for anchors 46

3.1

4 Mooring lines 46

4.1

5 Windlass 46

5.1 5.2 Working test on windlass

6 Equipment Number and equipment 47

6.1

7 Sailing yachts 47

7.1

Section 4 Non Structural Fuel Tanks

1 General 49

1.1

2 Metallic tanks 49

2.1 General2.2 Scantlings

3 Non-metallic tanks 49

3.1 General3.2 Scantlings3.3 Tests on tanks

4 RINA Rules for Charter Yachts 2006

Section 5 Loads

1 General 51

1.1

2 Definitions and symbols 51

2.1 General2.2 Definitions2.3 Symbols

3 Design acceleration 52

3.1 Vertical acceleration at LCG3.2 Transverse acceleration

4 Overall loads 52

4.1 General4.2 Longitudinal bending moment and shear force4.3 Design total vertical bending moment4.4 Transverse loads for twin hull yachts

5 Local loads 54

5.1 General5.2 Load points5.3 Design pressure for the bottom5.4 Design pressure for the side shell5.5 Design heads for decks5.6 Design heads for watertight bulkheads


CHAPTER 2STEEL HULLS


1 Field of application 63

1.1


2.1 Premise2.2 Definitions and symbols

3 Plans, calculations and other information to be submitted 63

3.1 3.2

4 Direct calculations 64

4.1 4.2

5 Bookling strength checks 64

5.1 Application5.2 Elastic buckling stresses of plates 5.3 Elastic buckling stresses of stiffeners5.4 Critical buckling stress

6 General rules for design 66

6.1

7 Minimum thicknesses 66

7.1

8 Corrosion protection 66

8.1 8.2 8.3

Section 2 Materials

1 General requirements 68

1.1

2 Steels for hull structures 68

2.1 2.2 Material factor K2.3 Information to be kept on board

3 Steels for forgings, castings and pipes 68

3.1 General requirements3.2 Forgings3.3 Castings3.4 Pipes


Section 3 Welding and Weld Connections

1 Welded connections 70

1.1 General requirements1.2 Base material1.3 Welding consumables and procedures1.4 Access to and preparation of joints1.5 Design

2 Type of connections 71

2.1 Butt welding2.2 Fillet welding types2.3 Scantling of welds

3 End connections of ordinary stiffeners 75

3.1

4 End connections of primary supporting members 76

4.1 Bracketed end connections4.2 Bracketless end connections

5 Cut-outs and holes 77

5.1 5.2 5.3 5.4 5.5

6 Stiffening arrangement 78

6.1 6.2 6.3 6.4 6.5

7 Riveted connections 78

7.1 7.2

8 Sealed connections 79

8.1

9 Inspection and tests 79

9.1 General

Section 4 Longitudinal Strenght

1 General 80

1.1 1.2

2 Bending stresses 80

2.1 2.2 2.3


3 Shear stresses 80

3.1

4 Calculation of the section modulus 80

4.1

Section 5 Plating


1.1

2 Keel 81

2.1 Sheet steel keel2.2 Solid keel

3 Bottom and bilge 81

3.1

4 Sheerstrake 82

4.1

5 Side 82

5.1 5.2

6 Openings in the shell plating 82

6.1 6.2 6.3

7 Local stiffeners 82

7.1 7.2 7.3

8 Cross-deck bottom plating 82

8.1

Section 6 Single Bottom

1 General 83

1.1 1.2 Longitudinal structure 1.3 Transverse structure


2.1

3 Longitudinal type structure 83

3.1 Bottom longitudinals3.2 Floors3.3 Girders


4 Transverse type structures 84

4.1 Ordinary floors4.2 Centre girder4.3 Side girders

5 Constructional details 84

5.1

Section 7 Double Bottom

1 General 85

1.1

2 Minimum height 85

2.1

3 Inner bottom plating 85

3.1

4 Centre girder 85

4.1

5 Side girders 85

5.1 5.2

6 Floors 86

6.1 6.2

7 Bracket floors 86

7.1

8 Bottom and inner bottom longitudinals 86

8.1

9 Bilge keel 86

9.1 Arrangement, scantlings and connections9.2 Bilge keel connection

Section 8 Side Structures

1 General 88

1.1


2.1

3 Ordinary stiffeners 88

3.1 Transverse frames3.2 Longitudinal stiffeners


4 Reinforced beams 88

4.1 Reinforced frames4.2 Reinforced stringers

5 Frame connections 89

5.1 General

6 Scantling of brackets of frame connections 89

6.1 6.2 Lower brackets of frames

Section 9 Decks

1 General 91

1.1


2.1

3 Deck plating 91

3.1 Weather deck3.2 Lower decks

4 Stiffening and support structures for decks 91

4.1 Ordinary stiffeners4.2 Reinforced beams4.3 Pillars

Section 10 Bulkheads

1 General 93

1.1

2 Symbols 93

2.1

3 Plating 93

3.1

4 Stiffeners 93

4.1 Ordinary stiffeners4.2 Reinforced beams

5 General arrangement 93

5.1 5.2

6 Non-tight bulkheads 94

6.1 Non-tight bulkheads not acting as pillars6.2 Non-tight bulkheads acting as pillars


Section 11 Superstructures

1 General 95

1.1

2 Boundary bulkhead plating 95

2.1

3 Stiffeners 95

3.1

4 Superstructure decks 95

4.1 Plating4.2 Stiffeners


CHAPTER 3ALUMINIUM HULLS



1.1


2.1 Premise2.2 Definitions and symbols


3.1 3.2


4.1

5 Buckling strength checks 100

5.1 Application5.2 Elastic buckling stresses of plating5.3 Critical buckling stresses5.4 Axially loaded stiffeners


6.1

7 Minimum thicknesses 102

7.1

Section 2 Materials

1 General requirements 103

1.1

2 Aluminium alloy structures 103

2.1 Aluminium alloys for hull structures, forgings and castings2.2 Extruded plates2.3 Tolerances2.4 Influence of welding on mechanical characteristics2.5 Material factor K for scantlings of aluminium alloy structural members2.6 Information to be kept on board

Section 3 Welding and Weld Connections

1 Welded connections 106

1.1 General requirements1.2 Welding procedures for aluminium alloys1.3 Access to and preparation of joints1.4 Design


2 Type of connections 107

2.1 Types of connections and preparations2.2 Butt welding2.3 Fillet welding types2.4 Continuous fillet welding2.5 Scantling of welds2.6 Strength of welding

3 End connections of ordinary stiffeners 112

3.1 3.2 3.3

4 End connections of primary supporting members 113

4.1 Bracketed end connections4.2 Bracketless end connections

5 Cut-outs and holes 114

5.1

6 Stiffening arrangement 114

6.1 6.2 6.3 6.4 6.5

7 Riveted connections 115

7.1 7.2

8 Sealed connections 115

8.1

9 Corrosion protection 115

9.1 9.2 9.3

10 Inspection and tests 115

10.1 General

Section 4 Longitudinal Strength

1 General 117

1.1 1.2


2.1 2.2 2.3

3 Shear stresses 117

3.1


4 Calculation of the section modulus 117

4.1

Section 5 Plating


1.1

2 Keel 118

2.1 Sheet steel keel2.2 Solid keel

3 Bottom and bilge 118

3.1

4 Sheerstrake 119

4.1

5 Side 119

5.1 5.2


6.1 6.2 6.3


7.1 7.2 7.3

8 Cross Deck bottom plating 119

8.1


1 General 120



2.1




4.1 Ordinary floors4.2 Centre girder


4.3 Side girders


5.1


1 General 122

1.1

2 Minimum height 122

2.1


3.1

4 Centre girder 122

4.1

5 Side girders 122

5.1 5.2

6 Floors 123

6.1 6.2

7 Bracket floors 123

7.1


8.1

9 Bilge keel 123

9.1 Arrangement, scantlings and connections9.2 Bilge keel connection


1 General 125

1.1


2.1


3.1 Transverse frames3.2 Longitudinal stiffeners




5 Frame connections 126

5.1 General

6 Scantling of brackets of frame connections 126

6.1 6.2 Lower brackets of frames

Section 9 Decks

1 General 128

1.1


2.1

3 Deck plating 128





1 General 130

1.1

2 Symbols 130

2.1

3 Plating 130

3.1

4 Stiffeners 130


5 General arrangement 130

5.1 5.2

6 Non-tight bulkheads 131

6.1 Non-tight bulkheads not acting as pillars6.2 Non-tight bulkheads acting as pillars


1 General 132

1.1



2.1

3 Stiffeners 132

3.1




CHAPTER 4REINFORCED PLASTIC HULLS



1.1


2.1 Premise2.2 Symbols2.3 Definitions


3.1 3.2


4.1


5.1 5.2 Minimum thicknesses

6 Construction 137

6.1 General6.2 Details of construction6.3 Connections of laminates6.4 Engine exhaust6.5 Tanks for liquids

Section 2 Materials

1 General 142

1.1

2 Definitions and terminology 142

2.1

3 Materials of laminates 142

3.1 Resins3.2 Reinforcements3.3 Core materials for sandwich laminates3.4 Adhesive and sealant material3.5 Plywood3.6 Timber3.7 Repair compounds3.8 Type approval of materials

4 Mechanical properties of laminates 144

4.1 General4.2 General


Section 3 Construction and Quality Control

1 Shipyards or workshops 147

1.1 General1.2 Moulding shops1.3 Storage areas for materials1.4 Identification and handling of materials

2 Hull construction processes 148

2.1 General2.2 Moulds2.3 Laminating2.4 Hardening and release of laminates2.5 Defects in the laminates2.6 Checks and tests

Section 4 Longitudinal Strength

1 General 150

1.1 1.2


2.1 2.2 2.3 Calculation of strength modulus

3 Shear stresses 151

3.1

Section 5 External Plating

1 General 152

1.1


2.1

3 Keel 152

3.1

4 Rudder horn 152

4.1

5 Bottom plating 152

5.1

6 Side plating and sheerstrake plating 153

6.1 6.2 Side plating


7.1


7.2 7.3


8.1 8.2 8.3 8.4

9 Cross-deck bottom plating 153

9.1


1 General 154



2.1




4.1 Ordinary floors4.2 Centre girder4.3 Side girders


5.1


1 General 156

1.1

2 Minimum height 156

2.1


3.1

4 Centre girder 156

4.1

5 Side girders 157

5.1 5.2


6 Floors 157

6.1 6.2


7.1


1 General 158

1.1


2.1


3.1 3.2 Longitudinals



Section 9 Decks

1 General 160

1.1


2.1

3 Deck plating 160





1 General 162

1.1

2 Symbols 162

2.1

3 Plating 162

3.1


4 Stiffeners 162


5 Tanks for liquids 162

5.1


1 General 163

1.1


2.1

3 Stiffeners 163

3.1



Section 12 Scantlings of Structures with Sandwich Construction

1 Premise 164

1.1

2 General 164

2.1 Laminating2.2 Vacuum bagging2.3 Constructional details

3 Symbols 164

3.1

4 Minimum thickness of the skins 165

4.1

5 Bottom 165

5.1

6 Side 165

6.1

7 Decks 166

7.1

8 Watertight bulkheads and boundary bulkheads of the superstructure 166

8.1


CHAPTER 5WOOD HULLS

Section 1 Materials

1 Suitable timber species 169

1.1

2 Timber quality 169

2.1 Planking2.2 Marine plywood and lamellar structures2.3 Certification and checks of timber quality2.4 Mechanical characteristics and structural scantlings

Section 2 Fastenings, Working and Protection of Timber

1 Fastenings 172

1.1 1.2

2 Timber working 172

2.1

3 Protection 172

3.1

Section 3 Building Methods for Planking

1 Shell planking 173

1.1 Simple skin 1.2 Double diagonal skin 1.3 Double longitudinal skin 1.4 Laminated planking in several cold-glued layers 1.5 Plywood planking 1.6 Double skin with inner plywood and outer longitudinal strakes 1.7 Fastenings and caulking 1.8 Sheathing of planking

2 Deck planking 174

2.1 Planking 2.2 Plywood 2.3 Plywood sheathed with laid deck 2.4 Longitudinal planking 2.5 Caulking


Section 4 Structural Scantlings of Sailing Yachts with or without Auxiliary Engine

1 General 178

1.1

2 Keel 178

2.1

3 Stempost and sternpost 178

3.1

4 Frames 178

4.1 Types of frames 4.2 Framing systems and scantlings

5 Floors 179

5.1 General5.2 Arrangement of floors5.3 Scantlings and fastenings

6 Beam shelves, beam clamps in way of masts, bilge stringers 181

6.1 Beam shelves6.2 Beam clamps in way of masts6.3 Bilge stringers6.4 End breasthooks

7 Beams 182

7.1 Scantlings of beams7.2 End attachments of beams7.3 Local strengthening7.4 Lower deck and associated beams

8 Planking 183

8.1 Shell planking 8.2 Deck planking8.3 Superstructures - Skylights8.4 Masts and rigging

Section 5 Structural Scantlings of Motor Yachts

1 General 190

1.1

2 Keel - stempost 190

2.1

3 Transom 190

3.1

4 Floors and frames 190

4.1 General 4.2 Bottom and side frames 4.3 Floors 4.4 Frame and beam brackets


5 Side girders and longitudinals 192

5.1

6 Beams 193

6.1

7 Beam shelves and chine stringers 193

7.1

8 Shell planking 194

8.1 Thickness of shell planking

9 Deck planking 194

9.1 Weather deck 9.2 Superstructure decks 9.3 Lower deck

Section 6 Watertight Bulkheads, Lining, Machinery Space

1 Wooden bulkheads 201

1.1

2 Steel bulkheads 201

2.1

3 Internal lining of hull and drainage 201

3.1

4 Machinery space structures 201

4.1


Part BHull

Chapter 1

GENERAL REQUIREMENTS

SECTION 1 GENERAL REQUIREMENTS

SECTION 2 HULL OUTFITTINGS

SECTION 3 EQUIPMENTS

SECTION 4 NON STRUCTURAL FUEL TANKS

SECTION 5 LOADS


Pt B, Ch 1, Sec 1


1 Rule application

1.1

1.1.1 Part B of the Rules consists of five chapters andapplies to hulls of length Loa, defined in 4.2, not less than24 m, for yachts of normal type, monohull craft or catama-rans, intended for unrestricted service which are to beclassed by RINA.

Chapter 1 applies in general to all yachts, irrespective of thematerial used for the construction of the hull.

Chapter 2 contains requirements relevant to the scantlingsof hull structures of steel yachts.

Chapter 3 contains requirements relevant to the scantlingsof hull structures of aluminium alloy yachts.

Chapter 4 contains requirements relevant to the scantlingsof hull structures of yachts constructed of composite materi-als.

Chapter 5 contains requirements relevant to the scantlingsof hull structures of wooden yachts.

Yachts of unusual form, speed or proportions or of typesother than those considered in Part B will be given specialconsideration by RINA, also on the basis of equivalence cri-terion.

Yachts built using a combination of the foregoing materialsare subject to the applicable requirements of the relevantchapters. Connections between different materials will bethe subject of special consideration by RINA.

2 Equivalents

2.1

2.1.1 In examining constructional plans, RINA may takeinto account material distribution and scantlings which aredifferent from those obtained by applying these require-ments, provided that longitudinal, transversal and localstrength are equivalent to those of the relevant Rule struc-ture and that such scantlings are found satisfactory by RINAalso on the basis of direct calculations of the structuralstrength.

In particular, the structures of yachts similar in performanceto high speed craft (HSC) may have scantlings in accord-ance with RINA's "Rules for the Classification of HighSpeed Craft".

In such case, the Master is to be provided with a yacht oper-ating manual indicating the appropriate speed for each seastate.

The use of RINA's "Rules for the Classification of HighSpeed Craft" for the scantlings of the structures of the a.m.yachts shall be agreed between the yard and RINA before

the submittance of the drawings for approval and the com-mencement of the hull.

Special structures not provided for in these Rules, such asdecks intended for the carriage of vehicles, side and sterndoors and helicopter decks, may have scantlings in accord-ance with the "Rules for the Classification of Ships".

3 Direct calculations for monohull and twin hull yacht

3.1 Direct calculations for monohull yachts

3.1.1 General Direct calculations are generally required to be carried out,at the discretion of RINA, to check the primary structures ofyacht which have unusual shapes and/or characteristics.

In addition, direct calculations are to be performed to checkthe scantlings of primary structures of yachts whenever, inthe opinion of RINA, hull shapes and structural dimensionsare such that the scantling formulae used in these Rules areno longer deemed to be effective.

By way of example, this may be the case in the followingsituations:

• elements of the primary transverse ring (beam, web andfloor) have very different cross-sectional inertia, so thatthe boundary conditions for each are not well defined;

• marked V-shapes, so that floor and web tend to degen-erate into a single element;

• complex, non-conventional geometry;

• presence of significant racking effects (yachts with manytiers of superstructure);

• structures contributing to longitudinal strength withlarge openings.

3.1.2 Loads In general, the following load conditions specified in a) tod) are to be considered.

The condition in d) is to be checked in yacht for which, inthe opinion of RINA, significant racking effects are antici-pated (yachts with many tiers of superstructure).

In relation to special structure or loading configurations,should some load conditions turn out to be less significantthan others, the former may be ignored at the discretion ofRINA. By the same token, it may be necessary to considerfurther load conditions specified by RINA in individualcases.

The vertical and transverse accelerations and the impactpressure p2 are to be calculated as stipulated in Sec. 5.

For each primary supporting member, the coefficient Fa,which appears in the formula for impact pressure, is to be


Pt B, Ch 1, Sec 1

calculated as a function of the area supported by the mem-ber.

In three dimensional analyses, special attention is to bepaid to the distribution of weights and buoyancy and to thedynamic equilibrium of the yacht.

In the case of three dimensional analyses, the longitudinaldistribution of impact pressure is considered individually ineach case by RINA. In general, impact pressure is to beconsidered as acting separately on each transverse sectionof the model, the remaining sections being subject to hydro-static pressure.

a) Load condition in still waterThe following loads are to be considered:• forces caused by weights present, distributed

according to the weight booklet of the yacht;• outer hydrostatic load in still water.

b) Combined load condition 1The following loads are to be considered:• forces caused by weights present, distributed

according to the weight booklet of the yacht;• forces of inertia due to the vertical acceleration av of

the yacht, considered in a downward direction.

c) Combined load condition 2The impact pressure acting on the bottom of the yacht isto be considered.

d) Combined load condition 3The following loads are to be considered:• forces caused by weights present, distributed

according to the weight booklet of the yacht;• forces of inertia due to the transverse acceleration av

of the yacht.

3.1.3 Structural model The primary structures of yachts of this type may usually bemodelled with beam elements, according to criteria stipu-lated by RINA. When, however, grounds for the admissibil-ity of such model are lacking, or when the geometry of thestructures gives reason to suspect the presence of high stressconcentrations, finite element analyses are necessary.

In general, the extent of the model is to be such as to allowanalysis of the behaviour of the main structural elementsand their mutual effects.

On yachts dealt with by these Rules, the stiffness of longitu-dinal primary members (girders and stringers) is, at leastoutside the machinery space, generally negligible com-pared with the stiffness of transverse structures (beams,floors and webs), or their presence may be taken intoaccount by suitable boundary conditions. It is thereforeacceptable, in general, to examine primary members in thisarea of the hull by means of plane analyses of transverserings.

In cases where such approximation is not acceptable, themodel adopted is to be three-dimensional and is to includethe longitudinal primary members.

In cases where loads act in the transverse direction (loadcondition 3), special attention is to be devoted to the mod-elling of continuous decks and platforms. If they are of suf-ficient stiffness in the horizontal plane and are sufficiently

restrained by fore- and after-bodies, such continuous ele-ments may withstand transverse deformations of primaryrings.

In such cases, notwithstanding the provisions above, it isstill permissible to examine bidimensional rings, by simulat-ing the presence of decks and platforms with horizontalsprings according to criteria specified by RINA.

3.1.4 Boundary conditions Depending on the load conditions considered, the follow-ing boundary conditions are to be assigned:

a) Load condition in still water and combined load condi-tions 1 and 2

• horizontal and transverse restraints, in way of thecrossing point of bottom and side shells, if the anglebetween the two shells is generally less than 135°,

• horizontal and transverse restraints, in way of thekeel, if the bottom/side angle is greater than approx-imately 135°.

b) Combined load condition 3

The vertical and horizontal resultants of the loads, ingeneral other than zero, are to be balanced by introduc-ing two vertical forces and two horizontal forces at thefore and aft ends of the model, distributed on the shellsaccording to the bidimensional flow theory for shearstresses, which are equal and opposite to half the verti-cal and horizontal resultants of the loads.Where a plane model is adopted, the resultants are tobe balanced by vertical and horizontal forces, distrib-uted as specified above and acting on the plane of themodel itself.

3.1.5 Checking criteria

a) For metal structures, the stresses given by the above cal-culations are to be not greater than the following allow-able values, in N/mm2:

• bending stress:

• shear stress:

• Von Mises equivalent bending stress:

where:

K : material factor defined in Chap. 2 for steeland Chap. 3 for aluminium alloy.

f’m : coefficient depending on the material, equalto:

- 1,0, for steel structures

- 2,15, for aluminium alloy structures

fs : safety coefficient, equal to:

- 1,00, for combined load conditions

- 1,25, for load condition in still water.

The compressive values of normal stresses and shearstresses are not to exceed the values of the critical

σam170

K f'm fs⋅ ⋅-----------------------=

τam90

K f'm fs⋅ ⋅-----------------------=

σeq am,200

K f'm fs⋅ ⋅-----------------------=


Pt B, Ch 1, Sec 1

stresses for plates and stiffeners calculated in Chap. 2and Chap. 3.In structural elements also subject to high longitudinalhull girder stresses, the allowable and critical stressesare to be reduced, in accordance with criteria specifiedby RINA.

b) For structures made of composite materials, the allowa-ble stresses are defined in Chap.4.

3.2 Direct calculations for twin hull yachts

3.2.1 General Direct calculations are generally required to be carried out,at the discretion of RINA, to check the primary structuresand connecting structures of the two hulls which have unu-sual characteristics.

In addition, direct calculations are to be carried out tocheck the structures connecting the two hulls for yachts inwhich the structural arrangements do not allow a realisticassessment of their stress level, based on simple models andon the formulae set out in these Rules.

3.2.2 Loads In general, the following load conditions specified in a) tod) are to be considered.

The condition in a) applies to a still water static conditioncheck.

The conditions in b) and c) apply to the check of the struc-tures connecting the two hulls. The condition in c) onlyrequires checking for yachts of L > 65 m and speed V > 45knots.

The condition in d) is to be checked in yacht for which, inthe opinion of RINA, significant racking effects are expected(yachts with many tiers of superstructure).

In relation to special structure or loading configurations,should some load conditions turn out to be less significantthan others, the former may be ignored at the discretion ofRINA. By the same token, it may be necessary to considerfurther load conditions specified by RINA in individualcases.

The vertical and transverse accelerations and the impactpressure p2 are to be calculated as stipulated in Sec. 5.

For each primary supporting member, the coefficient Fa,which appears in the formula for impact pressure, is to becalculated as a function of the area supported by the mem-ber.

In three-dimensional analyses, special attention is to bepaid to the distribution of weights and buoyancy and to thedynamic equilibrium of the yacht.

In the case of three-dimensional analyses, the longitudinaldistribution of impact pressure is considered individually ineach case by RINA. In general, impact pressure is to beconsidered as acting separately on each transverse sectionof the model, the remaining sections being subject to hydro-static pressure.

a) Load condition in still waterThe following loads are to be considered:• forces caused by weights present, distributed

according to the weight booklet of the yacht;

• outer hydrostatic load in still water.


Devono essere considerati:

• forces caused by weights present, distributedaccording to the weight booklet of the yacht;

• forces of inertia due to the vertical acceleration av ofthe yacht, considered in a downward direction.

c) Combined load condition 2

The following loads are to be considered:


• forces of inertia due to the vertical acceleration av ofthe yacht, considered in a downward direction;

• the impact pressure acting hemisymmetrically onone of the halves of the hull bottom.

d) Combined load condition 3

The following loads are to be considered:


• forces of inertia due to the transverse acceleration ofthe yacht.

3.2.3 Structural model In general, the primary structures of yachts of this type areto be modelled with finite element schematisations adopt-ing a medium size mesh.

At the discretion of RINA, detailed analyses with fine meshare required for areas where stresses, calculated withmedium-mesh schematisations, exceed the allowable limitsand the type of structure gives reason to suspect the pres-ence of high stress concentrations.

In general, the extent of the model is to be such as to allowanalysis of the behaviour of the main structural elementsand their mutual effects.

On yachts dealt with by these Rules, the stiffness of longitu-dinal primary members (girders and stringers) is, at leastoutside the machinery space, generally negligible com-pared with the stiffness of transverse structures (beams,floors and webs), or their presence may be taken intoaccount by suitable boundary conditions. It is thereforeacceptable, in general, to examine primary members in thisarea of the hull by means of plane analyses of transverserings.

In cases where such approximation is not acceptable, themodel adopted is to be three-dimensional and is to includethe longitudinal primary members.

In cases where loads act in the transverse direction (loadconditions 2 and 3), special attention is to be devoted to themodelling of continuous decks and platforms. If they are ofsufficient stiffness in the horizontal plane and are suffi-ciently restrained by fore- and after-bodies, such continuouselements may withstand transverse deformations of primaryrings.

In such cases, notwithstanding the provisions above, it isstill permissible to examine bidimensional rings, by simulat-ing the presence of decks and platforms with horizontalsprings according to criteria specified by RINA.


Pt B, Ch 1, Sec 1

3.2.4 Boundary conditions Depending on the load conditions considered, the follow-ing boundary conditions are to be assigned:

a) Load condition in still water

The vertical resultant of the loads, in general other thanzero, is to be balanced by introducing two verticalforces at the fore and aft ends of the model, both distrib-uted on the shells according to the bidimensional flowtheory for shear stresses, which are equal and oppositeto half the vertical resultant of the loads.Where a plane model is adopted, the vertical resultant isto be balanced by a single force, distributed as specifiedabove and acting on the plane of the model itself.


A vertical restraint is to be imposed in way of the keel ofeach hull.

c) Combined load condition 2 and 3

The vertical and horizontal resultants of the loads, ingeneral other than zero, are to be balanced by introduc-ing two vertical forces and two horizontal forces at thefore and aft ends of the model, distributed on the shellsaccording to the bidimensional flow theory for shearstresses, which are equal and opposite to half the verti-cal and horizontal resultants of the loads.Where a plane model is adopted, the resultants are tobe balanced by vertical and horizontal forces, distrib-uted as specified above and acting on the plane of themodel itself.

3.2.5 Checking criteria

a) a) For metal structures, the stresses given by the abovecalculations are to be not greater than the followingallowable values, in N/mm2:• bending stress:

• shear stress:

• Von Mises equivalent bending stress:

where:

K : material factor defined in Chap. 2 forsteel and Chap. 3 for aluminium alloy

f’m : coefficient depending on the material,equal to:

• 1,0, for steel structures

• 2,15, for aluminium alloy structuresfs : safety coefficient, equal to:

• 1,00, for combined load conditions

• 1,25, for load condition in still water.

The compressive values of normal stresses and shearstresses are not to exceed the values of the criticalstresses for plates and stiffeners calculated in Chap.2 and Chap. 3.In structural elements also subject to high longitudi-

nal hull girder stresses, the allowable and criticalstresses are to be reduced, in accordance with crite-ria specified by RINA.

b) For structures made of composite materials, the allowa-ble stresses are defined in Chap. 4.

4 Definitiond and symbols

4.1 General

4.1.1 The definitions and symbols given in 4.2 and 4.3apply to all Chapters of Part B.The definitions of symbols having general validity are notnormally repeated in the various Chapters, whereas themeanings of those symbols which have specific validity arespecified in the relevant Chapters.

4.2 Symbols4.2.1 LOA : Length overall, is the distance, in m, measured

parallel to the static load waterline, from theforeside of the stem to the after side of the sternor transom, excluding rubbing strakes and otherprojections excluding removable parts that canbe detached in a non destructive manner andwithout affecting the structural integrity of thecraft, e.g. pulpits at either ends of the craft, plat-forms, rubbing strakes and fenders.

L : scantling length, in m, on the full load water-line, assumed to be equal to the length on thefull load waterline with the yacht at rest;

LPP : Length between perpendiculars, is the distance,in m, measured on the full load waterline fromFP to AP.

LLL : Load Line length means 96% of the total lengthon a waterline of a ship at 85% of the leastmoulded depth measured from the top of thekeel, or the length from the fore-side of the stemto the axis of the rudder stock on that waterline,if that greater. In ship designed with a rake ofkeel the waterline on which this is measuredshall be parallel to the designed waterline.

FP : Foreword perpendicular, is the perpendicular atthe intersection of the full load waterline withthe fore side of the stem.

AP : After perpendicular , is the perpendicular at theintersection of the full load waterline with theafter side of the rudder post or to the centre ofthe rudder stock for yacht without a rudder post.In yachts with unusual stern arrangements orwithout rudder the position of AP and the rele-vant LPP will be specially considered

B : Maximum outside breadth, in metres.D : Depth, in metres, measured vertically on the

transverse section at the middle of length L,from moulded base line to the top of the deckbeam at side on the weather deck.

D1 : Depth, in metres, measured vertically on thetransverse section at the middle of length L,

σam170

K f'm fs⋅ ⋅-----------------------=

τam90

K f'm fs⋅ ⋅-----------------------=

σeq am,200

K f'm fs⋅ ⋅-----------------------=


Pt B, Ch 1, Sec 1

from the lower side of the bar keel, if any, or ofthe fixed ballast keel, if any, or of the drop keel,to the top of the deck beam at side on theweather deck.

T : Draft, in metres, measured at the middle oflength L, in metres, between the full load water-line and the lower side of the keel. In the caseof hulls with a drop or ballast keel, the lowerside of the keel is intended to mean the inter-section of the longitudinal plane of symmetrywith the continuation of the external surface ofthe hull.

T1 : Draft T, in metres, measured to the lower side -theoretically extended, if necessary, to the mid-dle of length L - of the fixed ballast keel, wherefitted, or the drop keel.

∆ : Displacement, in t, of the yacht at draught T.

V : Maximum design speed, in knots, of the yacht atdisplacement ∆.

s : Spacing of ordinary stiffeners, in metres.

S : Web frame spacing, in metresg.

4.3 Definitions

4.3.1 Rule frame spacing

The Rule frame spacing, sR, in m, of ordinary stiffeners isobtained as follows:

In general, spacing of transversal or longitudinal stiffeners isnot to exceed 1,2 times the Rule frame spacing.

4.3.2 Superstructure

The superstructure is a decked structure located above theweather deck, extending from side to side of the hull orwith the side plating not inboard of the shell plating morethan 4% of the local breadth.

Superstructures may be complete, where deck and sidesextend for the whole length of the yacht, or partial, wheresides extend for a length smaller than that of the yacht, evenwhere the deck extends for the whole length of the yacht.

Superstructures may be of different tiers in relation to theirposition in respect of the weather deck.

A 1st tier superstructure is one fitted on the weather deck, a2nd tier superstructure is one fitted on the 1st tier superstruc-ture, and so on.

4.3.3 Freeboard deck

Freeboard deck has the meaning given in annex I of ICCL.The freeboard deck is normally the uppermost completedeck exposed to the weather and sea, which has permanentmeans of closing all openings in the weather part thereof,and below which all openings in the sides of the ship are fit-ted with permanent means of watertight closing. In a shiphaving a discontinuous freeboard deck, the lowest line ofthe exposed deck and the continuation of that line parallelto the upper part of the deck is taken as the freeboard deck.

4.3.4 Weather deck

Is the uppermost complete weathertight deck fitted as anintegral part of the vessel's structure and which is exposedto the sea and the weather.

4.3.5 Virtual freeboard deck

Where the actual freeboard from the full load waterline tothe weather deck exceeds that required by ILLC '66 by atleast 1,8 m for yachts having LLL < 75 m, or at least 1,80 +0,01 (LLL - 75) for 75 < LLL < 125, or at least 2,30 m for LLL> 125 m, a virtual freeboard deck may be defined (hypotet-ically drawn below and parallel to the weather deck) and,for the determination of the superstructure tier, the super-structure above the weather deck may be considered as asecond tier and the second tier in respect to the weatherdeck may be considered as a third tier and so on. All the fit-ting above the weather deck, abaft the forward quarter, maybe considered in the same way".

The vertical distance as above defined between theassumed freeboard deck corresponding to the relevantwatertight weatherdeck and the minimum freeboard as cal-culated in accordance with the Load Line Requirementsmay be used to reduce the requirements for closing appli-ances for openings in the hull, superstructure, deckhouses,relevant sills above deck and height of air pipes and ventila-tors above deck, if not otherwise stated by the flag Adminis-tration.

4.3.6 Deckhouse

The deckhouse is a decked structure fitted on the weatherdeck, a superstructure deck or another deckhouse, havinglimited length and a spacing between the external longitu-dinal bulkheads less than 92% of the local breadth of theyacht.

4.3.7 Weathertight

A closing appliance is considered weathertight if it isdesigned to prevent the passage of water into the yacht inany sea condition.

4.3.8 Watertight

A closing appliance is considered watertight if it is designedto prevent the passage of water in either direction under ahead of water for which the surrounding structure isdesigned.

5 Subdivision, integrity of hull and superstructure

5.1 Number of watertight bulkheads

5.1.1 All Yachts are to have at least the following trans-verse watertight bulkheads:

• One collision bulkhead

• Two bulkheads forming the boundaries of the machin-ery spaces;as an alternative, the transom may beaccepted as aft transverse bulkhead.

Additional bulkheads may be required for yachts having tocomply with subdivision or damage stability criteria.

sR 0 350 0 005L,+,=


Pt B, Ch 1, Sec 1

5.1.2 Openings in watertight bulkheads and decks

The number of openings in watertight subdivision shall belimited to a minimum compatible with the proper workingof the yacht. Pipes and electrical cable carried out throughwatertight subdivision provided that the watertightness isensured by devices suitable in the opinion of RINA. Detailsrelevant to these devices and their installation on boardshall be sent to RINA for approval. Doors in watertight bulk-heads shall be approved watertight doors; additional char-acteristics regarding these doors are set out in Pt E. As far asthe collision bulkhead is concerned, in general a maximumof two pipes may pass through the collision bulkhead belowthe freeboard deck, unless otherwise justified. Such pipesare to be fitted with suitable valves operable from above thefreeboard deck and the valve chest is to be secured at thebulkhead inside the fore peak. Such valves may be fitted onthe after side of the collision bulkhead provided that theyare readily accessible under all service condition.

All valves are to be of steel, bronze or other approved duc-tile material. As a general rule, no accesses are to be fittedin the collision bulkhead. Special consideration will begiven in case of yachts with particular design. only if theaccess is positioned as far above the design waterline aspossible and its closing appliances are watertight.

5.2 Watertight bulkheads

5.2.1 A collision bulkhead is to be fitted which is to bewatertight up to the freeboard deck. This bulkhead is to belocated at a distance from the forward perpendicular FPLL ofnot less than 5 per cent of the length LLL of the yacht, andnot more than 8 per cent LLL .

5.2.2 Where any part of the ship below the waterlineextends forward of the forward perpendicular, e.g. a bul-bous bow, the distances, in metres, stipulated in 5.2.1 are tobe measured from a point either:

• at the midlength of such extension, or

• at a distance 1,5 per cent of the length LLL of the yachtforward of the forward perpendicular, or

• at a distance 3 metres forward of the forward perpen-dicular; whichever gives the smallest measurement.

5.2.3 The bulkhead may have steps or recesses providedthey within the limits in 5.2.1 or 5.2.2.

Where long forward superstructures are fitted, the collisionbulkhead is to be extended weathertight to the first tiersuperstructure deck.

5.2.4 Rina may, on a case by case basis, accept a distancefrom the collision bulkhead to the forward perpendiculargreater than the maximum specified in 5.2.1 and 5.2.2,provided that, in case of flooding of the space forward thecollision bulkhead, subdvision and stability calculations ineither the full load departure condition and the arrival con-dition show compliance with Damage Stability require-ments set out in part. E of Rina Rules for Charter Yachts.

5.3 Sea connections and overboard discharge

5.3.1 All openings to the sea located below the weatherdeck are to be equipped with a closing valve, if not other-wise stated by the flag Administration. This valve, made oftough metallic material highly resistant to corrosion, is to befitted on the shell directly or by means of a nozzle and pro-vided with means of control located in a position which iseasily accessible at all times and permanently marked.Overboard discharges are to be kept to a minimum andlocated, as far as practicable, above the full load waterline.

The sea connection for the engine cooling system shall beprovided both with a grill fitted directly on the shell using alocal stiffener and with a filter after the closing valve.

The filter is to be made of metal highly resistant to corro-sion, and is to be of substantial dimensions and easy toopen.

5.3.2 All pipes leading to the sea and located under thefull load waterline are to be of adequate thickness, and ofmetallic material highly resistant to corrosion and electro-chemically compatible with any different materials theymay be connected to.Joints for elbows, valves etc. are to be made of material ofthe same composition as the pipes, or, where this is notpracticable, of material which is electrochemically compat-ible.

The use of non-metallic pipes and valves will be speciallyconsidered.

5.3.3 Pipes for the discharge of exhaust from the enginesleading to the shell are to be structural and are to havestrength equivalent to that of the bottom structure.The material is to be suitable to withstand the temperaturesreached by the exhaust and, if composite material is used,the pipes are to be internally coated with self-extinguishingresin for a thickness of at least 1,5 mm.

5.4 Stern and side doors below the weather deck

5.4.1 Side/shell doors leading to a non watertight space

The strength of these doors shall be equivalent to that of thesurrounding structures. These doors shall be fitted withproper gaskets, in order to prevent the ingress of water, and,if of wide dimensions, shall be provided with at least 8securing devices (clips) for closure (the hinges may becounted in as a securing devices). The distance betweenadjacent clips shall not exceed 800mm and, in any case,the number of clips on each shorter side of the doors shallbe not less than 2. Different arrangements shall be agreedwith RINA.

Doors of standard dimensions need not to be in compliancewith the a.m. requirements but shall be approved watertightdoors.

The lower part of each of these openings shall be above thedeepest sea going condition. Where the sill of any suchdoor is below the deepest sea going condition, the arrange-ment is considered by RINA on a case by case basis.


Pt B, Ch 1, Sec 1

Where hydraulic securing devices are applied, the system isto be mechanically lockable in closed position. This meansthat in the event of loss of hydraulic liquid, the securingdevices remain locked.

Indication regarding the status of these doors shall be pro-vided on the navigation bridge (open/closed): in particular,not only the status of the door shall be displayed but eventhe status of the locking devices.

Doors are preferably to open outwards.

5.4.2 Side/shell doors leading to a watertight compartment containing devices necessary for the proper and safe working of the ship

See par. 5.4.1.

5.4.3 Side/shell doors leading to a watertight space not containing devices necessary for the proper and safe working of the ship

These doors may be weathertight. The scantling of themshall be the same of that of the adjacent structure and thedistance between the lower part of these doors and thedeepest water line shall be al least 600mm. A high levelbilge alarm shall be provided. In case of damage stabilitycalculation, the position of these doors shall be investi-gated; if any part of the door remains below the waterline instatical position after damage in any compartment, thespace protected shall be considered as flooded.

The freeboard between the lower part of the door and thewater line may be less than 600mm, provided that the doorshave the locking devices indicated in 5.4.1; otherwise, if aweathertight door is fitted and the freeboard as above indi-cated is less than 600mm, the volume of the space pro-tected by the weathertight door will not be included in thereserve of buoyancy (hydrostatic data and cross curves).Even in this case, the door status shall be alarmed onbridge.

In case in the watertight compartment protected by aweathertight side/shell door, a door leading to the internalof the yacht is fitted, this door shall be watertight approved,openable from both sides and alarmed on bridge. Its lowerpart shall be above the deepest aft water line in all seagoing conditions.

For additional characteristic relevant to this internal door,reference is to be made to the requirements set out in PartE.

5.4.4 DrawingsA drawing representing the structure of the side/shell doors,their locking devices and their height above water line shallbe sent in triplicate to RINA for approval, with enclosed ageneral arrangement showing the destination of the com-partment which the doors give access to and the machineryand/or sports craft fitted in.

5.4.5 Other fittingsRecesses for wells, gangways, winches, platforms, etc are tobe watertight and of strength equivalent to that of the adja-cent structures. Any penetrations for electrical wiring andpiping are to ensure watertight integrity. Discharges are tobe provided to prevent the accumulation of water in thenormal foreseeable situations of transverse list and trim.

5.5 Hatch on the weather deck

5.5.1 Hatches on the weather deck and deck above are tohave a strength equivalent to that of the adjacent structuresto which they are fitted and are to be weathertight. In gen-eral, hatches are to be hinged on the foreword side. For thecoaming of these hatches reference is to be made to therequirements set out in Part E.

5.5.2 Where the hatches may be required to be used as ameans of escape the securing arrangements are to be opera-ble from both sides.

5.5.3 Flush hatches on the weather deck should not, ingeneral, be fitted. Where they are foreseen they shall be:

• closed at sea;

• fitted in protected location;

• have at least two drains in the aft part leading over-board;

• fitted with gaskets;

• have at least 4 clips for size 600 x 600 mm;

• have non-oval hinges which can be considered as clips.

For dimensions bigger than 600 x 600 mm, the acceptanceis at the discretion of RINA. Drawings representing thehatches, their position on deck, their coamins and their sys-tem of closure to be sent for approval.

5.6 Sidescuttles and windows

5.6.1 General

In general, the requirements of this paragraph apply toyachts engaged in "short range" navigation. For the "unre-stricted" navigation, reference is to be made to RINA "Rulesfor the classification of the Ships". Appropriate national/international standard may also be used.

The following requirements apply to sidescuttles and rec-tangular windows providing light and air, located in posi-tions which are exposed to the action of the sea orinclement weather below and above the weather deck.

Sidescuttles and rectangular windows may be of "non-open-ing", "opening" or "non readily openable" type.

5.6.2 Zones for the determination of scantling

For the purpose of determining the scantlings of sidescuttlesand rectangular windows, the yacht may be subdivided intozones which are defined as follows:

• Zone A: Zone between the full load waterline and a line drawnparallel to the sheer profile and having its lowest pointnot less than 500 mm or 2,5% B whichever is greaterabove the full load waterline;

• Zone B: Zone above Zone A bounded at the top by the deckfrom which the freeboard is calculated;

• Zone C: Zone corresponding to the 1st tier of superstructures andabove.


Pt B, Ch 1, Sec 1

5.6.3 Scantling and arrangements of sidescuttles and rectangular windows

Sidescuttles and rectangular windows may be classified asfollows, depending on their constructional characteristics:

• (medium series) non-opening or non readily openabletype, with deadlight: Type B;

• (light series) non-opening or opening type, withoutdeadlight: Type C.

The following requirements apply:

• in Zone A neither side scuttles nor rectangular windowsare permitted;

• in Zone B in general only type B sidescuttles and rectan-gular windows are permitted;

• in Zone C even where protecting openings giving directaccess to spaces below deck, type C sidescuttles andrectangular windows are permitted. In any case, thepresence of deadlights, stormshutters and blanking isestablished in Part E.

For the thickness of toughened glasses of sidescuttles andrectangular windows, having surfaces not exceeding0,16m2, and fitted below the weather deck, see Table 1.

Table 1

For oval sidescuttles reference is to be made to the equiva-lent surface area.

Different thickness may also be accepted on the basis of anhydraulic pressure test, performed on a mock-up represent-ative of the arrangement, the result of which confirms thatthe proposed thickness is able to ensure watertight integrityat a pressure not less than 4 times the design pressure of thehull in that zone.

If exceptional cases and if not otherwise stated by flagAdministration, sidescuttles and rectangular windows withsurfaces exceeding 0,16 m2 may be accepted in Zone B.Their acceptance shall be addressed to RINA and will beaccepted case by case in relation to their number, type andlocation. Relevant drawings with dimensions of clear open-ing, thickness of glass and position in respect to the deepestwater line to be sent for approval.

The thickness of the glass for such sidescuttles/rectangularwindows fitted below the weather deck is given by the fol-lowing formula:

where:

p : design pressure in kN/m2 computed at thelower edge of the windows but not less than 20kN/m2.;

b : shorter side of the window in mm

β : 0,54 A - 0,078 A2 - 0,17

β : 0,75 for A > 3

a : long side of the window

A : ratio a/b.

Different thickness may also be accepted on the basis of anhydraulic pressure test, performed on a mock-up represent-ative of the arrangement, the result of which confirms thatthe proposed thickness is able to ensure watertight integrityat a pressure not less than 4 times the design pressure of thehull in that zone.

In any case, the thickness cannot be assumed less than 15mm.

In addition, tests on mock-ups representative of the arrange-ment as well as direct calculations for the zone of the sideconcerned may also be required in order to demonstrate thelocal structural adequacy.

Deadlights of the fixed or non-fixed type are to be arranged;however, they may be omitted, at the discretion of RINAand if not otherwise stated by flag Administration where theglass pane is of the laminated (shatterproof) type with apolycarbonate core of thickness greater than 3mm.

5.6.4 Windows above weather deckThe required thicknesses of toughened glass panes in stand-ard rectangular windows are given in Table 2 as a functionof the standard sizes of clear light

Table 2

The thickness of toughened glass panes in rectangular win-dows of other sizes is given by the following formula:

Clear light diameter (mm)

Thickness of toughned glass (mm)

Type B sydescuttles

(medium series)

Type C sydescuttles (light

series)

200250300350400450

88

10121215

666888

t 0 015b β p⋅,=

Nominal sizes (clear light) of rec-tangular window

(mm)

Thickness of tough-ened glass

(mm)

Total minimum number of clos-

ing appliances of opening type rec-tangular window

300x500355x500400x560450x630500x710560x800900x630

1000x7101100x800

666667889

444466688

Nota 1: Swing bolts and circular hole hinges of glass holdersof opening type rectangular windows are considered closingappliances.

t 0 005b β p⋅,=


Pt B, Ch 1, Sec 1

where:

p : design pressure in kN/m2 of the wall of thesuperstructure with the window

b : shorter side of the window in mm

β : 0,54 A - 0,078 A2 - 0,17

β : 0,75 for A > 3

a : long side of the window

A : ratio a/b.

Different thickness may also be accepted on the basis of anhydraulic pressure test, performed on a mock-up represent-ative of the arrangement, the result of which confirms thatthe proposed thickness is able to ensure watertight integrityat a pressure not less than 4 times the design pressure.

The thickness of toughened glass panes of windows of othershapes will be the subject of special consideration by RINAin relation to their shape.

RINA reserves the right to impose limitations on the size ofrectangular windows and require the use of glass panes ofincreased thickness in way of front bulkheads which areparticularly exposed to heavy seas.

5.6.5 Materials other than toughened glassMaterials other than toughened glass may be used for side-scuttles and windows above and below the weather deck.

The thickness of the sheets may be obtained by multiplyingthe Rule thickness for toughened glass by 1,3 in the case ofpolycarbonate sheets and 1,5 in the case of acrylic sheets.

The thickness of laminated glass is to be such that:

being:

te : equivalent thickness of the single sheet glasspane

ti : thickness of the single sheet in the laminate

n : number of sheets in the laminate.

5.7 Skylights

5.7.1 Skylights fitted on the weather deck may consideredas fitted in zone B and therefore, for "short range" naviga-tion their thickness shall be in accordance with par. 5.6.3or 5.6.5.

Their locking devices shall be the same required for flushhatches (see par. 5.5.3).

5.8 Outer doors

5.8.1 Doors in the superstructure's sideDoors of exposed bulkheads of superstructures are to be ofadequate dimensions and construction such as to guaranteetheir weathertight integrity.

The use of FRP for doors on the weather deck other thanmachinery spaces may be accepted, providing the doors aresufficient strong.

Where the doors may be required to be used as a means ofescape, the securing arrangements are to be operable fromboth sides.

The height of the coamings from the surface of the deck is tobe in accordance with the requirements set out in Part E.

The doors on the weather deck which give direct access tomachinery spaces are to have a minimum of six clips and tobe outward opening. Other doors on the weather deck to 1st

tier accommodation or other spaces protecting accessbelow may have four clips.

5.8.2 Sliding glass doors

Arrangements with sliding glass doors or glass walls aregenerally permissible only for the after end bulkhead ofsuperstructures.

The glass used is to be of the toughened type or equivalent.

The thickness may be determined using the formula in5.6.4, assuming for p the value:

"Short range" navigation

• 1 for 1st tier

• 0,5 above the 1st tier.

"Unlimited" navigation

• 1,5 for all tier of superstructure

The sills of these doors shall be in accordance with therequirements set out in Part E.

5.9 Drawings

5.9.1 A plan showing the position portlights, windows,skylights, external doors and glass walls is to be submitted;their dimensions, their sills is to be clearly indicated.

5.10 Ventilator

5.10.1 General

Accommodation spaces are to be protected from gas orvapour fumes from machinery, exhaust and fuel system.

The yacht is to be adequately ventilated throughout allspaces.

Reference is also to be made to any additional requirementsset out in Pt. E.

The machinery spaces shall be adequately ventilated so asto ensure that, when machinery therein is operating at fullpower in all weather conditions, an adequate supply of airis maintained to the spaces for the safety and the operationof the machinery, according to Manufacturer's information.

For the requirements for fire precaution see Part E.

The design and positioning of ventilator openings are to bedone with care, above all in the zone of high stress or inexposed zone. The deck plating in way of the coamings is tobe adequately stiffened.

The scantlings of ventilators exposed to the weather are tobe equivalent to those of the adjacent deck or bulkhead.

Ventilators are to be adequately stayed.

Ventilators which, for any reason, can be subjected to liquidpressure are to be made watertight and have scantlings suit-able for withstanding the foreseen pressure.

te2 ti1

2 ti2

2 … tiin

2+ +=


Pt B, Ch 1, Sec 1

5.10.2 Closing appliancesAll ventilator openings are to be provided with efficientweathertight closing appliances unless:• The height of the coaming is greater than 4,5 m if above

the weather deck or above exposed superstructuredecks within the foreword 0,25 L;

• The height of the coaming is greater than 2,3 m if else-where.

As a general rule, closing appliances are to be permanentlyattached to the ventilator coaming.

Ventilators are to be fitted with a suitable means of prevent-ing ingress of water and spray when open and have a suita-ble drainage arrangements leading overboard.

5.11 Air pipes

5.11.1 GeneralAir and sounding pipes are to comply with the requirementsof Pt C, Ch 1, Sec 9, [7] and Pt. E, Ch 5, par. 5.7.

5.11.2 Height of air pipes

For the height of air pipes from the upper surface of decksexposed to the weather to the point where water may haveaccess below reference is to be made to Pt.E.

5.12 Bulwarks, railings

5.12.1 General

Bulwarks or railings are to be arranged on exposed decks.

Where this is not practicable, handrails or stays are to beprovided.

Bulwarks are to be of strong construction and adequatelysupported.

Any bulwarks or gunwales without openings on the weatherdeck are to be provided with freeing port openings havingdimensions in accordance with ILLC'66 requirement's, ifnot otherwise stated by flag Administration (See also Pt E,Ch 1, Sec 6).


Pt B, Ch 1, Sec 2

SECTION 2 HULL OUTFITTINGS

1 Rudders and steering gear

1.1 General

1.1.1 These requirements apply to ordinary profiles rud-ders without any special arrangement for increasing therudder force, such as fins or flaps, steering propellers, etc.

Unconventional rudders of unusual type or shape and thosewith speeds exceeding 45 knots will be the subject of spe-cial consideration by RINA.

In such cases, the scantlings of the rudder and the rudderstock will be determined by means of direct calculations tobe agreed with RINA as regards the loads and schematisa-tion.

In general, the loads will be determined either by modeltests, or by measurements taken on similar yachts, or usingrecognised theories.

The stresses in N/mm2 are not to be greater than the follow-ing:

• torsional stress = 70/e

• Von Mises equivalent stress = 120/e

as defined in 1.2.1.

The "steering gear" of a yacht means all apparatus anddevices necessary for the operation of the rudder, or equiv-alent means of manoeuvre, constituted by:

• main steering gear, designed to ensure control of theyacht at the maximum navigational speed;

• auxiliary steering gear, enabling control of the yacht inthe event of an emergency due to mechanical break-down of the components of the main steering gear.

1.2 Rudder stock

1.2.1 Rudder subject to torque onlyThe diameter DT, in mm, of rudder stocks, assumed in solidbar and subject to torque only, is given by the following for-mula:

where:

A : total rudder area, in m2 bounded by the rudder'sexternal contour including the mainpiece;

R : horizontal distance, in metres, from the centro-ids of area to the centreline of pintles, to betaken not less than 0,12b, where b is the width,in metres, of the rudder, if the latter has a rec-tangular contour; for rudders with non-rectan-gular contours, b = A/h is to be taken, where his the rudder height, in m, in way of the cen-treline of pintles mentioned above;

V : maximum design speed, in knots, of the yacht atfull load draught.

In the case of sailing yachts, with or withoutauxiliary engine, the following formula is to beused for the calculation of V:

where L is the length as defined in Sec. 1;

e : 235 / RS; the minimum yield stress RS is to betaken not greater than 0,7 RM, where RM is theminimum ultimate tensile strength of the rudderstock material.

However, the diameter DT is not to be taken less20 e1/3, in mm.

For rudder stocks made of material which ismore corrosion resistant than mild steels, alower value for diameter DT than that obtainedas above may be accepted by RINA on a case-by-case basis. In no case is such value to bereduced by more than 10%.

The diameter of rudder stocks made of compos-ite materials may be derived using the aboveformulae, taking as the value RS for the calcula-tion of e, the value of shear tensile strength ofthe composite material.

The inertia of the composite rudder stock Ic is tobe not less than ImEm/Efc, where:

Im - the inertia of the Rule metal rudder stock

Em - the modulus of elasticity of the metal

Efc - the bending modulus of elasticity of thecomposite material.

The acceptance of rudder stocks made of com-posite material is, in any event, subject to aninspection of the fabrication procedure and,where appropriate, to comparative workingtests.

1.2.2 Tubular rudder stockThe diameter DTF, in mm, of rudder stocks subject to torqueand bending, as in the case of rudders with two bearings(with solepiece) and of space rudders (see types IA, IB and IIin Figure 2) is to be not less than the value obtained fromthe formula:

where:

DT : diameter, in mm, of the rudder stock, as definedand calculated in 1.2.1;

K : 1,08 + 0,06 ( H / R ) for type IA or type IB rud-ders;

1,08 + 0,24 ( H / R ) for type II rudders;

DT 12 A R V2 e⋅ ⋅ ⋅( )1 3⁄=

V 2 3 L0 5,,=

DTF K DT⋅=


Pt B, Ch 1, Sec 2

H : vertical distance, in metres, from the centroid ofthe area A to the lower end of the rudder stockbearing in way of the piece.

The diameter of the rudder, required in way of the main-piece bearing, is to be extended at the upper part to at least10% of the height of the bearing or to a height equivalent to2 DTF, whichever is the greater; beyond this limit, the rudderstock diameter may be gradually tapered so as to reach thevalue of DT in way of the coupling between rudder stockand tiller.

At the lower part, the diameter DTF is to be extended as faras the coupling between the rudder stock and the main-piece; in the absence of such coupling, the diameter maybe gradually tapered below the upper edge of the rudderblade.

1.2.3 Tubular rudder stock Where a tubular rudder stock is adopted, its inner diameterd1 and outer diameter d2, in mm, are to comply with the fol-lowing formula:

where D = DT, for rudders dealt with in 1.2.1, and D = DTF,for rudders dealt with in 1.2.2.

1.3 Coupling between rudder stock and mainpiece

1.3.1 Horizontal couplingsHorizontal flange couplings between the rudder stock andthe mainpiece when not integral are to have:

• flanges of dimensions such that the coupling bolts aredistributed on a circumference having a diameter notless than 2D or in a similar manner, where D is asdefined in 1.2.3;

• flanges of thickness not less than the diameter d of thebolts;

• bolts of diameter d, in mm, not less than 0,65 D/n0,5,where n is the number of bolts, which in no case is to beless than 4;

• bolts whose axes are at a distance not less than 1,2 dfrom the external edge of the flanges;

• bolt nuts provided with means of locking.

1.3.2 Cone couplingsCone couplings of the shape shown in Fig. 1 (with explana-tions of symbols used in a) and b) below are to have the fol-lowing dimensions:

a) Cone coupling with hydraulic arrangements for assem-bling and disassembling the coupling

Taper:

and, in any case,:

Between the nut and rudder gudgeon a washer is to befitted having a thickness not less than 0,13 dG and anouter diameter not less than 1,3 d0 and 1,6 dG, which-ever is the greater.

b) Cone coupling without hydraulic arrangements forassembling and disassembling the couplingTaper:

and, in any case,

The dimensions of the locking nut, in both (a) and (b)above, are given purely for guidance, the determination ofadequate scantlings being the responsibility of theDesigner.

In cone couplings of type (b) above, a key is to be fittedhaving a cross section 0,25 dT x 0,10 dT, and keyways inboth the tapered part and the rudder gudgeon.

In cone couplings of type (a) above, the key may be omit-ted. In this case the Designer is to submit to RINA shrink-age calculations and supply all data necessary for therelevant check.

All necessary instructions for hydraulic assembly and disas-sembly of the nut, including indication of the values of allrelevant parameters, are to be available on board.

Figure 1

d24 d1

4–d2

-----------------1 3⁄

D≥

1 20⁄ d1 d0–( ) ts⁄ 1 12⁄≤ ≤

tS 1 5 d1⋅,≥

dG 0 65 d1⋅,≥

tN 0 60 dG⋅,≥

dN 1 2 d0⋅,≥

dN 1 5 dG⋅,≥

1 12⁄ d1 d0–( ) ts⁄ 1 8⁄≤ ≤

tS 1 5 d1⋅,≥

dG 0 65 d1⋅,≥

tN 0 60 dG⋅,≥

dN 1 2 d0⋅,≥

dN 1 5 dG⋅,≥


Pt B, Ch 1, Sec 2

1.4 Rudder mainpiece and blade

1.4.1 Mainpiece typesThe rudder mainpiece is formed by the stock, extended intothe blade when the coupling does not exist, or, otherwise,by a solid or tubular bar, a double T or a box structure, as inthe case of rudders with double plating.

The arms or the webs supporting the blade are to be struc-turally connected to the mainpiece.

1.4.2 Plate ruddersThe following requirements apply to rudders made of hullplates of ordinary steel; plates of other metallic material,e.g. aluminium alloy or stainless steel, are permitted; theirscantlings will be stipulated on the basis of their character-istics in accordance with a criterion of equivalence.

Single-plate rudders are to have:• mainpiece with section equal, or equivalent, to that of

the stock in way of the upper edge of the blade, gradu-ally tapered in the lower half to not less than 50%;

• plate with thickness t = 5 + 0,11 (DT - 20 ) mm, to belinearly increased with the arm spacing s, when s isgreater than 750 mm;

• horizontal arms with solid rectangular section, or equiv-alent each having, at the root, section modulus, in cm3,Z = 7 + 0,8 (DT- 20 ); for DT < 60 mm, Z = 7:cm3 is tobe taken.

Double-plate rudders are to have:• mainpiece of section equal, or equivalent, to the section

specified for single-plate rudders;• thickness t, in mm, of the plating, including that of

upper or lower closing, and vertical and horizontalwebs, given by the following formula:

where:s : spacing of the horizontal webs, in mm, to

be taken for the calculation as not greaterthan 1000;

DT : rudder stock diameter, in mm, as defined in1.2.1;- welded connections complying with the

requirements of Chap. 2 for steel rud-ders, and Chap. 3 for aluminium alloyrudders;

- internal surfaces protected by painting;the filling of the rudder with light mate-rial of expanded type is permitted;

- drainage hole.

1.4.3 Rudders with blade made of glass reinforced plastics

Such rudders are to have, in particular:• stock and mainpiece, in solid or tubular bar, made of

hull steel or light alloy, and mainpiece arms, of thesame material, structurally connected to the mainpiece;

• blade made of a single plate or composed of two pre-formed plates, made of glass reinforced plastics, com-plying with the requirements of Chap. 4 and filled withlight material;

• mass per unit surface, m, in kg/m2, of the glass rein-forcement of the material, m = 0,6Vb, where V and bare as defined in 1.2.1. The thickness of the plate is, inany case, to be not less than 5 mm.

1.4.4 Cast ruddersFor rudders and their stocks obtained by casting, the type ofmaterial and the relevant mechanical characteristics are tobe submitted to RINA for examination.

Castings with sharp edges and sharp section changes are tobe avoided, in particular when stock and plating are cast inone piece.

1.5 Rudder bearings, pintles and stuffing boxes

1.5.1 Rudder bearingsRudder "bearings" means:

• the bearing supporting the radial load fitted at the rud-der trunk, that at the solepiece and that in way of thestock/tiller coupling;

• a bearing, or equivalent device, carrying the verticalload, in order to support the weight of the rudder;

• rudder stop devices, designed to prevent the rudderfrom lifting as necessary.

The rudder trunk bearing height h, in mm, is to be between1,5 D and 2 D, where D is the local stock diameter asdefined in 1.2.3.

Lower values of h, but in no case less than 1,2 D, may beaccepted except in the case of spade rudders, for which h ≥1,5 D is required.

If the rudder stock is lined in way of the trunk bearing (forinstance with stainless steel brush), the lining is to be shrunkon.

Any proposed welding overlay may be accepted subject tothe use of a welding process recognised as suitable byRINA.

1.5.2 PintlesThe minimum diameter DA, in mm, of the pintles, outside ofany lining or welding, is given by the following formula:

DA = c + 0,6 D

where:

c : 1, for rudders dealt with in 1.2.15, in other cases;

D : rudder stock diameter as defined in 1.2.3.The height of the pintle bearing surface is to be approxi-mately 1,2 DA, but in no case less than DA.

The tapering of any truncated cone-shaped part of the pin-tle, in way of the connection to the hull, is to be 1:6 withrespect to the diameter.

For any linig or welding, the requirements of 1.5.1 apply.

1.5.3 Sealing devicesIn rudder trunks which are open to the sea, a seal or stuffingbox is to be fitted above the deepest load waterline, to pre-vent water from entering the steering gear compartment andlubricant being washed away from the rudder carrier.

t DT0 45, 0 7 s 103⁄+,( )=


Pt B, Ch 1, Sec 2

If the top of the rudder trunk is below the deepest loadwaterline, two separate seals or stuffing boxes are to be pro-vided.

1.6 Steering gear and associated apparatus

1.6.1 Premise

These requirements apply to the most commonly used typesof steering gear, which are dealt with below; any differenttypes will be specially considered by RINA in each case.

1.6.2 Types of steering gear

Remote controlled steering gear of one of the followingtypes:

• tiller; hydraulic actuator of the tiller and associated pip-ing; valves and hydraulic pump controlled by rudderwheel;

• the above apparatus, with the addition of an electricpump feeding the actuator through distributor and gyro-pilot follow-up link.

1.6.3 Steering gear of remote controlled type with rope or chain

The rudder tiller, or quadrant, is to have:

• hub of height h ≥ DT, in mm, and thickness t ≥ 0,4 DT, inmm;

• section modulus Z, in cm3, in way of the connection tothe hub, given by the following formula:

where:

DT : Rule diameter, in mm, of the rudder stock sub-ject to torque only;

a : length, in mm, of the tiller, measured from therudder stock to the point of connection of ropeor chain to the stock;

b : 0,5 DT + t, in mm.

The tiller-stock coupling is to be of the type with squaresection, or with cylindrical section and key, and the tillerhub is to be bolted, in particular:

• the hub bolts are to have diameter db, in mm, not lessthan the value given by the formula:

where n is the number of bolts on each side of the hub;in any case the diameter db is to be not less than 12 mm;

• the coupling key is to have rounded edges, length, inmm, equal to the hub thickness, thickness, in mm, equalto 0,17 DT and section area, in mm2, equal to 0,25 DT

2.

Alternative arrangements will be subject of special consid-eration by RINA.

1.6.4 Steering gear with hydraulic or electro-hydraulic type remote control

The parts of such steering gear are to comply with the spe-cific requirements of Part C Chap. 1 Sec. 10 of these Rule.

Figure 2

Z 0 15DT

3

1000------------- a b–

a------------⋅ ⋅,≥

db0 4D,2n0 5,--------------=

Tipo IA Tipo IB Tipo II


Pt B, Ch 1, Sec 2

2 Propeller shaft brackets

2.1 Double arm brackets

2.1.1 Double arm propeller shaft brackets consist of twoarms forming an angle as near as practicable to 90°, andconverging into a propeller shaft bossing.Arms having elliptical or trapezoidal section with roundfairing are to have an area A, in cm2, at the root not lessthan that given by the following relationship:

where:dp : Rule diameter of the propeller shaft made of

steel with ultimate tensile strength Rm = 400measured inside the liner, if any, in mm,

Rma : minimum ultimate tensile strength, in N/mm2,of the material of the brackets.

The maximum thickness in way of the above section is tobe not less than 0,4 dp.

The boss is to have length of approximately 3 dp, but in nocase less than 3 dp, and thickness of approximately 0,25 dp.

When the brackets are connected by means of palms, thelatter are to have thickness not less than 0,2 dp and are to beconnected to the hull by means of bolts with nuts and locknuts on the internal hull structures, which are to be suitablystiffened to the satisfaction of RINA.

The thickness of the plating in the vicinity of the connectionis to be increased by 50%.

In the case of metal hulls and brackets of the same material,the connection between bracket and hull is to be carriedout by means of welding.

The brackets are to be continuous through the plating andto be connected internally to suitable transverse or longitu-dinal structures.

The plating in way of the bracket connection is to be suita-bly increased and connected to the arm bracket with fullpenetration welding.

2.2 Single arm brackets

2.2.1 Thew section modulus Z, in cm3, of the section atthe root (i.e. of the section, at the end of the bracket at theattachment to the plating of the connecting palm) is to be atleast equal to that given by the following formula:

where:dp : as defined in 2.1.1,K :

assuming K =1 when b/dp ≤ 6,5

b : the length of the arm to be measured from itsorigin on the propeller shaft boss to its intersec-tion with the shell plating or with the outsideplane of the palm.

The above formula is to be intended as applicable for mate-rial with ultimate tensile strength Rm = 400 N/mm2; in other

cases, the section modulus Z is to be modified as a functionof the tensile strength of the material.

The fillet radii between the section at the root of the bracketand the connecting palm are to be as large as practicable.The cross area of the bracket at the boss is to be not lessthan 60% of the area of the bracket at he palm or at theintersection with the shell plating.

With regard to the boss, the connecting palm and the con-nection to the hull, see 2.1.1.

3 Ballast

3.1

3.1.1 The typical ratio of the weight of external ballast tolight displacement is generally 0,4 ÷ 0,5.

The ballast may be internal or external to the hull.

In the first case, the ballast is to be permanently secured, byclips or equivalent means, to the resistant structures of thehull (floors, frames, etc.) but in no case to plating, on whichit is never to bear, so as not to shift even during rolling orpitching.

In the second case, the connection to the hull is to beeffected by means of bolts long enough to incorporate theheight of the ballast, either wholly or in part; such bolts areto pass through the hull, with a head (or nut and lock nut) atone end and a nut and lock nut at the other, towards theinside of the hull. The surface of the ballast keel head is tobe flush with the surface of the hull, the bolt holes are to befashioned with equipment designed to achieve an almostcomplete absence of play between bolt and hole, and thelocking of the nuts is to be uniform. The nuts are to rest onplates or large washers and to be left uncovered so that theymay be easily examined.

The diameter d, in mm, of the bolts (at the end of thethread) is generally given by the following formula:

where:

W : mass of the ballast, in kg;

hG : distance, in mm, from the centroid of the bal-last, to the plane of attachment of the ballast tothe hull;

σR : ultimate tensile strength of the bolt material, inN/mm2;

li : distance, in mm, between the two boltsarranged on the i-nth section.

A double row of bolts is to be fitted, each bolt having across-sectional area A = 0,6d2, and therefore diameter d1 =1,13A0,5, in mm.

There are to be at least 8 bolts, their diameter is to be atleast 14 mm, and they are to be made of bronze, stainlesssteel or highly galvanised steel.

Where direct calculations are carried out to determine thediameter of bolts, the degree of locking is to be taken intoaccount and a safety factor < 3,5 in relation to the ultimatetensile strength and ≥ 2 in relation to the yield stress of thebolt material is to be applied.

A 87 5, 10 3–⋅ dP2 1600 Rma+

Rma

-----------------------------⎝ ⎠⎛ ⎞⋅=

Z 0 14K dP3 10 3––⋅,=

b dp⁄6 5,

------------

d 11 WhG Σli σR⋅⁄[ ]= 0 5,


Pt B, Ch 1, Sec 2

4 Stabiliser arrangements

4.1 General

4.1.1 The scantlings, arrangement and efficiency of stabi-liser arrangements do not fall within the scope of Classifica-tion; nevertheless, the bedplates of the various components,the supporting structures and the watertight integrity are tobe examined.

4.2 Stabiliser arrangements

4.2.1 The stabiliser fin machinery is to be supported byadequately reinforced structures.

Drawings are to be submitted for approval showing theposition, the supporting structures and the loads transmit-ted.

4.2.2 The shell plating in way of stabilizer fins shall beadequately reinforced. In the case of fixed type stabiliserfins, the passage to the hull and the components necessaryfor the operation of the system, supported by adequatelyreinforced structures are to be arranged in a watertight boxwith an inspection opening fitted with a watertight cover.

In metal structures, the watertight box shall be at least of thesame thickness as the adjacent shell plating, but in no caseless than 12mm. The box shall be well stiffened. For GRPvessels, the scantling of the watertight boxes and their stiff-eners will be considered case by case. Where it is not prac-tical to provide a watertight box, particularly because of therestricted inside spaces, the arrangement will be speciallyconsidered by RINA.

4.3 Stabilising tanks

4.3.1 The tank structures are to comply with the require-ments for tank bulkheads, taking into account the maximumhead that may arise in service.

Where sloshing is foreseeable the scantlings will be the sub-ject of special consideration.

5 Thruster tunnels

5.1 Tunnel wall thickness

5.1.1 The thickness of the tunnel is to be in accordancewith the Manufacturer's specifications; in general, the thick-ness is to be not less than:

• For steel tunnels: the Rule thickness of the adjacentplating increased by 10% (but at least 2 mm), and in anycase not less than 7 mm.

• For light alloy tunnels: the Rule thickness of the adja-cent plating increased by 10% (but at least 1 mm), andin any case not less than 8 mm .

• For composite tunnels: the Rule thickness of the adja-cent plating increased by 25%; in any case the thicknessis to be not less than 8 mm.

5.2 Tunnel arrangement details

5.2.1 The system for connecting the tunnel to the hulldepends on the material used for the construction.

5.2.2 The tunnel is to be arranged between two floors ofincreased height or in a separate watertight compartment.

5.2.3 The thickness of the plating is to be locally increasedby 50% in way of the tunnel attachment.

5.2.4 The tunnel is to be connected to the plating bymeans of full penetration welding.

5.2.5 For tunnels in composite material, the weight of theconnecting laminate stiffener is to be equal to the weight ofthe bottom plating stiffener. The stiffener is to be arrangedon both sides of the plating laminate.

Prior to the connecting lamination, the surfaces of the tun-nel and the plating concerned are to be suitably cleanedand prepared and the edges of the cuts are to be sealed withresin.

6 Water-jet drive ducts

6.1

6.1.1 The thickness of the duct is to be in accordance withthe Manufacturer's specifications and, in general, is to benot less than that of the adjacent plating.

The duct is to be adequately supported, stiffened and fullyintegrated with the hull structure.

The water-jet drive supporting structures are to be able towithstand the loads induced by the propulsion system in thefollowing conditions:

• maximum thrust ahead

• maximum thrust at the maximum lateral inclination

• maximum reverse thrust (astern speed).

The foregoing loads are to be provided by the water-jetdrive Manufacturer and adequately documented.

All hull openings are to be adequately reinforced and tohave well rounded corners.

The thickness of the plating in the vicinity of the ductentrance is to be locally increased as stated in 5.2.3.

The Manufacturer is to assess the need to arrange suitablemeans of protection at the duct opening in order to preventthe ingress of foreign bodies which may damage the inter-nal mechanism.


Pt B, Ch 1, Sec 2

7 Crane support arrangements

7.1

7.1.1 Crane foundations shall be designed considering theworst combinations of the following loadings:- maximum load capacity- the weight of the crane itself;- wind;- crane accelerations resulting from the vessel's heel and

trim

Insert plates shall be provided in the deck in way of thecrane foundation; in order to avoid concentration of forces,these insert plates shall have suitable dimensions (in respectto the dimensions of the foundation), be suitably preparedand have round corners. The thickness of these inserts shallbe in accordance with the designer's calculations.

A drawing of this arrangement with all the forces acting andthe particular of the connection to the deck is to be sent forapproval.


Pt B, Ch 1, Sec 3

SECTION 3 EQUIPMENTS

1 General

1.1

1.1.1 The anchoring equipment required in 6 is intendedfor temporary mooring of a yacht within or near a harbour,or in a sheltered area.

The equipment is therefore not designed to hold a yacht offfully exposed coasts in rough weather or to stop a yachtwhich is moving or drifting. In such conditions the loads onthe anchoring equipment increase to such a degree that itscomponents may be damaged or lost owing to the highenergy forces generated.The anchoring equipment required in 6 is deemed suitableto hold a yacht in good holding ground where the condi-tions are such as to avoid dragging of the anchor. In poorholding ground the holding power of the anchors will besignificantly reduced.It is assumed that under normal circumstances a yacht willuse one anchor only.In any case the anchoring and mooring arrangementsshould meet the minimum requirements as required fromthe flag Administration.

2 Anchors

2.1

2.1.1 Anchors are to be manufactured in accordance withPt D, Ch 4, Sec.1

2.1.2 The mass, per anchor, given in Table 1 applies to"high holding power" anchors. When use is made of normaltype anchors, the mass shown in the table is to be multi-plied by 1,33.

When "very high holding power" anchors are used, themass of the anchors may be equal to 70% of that shown inTable 1 for stockless anchors.The actual mass of each anchor may vary by + or - 7% withrespect to that shown in Table 1, provided that the totalmass of the two anchors is at least equal to the sum of themasses given in the Table.The first anchor is to be positioned ready for use, while thesecond may be kept on board as a spare.

3 Chain cables for anchors

3.1

3.1.1 Chain cables are to have proportions in accordancewith recognised unified standards and to be of the steelgrade given in Table 1.

Grade 1 chain cables are generally not to be used in associ-ation with "high holding power" anchors; chain cables of atleast Grade 2 are to be used with "very high holding power"anchors.

4 Mooring lines

4.1

4.1.1 Mooring lines may be of wire, natural or syntheticfibre, or a mixture of wire and fibre.Where steel wires are used, they are to be of the flexibletype.Steel wires to be used with mooring winches, where thewire is wound on the winch drum, may be constructed withan independent metal core instead of a fibre core.The breaking loads shown in Table 1 refer to steel wires ornatural fibre ropes.Where synthetic fibre ropes are adopted, their size will bedetermined taking into account the type of material usedand the manufacturing characteristics of the rope, as well asthe different properties of such ropes in comparison withnatural fibre ropes.The equivalence between synthetic fibre ropes and naturalfibre ropes may be assessed by the following formula:

dove:δ : elongation to breaking of the synthetic fibre

rope, to be assumed not less than 30%;CRS : breaking load of the synthetic fibre rope, in kN;CRM : breaking load of the natural fibre rope, in kN;Where synthetic fibre ropes are used, rope diameters under20 mm are not permitted, even though a smaller diametercould be adopted in relation to the required breaking load.

5 Windlass

5.1

5.1.1 Windlasses are to be power driven and suitable forthe size of chain cable and is to have the characteristicsbelow.The windlass is to be fitted in a suitable position in order toensure an easy lead of the chain cables to and through thehawse pipes; the deck in way of the windlass is to be suita-bly reinforced.A suitable stopping device is to be fitted in order to preventthe anchor from shifting due to movement of the yacht.

5.1.2 For vessel having GT greater than 500, calculationsdemonstrating compliance with Pt B, Ch,10, Sec.4, par 3.7of RINA Rules for Ship shall be sent to Head Office together

CRS 7 4δ CRM⋅CRM

1 9⁄------------------⋅,=


Pt B, Ch 1, Sec 3

with detailed plans and an arrangement plan showing thefollowing components:

Shafting.

Gearing.

Brakes.

Clutches.

5.2 Working test on windlass

5.2.1 The working test of the windlass is to be carried outon board at the presence of the Surveyor.

5.2.2 The test is to demonstrate that the windlass worksadequately and has sufficient power to simultaneouslyweigh the two bower anchors (excluding the housing of theanchors in the hawse pipe) when both are suspended to55m of chain cable, in not more than 6 min.

5.2.3 Where two windlasses operating separately on eachchain cable are adopted, the weighing test is to be carriedout for both, weighing an anchor suspended to 82,5m ofchain cable and verifying that the time required for theweighing (excluding the housing of the anchors in thehawse pipe) does not exceed 9 min. Where the depth ofwater in the trial area is inadequate, or the anchor cable isless than 82,5 m, suitable equivalent simulating conditionswill be considered as an alternative.

6 Equipment Number and equipment

6.1

6.1.1 All yacths are to be provided with anchors, chaincables and ropes based on their Equipment Number EN, asshown in Table 1.

The equipment Number EN is to be calculated as follows:

where:

∆ : yacht displacement, in tonnes, as defined inSection 1

h :

a : distance, in m, from the summerload waterline amidships to theweather deck

hn : height, in m, at the centreline ofeach tier n of superstructures ordeckhouses having a breadthgreater than B/4.

A : area, in m2, in profile view, of the parts of thehull, superstructures and deckhouses above thesummer load waterline which are within thelength L of the yacht and also have a breadthgreater than B/4.

For yachts that have superstructures with the front bulkheadwith an angle of inclination aft, the equipment number canbe calculated as follows:

θn : angle of inclination with the horizontal axis aftof each front bulkhead

bn : greatest breadth, in m, of each tier n of super-structures or deckhouses having a breadthgreater than B/4.

For EN > 1060 the anchors, chain cables and ropes will befixed by RINA depending on the case.

6.1.2 When calculating h, sheer and trim are to be disre-garded, i.e. h is to be taken equal to the sum of freeboardamidships plus the height hn (at the centreline) of each tierof superstructures and deckhouses having a breadth greaterthan B/4.

Where a deckhouse having a breadth greater than B/4 isabove another deckhouse with a breadth of B/4 or less, theupper deckhouse is to be included and the lower ignored.

Screens or bulwarks 1,5 metres or more in height are to beregarded as parts of deckhouses when determining h and A.

In determining the area A, when a bulwark is more than 1,5metres in height the area above such height is to beincluded.

6.1.3 3 Drawing relevant to the equipment number to besent for approval; the drawing is to contain also informationon

- geometrical elements fo calculation

- list of equipment;

- construction and breaking load of steel wires;

- material, construction, breaking load and relevant elon-gation of synthetic ropes.

7 Sailing yachts

7.1

7.1.1 For sailing yachts (with or without auxiliary engine),the value of EN is to be calculated using the formula givenin 6.1.

EN ∆2 3⁄ 2h B 0 1A,+⋅+=

a Σhn+

EN ∆2 3⁄ 2 aB bn hn θsin n∑+⎝ ⎠⎛ ⎞ 0 1A,++=


Pt B, Ch 1, Sec 3

Table 1

ENStockless bower

anchorsChain cables for anchors Mooring lines

A<EN<B

No. (1)Mass per anchor (kg)

Total length

(m)

Diameter (mm)

No.Length

(m)

Breaking load kNA B

Studless chain

cable (2)

Chain cables with stud

Grade U1 steel

Grade U2 steel

Grade U3 steel

507090

110130150175205240280320360400450500550600660720780840910980

7090

110130150175205240280320360400450500550600660770780840910980

1060

11122222222222222222222

100120140160180200230260310360410460520580640700770840910980

106011501260

137,5165165

192,5192,5192,5220220220

247,5247,5247,5275275275

302,5302,5302,5330330

357,5357,5357,5

1112,512,514,514,517,517,51919

20,52224-----------

-111114141616

17,517,519

20,5222224262628303032323436

---

12,512,514141616

17,517,51919

20,5222224262628283032

-----

1111

12,512,51414161617

20,520,522242424242628

22233334444444444444444

607080809090909090

110110110110110130130130130140140140140140

263135353943475155596270788698

105118126138150160173184

(1) The second anchor is intended as a spare and it is not necessary to carry it as a bower anchor provided that, in the event of theloss of the first anchor, the sheet anchor can be readily removed from its position and arranged as a bower anchor.

(2) The diameters refer to Grade U1 steel chain cables; where Grade U2 or U3 steel studless chain cables are used, the diametersmay be reduced guaranteeing the same breaking load as the chain cable corresponding to Grade U1.


Pt B, Ch 1, Sec 4

SECTION 4 NON STRUCTURAL FUEL TANKS

1 General

1.1

1.1.1 Tanks for liquid fuel are to be designed and con-structed so as to withstand, without leakage, the dynamicstresses to which they will be subjected. They are to be fit-ted with internal diaphragms, where necessary, in order toreduce the movement of liquid.

Tanks are to be arranged on special supports on the hulland securely fastened to them so as to withstand the stressesinduced by movement of the yacht.

Tanks are to be arranged so as to be accessible at least forexternal inspection and check of piping.

Where their dimensions permit, tanks are to include open-ings allowing at least the visual inspection of the interior.

In tanks intended to contain fuel with a flashpoint below55°C determined using the closed cup test (petrol, keroseneand similar), the above openings are to be arranged on thetop of the tank.

Such tanks are to be separated from accommodation spacesby integral gastight bulkheads. Tanks are to be arranged inadequately ventilated spaces equipped with a mechanicalair ejector.

Upon completion of construction and fitting of all the pipeconnections, tanks are to be subjected to a hydraulic pres-sure test with a head equal to that corresponding to 2 mabove the tank top or that of the overflow pipe, whicheveris the greater.

At the discretion of RINA, leak testing may be accepted asan alternative, provided that it is possible, using liquid solu-tions of proven effectiveness in the detection of air leaks, tocarry out a visual inspection of all parts of the tanks withparticular reference to pipe connections.

2 Metallic tanks

2.1 General

2.1.1 Tanks intended to contain diesel oil or gas-oil are tobe made of stainless steel, nickel copper, steel or alumin-ium alloys.

Steel tanks are to be suitably protected internally and exter-nally so as to withstand the corrosive action of the salt inthe atmosphere and the fuel they are intended to contain.

The upper part of tanks is generally not to have weldededges facing upwards or be shaped so as to accumulatewater or humidity.

To this end, zinc plating may be used, except for tanksintended to contain diesel oil or gas-oil, for which internalzinc plating is not permitted.

Tanks are to be effectively earthed.

2.2 Scantlings

2.2.1 The thickness of metallic tank plating is to be not lessthan the value t, in mm, given by the following formula:

where:

s : stiffener spacing, in m;

hS : static internal design head, in m, to be assumedas the greater of the following values:

• vertical distance from the pdr (see below) toa point located 2 m above the tank top

• two-thirds of the vertical distance from thepdr to the top of overflow

K : where RS is the minimum yield stress, in

N/mm2, of the tank material. Where light alloysare employed, the value of RS to be assumed isthat corresponding to the alloy in the annealedcondition;

pdr : point of reference, intended as the lower edgeof the plate, or, for stiffeners, the centre of thearea supported by the stiffener.

In any case the thickness of the tank is to be not less than 2mm for steel and not less than 3 mm for light alloy.

The section modulus of stiffeners is to be not less than thevalue Z, in cm3, given by the formula:

where:

S : stiffener span, in m.

3 Non-metallic tanks

3.1 General

3.1.1 Fuel tanks may be made of non-metallic materials.The materials adopted are to withstand the corrosive actionof the fuel to be carried.

The acceptance of the non-metallic tanks will be subject totests on materials (such as and after immersion in the fuel tobe carried).

3.2 Scantlings

3.2.1 The scantlings of non-metallic tanks will be speciallyconsidered by RINA on the basis of the characteristics of the

t 4 s hS K⋅( )0 5,⋅ ⋅=

235RS

----------

Z 4 s S2 hS K⋅ ⋅ ⋅ ⋅=


Pt B, Ch 1, Sec 4

material proposed and the results of strength tests per-formed on a sample.

In general, for tanks made of composite material, the thick-ness t, in mm, of the plating and the module of stiffeners Z,in cm3, are to be not less, respectively, than the values:

where:

kof , k0 : as defined in Chap. 4;

s, S, hS : as defined in 2.2.

In any case, the thickness is to be not less than 8 mm withreinforcement not less than 30% in weight fraction.

The surface of the tanks is to be internally coated with resincapable of withstanding hydrocarbons and externallycoated with self-extinguishing resin.

3.3 Tests on tanks

3.3.1 GeneralPrior to their installation on board, tanks are to be subjectedto a hydraulic pressure test with a head equal to that corre-

sponding to 2 m above the tank top or that of the overflowpipe, whichever is the greater.

At the discretion of RINA, leak testing may be accepted asan alternative in accordance with the conditions stipulatedin 3.3.2.

3.3.2 Leak testing

Leak testing is to be carried out by applying an air pressureof 0,15 bar.

Prior to inspection of the tightness of welding, in the case ofmetallic tanks and pipe connections, it is recommendedthat the air pressure is raised to 0,2 bar and kept at this levelfor about 1 hour. The level may then be lowered to the testpressure before carrying out the welding tightness check ofthe tank and connections by means of a liquid solution ofproven effectiveness in the detection of air leaks.

The test may be supplemented by arranging a pressuregauge and checking that the reading does not vary overtime.

Leak testing is to be performed before any primer and/orcoating is applied. In the case of tanks made of compositematerial, the test is to be carried out before the surface isexternally coated with self-extinguishing resin.

t 6 s hS ko f⋅( )0 5,⋅ ⋅=

Z 15 s S2 hS K0⋅ ⋅ ⋅ ⋅=


Pt B, Ch 1, Sec 5

SECTION 5 LOADS

1 General

1.1

1.1.1 The static and dynamic design loads defined in thisSection are to be adopted in the formulae for scantlings ofhull and deck structures stipulated in Chapters 2, 3 and 4 ofPart B.

For yachts of speed exceeding 10 L0,5 knots or yachts ofunusual shape, additional information may be required inthe form of basin test results on prototypes.

Alternative methods for the determination of accelerationand loads may be taken into consideration by RINA also onthe basis of model tests or experimental values measured onsimilar yachts, or generally accepted theories.

In such case a report is to be submitted giving details of themethods used and/or tests performed.

Pressures on panels and stiffeners may be considered asuniform and equal to the value assumed in the point of ref-erence pdr as defined in 2.3.

2 Definitions and symbols

2.1 General

2.1.1 The definitions of the following symbols are valid forall of Part B. The meanings of those symbols which havespecific validity are specified in the relevant Chapters orSections.

2.2 Definitions

2.2.1 Displacement yachtA yacht whose weight is fully supported by the hydrostaticforces.

In general, for the purposes of this Section, a displacementyacht is a craft having V / L0,5 ≤ 4.

2.2.2 Semi-planing yachtA yacht that is supported partially by the buoyancy of thewater it displaces and partially by the dynamic pressuregenerated by the bottom surface running over the water.

2.2.3 Planing yachtA yacht in which the dynamic lift generated by the bottomsurface running over the water supports the total weight ofthe yacht.

2.2.4 ChineIn hulls without a clearly visible chine, this is the point ofthe hull in which the tangent to the hull has an angle of 50°on the horizontal axis.

2.2.5 BottomThe bottom is that part of the hull between the keel and thechines.

2.2.6 Side ShellThe side shell is that part of the hull between the chine andthe highest continuous deck.

2.3 Symbols2.3.1 βx : Deadrise of the transverse section under consid-

eration.In hulls without a clearly visible deadrise, this isthe angle formed by the horizontal axis and thestraight line joining keel and chine.

PpAV : Forward perpendicular: perpendicular at theintersection of the full load waterline plane(with the yacht stationary in still water) and thefore side of the stem.

PpAD : Aft perpendicular: perpendicular at the intersec-tion of the full load waterline plane (with theyacht stationary in still water) and the aft side ofthe sternpost or transom.

pdc : Design deck, intended as the first deck abovethe full load waterline, extending for at least 0,6L and constituting an effective support for side structures.

pdr : Point of reference, intended as the lower edgeof the plating panel or the centre of the areasupported by the stiffener, depending on thecase under consideration..

∆ : Displacement, in t, of the yacht at full loaddraught T. Where unknown, to be assumedequal to 0,42 · L · B · T.

CB : Block coefficient, given by the relationship:

CS : Support contour of the yacht, in m, defined asthe transverse distance,

: measured along the hull, from the chines to 0,5L. For twin hull yachts, CSis twice the distancemeasured along the single hull.

g : Acceleration of gravity = 9,81 m/s2.LCG : Longitudinal centre of gravity of the yacht;

where unknown, to be taken as located in thesection at 0,6 L from the PpAV.

aCG : Maximum design value of vertical accelerationat LCG, in g, provided by the Designer based onan assessment of the service conditions (speed,significant wave height) envisaged in thedesign.

CB∆

1 025L B T⋅ ⋅,-----------------------------------=


Pt B, Ch 1, Sec 5

V : Maximum service speed, in knots.

3 Design acceleration

3.1 Vertical acceleration at LCG

3.1.1 GeneralThe design vertical acceleration at LCG, aCG (expressed ing), is defined by the Designer and corresponds to the aver-age of the 1% highest accelerations in the most severe seaconditions expected. Generally, it is to be not less than:

where S is given by:

where:

Values of S reduced to as low as 80% of the foregoing valuemay be accepted, at the discretion of RINA, if justified onthe basis of the results of model tests or prototype tests.

The sea area to which the aforementioned value refers isdefined with reference to the significant wave height HS

which is exceeded for an average of not more than 10% ofthe year:

• Open-sea service: Hs ≥ 4,0 m;

If the design acceleration cannot be defined by theDesigner, the aCG value corresponding to the value of S cal-culated with the above-mentioned formula is to beassumed.

3.1.2 Longitudinal distribution of verticalacceleration

The longitudinal distribution of vertical acceleration alongthe hull is given by:

dove:

KV : Longitudinal distribution factor, defined in Fig-ure 1, equal to 2.x/L or 0,8, whichever is thegreater, where x is the distance, in m, from thecalculation point to the aft perpendicular;

aCG : Design acceleration at LCG (see 3.1).

Variation di aV in the trasverse direction may generally bedisregarded.

Figure 1

3.2 Transverse acceleration

3.2.1 Transverse acceleration, to be used in direct calcula-tions for yachts with many tiers of superstructure for whichsignificant racking effects are anticipated, is defined on thebasis of model tests and full-scale measurements.

In the absence of such results, transverse acceleration, in g,at the calculation point of the yacht may be obtained from:

where:

Hsl : permissible significant wave height, in m, atspeed V

r : distance of the calculation point from:

• 0,5 D for monohull yachts

• waterline at draught T, for twin hull.

4 Overall loads

4.1 General

4.1.1 Overall loads are to be used for the check of longitu-dinal strength of the yacht, as required, in relation to thematerial of the hull, in Chapters 2, 3 and 4.

4.2 Longitudinal bending moment and shear force

4.2.1 General The values of the longitudinal bending moment and shearforce are given, as a first approximation, by the formulae in4.2.2. For large yachts, the results of experimental tanktests may be taken into account.

If the actual distribution of weights along the yacht isknown, a more accurate calculation may be performed inaccordance with the procedure given in 4.2.3. RINAreserves the right to require calculations to be carried outaccording to 4.2.3 whenever deemed necessary.

4.2.2 Bending moment and shear force The total bending moments Mbl,H, in hogging conditions,and Mbl,S, in sagging conditions, in kN·m, are the greater ofthose given by the formulae in a) and b) below.

For yachts of L > 100 m, only the formula in b) is generallyto be applied; the formula in a) is to be applied whendeemed necessary by RINA on the basis of the motion char-acteristics of the yacht.

The total force Tbl, in kN, is given by the formula in c)below.

a) bending moment due to still water loads, wave inducedloads and impact loads

where aCG is the vertical acceleration at the LCG,defined in 3.1.

The same value of Mbl is taken for a yacht in saggingconditions or in hogging conditions.

aCG S VL0 5,---------⋅=

S 0 65CF,=

CF 0 2, 0 6, V L0 5,⁄( )⁄[ ] 0 32,≥+=

av kv aCG⋅=

at 2 5, HslL

------- 1 5 1 V L0 5,⁄6

-----------------+⎝ ⎠⎛ ⎞

2 rL---⋅ ⋅+⋅ ⋅=

MblH, MblS, 0 55 ∆ L CB 0 7,+( ) 1 aCG+( )⋅ ⋅ ⋅ ⋅,= =


Pt B, Ch 1, Sec 5

b) bending moment due to still water loads and waveinduced loads.

where:

Ms,H : still water hogging bending moment, in kN ·m, where not supplied, the following maybe assumed for the checks:

Ms,S : still water sagging bending moment, in kN ·m, where not supplied, the following maybe assumed for the checks:

S : parameter defined in 3.1.1 to be assumed =0,21 for displacement yachts

C : 6 + 0,02 L

For the purpose of this calculation, CB may not be takenless than 0,6.

c) Total shea force

where Mbl is the greater of Mbl,H and Mbl,S calculatedaccording to a) or b) above, as applicable.

4.2.3 Bending moment and shear force taking into account the actual distribution of weights

a) The distribution of quasi-static bending moment andshear force, due to still water loads and wave inducedloads, is to be determined from the difference in weightand buoyancy distributions in sagging and hogging foreach loading condition envisaged.

b) For calculation purposes, the following values are to betaken for the design wave:

• wave length, in m:

• wave height, in m:

• wave form: sinusoidal.

c) In addition, the increase in bending moment and shearforce, due to impact loads in the forebody area, for thesagging condition only, is to be determined as specifiedbelow. For the purpose of this calculation, the hull isconsidered longitudinally subdivided into a number ofintervals, generally to be taken equal to 20. For smalleryacht, this number may be reduced to 10 if justified, atRINA's discretion, on the basis of the weight distribu-tion, the hull forms and the value of the design accelera-tion aCG.For twin hull yachts, the following procedure is to be

applied to one of the hulls, i.e. the longitudinal distribu-tion of weight forces gi and the corresponding breadthBi are to be defined for one hull.The total impact, in kN, is:

where qSLi is the additional load, per length unit, inkN/m, per x/L ≥ 0,6 (see Figure 2), computed with thefollowing formula:

where:

∆xi : length of interval, in m

xi : distance, in m, from the aft perpendicular

Bi : yacht breadth, in m, at the uppermost deckin way of the coordinate xi; for twin hullyacht, Bi is the maximum breadth of onehull considered at the transverse sectionconsidered;

xi, Bi : to be measured at the centre of interval i

p0 : maximum hydrodynamic pressure, inkN/m2, calculated by the following formula:

av1 : design vertical acceleration in way of theforward perpendicular, as defined in C3.3;

G : weight force, in kN, calculated from the fol-lowing formula:

gi : weight per unit length, in kN/m, of intervali; for twin hull yachts gi is defined for onehull;

xW : distance, in m, of LCG from the midshipperpendicular, calculated by the followingformula:

r0 : radius of gyration, in m, of weight distribu-tion, calculated as follows:

normally

(guidance values)

xSL : distance, in m, from the centre of the sur-face FSL to the midship perpendicular, cal-culated from the following formula:

fSL :

MblH, MsH, 0 95 S C L2 B CB⋅ ⋅ ⋅ ⋅ ⋅,+=

MblS, MsS, 0 55 S C L2 B CB 0 7,+( )⋅ ⋅ ⋅ ⋅ ⋅,+=

MsH 85 C L2 B CB 0 7,+( )10 3–⋅ ⋅ ⋅ ⋅=

MsS 63 C L2 B CB 0 7,+( )10 3–⋅ ⋅ ⋅ ⋅=

Tt3 1 Mbl⋅,

L-----------------------=

λ L=

h L

15 L20------+

-------------------=

FSL qSLi∑ xi∆⋅=

qSLi p0 Bi 2 π xi

L---- 0 6,–

⎝ ⎠⎛ ⎞⋅ ⋅sin⋅ ⋅=

p0av1 G r0 xW

2+( )⋅ ⋅fSL r0

2 0 5 L xSL zW–( ) xSL xW⋅–⋅ ⋅,+[ ]⋅-------------------------------------------------------------------------------------------------=

⎝ ⎠⎛ ⎞p

G gi xi∆⋅∑=

xW

gi xi∆ xi⋅ ⋅( )∑xi xi∆⋅( )∑

------------------------------------- 0 5 L⋅,–=

r0

gi xi∆ xi 0 5 L,–( )2⋅ ⋅[ ]∑

gi xi∆⋅( )∑----------------------------------------------------------------

⎝ ⎠⎜ ⎟⎜ ⎟⎛ ⎞

0 5,

=

0 2 L r0 0 25 L⋅,< <⋅,

xSL1fSL

----- xi∆ xi Bi⋅ ⋅( ) 2π xi

L---- 0 6,–

⎝ ⎠⎛ ⎞⋅sin 0 5 L,–⋅∑=

xi∆ Bi⋅( ) 2π xi

L---- 0 6,–

⎝ ⎠⎛ ⎞⋅ , in m2sin⋅∑


Pt B, Ch 1, Sec 5

Figure 2

d) The resulting load distribution qsi, in k/N, for the calcu-lation of the impact induced sagging bending momentand shear force is:

• For x / L < 0,6

where:

avi : total dimensionless vertical accelerationat the interval considered, calculated bythe following formula:

ah : acceleration due to heaving motion

ap : acceleration due to pitching motion

ah e ap : are relative to g

ah :

ap :

• For x / L ≥ 0,6

e) The impact induced sagging bending moment and shearforce are to be obtained by integration of the load distri-bution qsi along the hull. They are to be added to therespective values calculated according to a) and b) inorder to obtain the total bending moment and shear dueto still water loads, wave induced loads and impactloads.

4.3 Design total vertical bending moment

4.3.1 The design total vertical bending moment Mt, inkNxm, is to be taken equal to the greater of the values indi-cated in 4.2.2 a) and b), for planing or semi-planing yachts.For displacement yachts, the value of MT is to be takenequal to the greater of those given in 4.2.2 (b).

4.4 Transverse loads for twin hull yachts

4.4.1 General

For catamarans, the hull connecting structures are to bechecked for the load conditions specified in 4.4.2 and 4.4.3below. These load conditions are to be considered as act-ing separately.

The design moments and forces given in the following para-graphs are to be used unless other values are verified bymodel tests, full-scale measurements or any other informa-tion provided by the Designer.

For yacht of length L > 65 m or speed V > 45 knots, or foryachts with structural arrangements that do not permit arealistic assessment of stress conditions based on simplemodels, the transverse loads are to be evaluated by meansof direct calculations carried out in accordance with criteriaspecified in the individual Chapters or other criteria consid-ered equivalent by RINA.

4.4.2 Transverse bending moment and shear forceThe transverse bending moment Mbt in kN.m, and shearforce Tbt, in kN.m, are given by:

where:

b : transverse distance, in m, between the centresof the two hulls;

aCG : vertical acceleration at LCG, defined in 3.1..

4.4.3 Transverse torsional connecting moment

The catamaran transverse torsional connecting moment, inkN.m, is given by:

where aCG is the vertical acceleration at LCG, defined in3.1, which need not be taken greater than 1,0 g for this cal-culation.

5 Local loads

5.1 General

5.1.1 The following loads are to be considered in deter-mining the scantlings of hull structures:

• impact pressure due to slamming, if expected to occur;

• external pressure due to hydrostatic heads and waveloads;

• internal loads.

External pressure generally determines the scantlings of sideand bottom structures, whereas internal loads generallydetermine the scantlings of deck structures.

Where internal loads are caused by concentrated masses ofsignificant magnitude (e.g. tanks, machinery), the capacityof the side and bottom structures to withstand such loads isto be verified according to criteria stipulated by RINA. In

qsi qbi gi avi⋅= =

avi ah ap xi 0 5 L,–( )⋅+=

FSL

G------- r0

2 xSL xW⋅–r0

2 xW2–

-----------------------------⋅

FSL

G------- xSL xW–

r02 xW

2–-------------------- , in m 1–⋅

qsi qbi qSLi–=

Mbt∆ b aCG g⋅ ⋅ ⋅

5--------------------------------=

Tbt∆ aCG g⋅ ⋅

4------------------------=

Mtt 0 125 ∆ L aCG g⋅ ⋅ ⋅ ⋅,=


Pt B, Ch 1, Sec 5

such cases, the inertial effects due to acceleration of theyacht are to be taken into account.

Such verification is to disregard the simultaneous presenceof any external wave loads acting in the opposite directionto internal loads.

5.2 Load points

5.2.1 Pressure on panels and strength members may beconsidered uniform and equal to the pressure at the follow-ing load points:

• for panels:

lower edge of the plate, for pressure due to hydrostatichead and wave load;

• for strength members:

centre of the area supported by the element.

Where the pressure diagram shows cusps or discontinuitiesalong the span of a strength member, a uniform value is tobe taken on the basis of the weighted mean value of pres-sure calculated along the length of the member.

5.3 Design pressure for the bottom

5.3.1 Planing and semi-planing yachts

The design pressure p, in kN/m2, for the scantlings of struc-tures on the bottom of the hull, plating and stiffeners is to beassumed as equal to the greater of the values p1 e p2 definedas follows:.

h0 : vertical distance, in m, from pdr to the full loadwaterline;

a : coefficient function of the longitudinal positionof pdr, equal to:

• 0,036 aft of 0,5 L

• 0,04/CB - 0,024 in way of PpAV

• values for intermediate positions obtainedby linear interpolation;

FL : coefficient given in Figure 3 as a function of thelongitudinal position of the pdr;

F1 : coefficient function of the shape and inclinationof the hull given by:

where bLCG is the deadrise angle, in degrees, ofthe section in way of the LCG;

Fa : coefficient given by:

where A1 is the surface, in m2, of the platingpanel considered or the surface of the area sup-ported by the stiffener;

aV : maximum design value of vertical acceleration,in g, at the transverse section considered.

The pressure p1 is, in any case, not to be assumed as < 10D.

5.3.2 Displacement yacthsFor the purpose of the evaluation of the design pressure forthe bottom, sailing yachts with or without auxiliary engineare also included as displacement yachts.

The pressure p, in kN/m2, for the scantlings of hull struc-tures, plating and stiffeners located below the full loadwaterline is to be taken as equal to the value p1, defined asfollows:

where h0 and a are as defined in 5.3.1.

The pressure p is, in any case, not to be assumed <10 D.

5.4 Design pressure for the side shell

5.4.1 Planing or semi-planing yachts

The pressure p, in kN/m2, for the scantlings of side struc-tures, plating and associated stiffeners is to be taken asequal to the value p1, defined as follows:

The pressure p1 in any case, not to be assumed as < 10 Dh1, where h1 is as defined in 5.4.2.

For the zones located forward of 0,3 L from the PpAV, thevalue p is to be not less than the value p2 defined as follows:

essendo:

a, h0 : as defined in 5.3.1

C1 : coefficient given by Figure 4 as a function of theload surface A, in m2, bearing on the elementconsidered; for plating, A = 2,5s is to be taken

C2 : coefficient given by Figure 5 as a function of CB

and the longitudinal position of the elementconsidered

kV : 0,625 . L + 0,25V

a : angle formed at the point considered by the sideand the horizontal axis (see Figure 6)

g : angle formed by the tangent at the waterline,corresponding to the draught T, taken at thepoint of intersection of the transverse section ofthe element considered, with the above water-line and the longitudinal straight line crossingthe above intersection (see Figure 7).

The value p2 may, in any case, be assumed as not greaterthan 0,5p, where p is the design pressure for the bottom asdefined in 5.3.1, calculated at the section considered.

5.4.2 Displacement yachtFor the purpose of the evaluation of the design pressure forthe side shell, sailing yachts with or without auxiliaryengine are also included as displacement yachts.

p1 0 24L0 5,, 1h0

2T-------–⎝ ⎠

⎛ ⎞ 10 h0 a L⋅+( )⋅+⋅=

p2 15 1 aV+( ) ∆L CS⋅------------- g FL F1 Fa⋅ ⋅ ⋅ ⋅ ⋅⋅=

F150 βX–

50 βLCG–-----------------------=

Fa 0 30, 0 15, 1 43, A1 T⋅ ⋅∆

-------------------------------⎝ ⎠⎛ ⎞log⋅–=

p1 0 24L0 5,, 1h0

2T-------–⎝ ⎠

⎛ ⎞ 10 h0 a L⋅+( )⋅+⋅=

p1 66 25, a 0 024,+( ) 0 15L, h0–( )⋅ ⋅=

p2 C1= kV( 0 6 senγ+, 90 α–( )cos⋅[ ] C2+ L0 5, sen 90 α–( ) 2⋅ ⋅ ⋅


Pt B, Ch 1, Sec 5

The design pressure p, in kN/m2, for the scantlings of sidestructures located above the full load waterline is to betaken as equal to the value p1 defined as follows:

essendo:

a, h0 : as defined in 5.3.1

h1 : distance, in m, from the pdr to the straight lineof the beam of the highest continuous deck.

The pressure p1 in any case, not to be assumed as <10 h1 .

5.5 Design heads for decks

5.5.1 The design heads for the various decks are shown inTable 1.

Sheltered areas are intended to mean decks intended foraccommodation.

The design heads shown in Table 1 assume a uniformly dis-tributed load with mass density of 0,7 t/m3 and a conse-quent load per square metre of deck, in kN/m2, equal to 6,9h0.

Where distributed loads with mass density greater or lowerthan the above are envisaged, the value h0 will be modifiedaccordingly.

In the case of decks subject to concentrated loads, thescantlings of deck structures (plating and stiffeners) will alsoneed to be checked with the aforementioned loads.

Table 1

5.6 Design heads for watertight bulkheads

5.6.1 Subdivision bulkheadsThe scantlings of subdivision bulkheads, plating and associ-ated stiffeners are to be verified assuming a head hS equal tothe vertical distance, in m, from the pdr to the highest pointof the bulkhead.

5.6.2 Tank bulkheadsThe scantlings of tank bulkheads, plating and associatedstiffeners are to be verified assuming as h0, in m, the greaterof the following values:• vertical distance from the pdr to a point located at a

height h, in m, above the highest point of the tank givenby:

where the value of L is to be taken no less than 50 mand no greater than 80 m

• 2/3 of the vertical distance from the pdr to the top of theoverflow pipe.

p1 66 25, a 0 024,+( ) 0 15L, h0–( )⋅ ⋅=

Deck

EXPOSED WEATHER AREA SHELTERED

AREA(also partially

by deck-houses)

FWD0,075 L

fromFWD PP

AFT0,075 L

fromFWD PP

h0 h0 h0

Deck below pdc

- - 0,5

pdc 1,5 1,0 0,5

Decks over pdc 1,0 0,5 0,5

h0 1 0 05 L 50–( ),+[ ]=


Pt B, Ch 1, Sec 5

Figure 3


Pt B, Ch 1, Sec 5

Figure 4


Pt B, Ch 1, Sec 5

Figure 5


Pt B, Ch 1, Sec 5

Figure 6

Figure 7

INTERESTED TRANSVERSE SECTION


Part BHull

Chapter 2

STEEL HULLS


SECTION 2 MATERIALS

SECTION 3 WELDING AND WELD CONNECTIONS

SECTION 4 LONGITUDINAL STRENGHT

SECTION 5 PLATING

SECTION 6 SINGLE BOTTOM

SECTION 7 DOUBLE BOTTOM

SECTION 8 SIDE STRUCTURES

SECTION 9 DECKS

SECTION 10 BULKHEADS

SECTION 11 SUPERSTRUCTURES


Pt B, Ch 2, Sec 1


1 Field of application

1.1

1.1.1 Chapter 2 applies to monohull yachts with a hullmade of steel and a length L not exceeding 120 m, withmotor or sail power with or without an auxiliary engine.

For yachts made of steel and having lenght L greater than120 m, reference is to be made to RINA Rules for the Class-sification of Ships.

Multi-hulls or yachts with unusual shape, proportion andcharacteristics will be considered case by case.

In the examination of constructional plans, RINA may takeinto consideration material distribution and structural scant-lings other than those that would be obtained by applyingthese regulations, provided that structures with longitudinal,transverse and local strength not less than that of the corre-sponding Rule structure are obtained or provided that suchmaterial distribution and structural scantlings is adequate,in the opinion of RINA, on the basis of direct test calcula-tions of the structural strength (see Pt B, Ch1, Sec 1, par.3.1).

The structural scantlings of displacement yachts of L > 60 mmay be arranged by applying the provisions of the Rules forthe Classification of Ships.

This Chapter may also be used to check the structural scant-lings of hulls made of metals with superior mechanicalproperties, other than steel, such as titanium and its alloys.

In general the following types are considered usable in thefield of pleasure yachts:

• titanium: TiCP2, TiCP3, TiCP4;

• titanium alloys: Ti6AL4V grade 5, Ti5AL2.5Sn grade 6and Ti3AL2.5V grade 9.

For the scantlings of the plating and stiffeners, a coefficientK depending on the minimum yield strength of the materialused, is to be adopted.

The value of the minimum yield strength is, however, to benot more than 0,7 of the ultimate tensile strength of thematerial.

Higher values may be adopted, at the discretion of RINA,on condition that additional buckling strength and fatiguecalculations are carried out.

In any case use of these materials is subject to the examina-tion of the technical documentation of the manufacture ofthe material and the welding processes and tests that will beadopted.


2.1 Premise

2.1.1 The definitions and symbols in this Article are validfor all the Sections of this Chapter.

The definitions of symbols having general validity are notnormally repeated in the various Sections, whereas themeanings of those symbols which have specific validity arespecified in the relevant Sections.

2.2 Definitions and symbols

2.2.1

L : scantling length, in m, on the full load water-line, assumed to be equal to the length on thefull load waterline with the yacht at rest;

B : maximum breadth of the yacht, in m, outsideframes; in tests of the longitudinal strength oftwin hull yachts, B is to be taken as equal totwice the breadth of the single hull, measuredimmediately below the cross-deck;

D : depth of the yacht, in m, measured vertically inthe transverse section at half the length L, fromthe base line up to the deck beam of the upper-most continuous deck;

T : draft of the yacht, in m, measured vertically inthe transverse section at half the length L, fromthe base line to the full load waterline with theyacht at rest in calm water;

s : spacing of the ordinary longitudinal or trans-verse stiffener, in m;

∆ : displacement of the yacht outside frames, in t, atdraught T;

K : factor as a function of the mechanical propertiesof the steel used, as defined in Sec. 2.

3 Plans, calculations and other infor-mation to be submitted

3.1

3.1.1 Table 1 lists the structural plans that are to be pre-sented in advance to RINA in triplicate, for examination andapproval when required.

The Table also indicates the information that is to be sup-plied with the plans or, in any case, submitted to RINA forthe examination of the documentation.


Pt B, Ch 2, Sec 1

For documentation purposes, a copy of the following plan isto be submitted:

- general arrangement;

- capacity plan;

- lines plan;

Table 1

Where an *INWATERSURVEY (In-water Survey) notation isassigned the following plans and information are to be sub-mitted:

• Details showing how rudder pintle and bush clearancesare to be measured and how the security of the pintlesin their sockets are to be verified with the craft afloat.

• Details showing how stern bush clearances are to bemeasured with the craft afloat.

• Name and characteristics of high resistant paint, forinformation only.

3.23.2.1 In case a Builder for the construction of a new vessel of astandard design wants to use drawings already approved fora vessel similar in design and construction and classed withthe same class notation and the same navigation, the draw-ings may not be sent for approval , but the Request of Sur-vey for the vessel shall be submitted enclosed to a list of thedrawings the Builder wants to refer to and copy of theapproved drawings are to be sent to RINA.

Attention is to be paid even to possible additional flagadministartions requirements, which may cause differencesin the constructions.

It's Builder responsability to submit for approval any modifi-cation to the approved plans prior to the commencement ofany work.

Plan approval of standard design vessels is only valid solong as no applicable Rule changes take place. When theRules are amended, the plans are to be submitted for newapproval.

4 Direct calculations

4.1

4.1.1 As an alternative to those based on the formulae inthis Chapter, scantlings may be obtained by direct calcula-tions carried out in accordance with the provisions of Chap-ter 1 of Part B of these Rules.

Chapter 1 provides schematisations, boundary conditionsand loads to be used for direct calculations.

The scantlings are to be such as to guarantee that stress lev-els do not exceed the allowable values stipulated in theaforementioned Chapter.

4.2

4.2.1 In the case of use of materials with superior mechan-ical properties, other than steel, such as those indicated in1.1, the allowable stresses will be stipulated by RINA on thebasis of such properties and of any further fatigue testsand/or buckling checks which may be required.

5 Bookling strength checks

5.1 Application

5.1.1 Where required, the critical buckling strength ofsteel plating and stiffeners subject to compressivestresses is to be calculated as specified below.

5.2 Elastic buckling stresses of plates

5.2.1 Compressive stressThe elastic buckling strength, in N/mm2, is given by:

where:

PLANCONTAINING INFORMA-

TION RELEVANT TO:

• Midship section • main dimensions, maxi-mum operating speed V,design acceleration aCG forplaning or semi-planingyachts)

• materials and associatedmechanical properties

• for yacht having L>50 m, ifmono-hull and L> 40 m, ifmulti-hull, the maximumstill water bendingmoment is to be indicated

• displacement

• Longitudinal and trans-versal section

• Plan of the decks • openings• loads acting, if different

from Rule loads

• Shell expansion • openings

• Structure of the engineroom

• Watertight bulkheads and deep tank bulkheads

• openings• location of overflow

• Structure of stern/side door

• closing appliances

• Superstructures

• Support structure for crane

• design loads and connec-tions to the hull structures

• Rudder • materials of all compo-nents

• calculation speed

• Propeller shaft struts • material

σE 0 9 mc Et

1000 a⋅--------------------

⎝ ⎠⎛ ⎞

2

⋅ ⋅ ⋅,=


Pt B, Ch 2, Sec 1

to compressive stress

oppure:

with stiffeners perpendicular to compressivestress

E : Young's modulus, in N/mm2, to be taken equalto 2,06 . 105N/mm2 for steelstructures

t : thickness of plating, in mm

a : shorter side of the plate, in m

b : longer side of the plate, in m

c : coefficient equal to:

• 1,30 when the plating is stiffened by floorsor deep girders

• 1,21 when the plating is stiffened by ordi-nary stiffeners with angle- or T-sections

• 1,10 when the plating is stiffened by ordi-nary stiffeners with bulb sections

• 1,05 when the plating is stiffened by flat barordinary stiffeners.

ψ : ratio between the smallest and largest compres-sive stresses when the stress presents a linearvariation across the plate (0<ψ <1).

5.2.2 Shear stressThe elastic buckling stress, in N/mm2, is given by:

where:

and E, t, a and b are as defined in (a) above.

5.3 Elastic buckling stresses of stiffeners

5.3.1 Column buckling without rotation of the transverse section

For the column buckling mode (perpendicular to the planeof plating) the elastic buckling stress, in N/mm2, is given by:

E : Young's modulus, in N/mm2, to be taken equalto 2,06 . 105 N/mm2 for steelstructures

Ia : moment of inertia, in cm4, of the stiffener,including plate flange

A : cross-sectional area, in cm2, of the stiffener,including plate flange

I : span, in m, of the stiffener.

5.3.2 Torsional bucklingFor the torsional mode, the elastic buckling stress, inN/mm2, is given by:

where:E, I : defined in 5.3.1 above

m : number of half-waves, given in Table 2.

Table 2

It : St. Venant, moment of inertia of profile, in cm4,without plate flange, equal to:

or:

for flanged profile

Ip : polar moment of inertia of profile, in cm4, aboutconnection of stiffener to plate, equal to:

or:

IW : sectional moment of inertia of profile, in cm6,about connection of stiffener to plate, equal to:

or:

per flanged profiles.

where:hW : web height, in mmtW : web thickness, in mm

bf : flange width, in mmtf : flange thickness, in mm; for bulb profiles, the

mean thickness of the bulb maybe used

C : spring stiffness factor, exerted by supportingplate, equal to:

where:t : plating thickness, in mm,s : spacing of stiffeners, in m,

mC8 4,

ψ 1 1,+--------------------= fo r p la ting with sti ffeners parallel

mC c 1ab---

⎝ ⎠⎛ ⎞

2

+⋅=2 2 1,

ψ 1 1,+-------------------- for plating⋅

τE 0 9 mt E t1000 a⋅--------------------

⎝ ⎠⎛ ⎞

2

⋅ ⋅ ⋅,=

mt 5 34 4 ab---

2

⋅+,=

σE 0 001 EIa

A I2⋅------------⋅ ⋅,=

0<C<1 4<C<36 36<C<144 (m-1) m<C<m (m+1)

m 1 2 3 m

σEπ2 E IW⋅ ⋅104 Ip I2⋅ ⋅------------------------- m2 CK

m2-------+

⎝ ⎠⎛ ⎞ 0 385 E It

Ip

---⋅ ⋅,+⋅=

CKC I4⋅

π4 E IW⋅ ⋅---------------------- 106⋅=

hw tw3⋅

3--------------- 10 4– for flat bars⋅

13--- hw tw

3 bf tf3 1 0 63 tf

bf

----⋅,–⎝ ⎠⎛ ⎞⋅ ⋅+⋅ 10 4–⋅ ⋅

hw3 tw

3⋅3

---------------- 10 4– for f lat bars⋅

hw3 tw⋅3

--------------- hw2 bf tf⋅ ⋅+

⎝ ⎠⎛ ⎞ 10 4– for flanged profiles⋅

hw3 tw

3⋅36

---------------- 10 6– for f lat bars⋅

tf b⋅ f3 hw

2⋅12

------------------------ 10 6– for T profi les⋅

bf3 hw

2⋅12 bf hw+( )2⋅----------------------------------- tf[ bf

2 2bf hw 4hw2+⋅+( ) 3tw bf hw ] 10 6–⋅ ⋅ ⋅( )+⋅⋅

kp E t3⋅ ⋅

3s 1 1 33 kp hw t3⋅ ⋅ ⋅,1000 s tw

3⋅ ⋅-----------------------------------------+

⎝ ⎠⎛ ⎞⋅

-------------------------------------------------------------------- 10 3–⋅


Pt B, Ch 2, Sec 1

kp : 1 -ηp , not to be taken less than 0,

ηp : σp / σEp

σa : calculated compressive stress in the stiffener

σEp : elastic buckling stress of plating as calculated in5.2.1.

5.3.3 Web buckling

The elastic buckling stress, in N/mm2, is given by:

where:

E : defined in 5.3.1

tW, hW : defined in 5.3.2.

5.4 Critical buckling stress

5.4.1 Compressive stress

The critical buckling stress in compression, σC, for platingand stiffeners is given by:

essendo:

ReH : minimum yield stress of steel used, in N/mm2

σE : elastic buckling stress calculated according to5.2.1 and 5.3.2.

5.4.2 Shear stress

The critical buckling shear stress τC, for plating and stiffen-ers is given by:

where:

τC : 0,58 Reh

Reh : minimum yield stress of steel used, in N/mm2

τE : elastic buckling stress calculated according to5.2.2.

6 General rules for design

6.1

6.1.1 The hull scantlings required in this Chapter are ingeneral to be maintained throughout the length of the hull.

For yachts with length L greater than 50 m, reduced scant-lings may be adopted for the fore and aft zones, providedthat they are no less than those shown in Table 3.

In such case the variations between the scantlings adoptedfor the central part of the hull and those adopted for theends are to be gradual.

In the design, care is to be taken in order to avoid structuraldiscontinuities in particular in way of the ends of super-structures and of the openings on the deck or side of theyacht.

For yacht similar in performance to high speed hulls, a lon-gitudinal structure with reinforced floors, placed at a dis-tance of not more than 2 m, is required for the bottom.

Such interval is to be suitably reduced in the areas forwardof amidships subject to the forces caused by slamming.

7 Minimum thicknesses

7.1

7.1.1 The thicknesses of plating and stiffeners calculatedusing the formulae in this Chapter is to be not less than thevalues shown in Table 3.

Lesser thicknesses may be accepted provided that, in theopinion of RINA, their adequacy in terms of bucklingstrength and resistance to corrosion is demonstrated.

Where plating and stiffeners contribute to the longitudinalstrength of the yacht, their scantlings are to be such as tofulfil the requirements for yacht longitudinal strength stipu-lated in Sez.4.

8 Corrosion protection

8.1

8.1.1 All steel structures, with the exception of fuel tanks,are to be suitably protected against corrosion.

Such arrangements may consist of coating or, where appli-cable, cathodic protection.

The structures are to be clean and free from slag before thecoating is applied.

8.2

8.2.1 When a primer is used after the preparation of thesurfaces and prior to welding, as well as not impairing thelatter the composition of the primer is to be compatible withthe subsequent layers of the coating cycle.

The coating is to be applied with adequate thickness inaccordance with the Manufacturer's specifications.

8.3

8.3.1 Paint or other products containing nitrocellulose orother highly flammable substances are not to be used inmachinery or accommodation spaces.

σE 3 8 E tw

hw

------⎝ ⎠⎛ ⎞

2

⋅ ⋅,=

σc σE= i f σEReH

2--------≤

σc ReH 1 ReH

4 σe⋅-------------–

⎝ ⎠⎛ ⎞⋅= i f σE

ReH

2-------->

τc τE= i f τEτF

2----≤

τc τF 1 τF

4 τe⋅------------–

⎝ ⎠⎛ ⎞⋅= i f τE

τF

2---->


Pt B, Ch 2, Sec 1

Table 3

Member Minimum thickness (mm)

Keel, bottom plating t1 = 1,35 . L1/3 . K0,5

Side plating t2 = 1,15 . L1/3 . K0,5

Open strength deck plating t3 = 1,15 . L1/3 . K0,5

Lower and enclosed deck plating

t4 = t3 - 0,5

1st tier superstructure front bulkhead

t5 = t4

Superstructure bulkhead t6 = t5 - 1

Watertight subdivision bulkhead

t7 = t2 - 0,5

Tank bulkhead t8 = t2

Centre girder t9 = 1,75 . L1/3 . K0,5

Floors and side girders t10 = 1,30 . L1/3 . K0,5

Tubular pillars 0,03 d . K0,5 > 3,0 (1)

(1) d = diameter of the pillar, in mm


Pt B, Ch 2, Sec 2

SECTION 2 MATERIALS

1 General requirements

1.1

1.1.1 For hull construction and for fittings the materialsprescribed in this Section are to be used.

The acceptance of materials not foreseen in these Rules,such as those indicated in Section 1, will be decided caseby case, in general at the time of the approval of the rele-vant plans.

The materials, in the condition of supply, are to satisfy theprovisions laid down by IACS or, where relevant, those spe-cifically stipulated for individual cases; the materials are tobe approved in conformity with the applicable require-ments. For the types of materials foreseen in this Section,the prerequisites and requirements for approval are speci-fied in Part D of these Rules.

RINA reserves the right, subject to conditions specificallyagreed on, to accept materials other than those provided forin this Section.

These Rules presume that welding and other manufacturingprocesses, at low or high temperatures, are carried out inaccordance with normal good practice and in observanceof the applicable requirements of Part D. In particular, thelatter may include conditions of execution, such as therequirement that the welding is carried out with a certainpre-heating and/or that this or another process at low orhigh temperature should be followed by appropriate heattreatment.

Welding procedures are to be approved for the specific typeof material for which they are to be used, within the limitsand conditions laid down in Part D.

2 Steels for hull structures

2.1

2.1.1 In general, for the various hull structures, it is suffi-cient to use A steel type, having minimun yeld stressReh 235 N/mm2 , or AH type having minimum yeld stressequal to 315, 355 o 390 N/mm2 .

For particularly stressed structures, or structures that aresubject to low temperature working of considerable impor-tance, a superior type steel may be required, at the discre-tion of RINA.

In the case of yachts used for long periods in zones withtemperatures below 0°C, the types of steel for the varioushull structures will be decided in relation to the thicknessesused and the values of the external air temperature and seatemperature, which are to be supplied by the Designer.

2.1.2

When steels with a minimum guaranteed yield stress Rehgreater than 235 N/mm2 are used on a yacht, hull scantlingsare to be determined by taking into account the materia fac-tor K defined in 2.2.

2.2 Material factor K

2.2.1

The material factor K which appears in the formulae forstructural scantlings in this Chapter is a function of the min-imum guaranteed yield stress ReH and it's value is given inTable 1.

Table 1

In cases where the use of steels with intermediate values isallowed, the value of factor K may be determined by linearinterpolation.

Acceptance of the use of steels or materials such as thoseindicated in 1.1, having ReH > 390 N/mm2, is subject tospecial consideration by RINA, which reserves the right tostipulate the relevant conditions.

2.3 Information to be kept on board

2.3.1

A plan is to be kept on board indicating the steel types andgrades adopted for the hull structures, the extent and loca-tion of higher tensile steel together with details of specifica-tion and mechanical properties, and any recommendationsfor welding, working and treatment of these steels.

3 Steels for forgings, castings and pipes

3.1 General requirements

3.1.1 For structural members for which approval of theassociated plans is not required, except when otherwiseprescribed, weldable steels having an ultimate tensilestrength Rm of between 400 and 640 N/mm2 are to be usedand the other mechanical and chemical properties are to bein accordance with the relevant requirements of Part D; the

Reh N/mm2 K

235 1

315 0,78

355 0,72

390 0,70


Pt B, Ch 2, Sec 2

aforesaid steels are also to be approved, when required, inaccordance with the relevant provisions of Part D.

For structural members for which the approval of the asso-ciated plans is required, the provisions of 3.2 and 3.3apply.

3.2 Forgings

3.2.1 Forgings for structural members for which the checkof the scantling is required are to have the chemical andmechanical properties prescribed for the type of steel indi-cated in the relevant approved plans.

For the purpose of testing, when required, to be carried outin conformity with the relevant requirements of Part D, theaforesaid forgings are considered Class 1. (see Pt D, Ch 2,Sec 3)

3.3 Castings

3.3.1 Cast parts intended for stems, rudder parts, parts ofsteering gear and fittings in general, for which the check ofscantlings is required, except when otherwise prescribed, Cand C-Mn weldable steel of quality 1 may be used, with aminimum tensile strength Rm equal to 400 N/mm2 or 440N/mm2, in accordance with the provisions of Part D of the

Rules. In the case of structural members subject to highstresses, the use of quality 2 steel may be required. For the purpose of testing, when required, to be carried outin accordance with the requirements of Part D of the Rules,the aforesaid castings, irrespective of their quality, are con-sidered Class 1.

The welding of cast parts welded to main plating contribut-ing to hull strength members is subject to special approval;at the discretion of RINA, additional tests and provisionsmay be stipulated such as, in particular, resilience require-ments related to those of the plating to which the castingsare to be welded and non-destructive tests.

3.4 Pipes

3.4.1 Steels may be adopted of types 37, 42 or 52, inaccordance with the relevant requirements of Part D of theRules, as indicated in the approved plans of the structuralmembers for which pipes are used. The category ST or P ofthe pipes is to be specified, according to the requirementsof Part D. The use of steels other than those mentioned above is sub-ject to special approval by RINA, depending on the relevantchemical and mechanical properties.

Pipes, when required, are to be tested in accordance withthe relevant requirements of Part D.


Pt B, Ch 2, Sec 3


1 Welded connections


1.1.1 For fabrication by welding and qualification of weld-ing procedures the requirements of Part D, Ch 5 of theseRules apply and, in particular, the adoption of procedures issubject to approval in advance by RINA. Furthermore, theindividual shipyards are to be authorized by RINA for theuse of welding procedures using welders authorized byRINA.

Welding of the various types of steel is to be carried out bymeans of welding procedures approved for the purpose andthe various welding procedures and consumables are to beused within the limits of their approval and in accordancewith the conditions of use specified in the respectiveapproval documents.

As a general rule, the quality standard adopted by the ship-yard is to be submitted to RINA and applies to all construc-tions.

The work is to be carried out to the satisfaction of theattending Surveyor and the classification is dependentupon the work carried out with the approved plans and aquality of constructions that fall into the limits set out byRINA or other recognized international bodies (i.e.: IACS).

Deviations from the approved plans shall be discussed asfirst instance with the attending Surveyor; If not agreed withhim, these are subject to the approval of the Head Office. Inany case, these deviations shall be reported to the HeadOffice.

Minor repairs are to be agreed with the attending Surveyor;repairs which affect the structural integrity are to be dis-cussed with the Builder and relevant drawing to be sent forapproval.

In general, the acceptable (quality standards of) construc-tion defects (such as surfaces defects, structural misalign-ment and fit, post welding plate deformation) are thosewhich fall into the limits set out by IACS Recommendations.

1.2 Base material

1.2.1 The requirements of this Section apply for the weld-ing of hull structural steels of the types considered in Part Dor other types accepted as equivalent by RINA.

1.3 Welding consumables and procedures

1.3.1 Approval of welding consumables andproceduresWelding consumables and welding procedures adopted areto be approved by RINA. The requirements for the approvalof welding consumables are given in Pt D, Ch 5, Sec 2.

The requirements for the approval of welding proceduresfor the individual users are given in Pt D, Ch 5, Sec 4 andPt D, Ch 5, Sec 5.

The approval of the welding procedure is not required inthe case of manual metal arc welding with approved cov-ered electrodes, except in the case of one side welding onrefractory backing (ceramic).

1.3.2 Consumables

For welding of hull structural steels, the minimum consum-able grades to be adopted are specified in Tab 1 dependingon the steel grade.

For welding of other materials, the consumables indicatedin the welding procedures to be approved are consideredby RINA on a case by case basis.

Table 1 : Consumable grades

1.3.3 Electrodes for manual welding

Basic covered electrodes are to be used for the welding ofstructural members made in higher strength steels and, irre-

Steel grade

Consumable minimum grade

Butt welding, partial and full T penetration welding

Fillet welding

A 1 1

B - D 2

E 3

AH32 - AH36DH32 - DH36

2Y 2Y

EH32 - EH36 3Y

FH32 - FH36 4Y

AH40 2Y40 2Y40

DH40 - EH40 3Y40

FH40 4Y40

Note 1:Welding consumables approved for welding higher strength steels (Y) may be used in lieu of those approved for welding normal strength steels having the same or a lower grade; welding consumables approved in grade Y40 may be used in lieu of those approved in grade Y having the same or a lower grade.Note 2:In the case of welded connections between two hull struc-tural steels of different grades, as regards strength or notch toughness, welding consumables appropriate to one or the other steel are to be adopted.


Pt B, Ch 2, Sec 3

spective of the steel type, for the welding of special and pri-mary structural members.

Non-basic covered electrodes are generally allowed formanual fillet welding of structural members of moderatethickness (gross thickness less than 25 mm) made in normalstrength steels.

1.4 Access to and preparation of joints

1.4.1 For the correct carrying out of joints, sufficientaccess, in relation to the welding procedure used and to theposition of the weld itself, is to be ensured.

The structural parts to be welded to those adjacent are to bethoroughly cleaned before welding even if the componentsof the structure itself have been pickled beforehand. Suchcleaning is to be carried out using suitable mechanicalmeans, such as stainless steel wire brushes, in order to elim-inate oxides, grease, paint and other foreign bodies thatcould produce defects in the weld.

Adequate protection from the weather is to be provided toparts being welded; in any event, such parts are to be dry.In case of cold weather, screening to prevent too rapidcooling to be provided.

In welding procedures using bare, cored or coated wireswith gas shielding, the welding is to be carried out inweather protected conditions, so as to ensure that the gasoutflow from the nozzle is not disturbed by winds anddraughts.

The alignment of joints, methods of tack welding and backchipping are to be appropriate to the type of joint and to theweld position and are to satisfy RINA requirements stipu-lated for the use of the procedure adopted.

Welded temporary attachments used to aid construction areto be removed carefully by grinding, cutting or chipping.The surface of the material is to be finished smooth bygrinding followed by crack detection.

Any defects in the structure resulting from the removal oftemporary attachments are to be prepared, efficientlywelded and ground smooth so as to achieve a defect freerepair.

1.5 Design

1.5.1 For the various structural details typical of weldedconstruction in shipbuilding and not dealt with in this Sec-tion, IACS standards and the rules of good practice are toapply as agreed by RINA; particular consideration is to begiven to the overall arrangement and structural details ofhighly stressed parts of the hull.

2 Type of connections

2.1 Butt welding

2.1.1 General

In general, butt connections of plating are to be full penetra-tion, welded on both sides except where special proceduresor specific techniques, considered equivalent by RINA, areadopted.

Connections different from the above may be accepted byRINA Society on a case by case basis; in such cases, the rel-evant detail and workmanship specifications are to beapproved.

2.1.2 Welding of plates with different thicknesses

In the case of welding of plates with a difference in grossthickness equal to or greater than:

• 3 mm, if the thinner plate has a gross thickness equal toor less than 10 mm;

• 4 mm, if the thinner plate has a gross thickness greaterthan 10 mm

a taper having a length of not less than 4 times the differ-ence in gross thickness is to be adopted for connections ofplating perpendicular to the direction of main stresses. Forconnections of plating parallel to the direction of mainstresses, the taper length may be reduced to 3 times the dif-ference in gross thickness.

When the difference in thickness is less than the above val-ues, it may be accommodated in the weld transitionbetween plates.

2.1.3 Edge preparation, root gap

The cut of the joint edges, to be carried out in general bymechanical means, is to be regular and without raggededges or notches.

The acceptable root gap is to be in accordance with theadopted welding procedure and relevant bevel preparation.

2.1.4 Butt welding on permanent backing

Butt welding on permanent backing, i.e. butt weldingassembly of two plates backed by the flange or the faceplate of a stiffener, may be accepted where back welding isnot feasible or in specific cases deemed acceptable by theRINA.

The type of bevel and the gap between the members to beassembled are to be such as to ensure a proper penetrationof the weld on its backing and an adequate connection tothe stiffener as required.

2.1.5 Plate misalignment in butt connections

The misalignment m, measured as shown in Fig 1, betweenplates with the same gross thickness t is to be less than0,15t, without being greater than 3 mm, where t is the grossthickness of the thinner abutting plate.


Pt B, Ch 2, Sec 3

Figure 1 : plate misalignment in butt connections

2.1.6 Section, bulbs and flat bars

When lengths of longitudinals of the shell plating andstrength deck within 0,6 L amidships, or elements in gen-eral subject to high stresses, are to be connected together bybutt joints, these are to be full penetration.

2.1.7 Butt joints between T-bar, L-bar or bulb of different height

When "a", the difference in height between the two mem-bers to be jointed, is less than 6mm, this difference may bebuilt up by welding.

When the a.m. difference is more than 6mm, the higher barshall be lowered for a length of at least 50 x a, in order toavoid local stresses (30 x a if the bars to be connected arenot primary members of the structure).

2.1.8 Insert plates and doublers (slot welding)

A local increase in plating thickness is generally to beachieved through insert plates. Local doublers, which arenormally only allowed for temporary repair, may howeverbe accepted by RINA on a case by case basis.

In any case, doublers and insert plates are to be made ofmaterials of a quality at least equal to that of the plates onwhich they are welded.

Slot welds are to be of appropriate shape (in general oval)and dimensions, depending on the plate thickness, and maynot be completely filled by the weld.

The distance between two consecutive slot welds is to benot greater than a value which is defined on a case by casebasis taking into account:

- the transverse spacing between adjacent slot weld lines

- the stresses acting in the connected plates

- the structural arrangement below the connected plates.

2.1.9 Insert plates (butt welding)

Where thick insert plates are butt welded to thin plates, theedge of the thick plate shall be tapered.

The slope of the taper shall be in accordance with Pt B, Ch2, Sec 3, 2.1.2.

The corners of insert plates are to be suitably radiused.

2.2 Fillet welding types

2.2.1 Fillet welding of T type joints, or cross joints withstraight edges may be of the following types (see also Table3):

a) continuous fillet welding (double continuous bead,D.C.);

b) intermittent fillet welding as staggered welding (A) orchain welding (C) with length d and spacing p.

Figure 2 : intermittent staggered welding A

Figure 3 : intermittent chain welding (C)

2.2.2 Continuous fillet weldingContinuous fillet welding is always to be adopted:

• for watertight connections;• for structures in way of stabilizers, thruster, foundations

and other highly stressed area;

• for structure members to plating in way of end connec-tions and scallops;

• at the ends of connections for a length of at least 75mm;

• round lap connections and at the ends of brackets, lugsand scallops.

Continuous fillet welding may also be adopted in lieu ofintermittent welding wherever deemed suitable.

2.2.3 Fillet welding crossing butt weldingWhere stiffening members are attached by continuous filletwelds and cross completely finished butt welds, these weldsare to be made flush in way of the contact point. Similarly,for butt welds in webs of stiffening members, the butt weldis to be completed and generally made flush with the stiff-ening member before the fillet weld is made. Otherwise, ascallop is to be arranged in the web of the stiffening mem-ber. Scallops are to be of such size, and in such a position,


Pt B, Ch 2, Sec 3

that a satisfactory weld can be made at the edges without innotching the butt weld of the plate.

2.2.4 Misalignment in cruciform connections

The misalignment m in cruciform connections, measuredon the median lines as shown in Fig 4, is to be less than t/2,in general, where t is the gross thickness of the thinner abut-ting plate.

RINA may require lower misalignment to be adopted forcruciform connections subjected to high stresses.

Figure 4 : Misalignment in butt connections

2.3 Scantling of welds

2.3.1 For T-joints with straight edges, the scantling of thebead is given, as a function of the thickness of the T web, inTable 2.

The scantling of the welds for hull structures is given inTable 3 in which, for individual cases, the following areshown:

a) continuous welding with double type a bead (D.C. a) ortype b (D.C. b);

b) intermittent welding of type A or C, on continuousedges, with type a bead and spacing p.

As an alternative to intermittent welding of type A or C, theequivalent of D.C. may be used with, however, a minimumside of 3 mm for thicknesses not greater than 6mm, and of 4mm for thicknesses exceeding 6 mm.

Welding on scalloped edges, as an alternative to intermit-tent welding, is in general not allowed except in individualcases, to be specially considered by RINA, and for whichthe following is required:- -weld bead of type a; - -notch length equal to 150 mm;- -tooth length not less than 90 mm and such that the

combination of the length, pitch, and side of the bead isthe equivalent of the Rule scantling of the intermittentwelding shown in Table 2.

Scalloped welding is not allowed at the ends of beams, inway of parts subject to concentrated loads, and in structuressubject to noticeable vibrations, and it may also be unac-ceptable in other individual cases, at RINA's discretion,both in relation to types and levels of stress in the structuresand to the test results for authorisation of the procedures tobe followed.

Figure 5 : beads dimensions

Table 2 : Leg and throat of beads

MANCA LA FIGURA

throatthickness

leg

leg

Thickness ofthe structural

member

Type a bead Type b bead

Leg (1)Corresponding throat

(approximate) (1)Leg (1)

Corresponding throat (approximate) (1)

mm mm mm mm mm

3 ÷ 4,5 3,5(3) 2,5(2) 3 2

4,5 ÷ 6 5(4,5) 3,5(3) 4 3

6,5 ÷ 8 6(5) 3,5(3,5) 4 3

8 ÷ 10 7(6) 5(4) 5 3,5

10,5 ÷ 12 8(7) 5,5(5) 6 4

12,5 ÷ 14 8,5 6 6,5 4,5

(1) Where D.C. a welding is required, the value indicated in the corresponding brackets may be taken


Pt B, Ch 2, Sec 3

Table 3 : Scantlings of welds

14,5 ÷ 16 9 6,5 7 5

16,5 ÷ 18 10 7 8 6,5

18,5 ÷ 20 11 7,5 9 6,5

20,5 ÷ 22 12 8,5 10 7

22,5 ÷ 24 13 9 11 7,5

24,5 ÷ 26 14 10 12 8,5

Member Weld

1 - Trasverse type structure

Floors to:

- shell plating C140 within 0,25 L AV; A280 inside after peak; A340 elsewhere

- top of double bottom C150 inside engine; A340 elsewhere

- centre girder C150 inside engine; A340 elsewhere

- side girder C280

Watertight floors D.C. b

Centre girder to:

- keel D.C. b where watertight: C120 elsewhere

- top of double bottom D.C. b where watertight: C150 inside engine; C180 elsewhere

Side girder to:

- shell plating A300


Watertight girder and double bottom margin D.C. b

Frames of shell plating D.C. b inside after peak for 2-propeller hulls; A240 inside peaks and tanks;A340 elsewhere

Beams to deck plating A300 inside tanks; A340 elsewhere

2. Longitudinal type stucture

Bottom longitudinals to shell plating C140 within L from the bow: A280 elsewhere

Side and deck longitudinals to relevant plating A300

Top longitudinals of double bottom A300

Web to face plate of composed ordinary longitudinals A340; at the ends (1) D.C. b

Reinforced floors, frames and beams having face plate area

≤20cm2:

- to plating A240; at the ends C150

- to face plate A360; at the ends A240

3. Foundations of main engines and thrust shaft:

Girders to shell plating C130

(1) "End" means a length at each end, 15% the length of the gross span.(2) Where slots are adopted due to inaccessibility, they are generally to have: length = 75 mm; breadth = 3 ÷ 4% t, where t = thickness of plating; pitch

= 150 mm; weld leg length = t - 0,5 mm to be carried out on the outline of the slot; supporting plate with breadth 40 ÷ 60 mm and thickness 1,2 ÷1,5 t


member





mm mm mm mm mm



Pt B, Ch 2, Sec 3

3 End connections of ordinary stiffen-ers

3.1

3.1.1 Where ordinary stiffeners are continuous throughprimary supporting members, they are to be connected to

the web plating so as to ensure proper transmission ofloads, e.g. by means of one of the connection details shownin Fig 6 to Fig 9.Connection details other than those shown in Fig 6 to Fig 9may be considered by RINA on a case by case.

Girders to bed plates D.C. a

Girder to top of double bottom

Floors to girder, to top of double bottom and to bed plates D.C. a

4. Subdivision bulkheads

Plating to borders D.C. b

Stiffeners to plating A340; C150 at the ends, if not squared

5. Tank bulkheads

Plating to borders D.C. on bottom; D.C. b elsewhere

Ordinary stiffeners to plating A300

Reinforced beams having span between 3 and 5 m and

face plate area ≤20 cm2:

- to plating C120 at the ends; C180 elsewhere

- to face plate C150 at the ends; A240 elsewhere

6. Not-watertight bulkheads see 4 above

7. Rudder

Plating to horizontal diaphragms and vertical diaphragmswhich do not constitute spindle

A300 (2)

Ordinary stiffeners to vertical diaphragms constitutingspindle

D.C. b

8. Superstructures

Boundary bulkheads to support deck and to upper deck

Ordinary stiffeners to bulkheads D.C. b

For other parts see previous items A340

9. Pillars

Tubular pillars to ends D.C. b

10. Primary supporting members in general

(a=sectional area of the face plate or flange, incm2)

a≤20 cm2

- connection to plating C180 at the ends; A260 elsewhere

- connection to face plating C180 at the ends; A340 elsewhere

20<a≤65 cm2

- connection to plating C160 at the ends; C o A220 elsewhere


Member Weld

(1) "End" means a length at each end, 15% the length of the gross span.(2) Where slots are adopted due to inaccessibility, they are generally to have: length = 75 mm; breadth = 3 ÷ 4% t, where t = thickness of plating; pitch

= 150 mm; weld leg length = t - 0,5 mm to be carried out on the outline of the slot; supporting plate with breadth 40 ÷ 60 mm and thickness 1,2 ÷1,5 t


Pt B, Ch 2, Sec 3

Figure 6 : End connection of ordinary stiffener with-out collar plate

Figure 7 : End connection of ordinary stiffener with collar plate

Figure 8 : End connection of ordinary stiffener with one large collar plate

Figure 9 : End connection of ordinary stiffener with two large collar plates

In all the above connections, the radius of the all the scal-lops in the primary member around the stiffener shall be atleast 20mm.

The extension of the collar plate above the primary membershall be at least 3 t, where t is the thickness of the collarplate.

3.1.2 Where ordinary stiffeners are cut at primary support-ing members, brackets are to be fitted to ensure the struc-tural continuity.

The net thickness of brackets is to be not less than that ofordinary stiffeners. Brackets with net thickness, in mm, less

than 15Lb, where Lb is the length, in m, of the free edge ofthe end bracket, are to be flanged or stiffened by a weldedface plate. The net sectional area, in cm2, of the flangededge or face plate is to be at least equal to 10Lb .

3.1.3 Where necessary, RINA may require backing brack-ets to be fitted, as shown in Fig 10, in order to improve thefatigue strength of the connection.

Figure 10 : End connection of ordinary stiffener with backing bracket

4 End connections of primary support-ing members

4.1 Bracketed end connections

4.1.1 Arm lengths of end brackets are to be equal, as far aspracticable.

As a general rule, the height of end brackets is to be not lessthan that of the primary supporting

member.

4.1.2 The thickness of the end bracket web is generally tobe not less than that of the primary supporting memberweb.

4.1.3 The scantlings of end brackets are generally to besuch that the net section modulus of the primary supportingmember with end brackets is not less than that of the pri-mary supporting member at mid-span.

4.1.4 The width, in mm, of the face plate of end brackets isto be not less than 50(Lb+1), where Lb is the length, in m, ofthe free edge of the end bracket.

Moreover, the net thickness of the face plate is to be not lessthan that of the bracket web.

4.1.5 Stiffening of end brackets is to be designed such thatit provides adequate buckling web stability.

As guidance, the following prescriptions may be applied:

• where the length Lb is greater than 1,5 m, the web ofthe bracket is to be stiffened;

• the net sectional area, in cm2, of web stiffeners is to benot less than 16,5l, where l is the span, in m, of the stiff-ener;

• tripping flat bars are to be fitted to prevent lateral buck-ling of web stiffeners. Where the width of the symmetri-


Pt B, Ch 2, Sec 3

cal face plate is greater than 400 mm, additionalbacking brackets are to be fitted.

4.2 Bracketless end connections

4.2.1 As a general rule, in the case of bracketless crossingbetween primary supporting members (see Fig 11), thethickness of the common part of the web is to be not lessthan the value obtained, in mm, from the following for-mula:

where:

w : the lesser of w1 and w 2,MAX

w1 : gross section modulus, in cm3, of member 1

w 2,MAX: the greater value, in cm3, of the gross section mod-uli of members 2 and 3

Ω : Area, in cm2, of the common part of members 1, 2 and3.

In the absence of one of members 2 and 3 shown in Fig 11,the value of the relevant gross section modulus is to betaken equal to zero.

4.2.2 In no case may the thickness calculated according to4.2.1 be less than the smallest web net thickness of themembers forming the crossing.

4.2.3 In general, the continuity of the face plates is to beensured.

Figure 11 : Bracketless end connections of primary supporting members

5 Cut-outs and holes

5.1

5.1.1 Cut-outs for the passage of ordinary stiffeners are tobe as small as possible and well rounded with smoothedges.In general, the depth of cut-outs is to be not greater than50% of the depth of the primary supporting member.

5.2

5.2.1 Where openings such as lightening holes are cut inprimary supporting members, they are to be equidistantfrom the face plate and corners of cut-outs and, in general,their height is to be not greater than 20% of the web height.

5.3

5.3.1 Openings may not be fitted in way of toes of endbrackets.

5.4

5.4.1 Over half of the span of primary supporting mem-bers, the length of openings is to be not greater than the dis-tance between adjacent openings.At the ends of the span, the length of openings is to be notgreater than 25% of the distance between adjacent open-ings.

5.5

5.5.1 The cut-out is to be reinforced to one of the solutionsshown in Fig. 12 to Fig. 14:• continuous face plate (solution 1): see Fig 12• straight face plate (solution 2): see Fig 13• compensation of the opening (solution 3): see Fig 14• combination of the above solutions.

Other arrangements may be accepted provided they aresupported by direct calculations submitted to RINA forreview.

Figure 12 : Stiffening of large openings in primary supporting members - Solution 1

t 15,75WΩ------=

Ω

Member 3

Member 1

Member 2


Pt B, Ch 2, Sec 3


Figure 14 : Stiffening of large openings in primary supporting members - Solution 3 (inserted plate)

6 Stiffening arrangement

6.1

6.1.1 Webs of primary supporting members are generallyto be stiffened where the height, in mm, is greater than100t, where t is the web net thickness, in mm, of the pri-mary supporting member.

In general, the web stiffeners of primary supporting mem-bers are to be spaced not more than 110t.

6.2

6.2.1 6.2 As a general rule, tripping brackets (see Fig 15)welded to the face plate may be fitted:

o every fourth spacing of ordinary stiffeners, withoutexceeding 4 m

• at the toe of end brackets

• at rounded face plates

• in way of cross ties

• in way of concentrated loads.

Where the width of the symmetrical face plate is greaterthan 400 mm, backing brackets are to be fitted in way of thetripping brackets.

6.3

6.3.1 In general, the width of the primary supporting mem-ber face plate is to be not less than one tenth of the depth ofthe web, where tripping brackets are spaced as specified in6.2.

6.4

6.4.1 The arm length of tripping brackets is to be not lessthan the greater of the following values, in m:

where:

b : Height, in m, of tripping brackets, shown in Fig 15

st : Spacing, in m, of tripping brackets

t : Net thickness, in mm, of tripping brackets.

It is recommended that the bracket toe should be designedas shown in Fig 15.

6.5

6.5.1 6.5 Tripping brackets with a net thickness, in mm,less than 15Lb are to be flanged or stiffened by a weldedface plate.

Figure 15 : Primary supporting member: web stiffener in way of ordinary stiffener

7 Riveted connections

7.1

7.1.1 When riveted connections are employed, themechanical properties of the rivets are to be indicated on

the plans.

RINA may, at its discretion, require shear, tensile and com-pression tests to be carried out on representative specimensof riveted connections.

7.2

7.2.1 When rivets are used to connect materials of differ-ent types, precautions are to be taken against electrolyticcorrosion.

Whenever possible, the arrangements are to be such as toenable inspection in service without the need to removecoverings, etc.

t t

d 0,38b=

d 0,85b st

t---=


Pt B, Ch 2, Sec 3

8 Sealed connections

8.1

8.1.1 Where a sealing product is used to ensure airtight orwatertight integrity, product information is to be submittedtogether with evidence of its previous successful use.

9 Inspection and tests

9.1 General

9.1.1 Materials, workmanship, structures and welded con-nections are to be subjected, at the beginning of the work,during construction and after completion, to inspectionssuitable to check compliance with the applicable require-ments, approved plans and standards. Tests of welded connections by RINA Surveyors are, as arule, those indicated in (a) to (e) below. Irrespective of theextent of such tests, the building shipyard is responsible forseeing that working methods, procedures and sequencescomply with RINA requirements, approved plans and nor-

mal good practice. To this end, the shipyard is to provide itsown production control organisation.

a) Verification of compliance of basic materials with therequirements in Sec. 2 and of structures with approvedplans.

b) Verification of compliance of use and application con-ditions of welding processes with those approved andascertainment of the use of authorised welders.

c) Visual examination of the preparation, root bevelingand execution of welding of the connections of struc-tural parts (e.g. crossing of butt-welded joints of panelsor sheets of shell plating and strength deck, transversejoints of bent stringer plates, joints of inserts in way ofopenings, fillet welding of stiffeners, brackets, etc.). As ageneral rule, the surface of finished weld are to be as faras practicable smooth and free from undercut.

d) In addition to visual examination, X-ray examination ofthe welded joints, of an extension as deemed necessaryby the Surveyor. Ultrasonic testing is to be used forchecking butt or cruciform connections in full penetra-tion welding greater than 15mm. Ultrasonic and mag-netic particle examinations may also be required by theSurveyor in specific cases to verify the quality of thebase material.

e) Checking of any repairs.In case of presence of defects, the attending Surveyor mayask for the extent of non-destructive examination. Unac-ceptable defects shall be completely removed. The resultsof nde shall be recorded.


Pt B, Ch 2, Sec 4


SECTION 4 LONGITUDINAL STRENGHT

1 General

1.1

1.1.1 The structural scantlings prescribed in Chapter 2 arealso intended for the purposes of the longitudinal strengthof a yacht of length having L not exceeding 50 m for mono-hull yacht or 40 m for catamarans and openings on thestrength deck of limited size.

For yachts of greater length and/or openings of size greaterthan the breadth B of the hull and extending for a consider-able part of the length of the yacht, calculation of longitudi-nal strength is required.

1.2

1.2.1 To this end, longitudinal strength calculations are tobe carried out considering the load and ballast conditionsfor both departure and arrival.

2 Bending stresses

2.1

2.1.1 In addition to satisfying the minimum requirementsstipulated in the individual Sections of this Chapter, thescantlings of members contributing to the longitudinalstrength of monohull yacht and catamarans are to achieve asection modulus of the midship section at the bottom andthe deck such as to guarantee stresses not exceeding theallowable values.

Therefore:

where:

Wf, Wp : msection modulus at the bottom and the deck,respectively, of the transverse section, in m3

MT : design total vertical bending moment defined inChap.1, Sez.5.

f : 0,80 for planing yachts

f : 0,72 for displacement yachts

σs : mimimum yield stress of the material, inN/mm2.

2.2

2.2.1 The compressive value of normal stresses is not toexceed the value of the critical stresses for plates and stiff-eners calculated in Article 5 of the Sec.1.

2.3

2.3.1 The moment of inertia J of the midship section, inm4, is to be not less than the value given by the followingformulae.

For planing yachts:

For displacement yachts:

3 Shear stresses

3.1

3.1.1 The shear stresses in every position along the lengthL are not to exceed the allowable values; in particular.

where:

Tt : total shear in kN defined in Chap.1

σs, f : defined in 2

At : actual shear area of the transverse section, inm2, to be calculated considering the net area ofside plating and of any longitudinal bulkheads excluding openings.

4 Calculation of the section modulus

4.1

4.1.1 In the calculation of the modulus and inertia of themidship section, all the continuous members, plating andlongitudinal stiffeners are generally to be included, pro-vided that they extend for at least 0,4 L amidships.

σ f f σs N mm2⁄⋅≤

σp f σs N mm2⁄⋅≤

σ fMT

1000 Wf

----------------------- N mm2⁄=

σpMT

1000 Wp

------------------------ N mm2⁄=

J 5 32,= M 10 6–⋅ ⋅

J 5 90,= M 10 6–⋅ ⋅

Tt

At

----- 10 3– f σs⋅≤⋅

Pt B, Ch 2, Sec 5

SECTION 5 PLATING


1.1

1.1.1 s : spacing of ordinary longitudinal or transverse

stiffener, in mp : scantling pressure, in kN/m2, given in Chap.1,

Sec. 5K : factor defined in Sec. 2 of this Chapter.

2 Keel

2.1 Sheet steel keel

2.1.1 The keel plating is to have a width bCH, in mm,throughout the length of the yacht, not less than the valueobtained by the following equation:

and a thickness not less than that of the adjacent bottomplating increased by 2 mm.

2.2 Solid keel

2.2.1 The height and thickness of the keel, throughout thelength of the yacht, are to be not less than the values hCH etCH, in mm, calculated with the following equations:

Lesser heights and thicknesses may be accepted providedthat the effective area of the section is not less than that ofthe Rule section.

Lesser heights and thicknesses may also be acceptable if acentre girder is placed in connection with the solid keel.

The garboard strakes connected to the keel are each to havea width not less than 750 mm and a thickness not less thanthat of the bottom plating increased by 10%.

3 Bottom and bilge

3.1

3.1.1 Bottom plating is the plating up to the chine or to theupper turn of the bilge.

The thickness of the bottom plating and the bilge is to benot less than the greater of the values t1 e t2, in mm, calcu-lated with the following formulae:

where:

k1 : 0,11, assuming p=p1

: 0,07, assuming p=p2.

ka : coefficient as a function of the ratio S/s given inTable 1 below where S is the is the greaterdimension of the plating, in m.

k2 : curvature correction factor given by 1-(h/s) tobe taken not less than 0,7 where h is the dis-tance, in mm, measured perpendicularly fromthe chord s to the highest point of the arc ofplating between the two supports (see Figure 1).

The thickness of the plating of the bilge is, in any event, tobe taken as not less than the greater of the thicknesses of thebottom and side.

Sheet steel of plating connected to the stem or to the stern-post or in way of the propeller shaft struts is to have a thick-ness, in mm, not less than the value te given by:

and, in any event, equal to the thickness of the bottomincreased by 50%.

Table 1

bCH 4 5, L 600+⋅=

hCH 1 5, L 100+⋅=

tCH 0 35, L 6+⋅( ) K0 5,⋅=

S/s Ka

1 17,5

1,2 19,6

1,4 20,9

1,6 21,6

1,8 22,1

2,0 22,3

>2 22,4

t1 k1 k2 ka s p K⋅( )0 5,⋅ ⋅ ⋅ ⋅=

t2 8 s T K⋅( )0 5,⋅ ⋅=

te 0 05, L 6+⋅( ) K0 5,⋅=


Pt B, Ch 2, Sec 5

Figure 1

4 Sheerstrake

4.1

4.1.1 In the yachts having L > 50 a sheerstrake plate ofheight h, in mm, not less than 0,025 L and thickness not lessthan the greater of the values of the plating of the side andthe stringer plate is to be fitted.

In the case of sidescuttles or windows or other openingsarranged on the sheerstrake plate, the thickness is to beincreased sufficiently as necessary in order to compensatesuch openings.

In way of the ends of the bridge, the thickness of the sheer-strake is to be adequately increased.

5 Side

5.1

5.1.1 The thickness of side plating is to be not less than thegreater of the values t1 e t2, in mm, calculated with the fol-lowing formulae:

where k1, k2 e ka are as defined in 3.1.

5.2

5.2.1 The thickness of the transom is to be no less thanthat required for the bottom, for the part below the water-line, or for the side, for the part above the waterline.

In the event of water-jet drive systems, the thickness of thetransom will be the subject of special consideration.

6 Openings in the shell plating

6.1

6.1.1 Sea intakes and other openings are to be wellrounded at the corners and located, as far as possible, out-side the bilge strakes and the keel. Arrangements are to besuch as to ensure continuity of strength in way of openings.

An increase in the thickness of the local plating may berequired where the openings are of unusual dimensions.

6.2

6.2.1 Openings in the curved zone of the bilge strakesmay be accepted where the former are elliptical or fittedwith equivalent arrangements to minimise the stress con-centration effects. In any event, such openings are to belocated well clear of welded connections.

6.3

6.3.1 The internal walls of sea intakes are to have externalplating thickness increased by 1 mm, but not less than 6mm.

7 Local stiffeners

7.1

7.1.1 The thickness of plating determined with the forego-ing formulae is to be increased locally, generally by at least50%, in way of the stem, propeller shaft struts, rudder hornor trunk, stabilisers, anchor recesses, etc.

7.2

7.2.1 Where the aft end is shaped such that the bottomplating aft has a large flat area, RINA may require the localplating to be increased and/or reinforced with the fitting ofadditional stiffeners.

7.3

7.3.1 The thickness of plating is to be locally increased inway of inner or outer permanent ballast arrangements.

The thickness is to be not less than 1,25 that of the adjacentplating but no greater than that of the keel.

8 Cross-deck bottom plating

8.1

8.1.1 The thickness is to be taken, the stiffener spacing sbeing equal, no less than that of the side plating.

Where the gap between the bottom and the waterline is sosmall that local wave impact phenomena are anticipated,an increase in thickness and/or additional internal stiffenersmay be required.

h

S

t1 k1 k2 ka s p K⋅( )0 5,⋅ ⋅ ⋅ ⋅=

t2 6 5, s T K⋅( )0 5,⋅ ⋅=


Pt B, Ch 2, Sec 6


1 General

1.1

1.1.1 This Section stipulates the criteria for the structuralscantlings of a single bottom, which may be of either longi-tudinal or transverse type.

1.2 Longitudinal structure

1.2.1 The longitudinal type structure is made up of ordi-nary reinforcements placed longitudinally, supported byfloors. The floors may be supported by girders, which in turn maybe supported by transverse bulkheads, or by the sides of thehull.

1.2.2 A centre girder is to be fitted. Where the breadth of the floors exceeds 6 m, sufficient sidegirders are to be fitted so that the distance between themand the centre girder or the side does not exceed 3 m.

1.2.3 The bottom of the engine room is to be reinforcedwith a suitable web floor consisting of floors and girders;the latter are to extend beyond the engine room for a suita-ble length and are to be connected to any existing girders inother areas.

1.2.4 Additional bottom stiffeners are to be fitted in way ofthe propeller shaft struts, the rudder and the ballast keel.

1.3 Transverse structure

1.3.1 The transverse framing consists of ordinary stiffenersarranged transversally (floors) and placed at each framesupported by girders, which in turn are supported by trans-verse bulkheads or reinforced floors.


1.3.3 In way of the propeller shaft struts, the rudder hornand the ballast keel, additional floors are to be fitted withsufficiently increased scantlings.

1.3.4 The bottom of the engine room is to be reinforcedwith a suitable web floor consisting of floors and girders;the latter are to be fitted as a continuation of the existinggirders outside the engine room.

1.3.5 Floors of increased scantlings are to be fitted in wayof reinforced frames at the sides and reinforced beams onthe weather deck. Any intermediate floors are to be ade-quately connected to the ends.


2.1

2.1.1

s : spacing of ordinary longitudinal or transversestiffeners, in m;

p : scantling pressure, in kN/m2, given in Chap. 1

K : coefficient defined in Sec. 2 of this Chapter.

3 Longitudinal type structure

3.1 Bottom longitudinals

3.1.1 The section modulus of longitudinal stiffeners is tobe not less than the value Z, in cm3, calculated with the fol-lowing formula:

where:

k1 : 0,83 assuming p=p1

: 0,36 assuming p=p2

S : conventional span of the longitudinal stiffener,in m, equal to the distance between floors.

The bottom longitudinal stiffeners are preferably to be con-tinual through the transverse members. Where they are tobe interrupted in way of a transverse watertight bulkhead,brackets are to be provided at the ends.

3.2 Floors

3.2.1 The section modulus of the floors at the centreline ofthe span S is to be not less than the value ZM, in cm3, calcu-lated with the following formula.

where:

k1 : defined in 3.1.

b : half the distance, in m, between the two floorsadjacent to that concerned

S : conventional floor span equal to the distance,in m, between the two supporting members(sides, girders, keel with a dead rise edg > 12°).

In the case of a keel with a dead rise edge < 12° but > 8°,the span S is always to be calculated considering the dis-tance between girders or sides; the modulus ZM may, how-ever, be reduced by 40%.

If a side girder is fitted on each side with a height equal tothe local height of the floor, the modulus may be reducedby a further 10%.

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

ZM k1 b S2 K p⋅ ⋅ ⋅ ⋅=


Pt B, Ch 2, Sec 6

3.3 Girders

3.3.1 Centre girder

When the girder forms a support for the floor, the sectionmodulus is to be not less than the value ZPC, in cm3, calcu-lated with the following formula:

where:

k1 : defined in 3.1

bPC : half the distance, in m, between the two sidegirders if supporting or equal to B/2 in theabsence of supporting side girders

S : conventional girder span equal to the distance,in m, between the two supporting members(transverse bulkheads, floors).

Whenever the centre girder does not form a support for thefloors, the section modulus is to be not less than the valueZPC, in cm3, calculated with the following formula:

where:

k1 : defined in 3.1

b’PC : half the distance, in m, between the two sidegirders if present or equal to B/2 in the absenceof side girders

S : distance between the floors.

3.3.2 Side girders

When the side girder forms a support for the floor, the sec-tion modulus is to be not less than the value ZPL, in cm3,calculated with the following formula:

where:


bPL : half the distance, in m, between the two adja-cent girders or between the side and the girderconcerned


Whenever the side girder does not form a support for thefloors, the section modulus is to be not less than the valueZPL, in cm3, calculated with the following formula:

where:

k1 : defined in 3.1

b’PL : half the distance, in m, between the two adja-cent girders or between the side and the adja-cent girder


4 Transverse type structures

4.1 Ordinary floors

4.1.1 The section modulus for ordinary floors is to be notless than the value Z, in cm3, calculated with the followingformula:

where:

k1 : defined in 3.1

S : conventional span in m, of the floor equal to thedistance between the members which support it(girders, sides).

4.2 Centre girder

4.2.1 The section modulus of the centre girder is to be notless than the value ZPC, in cm3, calculated with the follow-ing formula:

where:


: 0,75 assuming p=p2.


S : conventional span of the centre girder, equal tothe distance, in m, between the two supportingmembers (transverse bulkheads, floors).

4.3 Side girders

4.3.1 The section modulus is to be not less than the valuethe value ZPL, in cm3, calculated with the following for-mula:

where:

k1 : defined in 4.2

bPL : half the distance, in m, between the two adja-cent girders or between the side and the girderadjacent to that concerned

S : conventional girder span equal to the distance,in m, between the two members which supportit (transverse bulkheads, floors).

5 Constructional details

5.1

5.1.1 The centre girder and side girders are to be con-nected to the stiffeners of the transom by means of suitablefittings.

The face plate of the girders may be gradually reduced toreach the dimensions of that of the transom stiffeners.

ZPC k1 bPC S2 K p⋅ ⋅ ⋅ ⋅=

ZPC k1 bPC′ S2 K p⋅ ⋅ ⋅ ⋅=

ZPL k1 bPL S2 K p⋅ ⋅ ⋅ ⋅=

ZPL k1 bPL′ S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=




Pt B, Ch 2, Sec 7


1 General

1.1

1.1.1 This Section stipulates the criteria for the structuralscantlings of a double bottom, which may be of either lon-gitudinal or transverse type.

The longitudinal type structure is made up of ordinary rein-forcements placed longitudinally, supported by floors.

The fitting of a double bottom with longitudinal framing isrecommended for planing and semi-planing yachts.

1.1.2 The fitting of a double bottom extending from thecollision bulkhead to the forward bulkhead in the machin-ery space or as near thereto as practicable, is requested foryacht of L > 50 m.

On yachts of L > 61 m a double bottom is to be fitted, as farpracticable, outside the machinery space extending forwardto the collision bulkhead and aft to the after peak bulkhead.

On yachts of L > 76 m the double bottom is to extend, as faras this is practicable, throughout the length of the yacht.

The double bottom is to extend transversally to the side soas to protect the bottom in the bilge area, as far as possible.

1.1.3 The dimensions of the double bottom, and in partic-ular the height, are to be such as to allow access for inspec-tion and maintenance.

In floors and in side girders, manholes are to be provided inorder to guarantee that all parts of the double bottom canbe inspected at least visually.

The height of manholes is generally to be not greater thanhalf the local height in the double bottom. When manholeswith greater height are fitted, the free edge is to be rein-forced by a flat iron bar or other equally effective reinforce-ments are to be arranged.

Manholes are not to be placed in the continuous centregirder, or in floors and side girders below pillars, except inspecial cases at the discretion of RINA.

1.1.4 Openings are to be provided in floors and girders inorder to ensure down-flow of air and liquids in every part ofthe double bottom.

Holes for the passage of air are to be arranged as close aspossible to the top and those for the passage of liquids asclose as possible to the bottom.

Bilge wells placed in the inner bottom are to be watertightand limited as far as possible in height and are to have wallsand bottom of thickness not less than that prescribed forinner bottom plating.

In zones where the double bottom varies in height or isinterrupted, tapering of the structures is to be adopted inorder to avoid discontinuities.

2 Minimum height

2.1

2.1.1 The height of the double bottom is to be sufficient toallow access to all areas and, in way of the centre girder, isto be not less than the value hDF, in mm, obtained from thefollowing formula:

The height of the double bottom is in any event to be notless than 700 mm. For yachts less than 50 m in length RINAmay accept reduced height.

3 Inner bottom plating

3.1

3.1.1 The thickness of the inner bottom plating is to be notless than the value t1, in mm,calculated with the followingformula:

dove:s : spacing of the ordinary stiffeners, in m.For yachts of length L < 50 m, the thickness is to be main-tained throughout the length of the hull.

For yachts of length L > 50 m, the thickness may be gradu-ally reduced outside 0,4 L amidships so as to reach a valueno less than 0,9 t1 at the ends.

Where the inner bottom forms the top of a tank intended forliquid cargoes, the thickness of the top is also to complywith the provisions of Sec.10.

4 Centre girder

4.1

4.1.1 A centre girder is to be fitted, as far as this is practi-cable, throughout the length of the hull. The thickness of the centre girder is to be not less than thefollowing value tpc, in mm:

5 Side girders

5.1

5.1.1 Where the breadth of the floors does not exceed 6m, side girders need not be fitted. Where the breadth of the floors exceeds 6 m, side girdersare to be arranged with thickness equal to that of the floors.

hdf 28B 32 T 10+( )+=

t1 0 04L, 5s 1+ +( )k=

tpc 0 008hdf, 2+=


Pt B, Ch 2, Sec 7

A sufficient number of side girders are to be fitted so that thedistance between them, or between one such girder and thecentre girder or the side, does not exceed 3 m.

The side girders are to be extended as far forward and aft aspracticable and are, as a rule, to terminate on a transversebulkhead or on a floor or other transverse structure of ade-quate strength.

5.2

5.2.1 Where additional girders are foreseen in way of thebedplates of engines, they are to be integrated into thestructures of the yacht and extended as far forward and aftas practicable.

Girders of height no less than that of the floors are to be fit-ted under the bedplates of main engines.

Engine foundation bolts are to be arranged, as far as practi-cable, in close proximity to girders and floors.

Where this is not possible, transverse brackets are to be fit-ted.

6 Floors

6.1

6.1.1 The thickness of floors tm, in mm, is to be not lessthan the following value:

Watertight floors are also to have thickness not less thanthat required in Sec.10 for tank bulkheads.

6.2

6.2.1 When the height of a floor exceeds 900 mm, verticalstiffeners are to be arranged.

In any event, solid floors or equivalent structures are to bearranged in longitudinally framed double bottoms in the fol-lowing locations:

• under bulkheads and pillars

• outside the machinery space at an interval no greaterthan 2 m

• in the machinery space under the bedplates of mainengines

• in way of variations in height of the double bottom.

Solid floors are to be arranged in transversely framed dou-ble bottoms in the following locations:


• in the machinery space at every frame

• in way of variations in height of the double bottom

• outside the machinery space at 2 m intervals.

7 Bracket floors

7.1

7.1.1 At each frame between solid floors, bracket floorsconsisting of a frame connected to the bottom plating and areverse frame connected to the inner bottom plating are tobe arranged and attached to the centre girder and the mar-gin plate by means of flanged brackets with a width offlange not less than 1/10 of the double bottom depth.

The frame section modulus Zc, in cm3, is to be not lessthan:

where:



S : frame span, in m, equal to the distance betweenthe mid-spans of the brackets connecting theframe/reverse frame.

The reverse frame section modulus is to be not less than85% of the frame section modulus.

Where tanks intended for liquid cargoes are arranged abovethe double bottom, the frame and reverse frame sectionmoduli are to be no less than those required for tank stiffen-ers as stated in Sec.10.

8 Bottom and inner bottom longitudi-nals

8.1

8.1.1 The section modulus of bottom stiffeners is to be noless than that required for single bottom longitudinals stipu-lated in Sec.6.

The section modulus of inner bottom stiffeners is to be noless than 85% of the section modulus of bottom longitudi-nals.

Where tanks intended for liquid cargoes are arranged abovethe double bottom, the section modulus of longitudinals isto be no less than that required for tank stiffeners as statedin Sez.10.

9 Bilge keel

9.1 Arrangement, scantlings and connec-tions

9.1.1 ArrangementWhere installed, bilge keels may not be welded directly onthe shell plating. An intermediate flat, or doubler, isrequired on the shell plating.

The ends of the bilge keel are to be sniped at an angle of15° or rounded with large radius. They are to be located inway of a transverse bilge stiffener. The ends of the interme-diate flat are to be sniped at an angle of 15°.

The arrangement shown in Fig 1 is recommended.

tm 0 008hdf, 0 5,+=

Zc k1 s S2 p K⋅ ⋅ ⋅ ⋅=


Pt B, Ch 2, Sec 7

Figure 1 : bilge keel arrangement

The arragement shown in figure 2 may also be accepted

Figure 2 : bilge keel arrangement

9.1.2 MaterialsThe bilge keel and the intermediate flat are to be made ofsteel with the same yield stress and grade as that of the bilgestrake.

9.1.3 ScantlingsThe net thickness of the intermediate flat is to be equal tothat of the bilge strake. However, this thickness may gener-ally not be greater than 15 mm.

9.2 Bilge keel connection

9.2.1 The intermediate flat, through which the bilge keel isconnected to the shell is to be welded as a shell doubler bycontinuous fillet welds.The butt welds of the doubler and bilge keel are to be fullpenetration and shifted from the shell butts.

The butt welds of the bilge plating and those of the doublersare to be flush in way of crossing, respectively, with thedoubler and with the bilge keel.


Pt B, Ch 2, Sec 8


1 General

1.1

1.1.1 This Section lays down the criteria for the scantlingsof the reinforcement structures of the side, which may be oflongitudinal or transverse type.

The longitudinal type structure consists of ordinary stiffenersplaced longitudinally supported by reinforced frames, gen-erally spaced not more than 2 m apart, or by transversebulkheads.

The transverse type structure is made up of ordinary rein-forcements placed vertically (frames), which may be sup-ported by reinforced stringers, by decks, by flats or by thebottom structures.

Reinforced frames are to be provided in way of the mast andthe ballast keel, in sailing yachts, in the machinery spaceand in general in way of large openings on the weatherdeck.


2.1

2.1.1


p : scantling pressure, in kN/m2, defined in Part B,Chap. 1, Sec. 5;

K : factor defined in Sec. 2 of this Chapter.

3 Ordinary stiffeners

3.1 Transverse frames

3.1.1 The section modulus of the frames is to be not lessthan the value Z, in cm3, calculated with the following for-mula:

where:



S : conventional frame span, in m, equal to thedistance between the supporting members.

The ordinary frames are to be well connected to the ele-ments which support them, in general made up of a beamand a floor.

3.2 Longitudinal stiffeners

3.2.1 The section modulus of the side longitudinals is tobe not less than the value Z, in cm3, calculated with the fol-lowing formula:

The section modulus of the frames is to be not less than thevalue Z, in cm3, calculated with the following formula:

where:



S : conventional span of the longitudinal, in m,equal to the distance between the supportingmembers, in general made up of reinforced fra-mes or transverse bulkheads.

4 Reinforced beams

4.1 Reinforced frames

4.1.1 The section modulus of the reinforced frames is tobe not less than the value Z, in cm3, calculated with the fol-lowing formula:

where:

k1 : 1 assuming p=p1

: 0,7 assuming p=p2

KCR : 0,9 for reinforced frames which support ordi-nary longitudinal stiffeners, or reinforced string-ers;

: 0,4 for reinforced frames which do not supportordinary stiffeners;

s : spacing, in m, between the reinforced frames orhalf the distance between the reinforced framesand the transverse bulkhead adjacent to theframe concerned;

S : conventional span, in m, equal to the distancebetween the members which support the rein-forced frame.

4.2 Reinforced stringers

4.2.1 The section modulus of the reinforced stringers is tobe not less than the value Z, in cm3,calculated with the fol-lowing formula:

where:

k1 : defined in 4.1

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 KCR s S2 K p⋅ ⋅ ⋅ ⋅ ⋅=

Z k1 KCR′ s S2 K p⋅ ⋅ ⋅ ⋅ ⋅=


Pt B, Ch 2, Sec 8

K’CR : • 0,9 for reinforced stringers which supportordinary vertical stiffeners (frames);

• 0,4 for reinforced stringers which do notsupport ordinary vertical stiffeners;

s : spacing,in m, between the reinforced stringersor 0,5 D in the absence of reinforced stringersor decks;

S : conventional span, in m, equal to the distancebetween the members which support thestringer, in general made up of transverse bulk-heads or reinforced frames.

5 Frame connections

5.1 General

5.1.1 End connections of frames are to be bracketed.

5.1.2 Tweendeck frames are to be bracketed at the top andwelded or bracketed at the bottom to the deck.In the case of bulb profiles, a bracket may be required to befitted at bottom.

5.1.3 Brackets are normally connected to frames by lapwelds. The length of overlap is to be not less than the depthof frames.

6 Scantling of brackets of frame con-nections

6.1

6.1.1 As a general rule, for yachts of length greater than50m, following scantlings may be followed:

6.1.2 Upper brackets of framesThe arm length of upper brackets connecting frames to deckbeams is to be not less than the value obtained, in mm,from the following formula:

where:

φ: coefficient equal to:• for unflanged brackets:

φ = 48• for flanged brackets:

φ = 43,5

w : required section modulus of the stiffener, in cm3, givenin [ 6.1.2] and [ 6.3.3] and depending on the type of con-nection,

t : bracket net thickness, in mm.

6.1.3 For connections of perpendicular stiffeners locatedin the same plane (see Fig 1) or connections of stiffenerslocated in perpendicular planes (see Fig 2), the requiredsection modulus is to be taken equal to:

where w1 and w2 are the required section moduli of stiffen-ers, as shown in Fig 1 and Fig 2.

6.1.4 For connections of frames to deck beams (see Fig 3),the required section modulus is to be taken equal to:

• for bracket "A":

• for bracket "B":

where w1 , w'1 and w2 are the required section moduli ofstiffeners, as shown in Fig 3.

Figure 1 : Connections of perpendicular stiffeners in the same plane

Figure 2 : Connections of stiffeners located in per-pendicular planes

d φ w 30+t

-----------------=

w w2= if w2 w1≤

w w1= if w2 w1>

wA w1= if w2 w1≤

wB w'1= need not to be greater then w1

w2

w1

d

d

w2

w1

d

d

theoriticalbracket

actualbracket


Pt B, Ch 2, Sec 8

Figure 3 : Connections of frames to deck bea

6.2 Lower brackets of frames

6.2.1 In general, frames are to be bracketed to the innerbottom or to the face plate of floors as shown in Fig 4.

Figure 4 : Lower brackets of frames

6.2.2 The arm lengths d1 and d2 of lower brackets offrames are to be not less than the value obtained, in mm,from the following formula:

where:

φ: coefficient equal to:• for unflanged brackets:

φ = 50• for flanged brackets:

φ = 45

w : required section modulus of the frame, in cm3,

t : Bracket thickness, in mm.

6.2.3 Where the bracket thickness, in mm, is less than15Lb , where Lb is the length, in m, of the bracket free edge,the free edge of the bracket is to be flanged or stiffened by awelded face plate.

The sectional area, in cm2, of the flange or the face plate isto be not less than 10Lb.

w2

w1

dA

w'1

dA

dB

d B

h'1

h'1

A

B

d1

d2

h

2 h

1,5

h

75

75

d φ w 30+t

-----------------=


Pt B, Ch 2, Sec 9

SECTION 9 DECKS

1 General

1.1

1.1.1 This Section lays down the criteria for the scantlingsof decks, plating and reinforcing or supporting structures.

The reinforcing and supporting structures of decks consist ofordinary reinforcements, beams or longitudinal stringers,laid transversally or longitudinally, supported by lines ofshoring made up of systems of girders and/or reinforcedbeams, which in turn are supported by pillars or by trans-verse or longitudinal bulkheads.

Reinforced beams together with reinforced frames are to beplaced in way of the mast in sailing yachts.

In sailing yachts with the mast resting on the deck or on thedeckhouse, a pillar or bulkhead is to be arranged in way ofthe mast base.


2.1

2.1.1

pdc : calculation deck, meaning the first deck abovethe full load waterline, extending for at least 0,6L and constituting an efficient support for thestructural elements of the side; in theory, it is toextend for the whole length of the yacht;

s : spacing of ordinary transverse or longitudinalstiffeners, in m;

h : scantling height, in m, the value of which isgiven in Part B, Chap. 1, Sec. 5;


3 Deck plating

3.1 Weather deck

3.1.1 The thickness of the weather deck plating, consider-ing that said deck is also a strength deck, is to be not lessthan the value t, in mm, calculated with the following for-mula:

In the yachts having L>50 m, a stringer plate is to be fittedwith width b, in m, not less than 0,025 L and thickness t, inmm, not less than the value given by the formula:

The stringer plate of increased thickness may be waived ifthe thickness adopted for the deck is greater than Rulethickness.

3.2 Lower decks


Where the deck is a tank top, the thickness of the deck is, inany event, to be not less than the value calculated with theformulae given in Sec.10 for tank bulkhead plating.

4 Stiffening and support structures for decks

4.1 Ordinary stiffeners

4.1.1 The section modulus of the ordinary stiffeners ofboth longitudinal and transverse (beams) type is to be notless than the value Z, in cm3, calculated with the followingformula:

where:

C1 : 1,44 for weather deck longitudinals

: 0,63 for lower deck longitudinals

: 0,56 for beams. S : conventional span, in m, equal to the distance

between the two supporting members.

4.2 Reinforced beams

4.2.1 The section modulus for girders and for ordinaryreinforced beams is to be not less than the value Z, in cm3,calculated with the following equation:

where:

b : average width of the strip of deck resting on thebeam, in m. In the calculation of b any open-ings are to be considered as non-existent

S : conventional span of the reinforced beam, in m,equal to the distance between the two support-ing members (pillars, other reinforced beams,bulkheads).

4.3 Pillars

4.3.1 Pillars are, in general, to be made of tubes. In tanksintended for liquid cargoes, open section pillars are to befitted.The section area of pillars is to be not less than the value A,in cm2, given by the formula:

t 1 9, s L K⋅( )0 5,⋅ ⋅=

t 2 4, s L K⋅( )0 5,⋅ ⋅=

t 1 15, s L K⋅( )0 5,⋅ ⋅=

Z 7 5, C1 s S2 K h⋅ ⋅ ⋅ ⋅ ⋅=

Z 4 75, b S2 K h⋅ ⋅ ⋅ ⋅=


Pt B, Ch 2, Sec 9

where:

Q : load resting on the pillar, in kN, calculated withthe following formula:

where:

A : area of the part of the deck restingon the pillar, in m2.

h : scantling height, defined in 2.1.1.

λ : the ratio between the pillar length and the mini-mum radius of gyration of the pillar cross-sec-tion.

4.3.2 Pillar connectionsHeads and heels of pillars are to be attached to the sur-rounding structure by means of brackets, insert plates sothat the loads are well distributed.

Insert plates may be replaced by doubling plates, except inthe case of pillars which may also work under tension suchas those in tanks.

In general, the thickness of doubling plates is to be not lessthan 1,5 times the thickness of the pillar.

Pillars are to be attached at their heads and heels by contin-uous welding.

Pillars are to be connected to the inner bottom at the inter-section of girders and floors.

Where pillars connected to the inner bottom are not locatedin way of intersections of floors and girders, partial floors orgirders or equivalent structures suitable to support the pil-lars are to be arranged.

A Q12 5, 0 045λ,–---------------------------------------=

Q 6 87, A h⋅ ⋅=


Pt B, Ch 2, Sec 10


1 General

1.1

1.1.1 The number and position of watertight bulkheadsare, in general, to be in accordance with the provisions ofChapter 1 of Part B.

Tanks" means the structural tanks that are part of the hulland intended to contain liquids (water, fuel oil or lube oil).

In order to contain fuel oil with a flashpoint ≤ 55° C, the useof independent metal tanks is required as stated in Chapter1 of Part B.

Tanks, complete with all pipe connections, are to be sub-jected to a hydraulic pressure test with a head above thetank top equal to h, as defined in Chap. 1, Sec. 5, or to theoverflow pipe, whichever is the greater.

At the discretion of RINA, leak testing with an air pressureof 0,15 bar may be accepted as an alternative, provided thatit is possible, using liquid solutions of proven effectivenessin the detection of air leaks, to carry out a visual inspectionof all parts of the tanks with particular reference to pipeconnections.

2 Symbols

2.1

2.1.1

s : spacing between the stiffeners, in m

S : conventional span, equal to the distance, in m,between the members that support the stiffenerconcerned

hs, ho : as defined in Part B, Chap. 1, Sec. 5

K : as defined in Chap. 2, Sec. 2.

3 Plating

3.1

3.1.1 The watertight bulkhead plating is to have a thick-ness not less than the value tS in mm, calculated with thefollowing formula:

The coefficient k1 and the scantling height h have the valuesindicated in Table 1.

Table 1

4 Stiffeners


4.1.1 The section modulus of ordinary stiffeners is to benot less than the value Z, in cm3, calculated with the fol-lowing formula:

The values of the coefficient c and of the scantling height hare those indicated in Table 2.


4.2.1 The horizontal webs of bulkheads with ordinary ver-tical stiffeners and reinforced stiffeners in the bulkheadswith ordinary horizontal stiffeners are to have a sectionmodulus not less than the value Z, in cm3, calculated withthe following formula:

C1 : 6, for subdivision bulkheads

: 10, for tank bulkheads

b : width, in m, of the zone of bulkhead resting onthe horizontal web or on the reinforced stiffener

h : scantling height indicated in Table 2.

Table 2

5 General arrangement

5.1

5.1.1 The structural continuity of the bulkhead verticaland horizontal primary supporting members with the sur-rounding supporting structures is to be carefully ensured.

tS k1 s h K⋅( )0 5,⋅ ⋅=

Bulkhead k1 h (m)

Collision bulkhead 4,35 hs

Watertight bulkhead 3,8 hs

Deep tank bulkhead 4,25 ho

Bulkhead h (m) c

Collisione bulkhead hs 0,78

Watertight bulkhead hs 0,63

Deep tank bulkhead ho 1

Z 7 5, s S2 h c K⋅ ⋅ ⋅ ⋅ ⋅=

Z C1 b S2 h c K⋅ ⋅ ⋅ ⋅ ⋅=


Pt B, Ch 2, Sec 10

5.2

5.2.1 Where vertical stiffeners are cut in way of watertightdoors, reinforced stiffeners are to be fitted on each side ofthe door and suitably overlapped; cross-bars are to be pro-vided to support the interrupted stiffeners.

6 Non-tight bulkheads

6.1 Non-tight bulkheads not acting as pillars

6.1.1 Non-tight bulkheads not acting as pillars are to beprovided with vertical stiffeners with a maximum spacingequal to:• 0,9 m, for transverse bulkheads• two frame spacings, with a maximum of 1,5 m, for lon-

gitudinal bulkheads.

6.2 Non-tight bulkheads acting as pillars

6.2.1 Non-tight bulkheads acting as pillars are to be pro-vided with vertical stiffeners with a maximum spacing equalto:• two frame spacings, when the frame spacing does not

exceed 0,75 m,• one frame spacing, when the frame spacing is greater

than 0,75 m.


Pt B, Ch 2, Sec 11


1 General

1.1

1.1.1 First tier superstructures or deckhouses are intendedas those situated on the uppermost exposed continuousdeck of the yacht, second tier superstructures or deckhousesare those above, and so on.

Where the distance from the hypothetical freeboard deck tothe full load waterline exceeds the freeboard that can hypo-thetically be assigned to the yacht the reference deck for thedetermination of the superstructure tier may be the deckbelow the one specified above, see Ch 1, Sec 1, [4.3.2].

When there is no access from inside superstructures anddeckhouses to 'tweendecks below, reduced scantlings withrespect to those stipulated in this Section may be acceptedat the discretion of RINA.

2 Boundary bulkhead plating

2.1

2.1.1 The thickness of the boundary bulkheads is to benot less than the value t, in mm, calculated with the follow-ing formula:


h : conventional scantling height, in m, the value ofwhich is to be taken not less than the value indi-cated in Table 1.

K : factor defined in Chap. 2, Sec. 2.

In any event, the thickness t is to be not less than the valuesshown in Chap. 2, Sec. 1, Table 2.

Table 1

3 Stiffeners

3.1

3.1.1 The stiffeners of the boundary bulkheads are to havea section modulus not less than the value Z, in cm3, calco-lato conla seguente formula:

where:

h : conventional scantling height, in m, defined in2

K : factor defined in Chap. 2, Sec. 2

s : spacing of the stiffeners, in m

S : span of the stiffeners, equal to the distance, inm, between the members supporting the stiff-ener concerned.

4 Superstructure decks

4.1 Plating

4.1.1 The superstructure deck plating is to be not less thanthe value t, in mm, calculated with the following formula:

where:


K : factor defined in Chap. 2, Sec.

h : conventional scantling height, in m, defined in2.1.

4.2 Stiffeners

4.2.1 The section modulus Z, in cm3, of both the longitudi-nal and transverse ordinary deck stiffeners is to be not lessthan the value calculated with the following formula:

where:

S : conventional span of the stiffener, equal to thedistance, in m, between the supporting mem-bers

s, h : as defined in 2.1.

Reinforced beams (beams, stringers) and ordinary pillars areto have scantlings as stated in Sec. 9.

Type of bulkhead h (m)

1st tier front 1,5

2nd tier front 1,0

Other bulkheads wherever situated 1,0

t 3 s K h⋅( )0 5,⋅ ⋅=

Z 3 5, s S2 h K⋅ ⋅ ⋅ ⋅=

t 3 s K h⋅( )0 5,⋅ ⋅=

Z 3 5, s S2 h K⋅ ⋅ ⋅ ⋅=


Part BHull

Chapter 3

ALUMINIUM HULLS


SECTION 2 MATERIALS


SECTION 4 LONGITUDINAL STRENGTH

SECTION 5 PLATING




SECTION 9 DECKS




Pt B, Ch 3, Sec 1



1.1

1.1.1 Chapter 3 of Section B applies to monohull yachtswith a hull made of aluminium alloy and a length L notexceeding 90 m, with motor or sail power with or withoutan auxiliary engine. Multi-hulls or hulls with a greater length will be consideredcase by case.

In the examination of constructional plans, RINA may takeinto consideration material distribution and structural scant-lings other than those that would be obtained by applyingthese regulations, provided that structures with longitudinal,transverse and local strength not less than that of the corre-sponding Rule structure are obtained or provided that suchmaterial distribution and structural scantlings prove ade-quacy, in the opinion of RINA, on the basis of direct testcalculations of the structural strength.

The formulae indicated in this Chapter are based on use ofan aluminium alloy having yield Strength, in the weldedcondition, Rp 0,2 = 110 N/mm2 (correspondig to a permanentelongation of 0,2%).

The scantlings of structures made with light alloys havingdifferent values of yield strength are obtained taking intoaccount coefficient K as defined in Section 2.


2.1 Premise

2.1.1 The definitions and symbols in this Article are validfor all the Sections of this Chapter. The definitions of symbols having general validity are notnormally repeated in the various Sections, whereas themeanings of those symbols which have specific validity arespecified in the relevant Sections.

2.2 Definitions and symbols

2.2.1 L : scantling length, in m, on the full load water-

line, assumed to be equal to of the length on thefull load waterline with the yacht at rest;

B : maximum breadth of the yacht, in m, outsideframes; in tests of the longitudinal strength oftwin hull yachts, B is to be taken as equal totwice the breadth of the single hull, measuredimmediately below the cross-deck;

D : depth of the yacht, in m, measured vertically inthe transverse section at half the length L, fromthe base line up to the deck beam of the upper-most continuous deck;

T : draft of the yacht, in m, measured vertically inthe transverse section at half the length L, fromthe base line to the full load waterline with theyacht at rest in calm water;

s : spacing of the ordinary longitudinal or tran-sverse stiffener, in m;

∆ : displacement of the yacht outside frames, in t,at draught T;

K : factor as a function of the mechanical proper-ties of the aluminium alloy used, as defined inSec. 2.


3.1

3.1.1 Table 1 lists the structural plans that are to be pre-sented in advance to RINA in triplicate, for examinationand approval when required.

The Table also indicates the information that is to be sup-plied with the plans or, in any case, submitted to RINA forthe examination of the documentation.

For documentation purposes, a copy of the following planis to be submitted:


- capacity plan;

- lines plan;


Pt B, Ch 3, Sec 1

Table 1





3.2

3.2.1 In case a Builder for the construction of a new vesselof a standard design wants to use drawings alreadyapproved for a vessel similar in design and construction andclassed with the same class notation and the same naviga-tion, the drawings may not be sent for approval , but theRequest of Survey for the vessel shall be submitted enclosed

to a list of the drawings the Builder wants to refer to andcopy of the approved drawings are to be sent to RINA.

Attention is to be paid even to possible additional flagadministartions requirements, which may cause differencesin the constructions.



4 Direct calculations

4.1

4.1.1 As an alternative to those based on the formulae inthis Chapter, scantlings may be obtained by direct calcula-tions carried out in accordance with the provisions of Chap-ter 1 of Part B of these Rules.

Chapter 1 provides schematisations, boundary conditionsand loads to be used for direct calculations.

The scantlings are to be such as to guarantee that stress lev-els do not exceed the allowable values stipulated in theaforementioned Chapter.

5 Buckling strength checks

5.1 Application

5.1.1 The critical buckling strength of aluminium alloyplating and stiffeners subject to compressive stresses is to becalculated as specified below.

5.2 Elastic buckling stresses of plating

5.2.1 Compressive stress

The elastic buckling strength, in N/mm2, is given by:

where:

mC : (1+ γ2)2 for compression-bending stress

m1 :

t :thickness of plating, in mm

E :Young's modulus, in N/mm2, to be taken equal to0,07 . 105 N/mm2 for aluminium alloy structures

a :shorter side of the plate, in m

c :unloaded side of the plate, in m

d :loaded side of the plate, in m

PLANCONTAINING INFORMATION

RELEVANT TO:

• Midship section • main dimensions, maximumoperating speed V, designacceleration aCG (for planingor semi-planing yachts)

• materials and associatedmechanical properties

• for yacht with L > 40 m, ifmulti-hull, or L> 50 m ifmono-hull state the maxi-mum vertical bendingmoment in still water

• development

• Longitudinal and tras-versal section

• Plan of the decks • openings• loads acting, if different

from Rule loads

• Plating development • openings

• Structure of the engineroom

• Watertight bulkheadsand deep tankbulkheads

• openings• location of air outlets

• Structure of stern/side door

• closing appliances

• Superstructures • openings• location of overflow

• Support structure for crane

• design loads and connec-tions to the hull structures

• Rudder • materials of all components• calculation speed

• Propeller shaft struts • material

σE 0 9 mc E ε t1000 a⋅--------------------

⎝ ⎠⎛ ⎞

2

⋅ ⋅ ⋅ ⋅,=

0 ψ 1≤ ≤( ) i f γ γ1<,

2 1,1 1, ψ+---------------- 1 γ2+( )2

for compression - bending⋅

0 ψ 1≤ ≤( ) i f γ γ1<,2 1,

1 1, ψ+---------------- 1 γ1

2+( )⋅


Pt B, Ch 3, Sec 1

ψ :ratio between the smallest and largest compressivestresses when the stress presents a linear variationacross the plate (0 < ψ < 1)

ε :coefficient equal to:•1,0, for edge d stiffened by a flat bar or bulb sec-

tion, if γ >1•1,1, for edge d stiffened by a flat bar or T-section,

if γ >1•1,1, · 1,0, for edge d stiffened by a flat bar or bulb

section, if γ<1•1,25 for edge d stiffened by a flat bar or T-section,

if γ<1.

5.2.2 Shear stressThe critical buckling stress, in N/mm2, is given by:

where:

and E, t and a are as defined in (a) above.b : longer side of the plate, in m.

5.3 Critical buckling stresses

5.3.1 Compressive stressThe critical buckling stress, in N/mm2, is given by:

dove:Rp0,2 : minimum yield stress of aluminium alloy used,

in N/mm2, in delivery conditionσE : elastic buckling stress calculated according to

5.2.1.

5.3.2 Shear stressThe critical buckling shear stress, in N/mm2, is given by:

where:τF : 0,58 Rp0,2

Rp0,2 : minimum yield stress of aluminium alloy used,in N/mm2, in delivery condition

τE : elastic buckling stress calculated according to5.2.2.

5.4 Axially loaded stiffeners

5.4.1 Elastic flexural buckling stressThe elastic flexural buckling stress σE, in N/mm2, is givenby:

where:

r :

I : moment of inertia of the stiffener, in cm4, calcu-lated with a plate flange of width equal to φ

φ : the smaller of:

800 . a

200 . a

S :area of the cross-section of the stiffener, in cm2,excluding attached plating

m :coefficient depending on boundary conditions,equal to:

•1, for a stiffener supported at both ends

•2, for a stiffener supported at one end and fixed atthe other

•4, for a stiffener fixed at both ends.

5.4.2 Local elastic buckling stressesLe tensioni elastiche di instabilità locali, in N/mm2, sonodate dalle seguenti formule:

• for flat bars

• for built-up stiffeners with symmetrical flange:

where:

hW : web height, in mm

tW : web thickness, in mm

bf : flange width, in mm

tf : flange hickness, in mm.


6.1


For yachts with length L greater than 50 m, reduced scant-lings may be adopted for the fore and aft zones, providedthat, with particular regard to plating, they are no less thanthose shown in Table 2.


γ cd--- not to be taken greater than 1,=

γ1

4 1 1, ψ+0 7,

--------------------–⎝ ⎠⎛ ⎞ 1–

3--------------------------------------------

⎝ ⎠⎜ ⎟⎜ ⎟⎜ ⎟⎛ ⎞

0 5,

=

τE 0 9 mt Et

1000 a⋅--------------------

⎝ ⎠⎛ ⎞

2

⋅ ⋅ ⋅,=

mt 5 34, 4 ab---

⎝ ⎠⎛ ⎞

2

⋅+=

σc σE= if σERp 0 2,

2-----------≤

σc Rp0 2, 1 Rp0 2,

4 σe⋅-------------–

⎝ ⎠⎛ ⎞⋅=

⎝ ⎠⎛ ⎞ i f σE

Rp0 2,

2----------->

τc τE= i f τEτF

2----≤

τc τF 1 τF

4 τe⋅------------–

⎝ ⎠⎛ ⎞⋅=

⎝ ⎠⎛ ⎞ if τE

τF

2---->

σE 69 1 r1000 c⋅--------------------

⎝ ⎠⎛ ⎞

2

m 104⋅ ⋅ ⋅,=

10 IS φ t 10 2–⋅ ⋅+---------------------------------

⎝ ⎠⎛ ⎞

0 5,

gyration radius in mm,

σE 55tw

hw

------⎝ ⎠⎛ ⎞

2

m 103⋅ ⋅ ⋅=

σE 27tw

hw

------⎝ ⎠⎛ ⎞

2

m 104 web⋅ ⋅ ⋅=

σE 11tw

hw

------⎝ ⎠⎛ ⎞

2

m 104 flange⋅ ⋅ ⋅=


Pt B, Ch 3, Sec 1


For yachts similar in performance to high speed craft, a lon-gitudinal structure with reinforced floors, placed at adistance of not more than 2 m, is required for the bottom.

Such interval is to be suitably reduced in the areas forwardof amidships subject to the forces caused by slamming.

7 Minimum thicknesses

7.1

7.1.1 In general, the thicknesses of plating stiffeners andcores of reinforced beams is to be not less than the mini-mum values shown in Table 2.

Lesser thicknesses may be accepted provided that, in theopinion of RINA, their adequacy in terms of bucklingstrength and resistance to corrosion is demonstrated.

Where plating and stiffeners contribute to the longitudinalstrength of the yacht, their scantlings are to be such as tofulfil the requirements for yacht longitudinal strength stipu-lated in Sec. 4.

Table 2

MemberMinimum thickness

(mm)

Keel, bottom plating t1 = 1,75 . L1/3 . K0,5

Side plating t2 = 1,50 . L1/3 . K0,5

Open strength deck plating t3 = 1,50 . L1/3 . K0,5

Lower and enclosed deck plating t4 = t3 - 0,5

1st tier superstructure front bulk-head

t5 = t1

Superstructure bulkhead t6 = t5 - 1,5

Watertight subdivision bulkhead t7 = t2 - 0,5

Tank bulkhead t8 = t2

Centre girder t9 = 2,3 . L1/3 . K0,5

Floors and side girders t10 = 1,70 . L1/3 . K0,5

Tubular pillars t11 = 0,05 d (1)

(1) d = diameter of the pillar, in mm


Pt B, Ch 3, Sec 2

SECTION 2 MATERIALS

1 General requirements

1.1

1.1.1 For hull construction and for fittings the aluminiumalloys indicated in this Section are to be used.

The acceptance of applications and aluminium alloys notforeseen in these Section will be decided case by case, ingeneral at the time of the approval of the relevant plans.

The materials, in the condition of supply, are to satisfy theprovisions laid down by IACS or, where relevant, those spe-cifically stipulated for individual cases; the materials are tobe approved, if requested, in conformity with the applicablerequirements. For the types of materials foreseen in thisSection, the prerequisites and requirements for approval,when requested, are specified in Part D.

RINA reserves the right, subject to conditions specificallyagreed on, to accept materials other than those provided forin this Section.

These Rules presume that welding and other manufacturingprocesses, at low or high temperatures, are carried out inaccordance with normal good practice and in observanceof the applicable requirements of Part D.

Welding procedures are to be approved for the specific typeof material for which they are to be used, within the limitsand conditions laid down in Part D.

2 Aluminium alloy structures

2.1 Aluminium alloys for hull structures, for-gings and castings

2.1.1 The designation of aluminium alloys used in thisSection complies with the numerical designation used inRRIAD (Registration Record of International Alloy Designa-tion).

The characteristics of aluminium alloys to be used in theconstruction of aluminium yacht are to comply with the rel-evant RINA requirements.

As a rule, series 5000 aluminium-magnesium or series 6000aluminium-magnesium-silicon alloys are to be used (seeTable 1).

The use of series 6000 alloys or extruded plates, for partsexposed to sea water atmosphere, will be considered on a

case-by-case basis by RINA, also taking into account theprotective coating applied.

The list of aluminium alloys given in Table 1 is not exhaus-tive. Other aluminium alloys may be considered, providedthat the specifications (manufacture, chemical composition,temper, mechanical properties, welding, etc.) and the scopeof application are submitted to RINA for review.

In the case of welded structures, alloys and welding proc-esses are to be compatible and appropriate, to the satisfac-tion of RINA and in compliance with the relevantrequirements.

For forgings or castings, requirements for chemical compo-sition and mechanical properties will be defined in eachcase by RINA.

In the case of structures subjected to low service tempera-tures or intended for other particular applications, the alloysto be employed will be considered on a case-by-case basisby RINA, which will define the acceptance requirementsand conditions.

Unless otherwise specified, Young's modulus for alumin-ium alloys is to be taken equal to 70000 N/mm2 and Pois-son's ratio equal to 0,33.

2.2 Extruded plates

2.2.1 Extrusions with built-in plating and stiffeners,referred to as extruded plating, may be used.

In general, the application is limited to decks and deck-houses. Other uses may be permitted at the discretion ofRINA.

Extruded plating is preferably to be oriented so that the stiff-eners are parallel to the direction of main stresses.

Connections between extruded plating and primary mem-bers are to be given special attention.

2.3 Tolerances

2.3.1 The under-thickness tolerances of plates and rolledsections are to be in accordance with Table 2.

The under-thickness tolerances of extruded plates are to bein accordance with Table 3.

The responsibility for maintaining the required toleranceslies with the Manufacturer, who is also to inspect the sur-face condition of the material.


Pt B, Ch 3, Sec 2

Table 1 : Aluminium alloys for welded construction

Guaranteed mechanical characteristics (1)

Aluminium alloy Unwelded condition Welded condition

Alloy (2) Condition Products Thickness (mm) Rp0,2(N/mm2)

(4)Rm (N/mm2)

(5)R’p,02 (N/mm2)

(4)R’m (N/mm2)

(5)

5083

0/H111 rolled t ≤ 50 125 275 125 275

H321 rolled t ≤ 40 215 305 125 275

0 extruded all 110 270 110 270

5086

0/H111 rolled all 100 240 100 240

H321 rolled all 185 275 100 240

0 extruded all 95 240 95 240

53830/H111 rolled t ≤ 40 145 290 145 290

H321 rolled t ≤ 40 220 305 145 290

5059

0/H111 rolled t ≤ 40 155 300 155 300

H321rolled t ≤ 20 270 370 155 300

rolled 20 < t ≤ 40 260 360 155 300

54540/H111 rolled all 85 215 85 215

F rolled all 100 210 100 210

5754 0/H111 rolledt ≤ 6 80 190 80 190

t > 6 70 190 70 190

6005 T5 / T6

closed extrusionst ≤ 6 215 255 105 165

6 < t ≤ 25 200 250 100 165

open extrusionst ≤ 10 215 260 95 165

10 < t ≤ 25 200 250 80 165

6060 (3) T5 extrudedt ≤ 6 150 190 65 115

6 < t ≤ 25 130 180 65 110

6061 (6) T6 extruded t ≤ 25 240 260 115 155

6082 T6 extruded t ≤ 15 255 310 115 170

6106 T5 extruded t ≤ 6 195 240 65 130

6351 T5 extruded t ≤ 25 240 260 140 165

(1) The guaranteed mechanical characteristics in this Table correspond to general standard values. For more information, refer tothe minimum values guaranteed by the product supplier.

(2) Other grades or tempers may be considered, subject to the agreement of RINA.(3) 6060 alloy is not to be used for structural members subject to impact loads (e.g. bottom longitudinals). The use of alloy 6106 is

recommended in such cases.(4) Rp,02, R’p,02 are the minimum guaranteed yield stresses at 0,2% in unwelded and welded condition, respectively.(5) Rm, R’m are the minimum guaranteed tensile strengths in unwelded and welded condition, respectivelysono le minime garantite

tensioni di rottura in condizioni non saldate e saldate rispettivamente. (6) For structures in direct contact with water are generally not permitted.


Pt B, Ch 3, Sec 2

Table 2

Table 3

2.4 Influence of welding on mechanical cha-racteristics

2.4.1 Welding heat input lowers locally the mechanicalstrength of aluminium alloys hardened by work hardening(series 5000 other than condition 0 or H111) or by heattreatment (series 6000). Consequently, where necessary, a drop in mechanical char-acteristics of welded structures is to be considered in theheat-affected zone, with respect to the mechanical charac-teristics of the parent material.

The heat-affected zone may be taken to extend 25 mm oneach side of the weld axis.

Aluminium alloys of series 5000 in condition 0 (annealed)or H111 (annealed flattened) are not subject to a drop inmechanical strength in the welded areas.

Aluminium alloys of series 5000 other than condition 0 orH111 are subject to a drop in mechanical strength in thewelded areas. The mechanical characteristics to considerare normally those of condition 0 or H111. Highermechanical characteristics may be taken into account, pro-vided they are duly justified.

Aluminium alloys of series 6000 are subject to a drop inmechanical strength in the vicinity of welded areas. Themechanical characteristics to be considered are normallyindicated by the supplier.

2.5 Material factor K for scantlings of alumi-nium alloy structural members

2.5.1 The value of the material factor K, which appears inthe formulae for checking scantlings of structural membersgiven in this Chapter, is equal to:

where:

Rp 0,2 : minimum guaranteed yield stress, in N/mm2, ofthe aluminium alloy in the condition of supply

η : joint coefficient for the welded assembly, corre-sponding to the aluminium alloy considered,given in Table 4, in which:

R’p 0,2 : minimum guaranteed yield stress, in N/mm2, ofthe aluminium alloy as welded, i.e.:

• in condition 0 or H111 for alloys of series5000 (see 2.4)

• indicated by the supplier for alloys of series6000 (see 2.4).

For welded constructions in hardened aluminium alloys(series 5000 other than condition 0 or H111 and series6000), greater characteristics than those in annealed orwelded condition may be considered, provided that weldedconnections are located in areas where stress levels areacceptable for the alloy considered in annealed or weldedcondition.

In the event of welding of two different aluminium alloys,the material factor K to be considered for the scantlings isthe greater of the two.

Table 4

2.6 Information to be kept on board

2.6.1 A plan is to be kept on board indicating the allumin-ium alloys, the condition and type of product adopted forthe hull structures, the extent and location together withdetails of specification and mechanical properties, and anyrecommendations for welding, working and treatment.

As-built thickness tmm

Under-thickness tolerancesmm

t ≤ 8 0,3

8 < t ≤ 12 0,5

12 < t ≤ 20 0,7

t > 20 1

As-built thickness tmm

Under-thickness tolerancesmm

t ≤ 6 0,3

6 < t ≤ 10 0,4

Aluminium alloy η

• Alloys without work-hardening treatment(series 5000 in annealed condition 0 orannealed flattened condition H111)

1

• Alloys hardened by work hardening(series 5000 other than condition 0 orH111)

R’p 0,2/Rp 0,2

• Alloys hardened by heat treatment (series6000)

R’p 0,2/Rp 0,2

(1) When no information is available, the coefficient η maybe taken equal to the metallurgical efficiency coeffi-cient defined in Table 1, to be taken not less than 0,4 orgreater than 0,53.

K 110η Rp0 2,⋅-------------------=


Pt B, Ch 3, Sec 3


1 Welded connections


1.1.1 For fabrication by welding and qualification of weld-ing procedures the requirements of Part D, Ch 5 of theseRules apply and, in particular, the adoption of procedures issubject to approval in advance by RINA.

Furthermore, the individual shipyards are to be authorizedby RINA for the use of welding procedures using weldersauthorized by RINA.

Welding of the various types of aluminium alloy is to becarried out by means of welding procedures approved forthe purpose and the various welding procedures and con-sumables are to be used within the limits of their approvaland in accordance with the conditions of use specified inthe respective approval documents.

As a general rule, the quality standard adopted by the ship-yard is to be submitted to RINA and applies to all construc-tions.

The work is to be carried out to the satisfaction of theattending Surveyor and the classification is dependentupon the work carried out with the approved plans and aquality of constructions that fall into the limits set out byRINA or other recognized international bodies (i.e.: IACS).

Deviations from the approved plans shall be discussed asfirst instance with the attending Surveyor; If not agreed withhim, these are subject to the approval of the Head Office. Inany case, these deviations shall be reported to the HeadOffice.

Minor repairs are to be agreed with the attending Surveyor;repairs which affect the structural integrity are to be dis-cussed with the Builder and relevant drawing to be sent forapproval.

In general, the acceptable (quality standards of) construc-tion defects (such as surfaces defects, structural misalign-ment and fit, post welding plate deformation) are thosewhich fall into the limits set out by IACS Recommendations.

1.2 Welding procedures for aluminium alloys

1.2.1 Welding procedures accepted for the construction ofhulls are those semi-automatic with protection of argon gasor of argon-helium gas mix, with continuous fusible wire inAl-Mg-G5 alloy, with manual welding process, called MIG(metal-arc inert gas), and manual with argon gas protection,with a filler rod in the aforesaid alloy and torch having nonfusible tungsten electrode, called TIG (tungsten-arc inertgas). Welding procedures and filler materials other than the

above will be individually considered by RINA forapproval.

In particular, the following details are to be provided for theauthorization to use welding procedures in production:

a) category and grade of basic and filler materials

b) principal methods: type of joint (butt-welded, corner,etc.); preparation of joints (thickness, caulking, rightedges, etc.); welding position (flat, vertical, front, etc.)and other parameters (voltage, amperage, gas supply,etc.)

c) welding conditions: cleaning methods of the edges tobe welded; protection from atmospheric agents, etc

d) special operating requirements for butt-welded joints,e.g. plating: welding to start and end on heels outsidejoints; reverse chipping; provision for repair followingany arc interruptions

e) type and extension of production checks.

1.3 Access to and preparation of joints

1.3.1 For the correct carrying out of joints, sufficientaccess, in relation to the welding procedure used and to theposition of the weld itself, is to be ensured.

The structural parts to be welded to those adjacent are to bethoroughly cleaned before welding even if the componentsof the structure itself have been pickled beforehand. Suchcleaning is to be carried out using suitable mechanicalmeans, such as stainless steel wire brushes, in order to elim-inate oxides, grease, paint and other foreign bodies thatcould produce defects in the weld.

Adequate protection from the weather is to be provided toparts being welded; in any event, such parts are to be dry.In case of cold weather, screening to prevent too rapidcooling to be provided.

In welding procedures using bare, cored or coated wireswith gas shielding, the welding is to be carried out inweather protected conditions, so as to ensure that the gasoutflow from the nozzle is not disturbed by winds anddraughts.

The alignment of joints, methods of tack welding and backchipping are to be appropriate to the type of joint and to theweld position and are to satisfy RINA requirements stipu-lated for the use of the procedure adopted.

Welded temporary attachments used to aid construction areto be removed carefully by grinding, cutting or chipping.The surface of the material is to be finished smooth bygrinding followed by crack detection.

Any defects in the structure resulting from the removal oftemporary attachments are to be prepared, efficiently


Pt B, Ch 3, Sec 3

welded and ground smooth so as to achieve a defect freerepair.

1.4 Design

1.4.1 For the various structural details typical of weldedconstruction in shipbuilding and not dealt with in this Sec-tion, IACS standards and the rules of good practice are toapply as agreed by RINA; particular consideration is to be

given to the overall arrangement and structural details ofhighly stressed parts of the hull.

2 Type of connections

2.1 Types of connections and preparations

2.1.1 With MIG and TIG procedures, the preparations ofthe edges indicated in Table 1 are recommended.

Table 1 : Preparations for the welding of aluminium alloys

2.2 Butt welding

2.2.1 General

In general, butt connections of plating are to be full penetra-tion, welded on both sides except where special procedures

or specific techniques, considered equivalent by RINA, areadopted.

Connections different from the above may be accepted byRINA on a case by case basis; in such cases, the relevantdetail and workmanship specifications are to be approved.

Preparation ofedges Caulking dimensions (1) NotesMIG

s = 1,5 -2b = 0 - 2

Welding on one side. Reverse support may be used.

s = 5 - 25b = 0 - 3c = 1,5 - 3α = 60 - 90°

Back chipping with intervals is to be effected.

s = 8 - 25b = 3 - 7c = 2 -4α = 40 - 60°

Smaller angles up to 15 mm in thickness may be used withthe greater distance to the top.

s = 12 - 25b = 0 - 2c = 3 - 5α = 50 - 67°

Allowed especially for automatic welding. Semi-automa-tic processes may be back chipped at the top before thereverse runs.

TIG

s ≤ 2

s ≤ 4b = 0 - 2

Welding on one side.

s = 4 - 10b = 0 - 2α = 60 - 70°

The support may be used in horizontal position.

(1) The caulking dimensions are identified by the following parameters:s = thickness of base material, in mmb = distance to the top, in mmc = shoulder, in mmα = caulking angle.


Pt B, Ch 3, Sec 3

2.2.2 Welding of plates with different thicknesses

In the case of welding of plates with a difference in grossthickness equal to or greater than:

• 3 mm, if the thinner plate has a gross thickness equal toor less than 10 mm;

• 4 mm, if the thinner plate has a gross thickness greaterthan 10 mm

a taper having a length of not less than 4 times the differ-ence in gross thickness is to be adopted for connections ofplating perpendicular to the direction of main stresses. Forconnections of plating parallel to the direction of mainstresses, the taper length may be reduced to 3 times the dif-ference in gross thickness.

When the difference in thickness is less than the above val-ues, it may be accommodated in the weld transitionbetween plates.

2.2.3 Edge preparation, root gap

The cut of the joint edges, to be carried out in general bymechanical means, is to be regular and without raggededges or notches.

The acceptable root gap is to be in accordance with theadopted welding procedure and relevant bevel preparation.

2.2.4 Butt welding on permanent backing

Butt welding on permanent backing, i.e. butt weldingassembly of two plates backed by the flange or the faceplate of a stiffener, may be accepted where back welding isnot feasible or in specific cases deemed acceptable byRINA.

The type of bevel and the gap between the members to beassembled are to be such as to ensure a proper penetrationof the weld on its backing and an adequate connection tothe stiffener as required.

2.2.5 Plate misalignment in butt connections

The misalignment m, measured as shown in Fig 1, betweenplates with the same gross thickness t is to be less than0,15t, without being greater than 3 mm, where t is the grossthickness of the thinner abutting plate.

2.2.6 Section, bulbs and flat bars

When lengths of longitudinals of the shell plating andstrength deck within 0,6 L amidships, or elements in gen-eral subject to high stresses, are to be connected together bybutt joints, these are to be full penetration.

Figure 1 : Plate misalignment in butt connections

2.2.7 Butt joints between T-bar, L-bar or bulb of different height

When "a", the difference in height between the two mem-bers to be jointed, is less than 6mm, this difference may bebuilt up by welding;

When the a.m. difference is more than 6mm, the higher barshall be lowered for a length of at least 50 x a, in order toavoid local stresses (30 x a if the bars to be connected arenot primary members of the structure).

2.2.8 Insert plates and doublers (slot welding)A local increase in plating thickness is generally to beachieved through insert plates. Local doublers, which arenormally only allowed for temporary repair, may howeverbe accepted by RINA on a case by case basis.

In any case, doublers and insert plates are to be made ofmaterials of a quality at least equal to that of the plates onwhich they are welded.

Slot welds are to be of appropriate shape (in general oval)and dimensions, depending on the plate thickness, and maynot be completely filled by the weld.

The distance between two consecutive slot welds is to benot greater than a value which is defined on a case by casebasis taking into account:- the transverse spacing between adjacent slot weld lines- the stresses acting in the connected plates- the structural arrangement below the connected plates.

2.2.9 Insert plates (butt welding) Where thick insert plates are butt welded to thin plates, theedge of the thick plate shall be tapered.The slope of the taper shall be in accordance with Pt B, Ch2, Sec 3, par. 2.1.2.

The corners of insert plates are to be suitably radiused.


Pt B, Ch 3, Sec 3

2.3 Fillet welding types

2.3.1 Fillet welding of T type joints, or cross joints withstraight edges may be of the following types (see also Table3):

a) continuous fillet welding (double continuous bead,D.C.);

b) intermittent fillet welding as staggered welding (A) orchain welding (C) with length d and spacing p.

Figure 2 : Intermittent staggered welding A

Figure 3 : Intermittent chain welding (C)

2.4 Continuous fillet welding

2.4.1 Continuous fillet welding is always to be adopted:

• for watertight connections;

• for structures in way of stabilizers, thruster, foundationsand other highly stressed area;

• for structure members to plating in way of end connec-tions and scallops;

• at the ends of connections for a length of at least 75mm;

• round lap connections and at the ends of brackets, lugsand scallops.

Continuous fillet welding may also be adopted in lieu ofintermittent welding wherever deemed suitable.

2.4.2 Fillet welding crossing butt welding

Where stiffening members are attached by continuous filletwelds and cross completely finished butt welds, these weldsare to be made flush in way of the contact point. Similarly,for butt welds in webs of stiffening members, the butt weldis to be completed and generally made flush with the stiff-ening member before the fillet weld is made. Otherwise, ascallop is to be arranged in the web of the stiffening mem-ber. Scallops are to be of such size, and in such a position,that a satisfactory weld can be made at the edges without innotching the butt weld of the plate.

2.4.3 Misalignment in cruciform connectionsThe misalignment m in cruciform connections, measuredon the median lines as shown in Fig 4, is to be less than t/2,in general, where t is the gross thickness of the thinner abut-ting plate.

RINA may require lower misalignment to be adopted forcruciform connections subjected to high stresses.

Figure 4 : Misalignment in butt connections

2.5 Scantling of welds

2.5.1 For T-joints with straight edges, the scantling of thebead is given, as a function of the thickness of the T web, inTable 2.

The scantling of the welds for hull structures is given inTable 3 in which, for individual cases, the following areshown:

a) continuous welding with double type a bead (D.C. a) ortype b (D.C. b);

b) intermittent welding of type A or C, on continuousedges, with type a bead and spacing p.

As an alternative to intermittent welding of type A or C, theequivalent of D.C. may be used with, however, a minimumside of 3 mm for thicknesses not greater than 6mm, and of 4mm for thicknesses exceeding 6 mm.

Welding on scalloped edges, as an alternative to intermit-tent welding, is in general not allowed except in individualcases, to be specially considered by RINA, and for whichthe following is required:

- weld bead of type a;

- notch length equal to 150 mm;

- tooth length not less than 90 mm and such that the com-bination of the length, pitch, and side of the bead is the


Pt B, Ch 3, Sec 3

equivalent of the Rule scantling of the intermittent weld-ing shown in Table 3.

Scalloped welding is not allowed at the ends of beams, inway of parts subject to concentrated loads, and in structuressubject to noticeable vibrations, and it may also be unac-ceptable in other individual cases, at RINA's discretion,both in relation to types and levels of stress in the structuresand to the test results for authorization of the procedures tobe followed.

2.6 Strength of welding

2.6.1 The effective length, in mm, of the fillet welding isgiven by:

where d is the actual length, in mm, of the fillet welding.

Table 2 : Leg and throat of fillet beads

Figure 5 : Beads dimensions

de d= 20–


member





mm mm mm mm mm

3 ÷ 4,5 3,5(3) 2,5(2) 3 2

4,5 ÷ 6 5(4,5) 3,5(3) 4 3

6,5 ÷ 8 6(5) 3,5(3,5) 4 3

8 ÷ 10 7(6) 5(4) 5 3,5

10,5 ÷ 12 8(7) 5,5(5) 6 4

12,5 ÷ 14 8,5 6 6,5 4,5

14,5 ÷ 16 9 6,5 7 5

16,5 ÷ 18 10 7 8 6,5

18,5 ÷ 20 11 7,5 9 6,5

20,5 ÷ 22 12 8,5 10 7

22,5 ÷ 24 13 9 11 7,5

24,5 ÷ 26 14 10 12 8,5


throatthickness

leg

leg


Pt B, Ch 3, Sec 3

Table 3 : Scantlings of welds

Member Weld

1 - Trasverse type structure

Floors to:

- shell plating C140 within 0,25 L AV; A280 inside after peak; A340 elsewhere


- centre girder C150 inside engine; A340 elsewhere

- side girder C280

Watertight floors D.C. b

Centre girder to:

- keel D.C. b where watertight: C120 elsewhere

- top of double bottom D.C. b where watertight: C150 inside engine; C180 elsewhere

Side girder to:

- shell plating A300


Watertight girder and double bottom margin D.C. b

Frames of shell plating D.C. b inside after peak for 2-propeller hulls; A240 inside peaks and tanks;A340 elsewhere

Beams to deck plating A300 inside tanks; A340 elsewhere

2. Longitudinal type stucture

Bottom longitudinals to shell plating C140 within L from the bow: A280 elsewhere

Side and deck longitudinals to relevant plating A300

Top longitudinals of double bottom A300

Web to face plate of composed ordinary longitudinals A340; at the ends (1) D.C. b

Reinforced floors, frames and beams having face plate area

≤20cm2:

- to plating A240; at the ends C150

- to face plate A360; at the ends A240

3. Foundations of main engines and thrust shaft:

Girders to shell plating C130

Girders to bed plates D.C. a

Girder to top of double bottom

Floors to girder, to top of double bottom and to bed plates D.C. a

4. Subdivision bulkheads

Plating to borders D.C. b

Stiffeners to plating A340; C150 at the ends, if not squared

5. Tank bulkheads

Plating to borders D.C. on bottom; D.C. b elsewhere

Ordinary stiffeners to plating A300

Reinforced beams having span between 3 and 5 m and

face plate area ≤20 cm2:

- to plating C120 at the ends; C180 elsewhere

- to face plate C150 at the ends; A240 elsewhere

(1) "End" means a length at each end, 15% the length of the gross span.(2) Where slots are adopted due to inaccessibility, they are generally to have: length = 75 mm; breadth = 3 ÷ 4% t, where t = thickness of plating;

pitch = 150 mm; weld leg length = t - 0,5 mm to be carried out on the outline of the slot; supporting plate with breadth 40 ÷ 60 mm and thickness1,2 ÷ 1,5 t


Pt B, Ch 3, Sec 3

3 End connections of ordinary stiffeners

3.1

3.1.1 Where ordinary stiffeners are continuous throughprimary supporting members, they are to be connected tothe web plating so as to ensure proper transmission ofloads, e.g. by means of one of the connection details shownin Fig 6 to Fig 9.

Connection details other than those shown in Fig 6 to Fig 9may be considered by RINA on a case by case.

Figure 6 : End connection of ordinary stiffenerwithout collar plate

Figure 7 : End connection of ordinary stiffenerwith collar plate

Figure 8 : End connection of ordinary stiffenerwith one large collar plate

6. Not-watertight bulkheads see 4 above

7. Rudder

Plating to horizontal diaphragms and vertical diaphragmswhich do not constitute spindle

A300 (2)

Ordinary stiffeners to vertical diaphragms constitutingspindle

D.C. b

8. Superstructures

Boundary bulkheads to support deck and to upper deck

Ordinary stiffeners to bulkheads D.C. b

For other parts see previous items A340

9. Pillars

Tubular pillars to ends D.C. b

10. Primary supporting members in general

(a=sectional area of the face plate or flange, incm2)

a≤20 cm2

- connection to plating C180 at the ends; A260 elsewhere


20<a≤65 cm2

- connection to plating C160 at the ends; C o A220 elsewhere


Member Weld

(1) "End" means a length at each end, 15% the length of the gross span.(2) Where slots are adopted due to inaccessibility, they are generally to have: length = 75 mm; breadth = 3 ÷ 4% t, where t = thickness of plating;

pitch = 150 mm; weld leg length = t - 0,5 mm to be carried out on the outline of the slot; supporting plate with breadth 40 ÷ 60 mm and thickness1,2 ÷ 1,5 t


Pt B, Ch 3, Sec 3

Figure 9 : End connection of ordinary stiffenerwith two large collar plates

In all the above connections, the radius of the all the scal-lops in the primary member around the stiffener shall be atleast 20mm.

The extension of the collar plate above the primary membershall be at least 3 t, where t is the thickness of the collarplate.

3.2

3.2.1 Where ordinary stiffeners are cut at primary support-ing members, brackets are to be fitted to ensure the struc-tural continuity.

The thickness of brackets is to be not less than that of ordi-nary stiffeners. Brackets with thickness, in mm, less than15Lb, where Lb is the length, in m, of the free edge of theend bracket, are to be flanged or stiffened by a welded faceplate. The sectional area, in cm2, of the flanged edge or faceplate is to be at least equal to 10Lb .

3.3

3.3.1 Where necessary, RINA may require backing brack-ets to be fitted, as shown in Fig 10, in order to improve thefatigue strength of the connection.

Figure 10 : End connection of ordinary stiffenerwith backing bracket

4 End connections of primary support-ing members

4.1 Bracketed end connections

4.1.1 Arm lengths of end brackets are to be equal, as far aspracticable.As a general rule, the height of end brackets is to be not lessthan that of the primary supporting member.

4.1.2 The thickness of the end bracket web is generally tobe not less than that of the primary supporting memberweb.

4.1.3 The scantlings of end brackets are generally to besuch that the section modulus of the primary supportingmember with end brackets is not less than that of the pri-mary supporting member at mid-span.

4.1.4 The width, in mm, of the face plate of end brackets isto be not less than 50(Lb+1), where Lb is the length, in m, ofthe free edge of the end bracket.Moreover, the thickness of the face plate is to be not lessthan that of the bracket web.

4.1.5 Stiffening of end brackets is to be designed such thatit provides adequate buckling web stability.As guidance, the following prescriptions may be applied:• where the length Lb is greater than 1,5 m, the web of

the bracket is to be stiffened;

• the sectional area, in cm2, of web stiffeners is to be notless than 16,5l, where l is the span, in m, of the stiffener;

• tripping flat bars are to be fitted to prevent lateral buck-ling of web stiffeners. Where the width of the symmetri-cal face plate is greater than 400 mm, additionalbacking brackets are to be fitted.

4.2 Bracketless end connections

4.2.1 As a general rule, in the case of bracketless crossingbetween primary supporting members (see Fig 11), thethickness of the common part of the web is to be not lessthan the value obtained, in mm, from the following for-mula:

where: w : the lesser of w1 and w2,MAX

w1 : gross section modulus, in cm3, of member 1w2,MAX : the greater value, in cm3, of the gross section

moduli of members 2 and 3Ω : Area, in cm2, of the common part of members

1, 2 and 3.In the absence of one of members 2 and 3 shown in Fig 11,the value of the relevant gross section modulus is to betaken equal to zero.

t 15 75wΩ----,=


Pt B, Ch 3, Sec 3

4.2.2 In no case may the net thickness calculated accord-ing to [4.2.1] be less than the smallest web net thickness ofthe mem bers forming the crossing.

4.2.3 In general, the continuity of the face plates is to beensured.

Figure 11 : Bracketless end connections ofprimary supporting members

5 Cut-outs and holes

5.1

5.1.1 Cut-outs for the passage of ordinary stiffeners are tobe as small as possible and well rounded with smoothedges.

In general, the depth of cut-outs is to be not greater than50% of the depth of the primary supporting member.

5.1.2 Where openings such as lightening holes are cut inprimary supporting members, they are to be equidistantfrom the face plate and corners of cut-outs and, in general,their height is to be not greater than 20% of the web height.

5.1.3 Openings may not be fitted in way of toes of endbrackets.

5.1.4 Over half of the span of primary supporting mem-bers, the length of openings is to be not greater than the dis-tance between adjacent openings.

At the ends of the span, the length of openings is to be notgreater than 25% of the distance between adjacent open-ings.

5.1.5 The cut-out is to be reinforced to one of the solutionsshown in Fig. 12 to Fig. 14:

• continuous face plate (solution 1): see Fig 12

• straight face plate (solution 2): see Fig 13

• compensation of the opening (solution 3): see Fig 14

• combination of the above solutions.

Other arrangements may be accepted provided they aresupported by direct calculations submitted to RINA forreview.



Figure 14 : Stiffening of large openings in primary supporting members - Solution 3 (inserted plate)

6 Stiffening arrangement

6.1

6.1.1 Webs of primary supporting members are generallyto be stiffened where the height, in mm, is greater than100t, where t is the web net thickness, in mm, of the pri-mary supporting member.

In general, the web stiffeners of primary supporting mem-bers are to be spaced not more than 110t.

Ω

Member 3

Member 1

Member 2

t t


Pt B, Ch 3, Sec 3

6.2

6.2.1 As a general rule, tripping brackets (see Fig 15)welded to the face plate may be fitted:• every fourth spacing of ordinary stiffeners, without

exceeding 4 m• at the toe of end brackets• at rounded face plates• in way of cross ties• in way of concentrated loads.

Where the width of the symmetrical face plate is greaterthan 400 mm, backing brackets are to be fitted in way of thetripping brackets.

6.3

6.3.1 In general, the width of the primary supporting mem-ber face plate is to be not less than one tenth of the depth ofthe web, where tripping brackets are spaced as specified in[6.2].

6.4

6.4.1 The arm length of tripping brackets is to be not lessthan the greater of the following values, in m:

where:b : Height, in m, of tripping brackets, shown in

Fig 15st : Spacing, in m, of tripping bracketst : Net thickness, in mm, of tripping brackets.It is recommended that the bracket toe should be designedas shown in Fig 15.

6.5

6.5.1 Tripping brackets with a net thickness, in mm, lessthan 15Lb are to be flanged or stiffened by a welded faceplate.

Figure 15 : Primary supporting member:web stiffener in way of ordinary stiffener

7 Riveted connections

7.1

7.1.1 When riveted connections are employed, themechanical properties of the rivets are to be indicated onthe plans.

RINA may, at its discretion, require shear, tensile and com-pression tests to be carried out on representative specimensof riveted connections.

7.2

7.2.1 When rivets are used to connect materials of differ-ent types, precautions are to be taken against electrolyticcorrosion.

Whenever possible, the arrangements are to be such as toenable inspection in service without the need to removecoverings, etc.

8 Sealed connections

8.1

8.1.1 Where a sealing product is used to ensure airtight orwatertight integrity, product information is to be submittedtogether with evidence of its previous successful use.

9 Corrosion protection

9.1

9.1.1 The hull, decks and other structures exposed to themarine environment are to be adequately protected againstcorrosion.

Paint and other protective coatings are to be suitable for theprotection of the structures in relation to their position.

9.2

9.2.1 The protection is to have adequate thickness and isto be applied in accordance with the Manufacturer's speci-fications.

The protection is to be compatible with any primer appliedpreviously.

9.3

9.3.1 Paint containing lead, mercury or copper are not tobe used for applications on aluminium alloys.

10 Inspection and tests

10.1 General

10.1.1 Materials, workmanship, structures and weldedconnections are to be subjected, at the beginning of thework, during construction and after completion, to inspec-tions suitable to check compliance with the applicablerequirements, approved plans and standards.

d 0 38b,=

d 0 85b st

t---,=


Pt B, Ch 3, Sec 3

Tests of welded connections by RINA Surveyors are, as arule, those indicated in (a) to (e) below. Irrespective of theextent of such tests, the building shipyard is responsible forseeing that working methods, procedures and sequencescomply with RINA requirements, approved plans and nor-mal good practice. To this end, the shipyard is to provide itsown production control organization.

a) Verification of compliance of basic materials with therequirements in Sec. 2 and of structures with approvedplans.

b) Verification of compliance of use and application con-ditions of welding processes with those approved andascertainment of the use of authorized welders.

c) Visual examination of the preparation, root bevelingand execution of welding of the connections of struc-tural parts (e.g. crossing of butt-welded joints of panelsor sheets of shell plating and strength deck, transverse

joints of bent stringer plates, joints of inserts in way ofopenings, fillet welding of stiffeners, brackets, etc.). As ageneral rule, the surface of finished weld are to be as faras practicable smooth and free from undercut.

d) In addition to visual examination, X-ray examination ofthe welded joints, of an extension as deemed necessaryby the Surveyor. Ultrasonic testing is to be used forchecking butt or cruciform connections in full penetra-tion welding greater than 15mm. Ultrasonic examina-tions may also be required by the Surveyor in specificcases to verify the quality of the base material.

e) Checking of any repairs.

In case of presence of defects, the attending Surveyor mayask for the extent of non-destructive examination. Unac-ceptable defects shall be completely removed. The resultsof nde shall be recorded.


Pt B, Ch 3, Sec 4



1 General

1.1

1.1.1 The structural scantlings prescribed in Chapter 3 arealso intended for the purposes of the longitudinal strengthof a yacht having length L not exceeding 45 m for mono-hull or 40 m for catamarans and openings on the strengthdeck of limited size.

For yachts of greater length and/or openings of size greaterthan the breadth B of the hull and extending for a consider-able part of the length of the yacht, calculation of the longi-tudinal strength is required.

1.2


2 Bending stresses

2.1

2.1.1 In addition to satisfying the minimum requirementsstipulated in the individual Chapters of these Rules, thescantlings of members contributing to the longitudinalstrength of monohull yacht and catamarans are to achieve asection modulus of the midship section at the bottom andthe deck such as to guarantee stresses not exceeding theallowable values.

Therefore:

where:

Wf, Wp : section modulus at the bottom and the deck,respectively, of the transverse section, in m3

MT : design total vertical bending moment defined inChap. 1, Sec. 5.



σs : minimum yield stress of the material, in N/mm2.

2.2

2.2.1 The compressive value of normal stresses is not toexceed the value of the critical stresses for plates and stiff-eners calculated in Article 5 of Sec. 1.

2.3

2.3.1 The moment of inertia J of the midship section, inm4, is to be not less than the value given by the followingformulae:

J = 16 . MT . 10-6 for planing yachts

J = 18 . MT . 10-6 for displacement yachts

3 Shear stresses

3.1


where:

Tt : total shear stress in kN defined in Chap. 1, Sec.5

σs, f : defined in 2

At : actual shear of the transverse section, in m2, tobe calculated considering the net area of sideplating and of any longitudinal bulkheadsexcluding openings.

4 Calculation of the section modulus

4.1

4.1.1 In the calculation of the modulus and inertia of themidship section, all the continuous members, plating andlongitudinal stiffeners are generally to be included, pro-vided that they extend for at least 0,4 L amidships.

σ f f σs N mm2⁄⋅≤

σp f σs N mm2⁄⋅≤

σ fMT

1000 Wf

----------------------- N mm2⁄=

σpMT

1000 Wp

------------------------ N mm2⁄=

Tt

At

----- 10 3– f σs⋅≤⋅

Pt B, Ch 3, Sec 5

SECTION 5 PLATING


1.1

1.1.1

s : spacing of ordinary longitudinal or transversestiffener, in m;

p : scantling pressure, in kN/m2, given in Chap. 1,Sec. 5;


2 Keel

2.1 Sheet steel keel

2.1.1 The keel plating is to have a length bCH, in mm,throughout the length of the yacht, not less than the valueobtained by the following equation:

and a thickness not less than that of the adjacent bottomplating increased by 2 mm.

2.2 Solid keel

2.2.1 The height and thickness of the keel, throughout thelength of the yacht, are to be not less than the values hCH

and tCH, in mm, calculated with the following equations:

Lesser heights and thicknesses may be accepted providedthat the effective area of the section is not less than that ofthe Rule section.

Lesser heights and thicknesses may also be acceptable if acentre girder is placed in connection with the solid keel.

The garboard strakes connected to the keel are each to havea width not less than 750 mm and a thickness not less thanthat of the bottom plating increased by 10%.

3 Bottom and bilge

3.1

3.1.1 Bottom plating is the plating up to the chine or to theupper turn of the bilge.

The thickness of the bottom plating and the bilge is to benot less than the greater of the values t1 and t2, in mm, cal-culated with the following formulae:

where:

k1 : 0,15, assuming p=p1

: 0,10, assuming p=p2.

ka : coefficient as a function of the ratio S/s given inTable 1 below where S is the is the greaterdimension of the plating, in m.

k2 : curvature correction factor given by 1-h/s to betaken not less than 0,7, where h is the distance,in mm, measured perpendicularly from thechord s to the highest point of the arc of platingbetween the two supports (see Figure 1).

Figure 1


Sheet steel of plating connected to the stem or to the stern-post or in way of the propeller shaft struts is to have a thick-ness, in mm, not less than the value te given by:

and, in any event, equal to the thickness of the bottomincreased by 50%.

bCH 4 5, L 600+⋅=

hCH 1 5, L 100+⋅=

tCH 0 35, L 6+⋅( ) K0 5,⋅=

t1 k1 k2 ka s p K⋅( )0 5,⋅ ⋅ ⋅ ⋅=

t2 11 s T K⋅( )0 5,⋅ ⋅=

h

S

te 1 3, 0 05, L 6+⋅( ) K0 5,⋅ ⋅=


Pt B, Ch 3, Sec 5

Table 1

4 Sheerstrake

4.1

4.1.1 In the yachts having L> 50 m, a sheerstrake plate ofheight h, in mm, not less than 0,025 L and thickness not lessthan the greater of the values of the plating of the side andthe stringer plate is to be fitted.

In the case of sidescuttles or windows or other openingsarranged on the sheerstrake plate, the thickness is to beincreased sufficiently as necessary in order to compensatesuch openings.

In way of the ends of the bridge, the thickness of the sheer-strake is to be adequately increased.

5 Side

5.1


where k1, k2 and ka are as defined in 3.1.

5.2

5.2.1 The thickness of the transom is to be no less thanthat required for the bottom, for the part below the water-line, or for the side, for the part above the waterline.

In the event of water-jet drive systems, the thickness of thetransom will be the subject of special consideration.


6.1


6.2

6.2.1 Openings in the curved zone of the bilge strakesmay be accepted where the former are elliptical or fittedwith equivalent arrangements to minimise the stress con-centration effects. In any event, such openings are to belocated well clear of welded connections.

6.3


7 Local stiffeners

7.1

7.1.1 The thickness of plating determined with the forego-ing formulae is to be increased locally, generally by at least50%, in way of the stem, propeller shaft struts, rudder hornor trunk, stabilisers, anchor recesses, etc.

7.2


7.3

7.3.1 The thickness of plating is to be locally increased inway of inner or outer permanent ballast arrangements. The thickness is to be not less than 1,25 that of the adjacentplating but no greater than that of the keel.

8 Cross Deck bottom plating

8.1

8.1.1 The thickness is to be taken, the stiffener spacing sbeing equal, no less than that of the side plating. Where the gap between the bottom and the waterline isreduced so that local wave impact phenomena are antici-pated, an increase in thickness and/or additional internalstiffeners may be required.

S/s Ka

1 17,5

1,2 19,6

1,4 20,9

1,6 21,6

1,8 22,1

2,0 22,3

>2 22,4

t1 k1 k2 ka s p K⋅( )0 5,⋅ ⋅ ⋅ ⋅=

t2 10 s T K⋅( )0 5,⋅ ⋅=


Pt B, Ch 3, Sec 6


1 General

1.1



1.2.1 The longitudinal type structure is made up of ordi-nary reinforcements placed longitudinally, supported byfloors. The floors may be supported by girders, which in turn maybe supported by transverse bulkheads, or by the sides of thehull.







1.3.3 In way of the propeller shaft struts, the rudder hornand the ballast keel, additional floors are to be fitted withsufficiently increased scantlings.

1.3.4 The bottom of the engine room is to be reinforcedwith a suitable web floor consisting of floors and girders;the latter are to be fitted as a continuation of the existinggirders outside the engine room.

1.3.5 Floors are to be fitted in way of reinforced frames atthe sides and reinforced beams on the weather deck. Anyintermediate floors are to be adequately connected to theends.


2.1

2.1.1


p : scantling pressure, in kN/m2, given in Chap. 1;

K : coefficient defined in Sec 2 of this Chapter.



3.1.1 The section modulus of longitudinal stringers is to benot less than the value Z, in cm2, calculated with the fol-lowing formula:

where:


: 0,7 assuming p=p2


The bottom longitudinal stringers are preferably to be con-tinual through the transverse members. Where they are tobe interrupted in way of a transverse watertight bulkhead,brackets are to be provided at the ends.

3.2 Floors


where:



S : conventional floor span equal to the distance,in m, between the two supporting members(sides, girders, keel with a dead rise edge >12°).

In the case of a keel with a dead rise edge ≤12° but > 8° thespan S is always to be calculated considering the distancebetween girders or sides; the modulus ZM may, however,be reduced by 40%.


Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

ZM k1 b S2 K p⋅ ⋅ ⋅ ⋅=


Pt B, Ch 3, Sec 6

3.3 Girders

3.3.1 Centre girder


where:





where:


b’PC : half the distance, in m, between the two sidegirders if present or equal to B/2in the absenceof side girders


3.3.2 Side girders


where:


bPL : half the distance, in m, between the two adja-cent girders or between the side and the girderconcerned



where:



S : distance between the floors, in m.


4.1 Ordinary floors


where:

k1 : defined in 3.1


4.2 Centre girder


where:


: 1,43 assuming p=p2.



4.3 Side girders

4.3.1 The section modulus is to be not less than the valueZPL, in cm3, calculated with the following formula:

where:

k1 : defined in 3.1




5.1


The face plate of the girders may be gradually reduced toreach the dimensions of that of the transom stiffeners.


ZPC k1 bPC′ S2 K p⋅ ⋅ ⋅ ⋅=


ZPL k1 bPL′ S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=




Pt B, Ch 3, Sec 7


1 General

1.1




1.1.2 The fitting of a double bottom extending from thecollision bulkhead to the forward bulkhead in the machin-ery space or as near thereto as practicable, is requested foryachts of L > 50 m.

On yachts of L > 61 m a double bottom is to be fitted out-side the machinery space extending, as possible, forwardto the collision bulkhead and aft to the after peak bulkhead.

On yachts of L > 76 m the double bottom is to extend, aspossible, throughout the length of the yacht.

The double bottom is to extend transversally to the side soas to protect the bottom in the bilge area, as far as possible.









2 Minimum height

2.1

2.1.1 The height of the double bottom is to be sufficient toallow access to all areas and, in way of the centre girder, isto be not less than the value hDF, in mm, obtained from thefollowing formula:

The height of the double bottom is in any event to be notless than 700 mm. For yacht less than 50 m in length RINAmay accept reduced height.


3.1

3.1.1 The thickness of the inner bottom plating is to be notless than the value t1, in mm, calculated with the followingformula:

where:s : spacing of the ordinary stiffeners, in m.

For yachts of length L < 50 m, the thickness is to be main-tained throughout the length of the hull.


Where the inner bottom forms the top of a tank intended forliquid cargoes, the thickness of the top is also to complywith the provisions of Sec. 10.

4 Centre girder

4.1

4.1.1 A centre girder is to be fitted, as far as this is practi-cable, throughout the length of the hull. The thickness of the centre girder is to be not less than thefollowing value tpc, in mm:

5 Side girders

5.1

5.1.1 Where the breadth of the floors does not exceed 6m, side girders need not be fitted.

Where the breadth of the floors exceeds 6 m, side girdersare to be arranged with thickness equal to that of the floors.

hdf 28B 32 T 10+( )+=

t1 1 4 0 04L, 5s 1+ +( )k,=

tpc 1 4 008hdf 2+( ),=


Pt B, Ch 3, Sec 7



5.2





6 Floors

6.1

6.1.1 The thickness of floors tm, in mm, is to be not lessthan the following value:

Watertight floors are also to have thickness not less thanthat required in Sec. 10 for tank bulkheads.

6.2

6.2.1 When the height of a floor exceeds 900 mm, verticalstiffeners are to be arranged.

In any event, solid floors or equivalent structures are to bearranged in longitudinally framed double bottoms in the fol-lowing locations.

• under buklheads and pillars

• outside the machinery space at an interval no greaterthan 2 m

• in the machinery space under the bedplates of mainengines

• in way of variations in height of the double bottom.

Solid floors are to be arranged in transversely framed dou-ble bottoms in the following locations:


• in the machinery space at every frame

• in way of variations in height of the double bottom

• outside the machinery space at 2 m intervals.

7 Bracket floors

7.1

7.1.1 At each frame between solid floors, bracket floorsconsisting of a frame connected to the bottom plating and areverse frame connected to the inner bottom plating are tobe arranged and attached to the centre girder and the mar-gin plate by means of flanged brackets with a width offlange not less than 1/10 of the double bottom depth.

The frame section modulus Zc, in cm3, is to be not lessthan:

where:



S : frame span, in m, equal to the distance betweenthe mid-spans of the brackets connecting theframe/reverse frame.

The reverse frame section modulus is to be not less than85% of the frame section modulus.

Where tanks intended for liquid cargoes are arranged abovethe double bottom, the frame and reverse frame sectionmoduli are to be no less than those required for tank stiffen-ers as stated in Sec. 10.


8.1

8.1.1 The section modulus of bottom stiffeners is to be noless than that required for single bottom longitudinals stipu-lated in Sec. 6.

The section modulus of inner bottom stiffeners is to be noless than 85% of the section modulus of bottom longitudi-nals.

Where tanks intended for liquid cargoes are arranged abovethe double bottom, the section modulus of longitudinals isto be no less than that required for tank stiffeners as statedin Sec. 10.

9 Bilge keel

9.1 Arrangement, scantlings and connec-tions

9.1.1 ArrangementWhere installed, bilge keels may not be welded directly onthe shell plating. An intermediate flat, or doubler, isrequired on the shell plating.

The ends of the bilge keel are to be sniped at an angle of15° or rounded with large radius. They are to be located inway of a transverse bilge stiffener. The ends of the interme-diate flat are to be sniped at an angle of 15°.

The arrangement shown in Fig 1 is recommended.

tm 0 008hdf, 0 5,+=

Zc k1 s S2 p K⋅ ⋅ ⋅ ⋅=


Pt B, Ch 3, Sec 7

Figure 1 : Bilge keel arrangement

The arragement shown in figure 2 may also be accepted.

9.1.2 Materials

The bilge keel and the intermediate flat are to be made ofthe same alloy as that of the bilge strake.

9.1.3 Scantlings

The net thickness of the intermediate flat is to be equal tothat of the bilge strake. However, this thickness may gener-ally not be greater than 15 mm.

Figure 2 : Bilge keel arrangement

9.2 Bilge keel connection

9.2.1 The intermediate flat, through which the bilge keel isconnected to the shell, is to be welded as a shell doubler bycontinuous fillet welds.

The butt welds of the doubler and bilge keel are to be fullpenetration and shifted from the shell butts.

The butt welds of the bilge plating and those of the doublersare to be flush in way of crossing, respectively, with thedoubler and with the bilge keel.


Pt B, Ch 3, Sec 8


1 General

1.1

1.1.1 This Section lays down the criteria for the scantlingsof the reinforcement structures of the side, which may be oflongitudinal or transverse type.

The longitudinal type structure consists of ordinary stiffen-ers placed longitudinally supported by reinforced frames,generally spaced not more than 2 m apart, or by transversebulkheads.


Reinforced frames are to be provided in way of the mastand the ballast keel, in sailing yachts, in the machineryspace and in general in way of large openings on theweather deck.


2.1

2.1.1


p : scantling pressure, in kN/m2, defined in Part B,Chap. 1, Sec. 5 ;



3.1 Transverse frames


where:


: 1 assuming p=p2



3.2 Longitudinal stiffeners


where:k1 : 1,6 assuming p=p1

: 0,7 assuming p=p2


4 Reinforced beams


4.1.1 The section modulus of the reinforced frames is to benot less than the value calculated with the following for-mula:

where:k1 : 1 assuming p=p1

: 0,7 assuming p=p2



s : spacing between the reinforced frames or halfthe distance between the reinforced frames andthe transverse bulkhead adjacent to the frameconcerned;



4.2.1 The section modulus of the reinforced stringers is tobe not less than the value calculated with the following for-mula:

where:k1 : defined in 4.1KCR : 1,92 for reinforced stringers which support ordi-

nary vertical stiffeners (frames); : 0,86 for reinforced stringers which do not sup-

port ordinary vertical stiffeners;

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 K p⋅ ⋅ ⋅ ⋅=

Z k1 KCR s S2 K p⋅ ⋅ ⋅ ⋅ ⋅=

Z k1 KCR′ s S2 K p⋅ ⋅ ⋅ ⋅ ⋅=


Pt B, Ch 3, Sec 8

s : spacing between the reinforced stringers or 0,5D in the absence of other reinforced stringers ordecks;


5 Frame connections

5.1 General

5.1.1 End connections of frames are to be bracketed.

5.1.2 'Tweendeck frames are to be bracketed at the topand welded or bracketed at the bottom to the deck.

In the case of bulb profiles, a bracket may be required to befitted at bottom.

5.1.3 Brackets are normally connected to frames by lapwelds. The length of overlap is to be not less than the depthof frames.

6 Scantling of brackets of frame con-nections

6.1

6.1.1 As a general rule, for yachts of length greater than50m, following scantlings may be followed:

6.1.2 Upper brackets of frames

The arm length of upper brackets connecting frames to deckbeams is to be not less than the value obtained, in mm,from the following formula:

where:

ϕ : coefficient equal to:

• for unflanged brackets:

ϕ = 48

• for flanged brackets:

ϕ = 43,5

w : required net section modulus of the stiffener, incm3, given in [6.1.3] and [6.3.3] and dependingon the type of connection,

t : bracket net thickness, in mm.

6.1.3 For connections of perpendicular stiffeners locatedin the same plane (see Fig 1) or connections of stiffenerslocated in perpendicular planes (see Fig 2), the requiredsection modulus is to be taken equal to:

where w1 and w2 are the required net section moduli ofstiffeners, as shown in Fig 1 and Fig 2.

6.1.4 For connections of frames to deck beams (see Fig 3),the required section modulus is to be taken equal to:

• for bracket “A”:

• for bracket “B”:

wB = w’1 need not be greater than w1

where w1 , w’1 and w2 are the required net section moduliof stiffeners, as shown in Fig 3.

Figure 1 : Connections of perpendicular stiffenersin the same plane

Figure 2 : Connections of stiffeners locatedin perpendicular planes

d ϕ w 30+t

-----------------=

w w2 if w2 w1≤=

w w1 if w2 w1>=

wA w1 if w2 w1≤=

wA w2 if w2 w1>=

w2

w1

d

d

w2

w1

d

d

theoriticalbracket

actualbracket


Pt B, Ch 3, Sec 8

Figure 3 : Connections of frames to deck beams

6.2 Lower brackets of frames

6.2.1 In general, frames are to be bracketed to the innerbottom or to the face plate of floors as shown in Fig 4.

Figure 4 : Lower brackets of main frames

6.2.2 The arm lengths d1 and d2 of lower brackets offrames are to be not less than the value obtained, in mm,from the following formula:

where:ϕ : coefficient equal to:

• for unflanged brackets:ϕ = 50

• for flanged brackets:ϕ = 45

w : required net section modulus of the frame, incm3,

t : Bracket net thickness, in mm.

6.2.3 Where the bracket thickness, in mm, is less than15Lb , where Lb is the length, in m, of the bracket free edge,the free edge of the bracket is to be flanged or stiffened by awelded face plate.

The sectional area, in cm2, of the flange or the face plate isto be not less than 10Lb.

w2

w1

dA

w'1

dA

dB

d B

h'1

h'1

A

B

d1

d2

h

2 h

1,5

h

75

75

d ϕ w 30+t

-----------------=


Pt B, Ch 3, Sec 9

SECTION 9 DECKS

1 General

1.1

1.1.1 This Section lays down the criteria and formulae forthe scantlings of decks, plating and reinforcing or support-ing structures. The reinforcing and supporting structures of decks consist ofordinary reinforcements, beams or longitudinal stringers,laid transversally or longitudinally, supported by lines ofshoring made up of systems of girders and/or reinforcedbeams, which in turn are supported by pillars or by trans-verse or longitudinal bulkheads.




2.1

2.1.1





3 Deck plating

3.1 Weather deck


In the yachts having L > 50 m a stringer plate is to be fittedwith width b, in m, not less than 0,025 L and thickness t, inmm, not less than the value given by the formula:

The stringer plate of increased thickness may be waived ifthe thickness adopted for the deck is greater than Rulethickness.

3.2 Lower decks

3.2.1 The thickness of decks below the weather deckintended for accommodation spaces is to be not less thanthe value calculated with the formula:




4.1.1 The section modulus of the ordinary stiffeners ofboth longitudinal and transverse (beams) type is to be notless than the value Z, in cm3, calculated with the followingequation:

where:

C1 : 1,44 for weather deck longitudinals

: 0,63 for lower deck longitudinals: 0,56 for beams.



where:

b : average width of the strip of deck resting on thebeam, in m. In the calculation of b any open-ings are to be considered as non-existent


4.3 Pillars

4.3.1 Pillars are, in general, to be made of tubes. In tanksintended for liquid cargoes, open section pillars are to befitted.

The section area of pillars is to be not less than the value A,in cm2, given by the formula:

where:

t 2 5, s L K⋅( )0 5,⋅ ⋅=

t 3 1, s L K⋅( )0 5,⋅ ⋅=

t 1 5, s L K⋅( )0 5,⋅ ⋅=

Z 7 5, C1 s S2 K h⋅ ⋅ ⋅ ⋅ ⋅=

Z 9 b S2 K h⋅ ⋅ ⋅ ⋅=

A 1 6Q,12 5, 0 045λ,–---------------------------------------=


Pt B, Ch 3, Sec 9

Q : load resting on the pillar, in kN, calculated withthe following formula:

where:A : area of the part of the deck resting

on the pillar, in m2.h : scantling height, defined in 2.1.1.


4.3.2 Pillar connectionsHeads and heels of pillars are to be attached to the sur-rounding structure by means of brackets, insert plates sothat the loads are well distributed.

Insert plates may be replaced by doubling plates, except inthe case of pillars which may also work under tension suchas those in tanks.

In general, the net thickness of doubling plates is to be notless than 1,5 times the net thickness of the pillar.

Pillars are to be attached at their heads and heels by contin-uous welding.

Pillars are to be connected to the inner bottom at the inter-section of girders and floors.

Where pillars connected to the inner bottom are not locatedin way of intersections of floors and girders, partial floors orgirders or equivalent structures suitable to support the pil-lars are to be arranged.

Q 6 87, A h⋅ ⋅=


Pt B, Ch 3, Sec 10


1 General

1.1


"Tanks" means the structural tanks that are part of the hulland intended to contain liquids (water, fuel oil or lube oil).

In order to contain fuel oil with a flashpoint ≤ 55° C, the useof independent metal tanks is required as stated in Chapter1 of Part B.

Tanks, complete with all pipe connections, are to be sub-jected to a hydraulic pressure test with a head above thetank top equal to h, as defined in Chap. 1, Sec. 5, or to theoverflow pipe, whichever is the greater.


2 Symbols

2.1

2.1.1



hS, h0 : as defined in Part B, Chap. 1, Sec. 5

K : as defined in Chap. 2, Sec. 2.

3 Plating

3.1



Table 1

4 Stiffeners





4.2.1 The horizontal webs of bulkheads with ordinary ver-tical stiffeners and reinforced stiffeners in the bulkheadswith ordinary horizontal stiffeners are to have a sectionmodulus not less than the value Z, in cm 3, calculated withthe following formula:

where:

C1 : 11,4 for watertight bulkheads

: 19 for deep tank bulkheads



Table 2

5 General arrangement

5.1

5.1.1 The structural continuity of the bulkhead verticaland horizontal primary supporting members with the sur-rounding supporting structures is to be carefully ensured.

tS k1 s h K⋅( )0 5,⋅ ⋅=

Bulkhead k1 h (m)

Collision bulkhead 5,6 hB

Watertight bulkhead 4,9 hB

Deep tank bulkhead 5,5 ho

Bulkhead h (m) c

Collision bulkhead hS 0,78

Watertight bulkhead hS 0,63

Deep tank bulkhead ho 1

Z 14 s S2 h c K⋅ ⋅ ⋅ ⋅ ⋅=

Z C1 b S2 h c K⋅ ⋅ ⋅ ⋅ ⋅=


Pt B, Ch 3, Sec 10

5.2

5.2.1 Where vertical stiffeners are cut in way of watertightdoors, reinforced stiffeners are to be fitted on each side ofthe door and suitably overlapped; cross-bars are to be pro-vided to support the interrupted stiffeners.

6 Non-tight bulkheads

6.1 Non-tight bulkheads not acting as pillars

6.1.1 Non-tight bulkheads not acting as pillars are to beprovided with vertical stiffeners with a maximum spacingequal to:• 0,9 m, for transverse bulkheads• two frame spacings, with a maximum of 1,5 m, for lon-

gitudinal bulkheads.

6.2 Non-tight bulkheads acting as pillars

6.2.1 Non-tight bulkheads acting as pillars are to be pro-vided with vertical stiffeners with a maximum spacing equalto:• two frame spacings, when the frame spacing does not

exceed 0,75 m,• one frame spacing, when the frame spacing is greater

than 0,75 m.


Pt B, Ch 3, Sec 11



1 General

1.1


Where the distance from the hypothetical freeboard deck tothe full load waterline exceeds the freeboard that can hypo-thetically be assigned to the yacht, the reference deck forthe determination of the superstructure tier may be the deckbelow the one specified above, see Ch 1, Sec 1, [4.3.5].



2.1



h : conventional scantling height, in m, the valueof which is is to be taken not less than the valueindicated in Table 1.

K : factor defined in Chap. 2, Sec. 2.

In any event, the thickness t is to be not less than the valuesshown in Chap. 2, Sec. 1, Table 2.

Table 1

3 Stiffeners

3.1

3.1.1 The stiffeners of the boundary bulkheads are to havea section modulus not less than the value Z, in cm3, calcu-lated with the following formula:

where:

h : conventional scantling height, in m, defined in2



S : span of the stiffeners, equal to the distance, inm, between the members supporting the stiff-ener concerned.


4.1 Plating


where:



h : conventional scantling height, in m, defined in2.1.

4.2 Stiffeners


where:

S : conventional span of the stiffener, equal to thedistance, in m, between the supporting mem-bers

s, h : as defined in 2.1.

Reinforced beams (beams, stringers) and ordinary pillars areto have scantlings as stated in Sec. 9.


1st tier front 1,5

2nd tier front 1,0


t 3 9, s K h⋅( )0 5,⋅ ⋅=

Z 6 5, s S2 h K⋅ ⋅ ⋅ ⋅=

t 3 9, s K h⋅( )0 5,⋅ ⋅=

Z 6 5, s S2 h K⋅ ⋅ ⋅ ⋅=

Part BHull

Chapter 4

REINFORCED PLASTIC HULLS


SECTION 2 MATERIALS

SECTION 3 CONSTRUCTION AND QUALITY CONTROL


SECTION 5 EXTERNAL PLATING




SECTION 9 DECKS



SECTION 12 SCANTLINGS OF STRUCTURES WITH SANDWICH CONSTRUCTION


Pt B, Ch 4, Sec 1



1.1

1.1.1 Chapter 4 of Section B applies to monohull yachtswith a hull made of composite materials and a length L notexceeding 60 m, with motor or sail power with or withoutan auxiliary engine.

Multi-hulls or hulls with a greater length will be consideredcase by case.

In the examination of constructional plans, RINA may takeinto consideration material distribution and structural scant-lings other than those that would be obtained by applyingthese regulations, provided that structures with longitudinal,transverse and local strength not less than that of the corre-sponding Rule structure are obtained or provided that suchmaterial distribution and structural scantlings prove ade-quate, in the opinion of RINA, on the basis of direct test cal-culations of the structural strength. (See Pt B, Ch 1, Sec 1,par. 3.1)


2.1 Premise

2.1.1 The definitions and symbols in this Article are validfor all the Sections of this Chapter.

The definitions of symbols having general validity are notnormally repeated in the various Sections, whereas themeanings of those symbols which have specific validity arespecified in the relevant Sections.

2.2 Symbols

2.2.1

γr : density of the resin; standard value 1,2 g/cm3;

γv : density of the fibres; standard value for glassfibres 2,56 g/cm3;

p : mass per area of the reinforcement of a singlelayer, in g/m2;

q : total mass per area of a single layer of the lami-nate, in g/m2;

gc : p/q = content of reinforcement in the layer; forlaminates in glass fibre the most frequent maxi-mum values of gc are the following, taking intoaccount that reinforcements are to be "wet" bythe resin matrix and compacted therein: 0,34for reinforcements in mat or cut filaments, 0,5for reinforcements in woven roving or cloth;

P : total mass per area of reinforcements in the lam-inate, in g/m2;

Q : total mass per area of the laminate, in gm2,excluding the surface coating of resin;

Gc : P/Q = content of reinforcement in the laminate;for laminates with glass fibre reinforcements thevalue of GC is to be not less than 0,30;

ti : thickness of a single layer of the laminate, inmm. In the case of glass reinforcements suchthickness is given by:

p being expressed in kg/m2;

tF : Σti = total thickness of the laminate.

2.3 Definitions

2.3.1

Reinforced plastic : a composite material consistingmainly of two components, amatrix of thermosetting resin andof fibre reinforcements, producedas a laminate through moulding;

Reinforcements : reinforcements are made up of aninert resistant material matrix ofthermosetting resin and of fibrereinforcements, encapsulated inthe matrix (resin) to increase itsresistance and rigidity. The rein-forcements usually consist ofglass fibres or other materials,such as aramid or carbon typefibres;

Single-skin laminate : reinforced plastic material with,in general, the shape of a flat orcurved plate, or moulded.

Sandwich laminate : material composed of two single-skin laminates, structurally con-nected by the interposition of acore of light material.


3.1

3.1.1 Plans with the scantlings, the layout and the majorstructures of the hull are to be submitted to RINA for exami-nation sufficiently in advance of commencement of thelaminating of the hull.

ti 0 33p 2 56,gc

------------- 1 36,–⎝ ⎠⎛ ⎞,=


Pt B, Ch 4, Sec 1

The plans are to indicate the scantlings and the minimummechanical properties of the laminates as well as the per-centage in mass of the reinforcement in the laminate.

In general, the following plans are to be sent for examina-tion in triplicate.

• the midship section and the transverse sections with themain dimensions of the construction shown and, forconstructions with an engine, the design speed and thedesign acceleration aCG;

• longitudinal & trasversal section and relevant typicalconnections details;

• decks plan;

• construction of the bottom, floors, girders;

• double bottom;

• lamination schedule;

• watertight and subdivision bulkheads;

• superstructures;

• engine and auxiliary foundations.

• structure of stern/side door and relevant closing appli-ances;

• support structure for crane with design loads;

The above-mentioned plans are also to contain the relativelamination details, the percentage, in mass, of the reinforce-ment, the type of resin, core materials characteristics, thesandwich construction process and the type of structuraladhesive utilized (if any). In the case of reinforcementsother than glass, the minimum mechanical properties of thelaminate are to be indicated.

A list of all materials used in the construction including thecommercial name and the relevant characteristic of eachcomponent such as gel coat, resin, fibre reinforcement, corematerial, fire retardant additives or resins, adhesive, corebonding materials, details of the process of sandwich con-struction and details of the materials used for grantingreserve of buoyancy (and method of installation) shall besent with the initial submission of plan and copy of this listshall be provided to the attending Surveyor.The drawing list above is for guidance purposes only; inparticular, the same plan may be relative to one or more ofthe subjects indicated.

Furthermore, for documentation purposes, a copy of the fol-lowing plan is to be submitted:


- capacity plan;

- lines plan;





3.2

3.2.1 In case a Builder for the construction of a new vesselof a standard design wants to use drawings alreadyapproved for a vessel similar in design and construction andclassed with the same class notation and the same naviga-tion, the drawings may not be sent for approval , but theRequest of Survey for the vessel shall be submitted enclosedto a list of the drawings the Builder wants to refer to andcopy of the approved drawings are to be sent to RINA.Attention is to be paid even to possible additional flagadministartions requirements, which may cause differencesin the constructions.



4 Direct calculations 4.1 4.1.1 As an alternative to those based on the formulae inthis Chapter, scantlings may be obtained by direct calcula-tions carried out in accordance with the provisions ofChap. 1, Sec. 1 of these Rules. Chapter 1 provides schematisations, boundary conditionsand loads to be used for direct calculations.The scantlings of the various structures are to be such as toguarantee that stress levels do not exceed the allowable val-ues stipulated in Table 1. The values in column 1 are to beused for the load condition in still water, while those in col-umn 2 apply to dynamic loads.

Table 1

MemberAllowable stresses

1 2

Keel, bottom plating 0,4 σ 0, 8 σ

Side plating 0,4 σ 0,8 σ

Deck plating 0,4 σ 0,8 σ

Bottom longitudinals 0,6 σt 0,9 σt

Side longitudinals 0,5 σt 0,9 σt

Deck longitudinals 0,5 σt 0, 9 σt

Floors and girders 0,4 σt 0,8 σt

Frames and reinforced side stringers 0,4 σt 0,8 σt

Reinforced beams and deck girders 0,4 σt 0,8 σt

Note 1:σ(N/mm2): the ultimate bending strength for single-skin

laminates; the lesser of the ultimate tensilestrength and the ultimate compressive strengthfor sandwich type laminates. In this case theshear stress in the core is to be no greater than0,5 Rt where Rt is the ultimate shear strength ofthe core material;

σt(N/mm2): the ultimate tensile strength of the laminate.


Pt B, Ch 4, Sec 1


5.1


For yachts with length L greater than 30 m, reduced scant-lings may be adopted for the fore and aft zones.



For high speed hulls, a longitudinal structure with rein-forced floors, placed at a distance of not more than 2 m, isrequired for the bottom.

Such spacing is to be suitably reduced in the areas forwardof amidships subject to the forces caused by slamming.

5.2 Minimum thicknesses

5.2.1 The thicknesses of the laminates of the various mem-bers calculated using the formulae in this Chapter are to benot less than the values, in mm, in Table 2.

Table 2

The minimum values shown are required for laminates con-sisting of polyester resins and glass fibre reinforcements.

For laminates made using reinforcements of fibres otherthan glass (carbon and/or aramid, glass and aramid), lowerminimum thicknesses than those given in Table 2 may beaccepted on the basis of the principle of equivalence.

In such case, however, the thickness adopted is to be ade-quate in terms of buckling strength.

This thickness is, in any case, to be submitted to head officefor approval.

6 Construction

6.1 General

6.1.1 The construction process shall be in accordancewith Sec 3.

6.2 Details of construction

6.2.1 The following requirements refer to the details ofconstruction and structural connections that are most fre-quently used. Other solutions will be considered by RINAin individual cases, on the basis of a criterion of equiva-lence and, in any case, the good practice and the past expe-riences shall be followed. Details of construction shall berepresented in the structural plan.

6.2.2 As a general concept, the continuity of the structuralmembers is to be maintained and every change of sectionshall be gradual.

In the intersections between longitudinal and transversalmembers, the shallower member shall, in general, be con-tinuous under the primary member.

To ensure efficient load transmission, particular care is tobe given to the alignment of the structure and the fitting ofsuitable brackets e.g: side to deck (frames with beams),transom/bulkhead to bottom/deck (transom stiffeners withbottom/deck girders and deck/bottom girders with bulkheadstiffeners).

The Surveyor may require for additional bonding reinforce-ment in case of lack of alignment and for increased endbrackets, if deemed of non sufficient dimensions.

6.2.3 The plating stiffeners (e.g. longitudinals or floors)which are not prefabricated are to be laid up layer by layeron the same plating before polymerization; particular atten-tion is to be given to the bond and the structural continuityat the ends and intersection.

6.2.4 Discontinuities and hard points in the laminates areto be avoided and, to this end:

• variations in laminate thickness are to be by a gradualtaper from the greatest thickness to the smallest; as ageneral rule, there shall be a taper of at least 20 timesthe difference of thickness and, in case of connectionbetween single skin and sandwich construction, thecore material of sandwich shall be tapered too and thelength of this taper shall be at least twice the thicknessof the core itself.

• in way of edges (e.g. bottom edges), steps and similar inlaminates, the single layers are not to be stopped but areto be led beyond the edges for at least 30 mm; everylayer of reinforcement is to have its end staggered withrespect to that of the adjacent layer;

MemberSingle-skin laminate

Sandwichlaminate (1)

Keel, bottom plating 5,5 4,5/3,5

Side plating 5 4/3

Inner bottom plating 5 4,5/3,5

Strength deck plating 4 3/2

Lower deck plating 3 2/2

Subdivision bulkhead plating

2,5 2/2

Tank bulkhead plating 4,5 4/3

Side superstructures 2,5 2/2

Front superstructures 3 2,5/2,5

Girders-floors - 2/2

Any stiffeners - 2 (2)

(1) The first value refers to the external skin, the secondrefers to the internal skin

(2) Intended to refer to the thickness of the layers encapsu-lating the core


Pt B, Ch 4, Sec 1

6.2.5 In the laminates, woven rovings with a mass per area> 600 g/m2 are not to be superimposed directly, but are tobe separated by the interpositioning of a mat, preferablywith a mass per area of < 450 g/m2 so as to achieve a moreeffective bond.

6.2.6 The structural materials (e.g. plywood) fitted in thelaminates (as insert or backing pad) for increasing the localstrength in way of the attachment of fitting are to have cleanand prepared surfaces so as to achieve a satisfactory bondand have beveled edges. Joints between successive layerare to be overlapped.

Single skin lamination in way of the attachments of fittingsmay be accepted provided that the local thickness is 1,5times the adjacent thickness, with the additional layers lam-inated beyond the extremities of the surrounding stiffeners.Sandwich structures shall be taken to single skin structuresin way of the attachment of fittings and suitably reinforced.

6.2.7 Where through hull fittings are provided, particularcare is to be taken to seal the hull laminate. In case of sand-wich structures, backing pad of suitable dimensions are tobe provided in order to avoid concentration of forces. Oth-erwise, the core in way of the fittings may be replaced witha solid or high density core always sealing the hull lami-nate.

6.2.8 Where the strength of a stiffener is impaired by anyopening or holes for drainage, compensation is to be pro-vided. In any case, as a general rule, the depth of drainageholes in the stiffeners shall not exceed 30% of the depth ofthe stiffener and shall be positioned at the quarter span ofthe stiffener; furthermore, in general, openings into web'sstiffeners are to have a depth not exceeding half of thedepth of the web and are to be so located that the edges arenot less than 25% of the web depth from the face laminate.

The length of these openings shall be not greater than thedepth of the web or 60% of the secondary member spacing,whichever is greater. Details to be sent for approval.

6.2.9 The corners of all openings are to be well rounded,with the openings supported on all sides. Openings ondecks are to be supported by beams and deck girdersarranged on the edges.

The edges of cut-outs for openings in single-skin laminatesare to be well sealed. Where they are exposed to liquids orto humid environments, they are to be sealed with two lay-

ers of mat of 450 g/m2 or its equivalent.

The edges of cut-outs for openings in sandwich laminatesare to be closed with a stiffener of thickness not less thanthat of the external skin. If no epoxide resin is used for thelamination, the first layer of such laminate is to be applied

with a mat of mass not exceeding 450 g/m2.

6.2.10 Pipes and cables passing through spaces filled withexpanded material are to be situated in plastic conduits soas to make removal and replacement easier.

6.2.11 The joints of the single layers of reinforcement of alaminate are to be overlap joints (see Figures 1, 2 and 3)and the joint of each layer is to be staggered with respect tothe two adjacent layers.

Figure 1 : Hull centreline structure

Figure 2 : Open type skeg

Bottom Keel

Bottom

Connectionzone


Pt B, Ch 4, Sec 1

Figure 3 : Typical transom boundaries

Figure 1: typycal for yachts fitted with skeg . Where a skegis not fitted, a centre line stiffener/girder is to be added.

Figure 2: open skeg If a deeper open skeg is provided, dia-phragm plates with upper closing flange may be required,with skeg filled up with foam.

Figure 3: Typical transom boundaries.

6.2.12 As far as the side shell and bottom shell connectionconcerns, a chine reinforcement shall always be provided;a structural foam infill shall be provided between the sideshell and the bottom shell along the chine line. Chine railsare to be over laminated on the inner surface of the hull. Incase of sandwich structures, they shall be returned to singleskin laminates al chine rail. Chine details are to be submit-ted for approval (enclosed to the drawing "typical Details").

6.3 Connections of laminates

6.3.1 GeneralConnections of laminates are to be made with joints that donot affect the strength and structural continuity of the lami-nates themselves.

Before proceeding with any connection the surfaces onwhich the layers are placed are to be cleaned thoroughlyand then brushed with a wire brush in order to raise thefibres of the laminate as much as possible. If a surface iscovered by gel coat, this is to be removed completely.

Laminates may be connected mechanically with corrosionresistant bolts, rivets or screws spaced at intervals such asnot to affect the effectiveness of the joint. Thin washers oflarge diameter are to be used under both the head and thenut of the bolts. An adhesive of suitable type having sealingcharacteristic may be incorporated within the joint. In anycase, the edges of the laminate and the holes are to be ade-quately sealed.

6.3.2 Butt-jointsButt joints are to be carried out as shown in Figure 4, whichis relevant to the joint of the keel of a prefabricated hull inhalves.

Figure 4

6.3.3 Hull to deck connection

Examples of watertight connection, of overlap type, for theconnection of an upper deck to a separately prefabricatedhull side are shown in Figures 5 and 6. Different solutionsmay be accepted.

The connection is obtained interposing, between the con-tact areas of the laminates to be joined, a compliant resin(or similar sealing adhesive product) and a mat on resin andoverlapping the joint itself, e.g. on the internal side of thehull, a butt strap made of laminate having a thickness notless than half of the lesser of the two laminates.

As an alternative to such a butt strap, a bolt connection maybe adopted, generally using steel bolts or rivets having adiameter d not less than the lesser thickness of the laminatesto be connected, spacing equal to 10 d and zigzag distribu-tion.

The head and the nut of the bolts and the riveting of rivetsare to be against a thin washers of large diameter. An adhe-sive of suitable type having sealing characteristic may beincorporated within the joint. In any case, the edges of thelaminate and the holes are to be adequately sealed and boltnuts are to remain securely fastened after tightening.

In narrow spaces, such as the stem in the zone of connec-tion between the deck and the hull, below the bulwark,dedicated holes are to be cut in order to reach the space tobe laminated.

Figure 5

B / 10 min


Pt B, Ch 4, Sec 1

Figure 6

6.3.4 House/Deck connectionAdequate support under the ends of houses is to be pro-vided in the form of webs, pillars or bulkheads in conjunc-tion with reinforced deck beams. The connection of thehouse to the deck is to be done avoiding stress concentra-tion and providing an adequate load distribution

6.3.5 Corner jointsCorner joints are normally used to connect stiffeners to plat-ing (longitudinals, frames, internal mouldings etc.) or forboundary connections of bulkheads (see Figure 7).

Figure 7

The scantlings of such connections are to be as follows:

• Ω shaped stiffeners: plate laminate connected to platinghaving a width not less than 50 mm (25 mm for the first

layer) plus 20 mm for each: 1000 g/m2 of subsequentlayers;

a) b) c)

d)

Seam accessiblefrom one side only

Pre-fabricatedsection


Pt B, Ch 4, Sec 1

• other stiffeners: two angle bars, each having side andscantlings as above except where stiffeners are of ply-wood, in which case the angle bars are to have a thick-ness not less than 0,25 t, t being the thickness of theplywood, but in any case no less than 2 mm;

• bulkheads: connections to the plating by means of twoangle bars, one on each side and each having:• side = 50 mm for the first layer plus 40 mm for each

1000 g/m2 of the subsequent layers;• thickness = 2 mm, or if greater, = 0,5 tmin, where tmin

is the lesser thickness of the layers to be connected.

The thickness of such angle bars, in the case of plywoodbulkheads, is to be equal to 2 mm or, if greater, equal to0,25 t, t being the thickness of the plywood.

Where access is not possible from one side, the only anglebar fitted is to have scantlings equivalent to those of the twoangle bars mentioned above.

The bulkheads to hull connections shall be realized by fill-ing with compliant resin or similar filler the contact zonebetween hull (girders and/or floors) and the bulkhead. Samearrangement in the upper connection between bulkheadand deck. Furthermore, the core of the stiffeners abovewhich the bulkheads are fitted is recommended to be ofhigh density type in way of the bulkheads.

Details of the compliant resins for structural filleting appli-cation to be used in the construction and the over bondingis to be submitted. Characteristics of compliant resins to beenclosed to the list required in par 3.1.1.

6.4 Engine exhaust

6.4.1 Engine exhaust discharge arrangements made oflaminates are to be of the water injection type with a nor-mal service temperature of approximately 70° C and a max-imum temperature not exceeding 120° C.

6.4.2 The resins used for the lamination are to be typeapproved and to have adequate resistance to heat and tochemical agents as well as a high deflection temperature.As a general rule, the exhaust ducts are to be internallycoated with two layers of mat of 600 g/m2 laminated withvinylester resin; a flame-retardant or self-extinguishing poly-ester resin with a low deflection at high temperature may beaccepted. Details of these resins are to be enclosed to thelist required in par 3.1.1 and general characteristic to bereported on relevant drawings.

6.4.3 Additives or pigments which may impair themechanical properties of the resin are not to be used.

6.4.4 laminated with a flame-retardant or self-extinguishingpolyester resin.

6.5 Tanks for liquids

6.5.1 Structural tanks, i.e. those that are part of the hulland intended to contain fuel oil or lube oil, are to be madefrom single-skin laminates. Minimum thickness is to be notless than 10 mm. For other tanks, the minimum allowedthickness of single skin laminates is 4,5mm.

The tank is to be isolated from the rest of the hull by meansof diaphragms made of laminates arranged inside all the(longitudinal and/or transverse) stiffeners such that, in theevent of damage to the stiffener laminate, the liquid con-tained cannot leak (from inside the stiffener) outside thetank.

Sandwich type laminates may be accepted subject to condi-tions laid down by RINA, and provided that, in any case,the thickness of the inner skin in contact with the liquid isnot less than 10 mm and that internal diaphragms arearranged separating the tank from the rest of the hull.

Internal structure and laminate are to be coated with a resinresistant to hydrocarbons and externally with one which isself-extinguishing, both resins being certified by the Manu-facturer (details of these resins to be enclosed to the listrequired in par 3.1.1).

Mechanical tests are to be carried out on samples of thelaminate "as is" shall be and after immersion in the fuel oilat ambient temperature for a week. After immersion themechanical properties of the laminate are to be not lessthan 80% of the values of the samples "as is". The samplesshall be sealed the on all sides (with the hydrocarbonsresistant resin or gealcoat as used in the construction) inorder to have produce a good tests.

The edges of the samples are to be adequately sealed inorder to prevent the infiltration of fuel oil inside the lami-nate.

6.5.2 Where the tank is formed by plywood bulkheads, itssurface is to be completely protected against the ingress ofliquid by means of a layer of laminate of thickness of atleast 4 mm.

6.5.3 Tanks, complete with all pipe connections, are to besubjected to a hydraulic pressure test with a head above thetank top equal to h, as defined in Chap. 1, Sec. 5, or to theoverflow pipe, whichever is the greater.



Pt B, Ch 4, Sec 2

SECTION 2 MATERIALS

1 General

1.1

1.1.1 In addition to those in this Section, provisionsregarding the characteristics and test and quality controlprocedures for the manufacture of composite materials arealso specified in Part D, Chap 6 of these Rules.

1.1.2 The basic laminate considered in this Chapter iscomposed of an unsaturated resin, in general polyester, andof glass fibre reinforcements in the form of mat alternatedwith woven roving. The construction may consist of a sin-gle-skin laminate, a sandwich laminate, or a combination ofboth.

The reinforcement contained in the laminate is not less than30% by weight; it is laid-up by hand, by mechanical pre-impregnation, or by spraying.

Laminates having a different composition or special systemsof lay-up will be considered by RINA on a case-by-casebasis upon submission of technical documentation illustrat-ing details of the procedure.

All of the materials making up the laminates are to haveproperties suitable for marine use in the opinion of theManufacturer. The products used in the production of thelaminates, whether single-skin or sandwich (resins, rein-forcements, stiffeners, cores, etc.), are to be type approvedby RINA; any structural parts in plywood are to be madewith material type approved by RINA. At the discretion ofthe latter, material type approved by other recognised Soci-eties may be accepted.

2 Definitions and terminology

2.1

2.1.1

Mat : Reinforcements made up of regu-larly distributed filaments on theflat with no particular orientationand held together by a bond so asto form a mat that can be rolledup. The filaments may be cut to apre-determined length or continu-ous.

Roving : Made up of parallel filaments.

Woven Roving : Made from the weaving of roving.Due to their construction theyhave continuous filaments.Woven rovings of different typesexist and can be differentiated by:the type of roving used in warp

and weft, the name of the distri-bution per unit of length, respec-tively in warp and weft.

Mat -woven Roving : Combined reinforcement madeup of a layer of mat with cut fila-ments superimposed on a layer ofwoven roving by stitching orbonding.

Hybrid : Reinforcement having fibres oftwo or more different types; a typ-ical example is that of glass fibrewith aramid type fibre.

Unidirectional : Reinforcement made up of fibresthat follow only one directionwithout interweaving.

Biaxial : Reinforcement made up of fibresthat follow two directions (0°-90°), without interweaving.

Quadriaxial : Reinforcement made up of paral-lel fibres in the direction of fillingand warp (0°, 90°) and in twooblique directions (+ 45°).

3 Materials of laminates

3.1 Resins

3.1.1 Resins used are to be of type approved by RINA formarine use.

Resins may be for laminating, i.e. form the matrix of lami-nates, or for surface coating (gel coat); the latter are to becompatible with the former, having mainly the purpose ofprotecting the laminate from external agents.

Polyester-orthophthalic type gel coat resins are not permit-ted. In the case of a hull constructed with a sandwich lami-nate on a male mould, the water resistance of the externalsurface will be the subject of special consideration.

Resins are to have the capacity for "wetting" the fibres of thelaminate and for bonding them in such a way that the lami-nate has suitable mechanical properties and, in the case ofglass fibre, not less than those indicated in 3.6.

The resins used are in general of the polyester, polyestervi-nylester or epoxide type; in any case, the resin is to have anultimate elongation of not less than 3,0% if on the surfaceand 2,5% if in the laminate.

Compliant resins used in different structural applicationsare, as a general rule, to be used always in conjunction withover bonding lamination. The acceptance of structural fil-lets of compliant resins alone, without over bonding lami-nation will be subject to special consideration after analysis


Pt B, Ch 4, Sec 2

of test results submitted by the manufacturer demonstratingequivalent strength to over bonding laminates.

Resins are to be used within the limits and following theinstructions supplied by the Manufacturer.

3.1.2 Resins additivesResin additives (catalysts, accelerators, fillers, wax additivesand colour pigments) are to be compatible with the resinsand suitable for their curing process. Catalysts which initi-ate the curing process of the resin and the acceleratorswhich govern the gelling and setting times are to be suchthat the resin sets completely in the environmental condi-tions in which manufacture is carried out. The Manufac-turer's recommendations for the level of catalyst andaccelerator to be mixed into the resins are to be followed.

The inert fillers are not to significantly alter the properties ofthe resin, with particular regard to the viscosity, and are tobe carefully mixed distributed in the resin itself in such away that the laminates have the minimum mechanicalproperties stated in these requirements.

Such fillers are not to exceed 13% (including 3% of anythixotropic filler) by weight of the resins.

The color pigments are not to affect the polymerizationprocess of the resin, are to be added to the resin as acolored paste and are not to exceed the maximum amount(in general 5%) recommended by the Manufacturer. Thethixotropic fillers of the resins for surface coating are not toexceed 3% by weight of the resin itself.

Details of the resins additives are to be enclosed in the listrequired in Sec 1, par 3.1.1.

3.1.3 Flame-retardant additivesWhere the laminate is required to have fire-retarding orflame-retardant characteristics, details of the proposedarrangements are to be submitted for examination.

Where additives are adopted for this purpose, they are to beused in accordance with the Manufacturer's instructions.

The results of tests performed by independent laboratoriesverifying the required characteristics are to be submitted.

Where fire-retarding or flame-retardant characteristics arerequired by the flag Administration, such properties are tobe approved by the relevant Administration, or by RINAwhen authorized by the former.

Details of flame-retardant additives are to be enclosed inthe list required in Sec 1, par 3.1.1.

3.2 Reinforcements

3.2.1 GeneralAll fibre reinforcements are to be of type approved byRINA. The reinforcement used and their characteristics areto be enclosed to the list required in Sec 1 par 3.1.1.

The reinforcements taken into consideration in theserequirements are mainly of fibres of three types: glass fibre,aramid type fibre and carbon type fibre.

The use of hybrid reinforcements obtained by coupling theabove-mentioned fibres is also foreseen.

Structures can be obtained using reinforcements of one ormore of the above-mentioned materials.

In the latter case the laminates may be made in alternatelayers, i.e. made up of layers of one material or using hybridreinforcements.

In any event, the manufacturing process is to be approvedin advance by RINA, and to this end a technical report is tobe sent illustrating the processes to be followed and thematerials (resins, reinforcements, etc.) used.

Reinforcements made of materials other than the precedingmay be taken into consideration on a case-by-case basis byRINA, which will stipulate the conditions for their accept-ance.

The materials are to be free from imperfections, discolora-tion, foreign bodies, moisture and other defects and storedand handled in accordance with the manufacturer's recom-mendations.

3.2.2 Glass fibreThe glass generally used for the manufacture of reinforce-ments is that called type "E", having an alkali content of notmore than 1%, expressed in Na2O.

Reinforcements manufactured in "S" type glass may also beused.

Such reinforcements are to be used for the lamination inhull resin matrices, with the procedure foreseen by theManufacturer, such that the laminates have the samemechanical properties required in the structural calcula-tions and for "E" type glass, these not being less than thoseindicated in 3.6.

Reinforcements in glass fibre are generally foreseen in theform of: continuous filament or chopped strand mat, roving,unidirectional woven roving and in combined products i.e.made up of both mat and roving.

3.2.3 Aramid type fibresReinforcements in aramid type fibres are generally used inthe form of roving or cloth of different weights (g/m2).

Such reinforcements can be used in the manufacture ofhulls either alone or alternated with layers of mat or rovingof "E" type glass.

Hybrid reinforcements, in which the aramid type fibres arelaid at the same time, in the same layer as "E" type glassfi-bres or carbon type fibres, may also be used.

3.2.4 Carbon-graphite fibresCarbon-graphite type fibres means those which are atpresent called "carbon" type, used in the form of productssuitable to be incorporated as reinforcements by themselvesor together with other materials like glass fibres or aramidtype fibres, in resin matrices for the construction of struc-tural laminates.

3.3 Core materials for sandwich laminates

3.3.1 Core materials are to be of type approved by RINA;these materials shall be used in accordance with manufac-turer's instructions and the method used in the sandwichconstruction shall be forwarded for information purposesenclosed to the list required in Sec 1, par 3.1.1.

The materials considered in these requirements are rigidexpanded foam plastics and balsa wood.


Pt B, Ch 4, Sec 2

Particular care is to be given to the handle of these materi-als which shall be in accordance to the manufacturer's rec-ommendations.

The use of other materials will be taken into considerationon a case-by-case basis by RINA, which will decide theconditions for acceptance on the basis of a criterion ofequivalence.

Polystyrene can only be used as buoyancy material.

3.3.2 "Rigid expanded foam plastics" means expandedpolyurethane (PUR) and polyvinyl chloride (PVC).

These materials, just as other materials used for cores, are tobe of the closed-cell type, resistant to environmental agents(salt water, fuel oils, lube oils) and to have a low absorptionof water characteristics.

Furthermore, they are to maintain a good level of resistanceup to the temperature of 60°C, and if worked in nonrigidsheets made up of small blocks, the open weave backingand the adhesive are to be compatible and soluble in theresin of the laminate.

3.3.3 Balsa wood is to be chemically treated againstattacks by parasites and mould and oven dried immediatelyafter cutting.

Its humidity is to be no greater than 12%; if worked in non-rigid sheets made up of small blocks, the open weave back-ing and the adhesive are to be compatible and soluble inthe resin of the laminate.

The balsa wood is to be laid-up with its grain at right-anglesto the fibres in the surface laminates.

3.3.4 The ultimate tensile strength of the core materials isto be not less than the values indicated in Table 1. Suchcharacteristic is to be ascertained by tests; in any case, corematerials for laminates having an ultimate tensile strength<0,4 N/mm2 are not acceptable.

3.3.5 For the constructions of sandwich structures with thedry vacuum bagging techniques core bonding paste are tobe used; their characteristics are to be enclosed in the list asper Sec 1, par 3.1.1. The construction procedures of suchsandwich structures will be subject to special considera-tion.

Table 1

3.4 Adhesive and sealant material

3.4.1 These materials are to be accepted by RINA beforeuse. Detail to be submitted enclosed to the list required inSec 1 par 3.1.1.

3.5 Plywood

3.5.1 Plywood for structural applications is to be marineplywood type approved by RINA.

Where it is used for the core of reinforcements or sandwichstructures, the surfaces are to be suitably treated to enablethe absorption of the resin and the adhesion of the laminate.

3.6 Timber

3.6.1 The use of timber is subject to special considerationby Head Office. In general, the designer will have to indi-cate on submitted drawings the assumed characteristicssuch as strength and density.

3.7 Repair compounds

3.7.1 Materials used for repairs are to be accepted byRINA before use.

For acceptance purposes, the manufacturer is to submit fullproduct details, and user instructions, listing the types ofrepair for which the system is to be used.

Dependent on the proposed uses, RINA may require sometests.

3.8 Type approval of materials

3.8.1 Recognition by RINA of the suitability for use (typeapproval) of materials for hull construction may berequested by the Manufacturer. The type approval of res-ins, fibre products of single-skin laminates and core materi-als of sandwich laminates is carried out according to therequirements set out in the relevant RINA Rules.

Table 2 lists the typical mechanical properties of fibrescommonly used for reinforcements.

4 Mechanical properties of laminates

4.1 General

4.1.1 The minimum mechanical properties in N/mm2 oflaminates made with reinforcements of "E" type glass fibremay be obtained from the formulae given in Table 3 as afunction of GC of the laminate as defined in Section 1.

These values are based on the most frequently used lami-nates made up of reinforcements of mat and roving type.

In the above-mentioned Table, the values indicated arethose corresponding to GC = 30, the minimum valueallowed of the content of glass reinforcement.

The minimum mechanical properties of the glass laminatesfound in testing, as a function of GC, are to be no less thanthe values obtained from the formulae of the above-men-tioned Table.

Materiale Density (kg/m3)Ultimate tensile

strength (N/mm2)

Balsa

96 1,1

144 1,64

176 2,1

Polyvinyl chloride (PVC)

55 0,73

90 1,3

Polyurethane(PUR)

60 0,4

90 0,5


Pt B, Ch 4, Sec 2

Laminates with reinforcements of fibres other than glass,described in 3.2, are to have mechanical properties that arein general greater than or at least equal to those given inTable 3, the reinforcement content being equal. RINAreserves the right to take into consideration possible lami-nates having certain properties lower than those given inTable 3, and will establish the procedures and criteria forapproval on case by case.

The scantlings indicated in this Chapter are based on thevalues of the mechanical properties of a laminate madewith reinforcements in "E" type glass, with a reinforcementcontent equal to 0,30.

Whenever the mechanical properties of the reinforcementare greater than those mentioned above, the scantlings maybe modified in accordance with the provisions of 3.6.2below.

The mechanical properties and the percentage of reinforce-ment are to be ascertained, for each yacht built, from testson samples taken preferably from the hull or, alternatively,having the same composition and prepared during the lam-ination of the hull ( for the tests to be carried out, s ee Pt D,Ch 6, Sec.3).

Table 2

Table 3

The values of the mechanical properties are to be no lessthan those used for the scantling of the structures.

Where certain values are in fact found to be lower thanthose used for the scantlings, but no lower than 85% of thelatter, RINA reserves the right to accept the laminate subjectto any conditions for acceptance it may stipulate.

4.2 General

4.2.1 Coefficients relative to the mechanical properties of laminates

The values of the coefficients Ko and Kof relative to themechanical properties of the laminates that appear in theformulae of the structural scantlings of the hull in this Chap-ter are given by:

Specific gravityTensile modulus of elastic-

ity N/mm2

Shear modulus of elasticity N/mm2 Poisson’s ratio

E Glass 2,56 69000 28000 0,22

S Glass 2,49 69000 (1) 0,20

R Glass 2,58 (1) (1) (1)

Aramid 1,45 124000 2800 0,34

LM Carbon 1,8 230000 (1) (1)

IM Carbon 1,8 270000 (1) (1)

HM Carbon 1,8 300000 (1) (1)

VHM Carbon 2,15 725000 (1) (1)

(1) Values supplied by the Manufacturer and agreed upon with RINA prior to use

1 2

Rm = ultimate tensile strength = 1278 G2c - 510 Gc + 123 85

E = tensile modulus of elasticity = (37 Gc - 4,75) . 103 6350

Rmc = ultimate compressive strength = 150 Gc + 72 117

Ec = compressive modulus of elasticity = (40 Gc - 6) . 103 6000

Rmf = ultimate flexural strength = (502 G2c + 107) 152

Et = flexural modulus of elasticity = (33,4 G2c + 2,2) . 103 5200

Rmt = ultimate shear strength = 80 Gc + 38 62

G = shear modulus of elasticity = (1,7 Gc + 2,24) . 103 2750

Rmti = ultimate interlaminar shear strength = 22,5 - 17,5 Gc 17

Ko 85 Rm⁄=


Pt B, Ch 4, Sec 2

where Rm and Rmf are the values, in N/mm2, of the ultimatetensile and flexural strengths of the laminate. Such valuesmay be calculated with the formulae in Table 3 for glassfibre reinforcements or obtained from mechanical tests onsamples of the laminate for other types of laminate.

Therefore, in the case of laminates with glass fibre havingGC = 30 (minimum allowed), it Is to be assumed that::

The values Ko and Kof are to be taken as not less than 0,5and 0,7, respectively, except in specific cases consideredby RINA on the basis of the results of tests carried out.

For laminates of sandwich type structures the coefficient isgiven by the formula:

where Rm is the ultimate tensile strength, in N/mm2, of thesurface laminate.

Kof152Rmf

----------⎝ ⎠⎛ ⎞

0 5,

=

Ko 1=

Kof 1=

Kof′ 85

Rm

------⎝ ⎠⎛ ⎞

0 5,

=


Pt B, Ch 4, Sec 3

SECTION 3 CONSTRUCTION AND QUALITY CONTROL

1 Shipyards or workshops

1.1 General

1.1.1 All construction are to be built using materials andworking process approved or accepted by RINA.

The Builder has to obtain the approval or acceptance of thematerials he uses; furthermore it is the Builder responsibilityto ensure that all the materials are used in accordance withthe manufacturer's instruction and recommendations.

Shipyards or workshops for hull construction are to be suit-ably equipped to provide the required working environ-ment according to these requirements, which are to becomplied with for the recognition of the shipyard or work-shop as suitable for the construction of hulls in reinforcedplastic. This suitability is to be ascertained by a RINA Sur-veyor, the responsibility for the fulfilment of the require-ments specified below as well as all other measures for theproper carrying out of construction being left to the ship-yard or workshop.

When it emerges from the tests carried out that the shipyardor workshop complies with the following provisions, usestype approved materials, and has a system of productionand quality control that satisfies the RINA Rules, so as toensure a consistent level of quality, the shipyard or work-shop may obtain from RINA a special recognition of suita-bility for the construction of reinforced plastic hulls.

The risks of contamination of the materials are to bereduced as far as possible; separate zones are to be pro-vided for storage and for manufacturing processes. Alterna-tive arrangements of the same standard may be adopted.

Compliance with the requirements of this Section does notexempt those in charge of the shipyard or workshop fromthe obligation of fulfilling all the hygiene requirements forwork stipulated by the relevant authorities.

1.2 Moulding shops

1.2.1 Where hand lay-up or spray lay-up processes areused for the manufacture of laminates, a temperature ofbetween 16° and 32°C is to be maintained in the mouldingshop during the lay-up and polymerisation periods. Smallvariations in temperature may be allowed, at the discretionof the RINA Surveyor, always with due consideration beinggiven to the resin Manufacturer's recommendations.Where moulding processes other than those mentionedabove are used, the temperatures of the moulding shop areto be established accordingly.

The relative humidity of the moulding shop is to be kept aslow as possible, preferably below 70%, and in any caselower than the limit recommended by the resin Manufac-turer. Significant changes in humidity, such as would lead

to condensation on moulds and materials, are to beavoided.

Instruments to measure the humidity and temperature are tobe placed in sufficient number and in suitable positions. Ifnecessary, due to environmental conditions, an instrumentcapable of providing a continuous readout and record ofthe measured values may be required.

Ventilation systems are not to cause an excessive evapora-tion of the resin monomer and draughts are to be avoided.

The work areas are to be suitably illuminated. Precautionsare to be taken to avoid effects on the polymerisation of theresin due to direct sunlight or artificial light.

1.3 Storage areas for materials

1.3.1 Resins are to be stored in dry, well-ventilated condi-tions at the temperature recommended by the resin Manu-facturer. If the resins are stored in tanks, it is to be possibleto stir them at a frequency for a length of time indicated bythe resin Manufacturer. When the resins are stored outsidethe moulding shop, they are to be brought into the shop indue time to reach the working temperature required beforebeing used.

Catalysts and accelerators are to be stored separately inclean, dry and well-ventilated conditions in accordancewith the Manufacturer's recommendations.

Fillers and additives are to be stored in closed containersthat are impervious to dust and humidity.

Reinforcements, e.g. glass fibre, are to be stored in dust-freeand dry conditions, in accordance with the Manufacturer'srecommendations. When they are stored outside the cut-ting area, the reinforcements are to be brought into the lat-ter in due time so as to reach the temperature of themoulding shop before being used.

Pre-impregnated reinforcements are to be stored in an areaset aside for the purpose. The quality control documenta-tion is to keep a record of the storage and depletion of thestock of such reinforcements.

Materials for the cores of sandwich type structures are to bestored in dry areas and protected against damage; they areto be stored in their protective covering until they are used.

1.4 Identification and handling of materials

1.4.1 In the phases of reception and handling the materialsare not to suffer contamination or degradation and are tobear adequate identification marks at all times, includingthose relative to RINA type approval. Storage is to be soarranged that the materials are used, whenever possible, inchronological order of receipt. Materials are not to be usedafter the Manufacturer's date of expiry, except when the lat-ter has given the hull builder prior written consent.


Pt B, Ch 4, Sec 3

2 Hull construction processes

2.1 General

2.1.1 The general requirements for the construction ofhand lay-up or spray lay-up laminates are set out below;processes of other types (e.g. by resin transfer, vacuum orpressurised moulding with mat and continuous filaments)are to be individually recognised as suitable by RINA.

2.2 Moulds

2.2.1 Moulds for production of laminates are to be con-structed with a suitable material which does not affect theresin polymerisation and are to be adequately stiffened inorder to maintain their shape and precision in form. Theyare also not to prevent the finished laminate from beingreleased, thus avoiding cracks and deformations. During construction, provision is to be made to ensure sat-isfactory access such as to permit the proper carrying out ofthe laminating.

Moulds are to be thoroughly cleaned, dried and brought tothe moulding shop temperature before being treated withthe mould release agents, which are not to have an inhibit-ing effect on the gel coat resin.

2.3 Laminating

2.3.1 The gel coat is to be applied by brush, roller orspraying device so as to form a uniform layer with a thick-ness of between 0,4 and 0,6 mm. Furthermore, it is not tobe left exposed for longer than is recommended by theManufacturer before the application of the first layer of rein-forcement. A lightweight reinforcement, generally not exceeding amass per area of 300 g/m2, is to be applied to the gel coatitself by means of rolling so as to obtain a content of rein-forcement not exceeding approximately 0,3.

In the case of hand lay-up processing, the laminates are tobe obtained with the layers of reinforcement laid in thesequence indicated in the approved drawings and eachlayer is to be thoroughly "wet" in the resin matrix and com-pacted to give the required weight content.

The amount of resin laid "wet on wet" is to be limited toavoid excessive heat generation.

Laminating is to be carried out in such a sequence that theinterval between the application of layers is within the lim-its recommended by the resin Manufacturer.

Similarly, the time between the forming and bonding ofstructural members is to be kept within these limits; wherethis is not practicable, the surface of the laminate is to betreated with abrasive agents in order to obtain an adequatebond.

When laminating is interrupted so that the exposed resingels, the first layer of reinforcement subsequently laid is tobe of mat type.

Reinforcements are to be arranged so as to maintain conti-nuity of strength throughout the laminate. Joints betweenthe sections of reinforcement are to be overlapped and stag-gered throughout the thickness of the laminate.

In the case of simultaneous spray lay-up of resin and cutfibres, the following requirements are also to be compliedwith:

• before the use of the simultaneous lay-up system, theManufacturer is to satisfy himself of the efficiency of theequipment and the competence of the operator;

• the use of this technique is limited to those parts of thestructure to which sufficiently good access may beobtained so as to ensure satisfactory laminating;

• before use, the spray lay-up equipment is to be cali-brated in such a way as to provide the required fibrecontent by weight; the spray gun is also to be calibrated,according to the Manufacturer's instruction manual,such as to obtain the required catalyst content, the gen-eral spray conditions and the appropriate length of cutfibres. Such length is generally to be not less than 35mm for structural laminates, unless the mechanicalproperties are confirmed by tests; in any event, thelength of glass fibres is to be not less than 25 mm;

• the calibration of the lay-up system is to be checkedperiodically during the operation;

• the uniformity of lamination and fibre content is to besystematically checked during production.

The manufacturing process for sandwich type laminates istaken into consideration by RINA in relation to the materi-als, processes and equipment proposed by the Manufac-turer, with particular regard to the core material and to itslay-up as well as to details of connections between prefabri-cated parts of the sandwich laminates themselves. The corematerials are to be compatible with the resins of the surfacelaminates and suitable to obtain strong adhesion to the lat-ter (Manufacturer’s instructions to be followed).

Attention is drawn, in particular, to the importance ofensuring the correct carrying out of joints between panels.

Where rigid core materials are used, then dry vacuum bag-ging techniques are to be adopted. Particular care is to begiven to the core bonding materials and to the holes pro-vided to ensure efficient removal of air under the core.Bonding paste is to be visible at these holes after vacuumbagging.

2.4 Hardening and release of laminates

2.4.1 On completion of the laminating, the laminate is tobe left in the mould for a period of time to allow the resin toharden before being removed. This period may vary,depending on the type of resin and the complexity of thelaminate, but is to be at least 24 hours, unless a differentperiod is recommended by the resin Manufacturer.

The hull, deck and large assemblies are to be adequatelybraced and supported for removal from the moulds as wellas during the fitting-out period of the yacht.

After the release and before the application of any specialpost-hardening treatment, which is to be examined byRINA, the structures are to be stabilised in the mouldingenvironment for the period of time recommended by theresin Manufacturer. In the absence of recommendations,the period is to be at least 24 hours.


Pt B, Ch 4, Sec 3

2.5 Defects in the laminates

2.5.1 The manufacturing processes of laminates are to besuch as to avoid defects, such as in particular: surfacecracks, surface or internal blistering due to the presence ofair bubbles, cracks in the resin for surface coating, internalareas with non-impregnated fibres, surface corrugation, andsurface areas without resin or with glass fibre reinforce-ments exposed to the external environment.

Any defects are to be eliminated by means of appropriaterepair methods to the satisfaction of the RINA Surveyor.

Dimensions and tolerances are to conform to the approvedconstruction documentation.

2.5.2 The responsibility for maintaining the required toler-ances rests with the Builder.

Monitoring and random checking by the Surveyor does notabsolve the Builder from this responsibility.

2.6 Checks and tests

2.6.1 Checks and tests are to be arranged during the lami-nation process by the hull builder, in accordance with therelevant quality system, and by the RINA Surveyor.

The hull builder is to maintain a constant check on the lam-inate.

Any defects found are to be eliminated immediately.

In general the following checks and tests are to be carriedout:

a) check of the mould before the application of the releaseagent and of the gel coat;

b) check of the thickness of the gel coat and the uniformityof its application;

c) c) check of the resin and the amount of catalyst, accele-rator, hardener and various additives;

d) check of the uniformity of the impregnation of reinfor-cements, their lay-up and superimposition;

e) check and recording of the percentage of the reinforce-ment in the laminate;

f) checks of any post-hardening treatments;

g) general check of the laminate before release from themould;

h) check and recording of the laminate hardness beforerelease from the mould;

i) check of the thickness of the laminate which, in general,is not to differ by more than 15% from the thicknessindicated in approved structural plans;

j) mechanical tests on laminates taken from the hull orprepared during the lamination of the hull (in accor-dance with Pt D, Ch 6, Sec 3).

The thicknesses of the laminates are, in general, to be meas-ured at not less than ten points, evenly distributed acrossthe surface.

The above-mentioned checks and tests are to be carried outas a rule in the presence of a RINA Surveyor; where theshipyard has a system of production organisation and qual-ity control certified by RINA, the checks may be carried outdirectly by the shipyard without the presence of a RINA Sur-veyor.

2.6.2 Where ultrasonic thickness gauges are used, relevanttools are to be calibrated against an identical laminate (ofmeasured thickness).

2.6.3 As a general rule, a method of validating the com-plete laminate tickness is to be agreed between the Builderand the Surveyor.


Pt B, Ch 4, Sec 4


1 General

1.1

1.1.1 The structural scantlings prescribed in this sectionare also intended as appropriate for the purposes of the lon-gitudinal hull strength of a yacht having length L notexceeding 40 m for monohull yacht or 35 m for catamaransand openings on the strength deck of limited size. For yachts of greater length and/or openings of size greaterthan the breadth B of the hull and extending for a consider-able part of the length of the yacht, a test of the longitudinalstrength is required.

The procedures for such test will be stipulated by RINA on acase-by-case basis in relation to the quality of the laminatesand the layout of the yacht.

As a guide, the criteria used by RINA for tests of longitudi-nal hull beam strength are shown below.

1.2


2 Bending stresses

2.1

2.1.1 In addition to satisfying the minimum requirementsstipulated in the individual Chapters of these Rules, thescantlings of members contributing to the longitudinalstrength of monohull yacht and catamarans are to achieve asection modulus of the midship section at the bottom andthe deck such as to guarantee stresses not exceeding theallowable values. Therefore:

where:

Wf, Wp : section modulus at the bottom and the deck,respectively, of the transverse section in m3

MT : design total vertical bending moment defined inChap. 1, Sec. 5.



σl : the lesser of the values of ultimate tensile andultimate compressive strength, in N/mm2, of thebottom and deck laminate.

2.2

2.2.1 In order to limit the flexibility of the hull structure,the moment of inertia J of the midship section, in m4, is gen-erally to be not less than the value given by the followingformulae:

J = 200 . MT . 10-6 for planing vessesls

J = 230 . MT . 10-6 displacement yachts.

2.3 Calculation of strength modulus

2.3.1 Reference is to be made to Table 1 for plating andTable 2 for longitudinals for calculation of the midship sec-tion modulus.

Table 1

Where there is a sandwich member, the two skins of thelaminate are to be taken into account for the purposes ofthe longitudinal strength only with their own characteris-tics. The cores may be taken into account only if they offerlongitudinal continuity and appreciable strength againstaxial tension-compression.

For each transverse section within the midship region, thesection modulus, in m3, is given by:

where:

P :

A :

F :

tp, tm, tf, Ep, Em, Ef,: values defiined in Table 1

tps, tms, tfs, Eps, Ems, Efs, Ips, Ims, Ifs, tpa, tma, tfa, Epa, Ema, Efa,Hpa,Hma, Hfa, np, nm, nf: values defiined in Table2

Im, C’ : length, in m, defined in Figure 1.

σ f fσ l≤

σp fσ l≤

σ fMT

1000 Wf

----------------------- N mm2⁄=

σpMT

1000 Wp

------------------------ N mm2⁄=

Deck Side shell Bottom

Mean thickness, in mm tp tm tf

Young’s modulus, in N/mm2 Ep Em Ef

Wp1Ep

----- C' P C'6----- A 1 F P–

F 0 5 A⋅,+---------------------------+

⎝ ⎠⎛ ⎞⋅ ⋅+⋅ 10 3–⋅ ⋅=

Wf1Ef

---- C' P C'6----- A 1 F P–

F 0 5 A⋅,+---------------------------+

⎝ ⎠⎛ ⎞⋅ ⋅+⋅ 10 3–⋅ ⋅=

tp B Ep np Ips tps Eps tpa Hpa Epa⋅ ⋅+⋅ ⋅( )⋅+⋅ ⋅

2 tm Im Em nm tms Ims Ems tma Hma Ema⋅ ⋅+⋅ ⋅( )⋅+⋅ ⋅[ ]

tfB2--- Ef nf Ifs t fs Efs tfa Hfa Efa⋅ ⋅+⋅ ⋅( )⋅+⋅ ⋅


Pt B, Ch 4, Sec 4

Table 2

Figure 1

3 Shear stresses

3.1


where:

Tt : total shear stress in kN defined in Chap. 1, Arti-cle 5.4

f : defined in 2

τ : shear stress of the laminate, in N/mm2

Αt : actual shear area of the transverse section, inm2, actual shear area of the transverse section,in m2, to be calculated considering the net areaof side plating and of any longitudinal bulk-heads excluding openings.

Deck Side shell Bottom

Flange

Mean thickness, in mm tps tms tfs

Young’s modulus, in N/mm2 Eps Ems Efs

Breadth in mm Ips Ims Ifs

Web

Equivalent thickness in Section I, in mm tpa tms tfa

Young’s modulus, in N/mm2 Epa Ems Efa

Height in mm Hpa Hma Hfa

Number of longitudinals np nm nf

Tt

At

----- 10 3– f τ⋅≤⋅


Pt B, Ch 4, Sec 5

SECTION 5 EXTERNAL PLATING

1 General

1.1

1.1.1 Bottom and side plating may be made using bothsingle-skin laminate and sandwich structure.

When the two solutions are adopted for the hull, a suitabletaper is to be made between the two types.

Bottom plating is the plating up to the chine or to the upperturn of the bilge.

When the side thickness differs from the bottom thicknessby more than 3 mm, a transition zone is to be foreseen.

.


2.1

2.1.1

S : larger dimension of the plating panel, in m

s : spacing of the ordinary longitudinal or trans-verse stiffener, in m

p : scantling pressure, in kN/m2, given in Chap. 1,Sec. 5

Kof, Ko : factors defined in Sec. 2 of this Chapter.

3 Keel

3.1

3.1.1 The keel is to extend the whole length of the yachtand have a breadth bCH, in mm, not less than the valueobtained by the following formula:

The thickness of the keel is to be not less than the value tCH,in mm, obtained by the following formula:

t being the greater of the values t1 e t2, in mm, calculated asspecified in 5 assuming the spacing s of the correspondingstiffeners.

Appraising s, and dead rise edge > 12° is considered as astiffener.

The thickness tCH is to be gradually tapered transversally, tothe thickness of the bottom and in the case of hulls having aU-shaped keel, the thickness of the keel is to extend, trans-versally, as indicated in Figure 2 b) in Section 1, taperingwith the bottom plating.

In yachts with sail and ballast keel, the thickness of the keelfor the whole length of the ballast keel is to be increased by

30%; this increase is to extend longitudinally to fore and aftof the ballast for a suitable length.

When the hull is laminated in halves, the keel joint is to becarried out as shown in Figure 5 in Section 1 or in a similarway.

4 Rudder horn

4.1

4.1.1 When the rudder is of the semi-spade type, such asType I B shown in Chapter 1, Section 2, Figure 2, the rele-vant rudder horn is to have dimensions and thickness suchthat the moment of inertia J, in cm4, and the section modu-lus Z, in cm3, of the generic horizontal section of the sameskeg, with respect to its longitudinal axis are not less thanthe values given by the following formulae:

where:

A : the rudder area, in m2, acting on the horn;

h : the vertical distance, in mm, from the skeg sec-tion to the lower edge of the pintle (rudderheel);

V : maximum design speed of the yacht, in knots.

5 Bottom plating

5.1

5.1.1 The thickness of bottom plating is to be not less thanthe greater of the values t1 e t2, in mm, calculated with thefollowing formulae:

where:

k1 : 0,26, when assuming p=p1

: 0,15, when assuming p=p2.

ka : coefficient as a function of the ratio S/s given inTable 1.


The minimum bottom shell thickness is to extent to thechine line or 150mm above the statical load waterline,whichever is the greater.

bCH 30L=

tCH 1 4t,=

J A h2 V2⋅ ⋅36

------------------------10 3–=

Z A h V2⋅ ⋅55

----------------------=

t1 k1 ka s kof p0 5,⋅ ⋅ ⋅ ⋅=

t2 16 s ko f D0 5,⋅ ⋅ ⋅=


Pt B, Ch 4, Sec 5

If the plating has a pronounced curve, as for example in thecase of the hulls of sailing yachts, the thickness calculatedwith the formulae above may be reduced multiplying by (1- f/s), f being the distance, in m, between the connectingbeam and the two extremities of the plating concerned andthe surface of the plating itself. This reduction may not beassumed less than 0,70.

In sailing yachts with or without auxiliary engine in way ofthe ballast keel, when the width of the latter is greater thanthat of the keel, the thickness of the bottom is to beincreased to the value taken for the keel.

Table 1

6 Side plating and sheerstrake plating

6.1

6.1.1 A sheerstrake plate of height h, in mm, not less than0,025 L and thickness tc, in mm, not less than the value inthe following formula is to be fitted:

where t is the greater of the thicknesses t1 e t2, calculated asstated in 6.2 below.

6.2 Side plating


where k1 and ka are as defined in 5.1.


7.1


The edges of openings are to be suitably sealed in order toprevent the absorption of water.

7.2

7.2.1 Openings in the curved zone of the bilge strakesmay be accepted where the former are elliptical or fittedwith equivalent arrangements to minimise the stress con-centration effects.

7.3


8 Local stiffeners

8.1

8.1.1 The thickness of plating determined with the forego-ing formulae is to be increased locally, generally by at least50%, in way of the propulsion engine bedplates, stem (thethickness is not required to be greater than that of the keelin this case), propeller shaft struts, rudder horn or trunk, sta-bilisers, anchor recesses, etc.

8.2


8.3

8.3.1 The thickness of plating is to be locally increased inway of inner or outer permanent ballast arrangements asindicated in 3.1.1.

8.4

8.4.1 The thickness of the transom is to be not less thanthat of the side plating for the portion above the waterline,or less than that of the bottom for the portion below thewaterline.

Where water-jets or propulsion systems are fitted directly tothe transom, the scantlings of the latter will be the subject ofspecial consideration.

In such case a sandwich structure with marine plywoodcore of adequate thickness is recommended.

9 Cross-deck bottom plating

9.1

9.1.1 The thickness is to be taken, the stiffener spacing sbeing equal, no less than that of the side plating.

Where the gap between the bottom and the waterline is sosmall that local wave impact phenomena are anticipated,an increase in thickness and/or additional internal stiffenersmay be required.

S/s Ka

1 17,5

1,2 19,6

1,4 20,9

1,6 21,6

1,8 22,1

2,0 22,3

>2 22,4

tc 1 30t,=

t1 k1 ka s kof p0 5,⋅ ⋅ ⋅ ⋅=

t2 12 s ko f D0 5,⋅ ⋅ ⋅=


Pt B, Ch 4, Sec 6


1 General

1.1



1.2.1 A centre girder is to be fitted. In the case of a keelwith a dead rise > 12°, the centre girder may be omitted butin such case the fitting of a longitudinal stringer is required.

Where the breadth of the floors exceeds 6 m, sufficient sidegirders are to be fitted so that the distance between themand the centre girder or the side does not exceed 3 m.





1.3.2 A centre girder is to be fitted. In the case of a keelwith a dead rise > 12°, the centre girder may be omitted butin such case the fitting of a longitudinal stringer is required.

Where the breadth of the floors exceeds 6 m, sufficient sidegirders are to be fitted so that the distance between themand the centre girder or the side does not exceed 3 m.



1.3.5 Floors are to be fitted in way of reinforced frames atthe sides and reinforced deck beams.

Any intermediate floors are to be adequately connected tothe ends


2.1

2.1.1


p : scantling pressure, in kN/m2, given in Chap. 1,Sec.5;

Ko : coefficient defined in Sec. 2 of this Chapter.



3.1.1 The section modulus of longitudinal stringers is to benot less than the value Z, in cm2, calculated with the fol-lowing formula:

where:


: 1 assuming p=p2


3.2 Floors


where:

k1 : 2,4 assuming p = p1

1,2 assuming p = p2


S : conventional floor span equal to the distance,in m, between the two supporting members(sides, girders, keel with a dead rise edge >12°).

In the case of a U-shaped keel or one with a dead rise edge≤12° but > 8° the span S is always to be calculated consid-ering the distance between girders or sides; the modulus ZM

may, however, be reduced by 40%.


Z k1 s S2 Ko p⋅ ⋅ ⋅ ⋅=

ZM k1 b S2 Ko p⋅ ⋅ ⋅ ⋅=


Pt B, Ch 4, Sec 6

3.3 Girders

3.3.1 Centre girder


where:


b’PC : half the distance, in m, between the two sidegirders if supporting or equal to B/2 in theabsence of supporting side girders



where:


b’PC : half the distance, in m, between the two sidegirders if present or equal to B/2 in the absenceof side girders


3.3.2 Side girders


where:


b’PL : half the distance, in m, between the two adja-cent girders or between the side and the girderconcerned



where:



S : distance between the floors, in m.


4.1 Ordinary floors


where:

k1 : defined in 3.1


4.2 Centre girder


where:

k1 : defined in 3.2



4.3 Side girders

4.3.1 The section modulus is to be not less than the valueZPL, in cm3, calculated with the following formula:

where:

k1 : defined in 3.2




5.1


ZPC k1 bPC S2 Ko p⋅ ⋅ ⋅ ⋅=

ZPC k1 bPC′ S2 Ko p⋅ ⋅ ⋅ ⋅=

ZPL k1 bPL′ S2 Ko p⋅ ⋅ ⋅ ⋅=

ZPL k1 bPL′ S2 Ko p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 Ko p⋅ ⋅ ⋅ ⋅=

ZPC k1 bPC S2 Ko p⋅ ⋅ ⋅ ⋅=

ZPL k1 bPL S2 Ko p⋅ ⋅ ⋅ ⋅=


Pt B, Ch 4, Sec 7


1 General

1.1




1.1.2 The fitting of a double bottom extending from thecollision bulkhead to the forward bulkhead of the machin-ery space, or as near thereto as practicable, is requested foryacht of L > 50 m.







The edges of the holes are to be suitably sealed in order toprevent the absorption of liquid into the laminate.



2 Minimum height

2.1

2.1.1 The height of the double bottom is to be sufficient toallow access to all areas and, in way of the centre girder, isto be not less than the value hdF, in mm, obtained from thefollowing formula:

The height of the double bottom is in any event to be notless than 700 mm. For yacht less than 50 m in length RINAmay accept reduced height.


3.1

3.1.1 The thickness of the inner bottom plating is to be notless than the value t1, in mm, calculated with the followingformula:

where:

s : spacing of the ordinary stiffeners, in m

kof : coefficients for the properties of the materialdefined in Sec. 2.

For yachts of length L <50 m the thickness is to be main-tained throughout the length of the hull.


Where the inner bottom forms the top of a tank intended forliquid cargoes, the thickness of the top is also to complywith the provisions of Sec. 10.

4 Centre girder

4.1

4.1.1 A centre girder is to be fitted, as far as this is practi-cable, throughout the length of the hull.

The thickness of the core of a sandwich type centre girder isto be not less than the following value tpc, in mm:

where kof is defined in Sec. 2.

Where a single-skin laminate is used for the centre girder,the thickness is to be not less than twice that defined above.

hdf 28B 32 T 10+( )+=

t1 1 3 0 04L, 5s 1+ +( )kof for gle skin laminate–sin,=

t1 0 04L, 5s 1+ +( )kof for sandwich laminate=

tpc 0 125L, 3 5,+( )kof=


Pt B, Ch 4, Sec 7

5 Side girders

5.1

5.1.1 Where the breadth of the floors does not exceed 6m, side girders need not be fitted.

Where the breadth of the floors exceeds 6 m, side girdersare to be arranged with thickness equal to that of the floors.



Watertight girders are to have thickness not less than thatrequired in Sec. 10 for tank bulkheads

5.2





6 Floors

6.1

6.1.1 The thickness of the core of sandwich type floors tm,in mm, is to be not less than the following value:

where kof is defined in Sec. 2.

Where a single-skin laminate is used for floors, the thick-ness is to be not less than twice that calculated above.

Watertight floors are also to have thickness not less thanthat required in Sec. 10 for tank bulkheads.

6.2

6.2.1 When the height of a floor exceeds 900 mm, verticalstiffeners are to be arranged. In any event, solid floors or equivalent structures are to bearranged in longitudinally framed double bottoms in the fol-lowing locations.• under buklheads and pillars• outside the machinery space at an interval no greater

than 2 m• in the machinery space under the bedplates of main

engines• in way of variations in height of the double bottom.

Solid floors are to be arranged in transversely framed dou-ble bottoms in the following locations:• under bulkheads and pillars• in the machinery space at every frame • in way of variations in height of the double bottom• outside the machinery space at 2 m intervals.


7.1

7.1.1 The section modulus of bottom stiffeners is to be noless than that required for single bottom longitudinals stipu-lated in Sec. 6. The section modulus of inner bottom stiffeners is to be noless than 85% of the section modulus of bottom longitudi-nals.

Where tanks intended for liquid cargoes are arranged abovethe double bottom, the section modulus of longitudinals isto be no less than that required for tank stiffeners as statedin Sec. 10.

tm 0 125L, 1 5,+( )kof=


Pt B, Ch 4, Sec 8


1 General

1.1

1.1.1 Where tanks intended for liquid cargoes arearranged above the double bottom, the section modulus oflongitudinals is to be no less than that required for tank stiff-eners as stated in Sec. 10.

The longitudinal type structure consists of ordinary stiffen-ers placed longitudinally supported by reinforced frames,generally spaced not more than 2 m apart, or by transversebulkheads.


Reinforced frames are to be provided in way of the mastand the ballast keel, in sailing yachts, in the machineryspace and in general in way of large openings on theweather deck.


2.1

2.1.1


p : scantling pressure, in kN/m2, defined in Part B,Chap. 1, Sec. 5 ;

Ko : factor defined in Sec. 2 of this Chapter.


3.1


where:


: 1,1 assuming p=p2



3.2 Longitudinals



: 1 assuming p=p2


4 Reinforced beams


4.1.1 The section modulus of the reinforced frames is to benot less than the value calculated with the following for-mula:

where:k1 : 1 assuming p=p1

: 0,7 assuming p=p2



s : spacing, in m, between the reinforced frames orhalf the distance between the reinforced framesand the transverse bulkhead adjacent to theframe concerned;



4.2.1 The section modulus of the reinforced stringers is tobe not less than the value calculated with the following for-mula:

where:k1 : defined in 4.1KCR : 2,5 for reinforced stringers which support ordi-

nary vertical stiffeners (frames); : 1,1 for reinforced stringers which do not sup-

port ordinary vertical stiffeners;

Z k1 s S2 Ko p⋅ ⋅ ⋅ ⋅=

Z k1 s S2 Ko p⋅ ⋅ ⋅ ⋅=

Z k1 KCR s S2 Ko p⋅ ⋅ ⋅ ⋅ ⋅=

Z k1 KCR′ s S2 Ko p⋅ ⋅ ⋅ ⋅ ⋅=


Pt B, Ch 4, Sec 8

s : spacing, in m, between the reinforced stringersor 0,5 D in the absence of other reinforcedstringers or decks;



Pt B, Ch 4, Sec 9

SECTION 9 DECKS

1 General

1.1

1.1.1 This Section lays down the criteria for the scantlingsof decks, plating and reinforcing or supporting structures.

The reinforcing and supporting structures of decks consist ofordinary reinforcements, beams or longitudinal stringers,laid transversally or longitudinally, supported by lines ofshoring made up of systems of girders and/or reinforcedbeams, which in turn are supported by pillars or by trans-verse or longitudinal bulkheads.




2.1

2.1.1




Ko, Kof : factor defined in Sec. 2 of this Chapter.

3 Deck plating

3.1 Weather deck


On yachts of L > 30 m a stringer plate is to be fitted withwidth b, in m, not less than 0,025 L and thickness t, in mm,not less than the value given by the formula

where ka is defined in 5.1 in Sec. 5.

3.2 Lower decks

3.2.1 The thickness of decks below the weather deckintended for accommodation spaces is to be not less thanthe value calculated with the formula:

where ka is defined in 5.1 in Sec. 5.




4.1.1 The section modulus of the ordinary stiffeners ofboth longitudinal and transverse (beams) type is to be notless than the value Z, in cm3, calculated with the followingequation:

where:

C1 : 1 for weather deck longitudinals: 0,63 for lower deck longitudinals: 0,56 for beams.



where:b : average width of the strip of deck resting on the

beam, in m. In the calculation of b any open-ings are to be considered as non-existent


4.3 Pillars

4.3.1 Pillars are, in general, to be made of steel or alumin-ium alloy tubes, and connected at both ends to plates sup-ported by efficient brackets which allow connection to thehull structure by means of bolts. Details to be sent forapproval.The section area of pillars is to be not less than the value A,in A, in cm2, given by the formula:

t 0 15, ka s kof L10 5,⋅ ⋅ ⋅ ⋅=

t 0 2, ka s kof L10 5,⋅ ⋅ ⋅ ⋅=

t 0 13, ka s kof L10 5,⋅ ⋅ ⋅ ⋅=

Z 14 s S2 h kof C1⋅ ⋅ ⋅ ⋅ ⋅=

Z 15 b S2 h ko⋅ ⋅ ⋅ ⋅=


Pt B, Ch 4, Sec 9

where:Q : load resting on the pillar, in kN, calculated with

the following formula:

where:A : area of the part of the deck resting

on the pillar, in m2.h : scantling height, defined in 2.1.1.


C : 1 for steel pillars

: 1,6 for aluminium alloy pillars.

4.3.2 Pillars are to be fitted on main structural members.Wherever possible, deck pillars are to be fitted in the samevertical line as pillars above and below, and effectivearrangements are to be made to distribute the load at theheads and heels of all pillars.

4.3.3 The attachment of pillars to sandwich structuresshould, in general, be through an area of single skin lami-nate. Where this is not practicable and the attachment ofthe pillar has to be by through bolting through a sandwichstructure then a wood, or other suitable solid insert is to befitted in the core in way.

A Q C⋅12 5, 0 045λ,–---------------------------------------=

Q 6 87, A h⋅ ⋅=


Pt B, Ch 4, Sec 10



1 General

1.1


The scantlings indicated in this Section refer to bulkheadsmade of reinforced plastic both in single-skin and in sand-wich type laminates.

Whenever bulkheads, other than tank bulkheads, are madeof wood, it is to be type approved marine plywood and thescantlings are to be not less than those indicated in Chapter5 of Part B.

Pipes or cables running in through watertight bulkhead areto be fitted with suitable watertight glands.

2 Symbols

2.1

2.1.1



hs, hB : as defined in Part B, Chap. 1, Sec. 5

ko, kof : as defined in Sec. 2 of this Chapter.

3 Plating

3.1



Table 1

4 Stiffeners





4.2.1 The horizontal webs of bulkheads with ordinary ver-tical stiffeners and reinforced stiffeners in the bulkheadswith ordinary horizontal stiffeners are to have a sectionmodulus not less than the value Z, in cm3, calculated withthe following formula:

where:

C1 : 10,7 for subdivision bulkheads

: 18 for tank bulkheads



Table 2

5 Tanks for liquids

5.1

5.1.1 See Sec 1 par 6.5.

tS k1 s ko f h0 5,⋅ ⋅ ⋅=

Bulkhead k1 h (m)

Collision bulkhead 5,8 hB

Watertight bulkhead 5,0 hB

Deep tank bulkhead 5,3 hs

Bulkhead h (m) c

Collision bulkhead hB 0,78

Watertight bulkhead hB 0,63

Deep tank bulkhead hs 1

Z 13 5, s S2 h c ko⋅ ⋅ ⋅ ⋅ ⋅=

Z C1 b S2 h ko⋅ ⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 11



1 General

1.1


Where the distance from the hypothetical freeboard deck tothe full load waterline exceeds the freeboard that can hypo-thetically be assigned to the yacht, the reference deck forthe determination of the superstructure tier may be the deckbelow the one specified above, see Ch 1, Sec 1, [4.3.2].



2.1


s : spacing between the stiffeners, in mh : conventional scantling height, in m, the value

of which is to be taken not less than the valueindicated in Table 1.

Kof : factor defined in Sec 2.

Table 1

In any event, the thickness t is to be not less than the valuesshown in Table 2 of Sec. 1 of this Chapter.

3 Stiffeners

3.1

3.1.1 The stiffeners of the boundary bulkheads are to havea section modulus not less than the value Z, in cm3, calcu-lated with the following formula:

where:h : conventional scantling height, in m, defined in

2 .1Ko : factor defined in Sec 2s : spacing of the stiffeners, in mS : span of the stiffeners, equal to the distance, in

m, between the members supporting the stiff-ener concerned.


4.1 Plating


where:s : spacing of the stiffeners, in mKof : factor defined in Sec 2h : conventional scantling height, in m, defined in

2.1.

4.2 Stiffeners


where:S : conventional span of the stiffener, equal to the

distance, in m, between the supporting mem-bers

s, h, Ko : as defined in 3.1.Reinforced beams (beams, stringers) and ordinary pillars areto have scantlings as stated in Sec. 9.


1st tier front 1,5

2nd tier front 1,0


t 3 7, s KOf h0 5,⋅ ⋅ ⋅=

Z 5 5, s S2 h Ko⋅ ⋅ ⋅ ⋅=

t 3 7, s KOf h0 5,⋅ ⋅ ⋅=

Z 5 5, s S2 h Ko⋅ ⋅ ⋅ ⋅=

Pt B, Ch 4, Sec 12

SECTION 12 SCANTLINGS OF STRUCTURES WITH SANDWICH

CONSTRUCTION

1 Premise

1.1

1.1.1 The sandwich type laminate taken into considerationin this Section is made up of two thin laminates in rein-forced plastic bonded to a core material with a low densityand low values for the mechanical properties.

The core material is, in general, made up of balsa wood,plastic foam of different densities or other materials (honey-comb) which deform easily under pressure or traction butwhich offer good resistance to shear stresses.

The thicknesses of the two skins are negligible compared tothe thicknesses of the core.

The thickness of the core is to be not less than 6 times theminimum thickness of the skins.

The thicknesses of the two skins are to be approximatelyequal; the thickness of the external skin is to be no greaterthan 1,33 times the net thickness of the internal skin.

The moduli of elasticity of the core material are negligiblecompared to those of the skin material.

Normal forces and flexing moments act only on the externalfaces, while shear forces are supported by the core .

The scantlings indicated in the following Articles of thisSection are considered valid assuming the above-men-tioned hypotheses.

The scantlings of sandwich structures obtained differentlyand/or with core materials or with skins not correspondingto the above-mentioned properties will be considered caseby case on the principle of equivalence, on submission offull technical documentation of the materials used and anytests carried out.

2 General

2.1 Laminating

2.1.1 Where the core material is deposited above a prefab-ricated skin, as far as practicable the former is to be appliedafter the polymerisation of the skin laminate has passed theexothermic stage.

2.1.2 Where the core is applied on a pre-laminated sur-face, even adhesion is to be ensured.

2.1.3 When resins other than epoxide resins are used, thelayer of reinforcement in contact with the core material is tobe of mat.

2.1.4 Prior to proceeding with glueing of the core, the lat-ter is to be suitably cleaned and treated in accordance withthe Manufacturer's instructions.

2.1.5 Where the edges of a sandwich panel are to be con-nected to a single-skin laminate, the taper of the panel isnot to exceed 30°. In zones where high density or plywood insert plates arearranged, the taper is not to exceed 45°.

2.2 Vacuum bagging

2.2.1 Where the vacuum bagging system is used, details ofthe procedure are to be submitted for examination. The number, scantlings and distribution of venting holes inthe panels are to be in accordance with the Manufacturer'sinstructions.

The degree of vacuum in the bagging system both at thebeginning of the process and during the polymerisationphase is not to exceed the level recommended by the Man-ufacturer, so as to avoid phenomena of core evaporationand/or excessive monomer loss.

2.3 Constructional details

2.3.1 In general the two skins, external and internal, are tobe identical in lamination and in resistance and elasticityproperties.In way of the keel, in particular in sailing yachts with a bal-last keel, in the zone where there are the hull appendages,such as propeller shaft struts and rudder horns, in way ofthe connection to the upper deck and in general where con-nections with bolts are foreseen, as a rule, single-skin lami-nate is to be used.

The use of a sandwich laminate in these zones will be care-fully considered by RINA bearing in mind the properties ofthe core and the precautions taken to avoid infiltration ofwater in the holes drilled for the passage of studs and bolts.

The use of sandwich laminates is also ill-advised in way ofstructural tanks for liquids where fuel oils are concerned.

Such use may be accepted by increasing the thickness ofthe skin in contact with the liquid, as indicated in Section10.

3 Symbols

3.1

3.1.1 S : conventional span of the strip of sandwich lam-

inate equal to the minimum distance, in m,


Pt B, Ch 4, Sec 12

between the structural members supporting thesandwich (bulkheads, reinforced frames);

p : scantling pressure, in kN/m2, as defined in PartB, Chap. 1, Sec. 5;

h : scantling height, in m, given in Part B, Chap. 1,Sec. 5;

Rto : ultimate tensile strength, in kN/m2, of the exter-nal skin;

Rti : ultimate tensile strength, in kN/m2, of the inter-nal skin;

Rco : ultimate flexural strength, in kN/m2, of theexternal skin;

Rci : ultimate flexural strength, in kN/m2, of the inter-nal skin;

t : ultimate shear strength, in kN/m2, of the corematerial of the sandwich;

h : net height, in mm, of the core of the sandwich.

4 Minimum thickness of the skins

4.1

4.1.1 The thickness of the skin laminate is to be sufficientto obtain the section modulus prescribed in the followingArticles; furthermore, it is to have a value, in mm, not lessthan that given by the following formulae:

a) Bottom

b) Side and weather deck

where:

to : thickness of the external laminate of the sand-wich

ti : thickness of the internal laminate of the sand-wich.

Thicknesses less than the minimums calculated with theabove formulae, though not less than those in Table 2, maybe accepted provided they are sufficient in terms of buck-ling strength.

In the case of a sandwich structure with a core in balsawood or polyurethane foam and other similar products, thecritical stress σCR, in N/mm2, given by the following for-mula, is to be not less than 1,1 σC:

essendo:

EF : compressive modulus of elasticity of the lami-nate of the skin considered, in, in N/mm2;

EA : compressive modulus of elasticity of the corematerial of the skin considered, in N/mm2;

GA : shear modulus of elasticity of the core material,in N/mm2;

σC : actual compressive strength on the skin consid-ered, in N/mm2

ν : Poisson coefficient of the laminate of the skinconsidered.

5 Bottom

5.1

5.1.1 The section moduli ZSo e ZSi, in cm3, correspondingto the external and internal skins, respectively, of a strip ofsandwich of the bottom 1 cm wide are to be not less thanthe values given by the following formulae:


: 0,4 assuming p=p2

The moment of inertia of a strip of sandwich 1 cm wide is tobe not less than the value IS, in cm4, given by the followingformula:

where:R : the greater of the ultimate compressive strengths

of the two skins, in N/mm2;ES : the mean of the four values of the compressive

and shear moduli of elasticity of the two skins,in N/mm2;

Z : ZSo or ZSi , in cm3, whichever is the greater.

The net height of the core ha, in mm, is to be not less thanthe value given by the formula:


: 0,2 assuming p=p2

6 Side

6.1

6.1.1 The section moduli ZSo and ZSi, in cm3, correspond-ing to the external and internal skins, respectively, of a stripof sandwich of the side 1 cm wide are to be not less thanthe values given by the following formulae:


: 0,4 assuming p=p2

to 0 50, 2 2, 0 25L,+( )⋅=

ti 0 40, 2 2, 0 25L,+( )⋅=

to 0 45, 2 2, 0 25L,+( )⋅=

ti 0 35, 2 2, 0 25L,+( )⋅=

σCR 0 4,EF EA GA⋅ ⋅( )

1 ν2–-------------------------------

1 3⁄

⋅=

ZSo k1 p S2 1Rco

-------⋅ ⋅ ⋅=

ZSi k1 p S2 1Rti

------⋅ ⋅ ⋅=

IS 40 S Z RES

----⋅ ⋅ ⋅=

hak1 p S⋅ ⋅

τ--------------------=

ZSo k1 p S2 1Rco

-------⋅ ⋅ ⋅=

ZSi k1 p S2 1Rti

------⋅ ⋅ ⋅=


Pt B, Ch 4, Sec 12

The moment of inertia of a strip of sandwich of the side 1cm wide is to be not less than the value IS, in cm4, given bythe following formula:

ù

where R and ES are as defined in Art. 5:



: 0,2 assuming p=p2

7 Decks

7.1

7.1.1 The section moduli ZSo and ZSi, in cm3, correspond-ing to the external and internal skins, respectively, of a stripof sandwich of the deck 1 cm wide are to be not less thanthe values given by the following formulae:

However, the modulus ZSo may be assumed not greaterthan that required for the side in 6.1, having the same .

The moment of inertia of a strip of sandwich 1 cm wide is tobe not less than the value IS, in cm4, given by the followingformula:

where R and ES are as defined in Art.5:

The net height of the core ha, in mm, is to be not less thanthe value given by the following formula:

8 Watertight bulkheads and boundary bulkheads of the superstructure

8.1

8.1.1 The scantlings shown in this Article apply both tosubdivision bulkheads and to tank bulkheads.

They may also be applied to boundary bulkheads of thesuperstructure assuming for h the relevant value indicatedin Chap. 4, Sec. 11.

The section modulus ZS, in cm3, and the moment of inertiaIS, in cm4, of a strip of sandwich 1 cm wide are to be notless than the values given by the following formulae:

where:

R : the greater of the ultimate compressive shearstrengths of the two skins, in N/mm2;

ES : the mean of the values of the compressive mod-uli of elasticity of the two skins, in N/mm2;


IS 40 S Z RES

----⋅ ⋅ ⋅=

hak1 p S⋅ ⋅

τ--------------------=

ZSo 15 h S2 1Rco

-------⋅ ⋅ ⋅=

ZSi 15 h S2 1Rti

------⋅ ⋅ ⋅=

IS 40 S Z RES

----⋅ ⋅ ⋅=

ha7 h S⋅ ⋅

τ------------------=

ZS 15 h S 1R---⋅ ⋅ ⋅=

IS 40 S Z RES

----⋅ ⋅ ⋅=

ha7 h S⋅ ⋅

τ------------------=


Part BHull

Chapter 5

WOOD HULLS

SECTION 1 MATERIALS

SECTION 2 FASTENINGS, WORKING AND PROTECTION OF TIMBER

SECTION 3 BUILDING METHODS FOR PLANKING

SECTION 4 STRUCTURAL SCANTLINGS OF SAILING YACHTS WITH OR WITHOUT AUXILIARY ENGINE

SECTION 5 STRUCTURAL SCANTLINGS OF MOTOR YACHTS

SECTION 6 WATERTIGHT BULKHEADS, LINING, MACHINERY SPACE


Pt B, Ch 5, Sec 1

SECTION 1 MATERIALS

1 Suitable timber species

1.1

1.1.1 The species of timber suitable for construction arelisted in Table 1 together with the following details:

• commercial and scientific denomination;• natural durability and ease of impregnation;• average physical-mechanical characteristics at 12%

moisture content.The durability classes are relative to the solid timber's resist-ance to moulds.

The suitability for use in the various hull structures is givenin Table 2.

The same species are suitable for the fabrication of marineplywood and lamellar structures in accordance with theprovisions of Article 2 below.

The use of timber species other than those stated in Table 1may be accepted provided that the characteristics of thespecies proposed are as similar as possible to those of oneof the species listed.

2 Timber quality

2.1 Planking

2.1.1 The timber is to be well-seasoned, free from sap-wood and any noxious organisms (moulds, insects, larvae,bacteria, etc.) which might impair its durability and struc-tural efficiency.

The moisture content at the time of use is to be not greaterthan 20% (according to the method UNI 8939 Planking -Check of batch moisture content).

Knots may be tolerated when they are intergrown, providedthat their diameter is less than 1/5 of the dimension parallelto such diameter, measured on the section of the knot. Thegrain is to be straight (the maximum admissible inclinationin relation to the longitudinal axis of the piece is equal to aratio of 1:10).Note 1: Timber with the above characteristics corresponds roughlyto Class 1 of UNI 8198 (Conifer planking - Classification on thebasis of mechanical resistance).

2.2 Marine plywood and lamellar structures

2.2.1 The suitable timber species and criteria for the use ofalternative species are listed in Table 1.

For marine plywood, the elevated temperatures reachedduring drying and pressing rule out the possibility of sur-vival of insects and larvae in the finished panels. Moreover,this factor contributes in enabling the marine plywood tohave a lower moisture content than that of solid timber of

the same species in the same ambient conditions, renderingit less prone to attacks of mould.

Therefore, assuming the same species of timber, the dura-bility of marine plywood is greater than that of solid timber.

In any case, the thickness of the individual layers constitut-ing the plywood or the lamellar structure is to be reduced indirect proportion to the durability of the species used; themaximum recommended thicknesses are listed in Table 1.

The minimum number of plywood layers used in the con-struction is 3 for thicknesses not greater than 6 mm and 5for greater thicknesses.

The marine plywood adopted for hull construction andstructural parts in general is to be type tested by RINA inaccordance with the relevant regulations.

2.3 Certification and checks of timber qual-ity

2.3.1 The quality of timber, plywood and lamellar struc-tures is to be certified as complying with the provisions of2.1 and 2.2 by the builder to the RINA Surveyor, who, inthe event of doubts or objections, will verify the circum-stances by performing appropriate checks.

Such certification is to refer to the checks carried out duringbuilding survey in the yard, relative to the following cha-racteristics:

a) for solid timber: mass density and moisture content;

b) for plywood and lamellar structures: glueing test.Such checks are not required for Quality Assurance mate-rial certified by RINA in pursuance of the relevant regula-tions.

2.4 Mechanical characteristics and struc-tural scantlings

2.4.1 The structural scantlings indicated in this Chapterapply to timber with the following density δ, in kg/m3, at amoisture content not exceeding 20%:

• bent frames: δ = 720

• non-bent frames keel and stem: δ = 640

• shell and deck planking, shelves and clamps, stringersand beams: δ = 560.

The scantlings given in the following Articles* may be mod-ified as a function of the density of the timber employedand its moisture content, in accordance with the relation-ship:

S1 : corrected section (or linear dimension)

S1 S K⁄=

K δe

δ---- U Ue–( ) 0 02,⋅+=


Pt B, Ch 5, Sec 1

S : Rule section (or linear dimension), obtained inaccordance with this Chapter

δ : density of the timber species (or plywood) used;δe : standard density of the timber species of refer-

ence;U : standard moisture content percentage (20% for

solid timber, 15% for plywood or lamellarstructures);

Ue : maximum expected moisture content balancefor the part considered, in service conditions.

Reductions in scantlings exceeding those obtained usingthe formulae above may be accepted on the basis of themechanical base characteristics of the timber, plywood orlamellar structures actually employed.

Table 1 : Basic physical/mechanical characteristics of timbers for construction

Commercial name

Origin (1)

Botanical name (2)

Mass density (kg/m3)

Natural durability

(3)

Ease of imprega-

tion (3)

Mechanical characteristics (4)

Rf

(N/mm2)Ef

(N/mm2)Rc

(N/mm2)Rt

(N/mm2)

DOUSSIEIROKO

KHAYAMAKORE’MAHOGANYOKOUME’ ELMOAK

SAPELE

SIPO

TECKWHITE OAKCHESTNUTCEDAR(Western Red)DOUGLAS FIR

LARCH

AfricaAfrica

AfricaAfrica

AmericaAfricaEurope Europe

Africa

Africa

AsiaAmerica Europe

America

America

Europe

Afzelia sppChlorophoraexcelsaKhaya sppTieghemella sppSwietenia sppAucoumea KleineanaUlmus sppQuercus robur e Q. petraeaEntandrophragma cylindricumEntandrophragmautileTectona grandisQuercus sppCastanea sppThuja plicata

PseudotsugamenziesilLarix decidua

800650

520660550440650710

650

640

680730600380

500

550

AA/B

CABDDB

C

B/C

AB/CB

B/C

C/D

C/D

44

4443

2/34

3

3/4

4443

3/4

3/4

11485

7486795189

125

105

100

1001205951

85

89

1600010000

96009300

103007800

1020015600

12500

12000

106001500085007600

13400

12800

6252

445046274368

56

53

58653731

50

52

14,012,0

10,011,08,56,7

11,013,0

15,7

15,0

13,012,67,46,8

7,8

9,4

Abbreviations:Natural durability

A = very durableB = durable (maximum permissible thickness for the fabrication of marine plywood 5 mm)C = not very durable (maximum permissible thickness for the fabrication of marine plywood 2,5 mm)D = not durable (maximum permissible thickness for the fabrication of marine plywood 2 mm)

Ease of treatment for impregnation1 = permeable2 = not very resistant3 = resistant4 = very resistant

Note(1) Area of natural growth(2) Unified botanical name (spp = different species)(3) Level of natural durability and ease of treatment for impregnation according to Standard EN 350/2(4) Mechanical characteristics with 12% moisture content, source: Wood Handbook: wood as an engineering material - 1987,

USDA- Ultimate flexural strength Rf (strength concentrated amidships)- Bending modulus of elasticity Ef (strength concentrated amidships)- Ultimate compression strength Rc (parallel to the grain)- Ultimate shear strength Rt (parallel to the grain).


Pt B, Ch 5, Sec 1

Table 2 : Guide for selections of construction timbers

SPECIES OF TIMBERDoug-

lasCedar(red) Iroko Larch Makore

Mahor-gany

Elm eng-lish

White oak

Oak Sapeli TeakSTRUCTURAL ITEM

Keel, hog, stern-post, dead-woods

II II II II II II III I

Stern II II II II II III IBilge stringer III II II III IBeam shelves clamps water-ways

III II II II II III I

Floors II II II II II IFrames grown or web frames

II (2) II II (1) II (1) III I

Frames, bent frames II (1) II (1)Planking below water-line

III II II II II II III I

Planking above water-line

III II III II II III I

Deck planking II III II IBeams, bottom girders II II II (2) II (2) II (1) II (1) IBrackets vertical II II (1) II

Bracket horizontal II I IGunwhale margin planks

II II II II

Note(1) The timber concerned may be employed either in the natural or in the laminated form.(2) The timber may be employed only in laminated form.Suitability of timber for use:I = very suitableII = fairly suitableIII = scarcely suitable


Pt B, Ch 5, Sec 2


SECTION 2 FASTENINGS, WORKING AND PROTECTION OF

TIMBER

1 Fastenings

1.1

1.1.1 Glues for timber fastenings are to be of resorcinic orphenolic type, i.e. durable and water-resistant in particular.Ureaformaldehyde glues may only be used in well-venti-lated parts of the hull not subject to humidity.

Glues are to be used according to the Manufacturer'sinstructions on timber with moisture content not exceeding15-18% or, for urea-type glues, 12,5-15%.

The parts to be glued are to be carefully prepared andcleaned and, in particular, all traces of grease are to beremoved.

Where rivets, screws and bolts are not made of material rec-ognised as suitable for resisting corrosion from the marineenvironment, they are to be hot galvanised in accordancewith a recognised standard. In the absence of such stand-ard, after rivets, screws and bolts have been hot galvanisedand subsequently machine finished, the protective zinccoating on their surfaces is to remain intact.

Through bolts are to be clinched on washers, or tightenedby a nut, also on washers. Nuts and washers are to be ofthe same material as that of the bolts.

Where connecting bolts go through shell planking or keel,they are to have heads packed with cotton or other suitablematerial.

Where screw fastenings are used for planking, the threadingis to penetrate the support frame for a distance equal to theplanking thickness.

1.2

1.2.1 The use of suitable glues in place of mechanicalconnections will be the subject of special consideration byRINA.In general, such replacement of fastening methods will beaccepted subject to the satisfactory outcome of tests, on

representative samples of the joints, conducted with proce-dures stipulated on the basis of the type of glue, the type ofconnection and any previous documented applications.

In any event, RINA reserves the right to require a minimumnumber of mechanical connections.

2 Timber working

2.1

2.1.1 Timber working is to be appropriate to the speciesand hardness of the timber, as well as to the type of hullconstruction, e.g. grown or web frames, lamellar structures,board or plywood planking.Lamellar structure is generally employed for bent structuralparts, with lamellas as continuous as possible or with scarfjoints and normally glued before bending.

The lamellas are generally to be made using the same spe-cies of timber.

The lamellas are generally to be made using the same spe-cies of timber.

The lamellas are to be arranged with their fibres parallel tothe length of the element to be constructed.

3 Protection

3.1

3.1.1 Inaccessible surfaces of internal hull structures areto be treated with a suitable wood preservative according tothe Manufacturer's instructions and compatible with theglues, varnishes and paints employed. The timber of theinternal bottom of the hull is to be smeared with oil or var-nish; any synthetic resins used as coating are to be appliedto dry timber with the utmost care.All cut edges of plywood are to be sealed with glue, paint orother suitable products such as to prevent the penetration ofmoisture along the end-grain.

Pt B, Ch 5, Sec 3

SECTION 3 BUILDING METHODS FOR PLANKING

1 Shell planking

1.1 Simple skin

1.1.1 Planks are to be arranged such that strake butts are atleast 1,20 metres apart from those of adjacent strakes and atleast three continuous strakes separate two butts arrangedon the same frame.

The butts of garboards are to be arranged clear of those inthe keel, and the butts of the sheerstrake are to be arrangedclear of those of the waterway.

Butts may be strapped or scarfed, and wooden straps are tohave thickness equal to that of the planking, width so as tooverlap adjacent strakes by at least 12 mm and length asnecessary for the connection while leaving a space forwater drainage between the strap edge and the frame.

Scarfs are to have length not less than 5 times the plankingthickness, to be centred on the frames and to be connectedby means of glueing and pivoting.

1.2 Double diagonal skin

1.2.1 This consists of an inner skin of thickness notexceeding 0,4 of the total thickness and an outer skinarranged longitudinally.

This consists of an inner skin of thickness not exceeding 0,4of the total thickness and an outer skin arranged longitudi-nally.

1.3 Double longitudinal skin

1.3.1 This consists of an inner and outer skin, arrangedsuch that the seams of the outer skin fall on the middle ofthe planks of the inner skin.

The inner skin is to have thickness not exceeding 0,4 of thetotal thickness and to be connected to the frames by meansof screws or nails and to the outer skin by means of screwsor through bolts. The outer skin is, in turn, to be connectedto the frames by means of through bolts. When framesother than laminated frames are employed, the use ofscrews is permitted. A suitable elastic compound layer is tobe arranged between the two skins.

1.4 Laminated planking in several cold-glued layers

1.4.1 The construction of cold moulded laminated plank-ing is to be effected in loco at a constant temperature.

It is therefore of the utmost importance that the Manufac-turer should be equipped with adequate facilities for thistype of construction.

The planks forming the laminate are to be of width andthickness adequate for the shape of the hull; the width isgenerally not to exceed 125 mm.

The number of layers is to be such as to obtain the requiredthickness.

1.5 Plywood planking

1.5.1 Plywood planking consists of panels as large as prac-ticable in relation to the shape of the hull. The butts are tobe suitably staggered from each other and from machineryfoundations.The connection of seams is to be achieved by means of glueand bolts; the connection of butts is to be effected by meansof scarfs or straps. Scarfs are to have length not less than 8times the thickness and, where effected in loco, to bebacked by straps, at least 10 times as wide as the thickness,glued and fastened.

The strap connection is to be effected using straps of thesame plywood.

1.6 Double skin with inner plywood and outer longitudinal strakes

1.6.1 This consists of two layers: one internal of plywood,arranged as described in 1.5, the other external, formed byplanks in longitudinal strakes arranged as described in 1.3.The plywood thickness is to be not less than 0,4 of the totalthickness.

1.7 Fastenings and caulking

1.7.1 Butt-straps on shell planking (see Figure 1) are to beconnected by means of through bolts of the scantlings givenin Table 6.1 for the connection of planking to frames, andare to be proportionate in number to the width a of panels,as follows:- a < 100 mm

3 bolts at each end of plank- 100 ≤ a < 100 mm

4 bolts at each end of plank- 200 ≤ a < 250 mm

3 bolts at each end of plank.

The number and scantlings of bolts to be used for connec-tion of planking to frames is given in Table1.

The following types of connection are to be adopted:- Type I framing: all through fastenings;- Type II framing with grown or laminated frames:

through bolts in way of bilge stringers or side longitudi-nals, wood screws for other connections;

- Type II framing with metal frames: all connectionsformed by through bolts with nuts;


Pt B, Ch 5, Sec 3

- Type III framing: connections as above depending onwhether bent, grown, laminated or steel frames are con-cerned.

All fastenings for strengthened frames in way of masts are tobe through fastenings.

When plywood planking is adopted, it is to be connected toframes by means of nails or screws spaced 75 mm apart andwith diameters as given in Table .

Planks of shell planking, if not glued, are to have caulkedseams and butts.

1.8 Sheathing of planking

1.8.1 When use is made of reinforced plastic or syntheticresin sheathing, the hull is to be prepared by carefully level-ling every joint and filling every bolt hole with suitablecompounds after adequate sinking of the bolts. The protec-tive sheathing is to cover keel, false keel and deadwood asfar as practicable, prior to the fitting of external ballast inthe keel, where envisaged.

When sheathing is applied, the moisture content of the tim-ber is to be as low as possible.

2 Deck planking

2.1 Planking

2.1.1 The butts of planks of two contiguous strakes are tobe spaced at least 1,20 metres apart; two plank butts on thesame beam are to be separated by at least three strakes ofcontinuous planking.

Butts are to be set onto a beam and may be simple orscarfed.

2.2 Plywood

2.2.1 Plywood panels are to be as long as possible. Thebutts are to be arranged clear of those of adjacent panelsand are to be strapped or otherwise set onto a strong beam.Longitudinal joints are to be set onto longitudinal structuresof sufficient width for the connection. All joints are to besealed watertight.

2.3 Plywood sheathed with laid deck

2.3.1 The butts of plywood panels are to be in accordancewith the specifications given in 2.2.1, while the distributionof plank butts is to comply with the provisions of 2.1.1.

2.4 Longitudinal planking

2.4.1 When longitudinal planking is adopted, each plankis to be fastened to beams by means of a wood screw or lat-eral nail. In addition, each plank may connected to thatad-jacent by means of a glued, sunk-in strip.Plywood planking is to be glued and riveted to beams, orotherwise fastened by means of screws with pitch not lessthan 75 mm and diameter in accordance with that shown inTable 1.

2.5 Caulking

2.5.1 Wood planking is to be caulked or made watertightby the application of a suitable elastic compound.Wooden dowels used to cover bolt holes are to be glued.


Pt B, Ch 5, Sec 3

Table 1 : Connections of shell and deck planking - scantlings of fastenings

Table 2 : Connections of shell and deck planking in plywood

Spessore fasciame

mm

SHELL PLANKING DECK PLANKING NUMBER OF FASTENINGS PER PLANK

Grown frame: laminated, or steel frames

Bent frames

Wood screws

diameter mm

Bolts with nuts

diameter mm

Width a of plank mm

diameter diameter

a < 100100 ≤ a<150

150 ≤ a<180

180 ≤ a<250

205 ≤ a<225

bolts with nuts mm

wood screws

mm

Copper nailsmm

copper nailsmm

182022242628303234363840424446485052

4,54,566777888899

1012121414

5555

5,55,55,56,56,577888

8,58,51010

4,55

6,56,56,56,56,57,57,57,57,59,59,59,51111

12,512,5

2,53

3,53,53,54,54,55

5,55,55,566-----

4,555

5,55,55,55,56,56,56,5777888

8,58,5

4,54,566666888889910101212

222211111111111111

222222222222222222

333322222222222222

333333333222222222

333333333333333333

Thickness of plywood

OVERLAP OF SEAMS

Width of butt-straps mm

DIAMETER OF FASTENINGS

shell and deck planking, on keel, stringers, shelves, or carlings

mm

Wood screws mm

Copper nails mm

68

10

252832

single fastening

150175200

single fastening

4,555

3,53,54,5

121416

353545

225250280

5,55,55,5

4,555

182022

455050 double fastenings

350350350 double fastenings

6,56,56,5

55,56

2426

6060

380380

77

6,56,5


Pt B, Ch 5, Sec 3

Figure 1 : Butt-straps on shell planking

1 - Frame

2 - Shell planking

3 - Butt - strap


Pt B, Ch 5, Sec 3

Figure 2 : Usual types of scarf-joints

1 - Plan scarph

2 - Hooked scarph

3 - Tabled scarph

4 - Tabled hooked scarph

5 - Double wedges


Pt B, Ch 5, Sec 4

SECTION 4 STRUCTURAL SCANTLINGS OF SAILING YACHTS

WITH OR WITHOUT AUXILIARY ENGINE

1 General

1.1

1.1.1 The scantlings in this Section apply to hulls of lengthL not exceeding 30 metres with round bottom of shape sim-ilar to that shown in Figures 1 and 2, and fitted with fixedballast or drop keel.

Yachts of length L exceeding 30 metres or hull shapes otherthan the above will be considered in each case on the basisof equivalence criter.

2 Keel

2.1

2.1.1 The scantlings of wooden keels are given in Table 1.

The keel thickness is to be maintained throughout thelength, while the width may be gradually tapered at theends so as to be faired to the stem and the sternpost.

The breadth of the rabbet on the keel for the first platingstrake is to be at least twice the thickness and not less than25 mm.

The wooden keel is to be made of a minimum number ofpieces; scarf joints may be permitted with scarf 6 times aslong as the thickness and tip 1/4 to 1/7 of the thickness ofthe hooked or tabled type, if bolted, or of the plain type, ifglued. It is recommended that scarfs should not bearranged near mast steps or ends of engine foundation gird-ers.

Where the keel is cut for the passage of a drop keel, thewidth is to be increased.

Where the mast is stepped on the keel, it is to be arrangedaft of the forward end of the ballast keel. Where this is notpracticable, effective longitudinal stiffeners are to be

arranged extending well forward and aft of the mast stepand effectively connected to the keel.

Bolted scarfs are to be made watertight by means of soft-wood stopwaters.

3 Stempost and sternpost

3.1

3.1.1 The stempost is to be adequately scarfed to the keeland increased in width at the heel as necessary so as to fitthe keel fairing.

Stempost scantlings are given in Table 1.

The sternframe is shown in Figure 3 and sternpost scantlingsare given in Table 1.

The lower portion of the sternpost is to be tenoned or other-wise attached to the keel. The connection is completed bya stern deadwood and a large bracket fastening togetherfalse keel, keel and post by means of through bolts.

The counter stern is to be effectively connected to the stern-post; where practicable, such connection is to be effectedby scarfs with through bolts.

The cross-sectional area of the counter stern at the connec-tion with the sternpost is to be not less than that of the latter;such area may be reduced at the upper end by 25%..

4 Frames

4.1 Types of frames

4.1.1 Bent frames

Bent frames consist of steam warped listels. Their widthand thickness are to be uniform over the whole length; theframes are to be in one piece from keel to gunwale and,where practicable, from gunwale to gunwale, running con-tinuous above the keel.

Table 1 : Keel, Stempost, Sternpost

: LengthL m

Keel Stempost Sternpost

Widthmm

Depthmm

at heel at head Depthmm

Depthmm

Width mm

Depthmm

Widthmm

Depthmm

24 26 28 30

435455470480

240255270290

240255270290

240255270290

190200215230

190200215230

190200215230

190200215230


Pt B, Ch 5, Sec 4

4.1.2 Grown framesGrown frames consist of naturally curved timbers con-nected by means of scarfs, or butted and strapped. Theirwidth is to be uniform, while their depth is to be graduallytapered from heel to head.

The length of scarfs is to be not less than 6 times the width,and they are to be glued.

4.1.3 Laminated framesLaminated frames consist of glued wooden layers. Theglueing may take place before forming where the latter isslight; otherwise it should be carried out in loco or be pre-fabricated by means of suitable strong moulds.

4.1.4 Metal framesSteel frames consist of angles properly curved and bevelledsuch that the flange to planking is closely fayed to the sameplanking.

4.2 Framing systems and scantlings

4.2.1 The admissible framing systems and the frame scant-lings are indicated in Tables 2 and 3:

Type I : all equal frames, of the bent type;

Type II : all equal frames, of grown, laminated or steelangle type;

Type III : frames of scantlings as required for Type II, butalternated with one, two or three bent frames.

These types are hereafter referred to, respectively, as TypeIII1, Type III2, Type III3.

When a frame spacing other than that specified in the Tableis adopted, the section modulus of the frame is to be modi-fied proportionally. For wooden rectangular sections, abeing the width and b the height of the Rule section for thespacing s, a1 and b2 the actual values for the assumed spac-ing s1, it follows that:

The width of frames is to be not less than that necessary forthe fastening; their depth is in any case to be assumed asnot less than 2/3 of the width, except where increasedwidth is required for local strengthening in way of masts.

The Table scantlings, duly modified where necessary for thespecific gravity of the timber and for the frame spacing, areto be maintained for 0,6 of the hull length amidships; out-side such zone, the following reductions may be applied:

• for bent or laminated frames: 10% in width,

• for grown frames: 20% in width throughout the lengthof the frame, and 20% in depth of the head,

• metal frames: 10% in thickness.

Frames may have a reduction in strength of 25% wherecold laminated planking is adopted in loco, in accordancewith the provisions of 8.

Frames are to be properly shaped so as to fit the plankingperfectly.

Where no floors are arranged, the frames are to be wedgedinto and fastened at the heels of the centreline structuralmember of the hull.

When internal ballast supported by the frames is arranged,the latter are to be increased in scantlings.

Frames adjacent to masts are to be strengthened on eachside as follows, or equivalent arrangements are to be pro-vided.

• Type I framing

Three grown frames are to be fitted, with scantlings asrequired for Type II framing, but with constant depthequal to that indicated in Table 3.2 for the heel. Suchframes are to be arranged instead of alternate bentframes. Otherwise, six consecutive bent frames with across-section increased by 60% in respect of that shownin the above-mentioned Table may be fitted.

• Type II framing

Three grown frames are to be fitted, with a cross-sectionincreased by 50% in respect of that required for the heelin the above-mentioned Table and constant depth.Such frames are to be alternated with ordinary grownframes. If alternate frames are adopted, they are to bestiffened by reverse frames of scantlings as prescribedfor the reverse frames of plate floors.

• Type III framing

Three grown frames with a cross-section increased by50% in respect of that required for the heel in theabove-mentioned Table, and constant depth, are to bearranged at Rule spacing, with one or two intermediatebent frames. If steel frames are adopted, three are to bestiffened by reverse frames with scantlings as requiredfor the frames of plate floors, and arranged with one ortwo intermediate bent frames.

Where, in way of the mast, a sufficiently strong bulkhead isprovided, such increased frames may be reduced in numberto two.

5 Floors

5.1 General

5.1.1 Floors may be made of wood or metal (steel or alu-minium alloy).

• Wooden floors, as a rule, may only be employed inassociation with grown frames and are to be flanked bythem.

• Metal floors are employed in association with eitherbent, grown or laminated frames, and are arranged onthe internal profile of the frames.

• Angle floors may be employed with either bent, grownor laminated frames, and may be arranged as shown inTable 1. When they are arranged with a flange inside,an angle lug is to be fitted in way of the throat, for theconnection to the wooden keel (see the above Table).

• Plate floors may be employed in association with eithergrown or angle frames (see the above-mentioned Table).The internal edge is to be provided with a reverse angleor a flange; in the latter case, the thickness is to beincreased by 10%.

a1 b12 a b2 s1

s----⋅=


Pt B, Ch 5, Sec 4

5.2 Arrangement of floors

5.2.1 Where Type I framing with bent frames is adopted(see Tables 2 and 3), floors are to be fitted inside 0,6 Lamidships as follows.

• on every second frame if the hull depth does not exceed2,75 metres and on every frame in hulls of greaterdepth;

• on every second frame inside 0,6 L amidships, and out-side such area over an extent corresponding to the len-gth on the waterline;

• on every third frame elsewhere.

Where Type III framing is adopted, a floor is to be fitted inway of every grown, laminated or angle frame. Where oneor two intermediate bent frames are arranged, and the

depth D exceeds 2,40 metres, floors are to be fitted on bentframes located inside 0,6 L amidships.

Where three intermediate bent frames are arranged, a flooris to be fitted on the central frame.

5.3 Scantlings and fastenings

5.3.1 The scantlings of floors are given in Tables 4 and 5.At the hull ends, the length of arms need not exceed onethird of the frame span.

Wooden floors are to be made of suitably grained or lami-nated timber, and their height at the ends is to be not lessthan half the height of the throat.

Where the ballast keel bolts cross wooden floors, the widthof the latter at the throat is to be locally increased, if neces-sary, so as to be not less than three and a half times thediameter of the bolt.

Table 2 : Frames

Table 3 : Frames

Depth D1

mm (1)

TYPE IBent frames only

TYPE IIGrown frames, or laminated frames, or steel frames only

spacing mm

Grown frames Laminated frames Steel frames

spa-cingmm

widthmm

depthmm

widthmm

depthmm width

mmdepthmm

Section modulus

cm3

Scantlingsmm (2)

at heel at head

3,00 3,20 3,40 3,60 3,80 4,00 4,20

215225235245255265

-

576267727782-

404346495255-

288305322340355375390408

616875818794100

748391100112124140

5358688092100117

8193103117122131143

525966748494102

3,14,46

7,910,212,514,5

50x50x560x30x665x50x775x50x680x60x790x60x790x60x8

(1) For hulls fitted with external ballast in the keel, 0,75 D1, may be assumed in place of 0,75 D1, where the ballast/light displace-ment ratio is less than approximately 0,25. For yachts with a drop keel, the value 1,15 D is taken in lieu of D1.

(2) The scantlings of bars are given for guidance purposes.Solution I is only applicable where D1 does not exceed 3,60 metres.The frame spacing is intended as that measured amidships of the frames widths.

DepthD1

mm (1)

TYPE IIIMain frames (grown or laminated) alternated with bent frames

Spacing between main frames and intermediate frames Bent frames

1 bent framemm

2 bent framesmm

3 bent framesmm

lengthmm

depthmm

3,00 3,20 3,40 3,60 3,80 4,00 4,20

515560590620650680

-

620650690725765800

-

695730770800840870

-

434548505356-

333539434751-

(1) For hulls fitted with external ballast in the keel, 0,75 D1, may be assumed in place of 0,75 D1, where the ballast/light displace-ment ratio is less than approximately 0,25. For yachts with a drop keel, the value 1,15 D is taken in lieu of D1.

Solution I is only applicable where D1, does not exceed 3,60 metres.The frame spacing is intended as that measured amidships of the frames widths.


Pt B, Ch 5, Sec 4

Table 4 : Frames

Table 5 : Frames

Lugs for the connection of angle or plate floors to thewooden keel, if penetrated by the ballast keel bolts, are tohave a flange width at least three times the diameter of thebolt and thickness equal to that of the plate floor plus 2,5mm..

At the end of the hull, when frames are continuous throughthe centre structure, floors need not be fitted; wheneverpracticable, however, the frames are to be attached to thecentre structure by means of three through-bolts.

Floors are to be connected to frames by at least three boltsfor arms with length l < 250 mm and at least 6 bolts forgreater l; for diameters of bolts, see Table 10.

6 Beam shelves, beam clamps in way of masts, bilge stringers

6.1 Beam shelves

6.1.1 The cross-sectional area of beam shelves through 0,6L amidships is to be not less than that indicated in Table 6.Outside such zone, the cross-section may be graduallydecreased to reach, at the end, a value equal to 75% of thatshown.

The cross-section to be considered is to be inclusive of thedappings for fixing of beams.

Where beam shelves are made of two or more pieces, theconnection is to be effected by means of glued scarfs ade-quately arranged so as to be staggered in respect of thesheerstrake, waterway and bracket joints.

Scarfs are generally arranged vertically.

When the weather deck is not continuous owing to thepresence of raised decks, the shelf is to extend to the hullend or, alternatively, stiffeners are to be fitted to preventexcessive discontinuity due to the interruption of the deck.The scantlings of frames may be required to be increased.

Where angle frames are employed, reverse lugs are to be fit-ted in order to allow connection to the beam shelf. WhenType III framing is adopted, the shelf is to rest on the bentframes with interposition of suitable chocks.

The shelves are to be connected to each frame by a throughbolt for heights < 180 mm and by two through bolts forgreater heights. If metal frames are adopted, bolting of theshelf is to be effected on a reverse lug. For bolt scantlings,see Table 10.

DepthD1

mm (1)

FLOORS ON BENT FRAMES Plate floors on grown or steel floors

Length of armsmm

forged steel angle floors (2)

at throatmm

at the endsmm

sectionmodulus

cm3

scantlings mm

for 2/3 Lamidships

mm

outside 2/3 L amidships

mm

3,00 3,20 3,40 3,60 3,80 4,00 4,20

430465495530

---

29x1531x1633x1735x17

---

24x625x627x628x6

---

1,41,41,51,5---

40x40x440x40x440x40x440x40x4

---

300x5320x5330x5340x6345x6350x6360x6

200x4220x4230x4240x4245x4250x4260x4

(1) For hulls fitted with external ballast in the keel, 0,75 D1 may be assumed in place of D1, può essere assunto 0,75 D1, where theballast/light displacement ratio is less than approximately 0,25. For yachts with a drop keel, the value 1,15 D is taken in lieu ofD1.

(2) The scantlings of angle floors are given for guidance purposes.

DepthD1

mm (1)

FLOORS ON GROWN OR LAMINATED FRAMES

Length of arms forged floors wooden floors steel angle floors (2)

for 3/5 L amidships

mm

outside 3/5 L amid-

ship mm

at throat mm

at the endsmm

widthmm

depthmm

section modulus

cm3

scantlingsmm

3,00 3,20 3,40 3,60 3,80 4,00 4,20

580610650680720750780

430460500530560590620

56x2260x2464x2669x2873x3077x3180x31

50x1252x1354x1456x1658x1761x1863x20

51566064707580

135148160170180190200

2,403,605,706,906,909,0010,0

45x45x550x50x655x55x860x60x860x60x865x65x970x70x9

(1) For hulls fitted with external ballast in the keel, 0,75 D1, may be assumed in place of 0,25 circa. where the ballast/light dis-placement ratio is less than approximately 0,25. For yachts with a drop keel, the value 1,15 D is taken in lieu of D1.

(2) The scantlings of angle floors are given for guidance purposes.


Pt B, Ch 5, Sec 4

6.2 Beam clamps in way of masts

6.2.1 In way of masts, a beam clamp is to be arranged, oflength approximately equal to the hull breadth in the sameposition.

Such clamp, with cross-section equal to approximately75% of that required for shelves, may be arranged so that itswider side is faying to the beams and leaning against theshelf or, alternatively, it may be arranged below the shelf.

6.3 Bilge stringers

6.3.1 In hulls with Type I or Type III framing, a bilgestringer is to be arranged, having cross-section for 0,6 Lamidships not less than that given in Table 6. Outside suchzone, the cross-section may be decreased to reach, at theends, a value equal to 75% of that required.

The greater dimension of the stringer is to be arrangedagainst the frames.

When the stringer is built of two or more pieces, these areto be connected by means of glued scarfs parallel to theplanking. Such scarfs are to be properly staggered in theport and starboard stringers and arranged clear of the jointsof other longitudinal elements.

Where angle frames are adopted, these are to be connectedto the stringer by means of a reverse lug.

When Type III framing is adopted, chocks are to be fitted forthe connection between stringer and intermediate bentframes.

In lieu of a bilge stringer, two side stringers having cross-section equal to 60% of that required for the bilge stringermay be fitted.

6.4 End breasthooks

6.4.1 The beam shelves and the stringers are to be con-nected to each other at the hull ends, and with the cen-treline structure, by means of suitable breasthooks orbrackets.

In hulls with exceptionally raked ends, such breasthooksare to be given adequate attention.

7 Beams

7.1 Scantlings of beams

7.1.1 The scantlings of beams are given in Table 7. Wherethe spacing adopted is other than that shown in the Table,the scantlings, following correction as necessary for theweight of the timber employed, are to be modified inaccordance with the following relationship:

where a and b are the width and height of the Rule cross-section, a1 and b2 are the width and height of the modifiedsection, s is the Rule spacing, and s1 the assumed spacing.

Laminated beams may be reduced in width by 15%.

Strong beams are to be fitted in way of openings whichcause more than two beams to be cut and in way of masts,when deemed necessary by RINA.

Table 6 : Beam shelves and bilge stringers

Table 7 : Beams

a1 b12 a b2 s1

s----⋅=

Length L(m)

Cross-sectional area of beam shelvescm2

Cross-sectional area of bilge stringerscm2

24 26 28 30

190220250280

140160175190

Length of beam

m

Spa-cingmm

ORDINARY BEAMS FOR 3/5 L AMIDSHIPS

ORDINARY BEAMS OUTSIDE 3/5 L AMIDSHIPS, HALF BEAMS

STRONG BEAMS

Width

mm

DepthWidthmm

DepthWidth.

mm

Depth

at mid-beammm

at beam endsmm

at mid-beammm

at beam endsmm

at mid-beammm

at beam endsmm

3,003,504,004,505,005,506,006,507,007,50

350390430480520560600640680720

45515762687278838695

72809099106114121129132146

505763697580869296

105

39474852575962646769

54616774808795103113125

43485357626569717476

617278859398107116128140

8191101111120128136144156168

617278859398107116128140


Pt B, Ch 5, Sec 4

Table 8 : Vertical knees of beams

7.2 End attachments of beams

7.2.1 Beams are to be dovetailed on the shelf. When ply-wood deck planking is employed, in place of the dovetail asimple dapping may be adopted, having depth not less than1/4 of the beam depth; in this case, the beam is to be fas-tened to the shelf by means of a screw or pin.

Vertical knees are to be fitted, to the extent required inTable 8, to strong beams and to suitably distributed ordi-nary beams. Each arm of the knees is to be connected tothe shelf and the frame by means of 4 bolts, which need notgo through the planking, with a diameter as shown in Table10.

Bulkheads of adequate scantlings, connected to the beamand frame, can be considered as substitutes for knees.

At the ends of the hull, the length of knee arms may be notmore than one third of the span of the beam or frame.

In the above-mentioned Table, the scantlings of forged plateknees are given; the depth at the throat is to be not less than1,6 h for naturally curved wooden knees and not less than

1,4 h for laminated wooden knees, h being the depth atheel of a grown frame.

Horizontal knees are to be fitted in way of hatch-end beamsand beams adjacent to mast wedgings. These knees neednot be arranged when plywood deck planking is adopted.

7.3 Local strengthening

7.3.1 The beams and decks are to be locally strengthenedat the attachments of halliards, bollards and cleats, at sky-light ends, and in way of foundations of winches.

In way of mast weldings, four strong beams are to be fitted,with scantlings as prescribed in Table 7, but constant sec-tion equal to that indicated for amidships. The beams are tobe arranged, as far as practicable, in proximity of the webframes dealt with in 4.2.

All openings on deck are to be properly framed so as toconstitute an effective support for half beams.

7.4 Lower deck and associated beams

7.4.1 In hulls with depth, measured from the upper side ofthe wooden keel to the weather deck beam at side > 3 m,metres, a lower deck or cabin deck is to be arranged and fit-ted with beams having scantlings not less than 60% of thoseof the weather deck.When the depth, measured as specified above, exceeds 4,3metres, vertical knees are to be arranged no smaller inscantlings than prescribed in Table 8 as a function of thebeam span, and in number equal to half of those requiredfor the weather deck.

8 Planking

8.1 Shell planking

8.1.1 The basic thickness of shell planking is given inTable 9.Such thickness is to be modified as follows.

If the frame spacing is other than that indicated in Table 2,the thickness is to be increased where there is greater spac-ing, or may be reduced where there is smaller spacing, by:- 6 mm for every 100 mm of difference if Type I framing

is adopted;- 4 mm for every 100 mm of difference if Type II or III fra-

ming is adopted.

After correction for spacing as indicated above, and for theweight of the timber, where necessary, the planking thick-ness may be reduced: by 10% if arranged in diagonal orlongitudinal double skin; by 10% if laminated and coldmoulded in loco, when the frames are reduced in scantlingsby 25% in respect of the value given in Table 2; the thick-ness may be decreased by 25% where the frames have notbeen reduced in respect of the requirements of the Table.

When plywood is employed, the thickness may be reducedin relation to the type of framing adopted; the maximumreduction permitted is 25%.

Sheathing of the hull is not required; where envisaged, e.g.in copper or reinforced plastics, it will be considered byRINA on a case-by-case basis (see Sec 6. para. 1.8).

Length of beams

m

Number (1) of knees on

each side

LENGTH OF ARMS FORGED KNEES STEEL ANGLE KNEESPLATE KNEES

thicknessmm

for 3/5 L amidships

mm

outside 3/5 L amidships

mm

at throatmm

at the ends mm

dimensiona-mento (2)

mm

sectionmodulus

cm3

3,003,504,004,505,005,506,006,507,007,50

56789

1010111212

400440490530570610650700740780

320350390420450490520560590620

34x1741x2048x2353x2657x2862x3067x3272x3478x3581x37

30x737x742x846x949x1052x1154x1255x1457x1658x17

40x40x550x50x555x55x560x60x675x50x675x50x790x60x790x60x8100x65x7100x65x8

1,703,004,305,907,509,30

11,5014,0016,0019,00

4445556667

(1) The number of knees is given on the basis of the maximum breadth B of the hull, using the column for the length of beam.(2) The scantlings of angles are only given as indications.


Pt B, Ch 5, Sec 4

8.2 Deck planking

8.2.1 Deck planking may be:

• constituted by planks parallel to the gunwale limited bya stringer board at side and by a kingplank at the centre-line;

• plywood;

• plywood with associated planks as above.

The thickness of the deck is given in Table 9 and is subjectto the following modifications:

• if the beam spacing is other than that indicated in Table7, the thickness is to be modified by 3 mm for every 100mm of variation in spacing;

• if plywood is employed, the thickness may be reducedby 30%;

• if plywood is adopted in association with planking, thespecific mass of the plywood/planking assembly is to be

not less than 430 kg/m3, and the combined thicknessmay be reduced by 30%. In addition, the plywood thi-ckness is to be not less than 30% of the combined thick-ness, or less than 6,5 mm; when the planking thicknessis less than 19 mm, the seams are to be made watertightby the application of a suitable elastic compoundapproved by RINA.

A further reduction of 1,5 mm may be applied to the deckthickness when the deck is sheathed with nylon, reinforcedplastics or other approved coverings.

The fixed fittings on deck, in particular winches, wind-lasses, ballards and fairleads, are to be well secured on suit-able basements and isolated by means of coatings ofappropriate materials. Before applying such insulatingmaterials to the basements, the timber is to be protected bysuitable preservative solutions or paints.

Guardrail stanchions are to be fastened by at least two pins,one of which is to be a through pin.

Table 9 : Planking - basic thickness

Table 10 : Floor fastenings

LengthLm

Shell and deck planking mm

Deck planking in deckhouses and coachroofs

mm

Coamings of coachroofs mm

24 26 28 30

45,547,55052

26272829

36363636

Depth of yachtDm

Diameter of bolts

at throat in the arms

Grown, or laminated, or steel frames

mm

Bent framesmm

Grown, or laminated, or steel frames

mm

Bent framesmm

≤2,4 2,6 2,8 3

3,2 3,4 3,6 3,8 4

4,2

12121414161820202022

89

1012121414---

891012121414141616

8888999---

FASTENINGS OF LONGITUDINAL STRUCTURES

Length of yachtLm

Diameter of bolts

Centreline structures of yachts

mm

Scarfs and breasthook armsmm

Beamshelves and beam kneesmm

24 26 28 30

20202222

14141618

11111214


Pt B, Ch 5, Sec 4

8.3 Superstructures - Skylights

8.3.1 When coachroofs are adopted, the opening on deckis to be well framed and the coaming on the weather deckis to be not less in thickness than that required in Table 9.

The coachroof deck is to have sheathing as prescribed inTable 9, though such sheathing may be reduced in thick-ness in accordance with the specifications in 8.2 for theweather deck. If the beam spacing is other than that indi-cated in Table 5, the thickness is to be modified by 3 mmfor every 100 mm of difference in spacing.

When deckhouses are adopted, they are to have a coamingfastened to the beams and carlings by means of throughbolts.

The structure of deckhouses is to be similar to that requiredfor coachroofs. Depending on their size, deckhouses are tobe adequately stiffened to the satisfaction of RINA.

Deck openings for skylights are to be well framed and pro-vided with shutters of adequate thickness.

8.4 Masts and rigging

8.4.1 Each yacht is to be provided with masts, rigging andsails sufficient in number and in good condition. The scant-lings of masts and rigging are left to the experience of build-ers and shipowners. Care will be taken by the RINASurveyor, however, in verifying that the attachments of

shrouds and stays to the hull are such as to withstand atleast twice the load expected on such rigging.The mast step is to be of strong construction, and is to beextended so as not to be connected to the transverse andlongitudinal framing of the bottom of the hull. The wedgingon deck is to be provided with watertight means.

When the mast rests on deck, the underlying structure is tobe strengthened in way such as to avoid giving way. If themast rests on a coachroof, the hull is to be strengthened inway by means of a bulkhead or a stiffened frame.

For shrouds and stays in wire and not in rod, the breakingloads of wires in galvanised steel 160 UNI 4434, in spiralshape, 1x19 wires (col. 1), and in stainless steel AISI 31618/10 (ASTM-A 368-55) 1x19 wires, in spiral shape (col. 2)are included below for information purposes.

Table 11

Diameter(mm)

Metallic

cross-sec-tion

(mm2)

Breaking load kN

Col. 1 Col. 2

345678

1012

5,379,5514,221,529,238,259,786,0

7,7513,7321,1030,9041,6054,9465,73

122,63

7,3613,7320,6029,4340,2252,9783,39

117,72


Pt B, Ch 5, Sec 4

Figure 1 : Sailing yachts - Constructional profile

1-

Woo

d k

eel

2-

Exte

rnal

bal

last

3-

Hog

4-

Rabb

et

5-

Stem

post

6-

Ster

npos

t

7-

Knee

8-

Rud

der

9-

Prop

elle

r ape

rture

10 -

Floo

rs

11 -

Mai

nmas

t ste

p

12 -

Mizz

en st

ep

13 -

Ster

n co

unte

r

14 -

Uppe

r ste

rn

15 -

Fram

es

16 -

Strin

gers

17 -

Shel

ves

18 -

Beam

s


Pt B, Ch 5, Sec 4

Figure 2 : Midship section

1-Wood keel

10-Shelf

11-Beam clamp

12-Half beams

13-Deck planking

14-Waterway

15-Seam

16-Stay seam

17-Carling

18-Coaming "Coachroof"

19-Side planking "Coachroof"

20-Beam "Coachroof"

21-Shelf "Coachroof"

22-Top "Coachroof"

2-Ballast

3-Frame

9-Sheerstrake

4-Floor

5-Stringers

6-Bottom simple planking

7-Planking inner skin

8-Planking outer skin


Pt B, Ch 5, Sec 4

Figure 3 : Sternframe

1-

Woo

d k

eel

2-

Exte

rnal

bal

last

10-

Hog

6-

Heel

pie

ced

l

7-

Rud

der

8-

Prop

elle

r ape

rture

9-

Ster

n co

unte

r

3-

Rabb

et

4-

Ster

npos

t

5-

Knee


Pt B, Ch 5, Sec 4

Figure 4 : Typical floors

ANGLE FLOOR

ANGLE FLOOR

WOOD FLOOR

PLATE FLOOR

L = lenght of arms

h = height of floor


Pt B, Ch 5, Sec 5

SECTION 5 STRUCTURAL SCANTLINGS OF MOTOR YACHTS

1 General

1.1

1.1.1 The scantlings in this Section apply to yachts oflength L ≤ 35 metres with a chine hull of the type shown inFigures 1 and 2 and speed not exceeding 40 knots.For yacht which differ substantially from the above asregards dimensions and/or speed, or yachts with roundkeels, the scantlings are determined by equivalence criteria.

2 Keel - stempost

2.1

2.1.1 The minimum breadth of the keel and the aggregatecross-sectional area of keel and hog frame are given inTable 1.Such scantlings are to be maintained up to the stem end,while they may be reduced by 30% at the stern end.

Where they are made from a number of pieces, the keel andhog frame are to be scarfed. The scarfs are to be 6 times thethickness and of hooked or tabled type, if bolted, or of plaintype, if glued; the length may be reduced to not less than 4times the thickness where the scarf is bolted and glued.

The keel scarfs are to be spaced not less than 1,5 metresapart from those of the hog frame.

Stempost scantlings are given in Table 1 and a typical stern-frame is shown in Figure 3.

3 Transom

3.1

3.1.1 In chine hulls, the sternpost is replaced by a tran-som.

The transom structure consists of a frame having profileparts with a cross-section not less than 120% of bottomframes, side frames or beams; moreover, the structure's ver-tical stiffeners, arranged in way of keel and bottom girders,are to have a cross-section with a height equal to that of theside frames and width increased by 50%.

The stiffeners above are generally to be spaced not morethan 600 mm apart.

The thickness of transom planking is to be equal to thatgiven in Table 2 (col. 2), with any modifications required inaccordance with those specified for shell planking.

4 Floors and frames

4.1 General

4.1.1 The ordinary framing of the hull is divided into threeparts:

- bottom frames, comprising those between the keel andthe chine stringers;

- side frames, comprising those between the chine string-ers and the waterways;

- beams.

The bottom frames, generally made of two pieces, one portand one starboard of the keel, are butted in way of the cen-treline and connected by means of a double plywood floor.

The side frames are in one piece connected to the bottomframes by means of double plywood brackets.

The beams are connected to the side frames by means ofdouble plywood brackets.


Pt B, Ch 5, Sec 5

Table 1 : Keel and stempost

4.2 Bottom and side frames

4.2.1 Frame scantlings are given in Tables 3, 4 and 5,where three different types of frames are considered:

Type I : solid or laminated frames, of constant scantlingsthroughout the length of the hull;

Type II : solid or laminated frames, alternated with oneor two bent frames. Only the former are con-nected by means of floors and brackets; thescantlings are as prescribed for Type I frames;

Type III : solid or laminated frames, associated with bentlongitudinals; this type of framing is to be asso-ciated with double-skin cross planking or coldmoulded laminated multi-layer planking or,alternatively, with plywood planking.

4.3 Floors

4.3.1 The floors connecting bottom frames (see 4.1) are tohave thickness equal to half that required for the latter,extend at the yacht's centreline to a height not less thantwice that prescribed for the heel of such frames and over-

lap the frames by a distance not less than 2,5 times theirdepth so as to constitute an effective connection by meansof glue and clenched bolts. The space between the twofloors above the frames is to be fitted with a chock; alterna-tively, the frames may be shaped so as to have, at the cen-treline, a depth above the keel equal to that required for theheel of the frames. For floors, see Figure 4.

4.4 Frame and beam brackets

4.4.1 The connection of bottom frames to side frames andof the latter to beams is to be achieved be means of doublebrackets similar to those described for floors, but overlap-ping both frames and beams by a distance not less thantwice their respective depths (see Figures 5 and 6).

In lieu of the brackets above, the frame-beam connectionmay be effected by simply overlapping, preferably dovetail-ing the beam on the shelf (with glueing and pivoting), andprovided that transverse bulkheads are arranged, with spac-ing not exceeding approximately 2 metres, so as to consti-tute main transverse strengthening elements of the hull, andthat no superstructure is arranged on the weather deck.

Table 2 : Shell and deck planking

Table 3 : Frames

LengthL

m

KEEL STEMPOST

Minimum breadth

mm

Cross-section of keel or keel and hog (1)

cm2

Width at heel and at head

mm

Cross-section at heel

cm2

Cross-section at head

cm2

1 2 3 4 5 6 24 26 28 30

230245260280

413462516570

230245260280

413462516570

289324361399

(1) Where there is no hog frame, a reduction in keel area of 10% in respect of that prescribed may be permitted. A keel cross-sec-tion reduced such as to be not less than 0,85 of that given in col. 3 may be accepted provided that the difference is compen-sated by an increased cross-section of girders.

LenghtLm

SHELL PLANKING Weather deck planking

mm

Deck of superstructures (quarterdeck, deckhouses, coachroofs, trunks)

mmType I and II framing

mmType III framing

mm

1 2 3 4 5

24 26 28 30

323436

37,5

28,53032

33,5

323436

37,5

21212121


Pt B, Ch 5, Sec 5

Table 4 : Frames

5 Side girders and longitudinals

5.1

5.1.1 On bottom frames, at least two continuous girdersare to be fitted each side, with a cross-section not less than90 cm2.

Such girders, continuous over bottom frames, are to be con-nected to the bottom planking by means of chocks betweenframes, set on a bent longitudinal continuous through the

floors and connected to the planking. The chocks and thebent longitudinal may be omitted, but in such case the bot-tom planking thickness given in Table 2 is to be augmentedsuch as to achieve a cross-section throughout the bottomincreased by at least half that of the longitudinals.

A similar longitudinal, but with a cross-section reduced to0,65 of those described above and not fastened to theplanking, is to be fitted on side frames.

Such longitudinal may be omitted where Type III framing isadopted.

Table 5 : Frames

Table 6 : Frames

DepthDm

TYPE I FRAMING (EITHER GROWN, OR LAMINATED FRAMES ONLY)

Spac-ing of webmm

BETWEEN KEEL AND CHINE BETWEEN CHINE AND DECK

Grown frames Laminated frames Grown frames Laminated frames

width.mm

depthwidth.mm

depthmm

widthmm

depthwidth.mm

depthmmat heel

mmat head

mmat heel

mmat head

mm

3,0 3,1 3,3 3,5 3,7 3,9

322340355375390408

353944505560

127140148162178200

116127135148162182

353944505560

93104113125135157

353944505560

103117122131143156

90108110115123130

353944505560

8594

103114125143

DepthD

mm

TYPE II FRAMING (EITHER GROWN OR LAMINATED FRAMES WITH BENT FRAMES IN BETWEEN)

Spacing between main frames and alternate frames Bent frames

one bent framemm

two bent framemm

three bent framesmm

widthmm

depthmm

3,0 3,1 3,3 3,5 3,7 3,9

560590620

---

650690725

---

730770800

---

363840---

252730---

DepthDm

TYPE III FRAMING (GROWN OR LAMINATED FRAMES OR BENTWOOD LONGITUDINALS)

Spacing of web

mm

BETWEEN KEEL AND CHINE BETWEEN CHINE AND DECK

Grown frames Laminated frames Grown frames Laminated frames

widthmm

depthwidthmm

depthmm

widthmm

depthwidthmm

depthmmat heel

mmat head

mmat heel

mmat head

mm

3,0 3,1 3,3 3,5 3,7 3,9

640680710750780820

374146525862

148160176192208232

126136150163176197

374146525862

92103112124135156

374146525862

104112122135146160

94106110115122129

374146525862

8493

103113123142


Pt B, Ch 5, Sec 5

6 Beams

6.1

6.1.1 The arrangement of beams is generally to be carriedout as follows:- for hulls with Type I framing: beams on every frame;- for hulls with Type II or III framing: beams in way of

solid or laminated frames, with bracket connection andintermediate beams, without brackets, let into the shelf.

Beams are to have width equal to that of the frames towhich they are connected and section modulus, in cm3,not less than:

At the ends of large openings, beams are to be fitted havinga section modulus, in cm3, not less than:

where:Z1,Z2 : section modulus of beams without planking

contribution, in cm3

a : width of beams, in cm s : beam spacing, in cmK1,K2 : coefficient given by Table 7 as a function of the

beam span.Where laminated beams are arranged, the section moduliZ1 and Z2 may be reduced to 0,85 of those indicated above.

Table 7

7 Beam shelves and chine stringers

7.1

7.1.1 The cross-sectional area of beam shelves and chinestringers is to be not less than that given by Table 8 belowas a function of L and to have the ratio h/t < 3, where h isthe depth and t the thickness of the bar.

The cross-section of shelves and stringers is to be consid-ered as inclusive of the dappings for beam and frame ends.

Table 8

DepthDm

TYPE III FRAMING (GROWN OR LAMINATED FRAMES OR BENTWOOD LONGITUDINALS)

BENTWOOD LONGITUDINALS

spacingmm

between keel and chine between chine and deck

widthmm

depthmm

widthmm

depth mm

3,0 3,1 3,3 3,5 3,7 3,9

285300315330345360

454850535558

303336394245

454850535558

252730333639

Z1 K1 a s⋅ ⋅=

Z2 K2 a s⋅ ⋅=

Beam span(m)

Coefficients for calculation of beam section mod-ulus

K1 K2

At thecentreline

At the endsAt the

centrelineAt the end

≤22,53

3,54

4,55

5,56

6,57

7,5

14,318

22,224,728,330,632,435,136,938,739,640,5

6,438,5

10,712,513,914,916,317,118,119,520,523

2331

38,643,648,752,556,860

63,570

73,581

11,415,117,722,223,625,227,728,731,835

40,245,4

Length L of the hull(m)

Cross-sectional area of beam shelves (cm2)

Cross-sectional area of chine stringers (cm2)

242628303235

95110125140155177

112128140152164182


Pt B, Ch 5, Sec 5

8 Shell planking

8.1 Thickness of shell planking

8.1.1 The basic thickness of shell planking is given in Table2.

If the frame spacing is other than that shown in Table 3, theplanking thickness is to be increased or may be reduced,accordingly, by 10% for every 100 mm of difference.

After correction for spacing, the planking thickness may bereduced:

- by 10% if a diagonal or longitudinal double-skin plank-ing is adopted;

- by 15% if composite planking constituted by inner ply-wood skin and one or two outer longitudinal diagonalstrakes is adopted;

- by 25% if laminated planking (i.e. at least three cold-moulded layers) or plywood is adopted.

Moreover, the plywood thickness is to be not less than 30%of the total thickness or less than 6 mm.

yachts with speed > 25 knots are to have bottom frames(floors and longitudinals) stiffened in respect of the scant-lings in this Section and planking thickness increased as fol-lows (for deadrise = 25°) in respect of the values in Table 2:

- speed from 26 to 30 knots: 5%

- speed from 31 to 35 knots: 10%

- speed from 36 to 40 knots: 15%.

When the deadrise is between 25° and 30° and outer longi-tudinal strakes are fitted on the bottom planking, the aboveincrease in thickness may be reduced but is generally to beno less than half of the percentage values above.

9 Deck planking

9.1 Weather deck

9.1.1 Deck planking may be constituted by planks flankedby a stringer board at side and by a kingplank at the cen-treline. Such planking may be solely plywood or plywoodwith associated planking arranged as described above.The thickness of deck planking is given in Table 2. If thebeam spacing is other than that prescribed in 4.2, the plank-ing thickness is to be increased or may be reduced, accord-ingly, by 10% for every 100 mm of difference.

After correction for spacing, the planking thickness may bereduced by 30% if plywood or plywood associated withplanking is employed.

Moreover, the plywood thickness is to be not less than 30%of the total thickness or less than 6 mm.

9.2 Superstructure decks

9.2.1 The thickness of planking of superstructure decks isgiven in Table 2.Such thickness is subject to the reductions and increases forweather deck planking as provided for in 9.1.

9.3 Lower deck

9.3.1 In hulls with depth, measured between the upperkeel side and the weather deck beam, greater than or equalto 3,10 metres, a lower or cabin deck is to be arranged,with beams having a section modulus not less than 60% ofthat prescribed in Article 6 for weather deck beams andeffectively fastened to the sides by means of a shelf with aross-sectional area not less than 2/3 of that required in Table8.When the depth, as measured above, exceeds 4,30 metres,the fastening of beams to side is to be completed by meansof plywood brackets arranged at least at every second beamand having scantlings as prescribed in 4.4.

The scantlings of the deck planking are to be not less thanthose required in 9.2.


Pt B, Ch 5, Sec 5

Figure 1 : Motor yachts - Constructional profile

1 -

Kee

l

2 -

Hog

3 -

Gro

wn

fram

e

4 -

Chi

ne s

trin

ger

5 -

Ben

t fra

me

6 -

Ste

mpo

st

8 -

Ste

m

7 -

Apr

on

9 -

She

lf

10 -

Kne

e

11 -

Tra

nsom

stif

fene

rs

12 -

Tra

nsom

fram

e

13 -

Tra

nsom

fram

e

14 -

Chi

ne k

nees

15 -

Flo

ors

16 -

Bea

m k

nees

17 -

Bea

m


Pt B, Ch 5, Sec 5

Figure 2 : Midship section

1 -

Kee

l2

- H

og

3 -

Bot

tom

fram

e4

- S

ide

fram

e

5 -

Dou

ble

knee

6 -

Chi

ne7

- B

ent f

ram

e

8 -

Bea

m9

- D

oubl

e kn

ee

10-

Bot

tom

str

inge

rs11

- D

eadw

ood

12-

Sid

e st

ringe

rs13

- S

helf

14-

Car

ling

15-

Bot

tom

and

sid

e pl

anki

ng -

Inne

r sk

in

16-

Bot

tom

and

sid

e pl

anki

ng -

Out

er s

kin

17-

Dec

k pl

anki

ng -

Inne

r sk

in18

- D

eck

plan

king

- O

uter

ski

n19

- W

ater

way


Pt B, Ch 5, Sec 5

Figure 3 : Stem

1 -

Kee

l

2 -

Hog

3 -

Ste

m

4 -

Ste

mpo

st

5 -

Apr

on


Pt B, Ch 5, Sec 5

Figure 4 : Detail of floor

1 -

Kee

l

2- H

og

3 -

Bot

tom

fram

e

4 -

Bot

tom

str

inge

r

5 -

Ben

t fra

me

6 -

Pla

nkin

g -

Inne

r sk

in

7 -

Pla

nkin

g -

Out

er s

kin

8 -

Dou

ble

floor


Pt B, Ch 5, Sec 5

Figure 5 : Detail of floor

1 -

Bot

tom

fram

e

2 -

Sid

e fr

ame

3 -

Dou

ble

knee

s

4 -

Chi

ne s

trin

ger

5 -

Pla

nkin

g -

Inne

r sk

in

6 -

Pla

nkin

g -

Out

er s

kin

7 -

Chi

ne


Pt B, Ch 5, Sec 5

Figure 6 : Detail of gunwale connection

1 -

Sid

e fr

ame

2 -

Bea

m

3 -

Dou

ble

knee

s

4 -

She

lf

5 -

Hul

l pla

nkin

g -

Inne

r sk

in

6 -

Hul

l pla

nkin

g -

Out

er s

kin

7 -

Dec

k pl

anki

ng -

Inne

r sk

in

8 -

Dec

k pl

anki

ng -

Out

er s

kin

9 -

Wat

erw

ay

10 -

Rub

bing

pie

ce


Pt B, Ch 5, Sec 6

SECTION 6 WATERTIGHT BULKHEADS, LINING, MACHINERY

SPACE

1 Wooden bulkheads

1.1

1.1.1 Wooden watertight bulkheads normally consist ofplywood boards of adequate thickness in relation to the hullsize and the spacing and strength of stiffeners. Glues fortimber fastenings are to be of resorcinic or phenolic type,i.e. durable and water-resistant in particular.As regards the number of watertight bulkheads, attention isdrawn to the provisions of Chapter I of Part B.

The plywood, normally arranged in vertical panels, is to bescarfed or strapped in way of vertical stiffeners.

Connection to the hull is to be effected by means of agrown or laminated frame and made watertight by packingwhere necessary.

2 Steel bulkheads

2.1

2.1.1 Steel watertight bulkheads are to be of thickness asshown in Table 1 as a function of the spacing of stiffenersand the height of the bulkhead.The scantlings are given on the assumption that the loweststrake is horizontal and subsequent strakes vertical. Whenall strakes are horizontal, the thickness of the third andhigher strakes may be decreased by a maximum of 0,5 mmper strake so as to reach a reduction of 25%, in respect ofthe Table thickness, for the highest strake.

If the spacing is other than that shown in the Table, thethickness is to be modified by 0,5 mm for every 100 mm ofdifference in spacing. The spacing of vertical stiffeners isnot to exceed 600 mm for the collision bulkhead.

The scantlings of vertical stiffeners, in cm3, without endconnections are to be not less than:

where:

Z : section modulus of vertical stiffener with associ-ated strip of plating one spacing wide, in cm3

h : distance from midpoint of stiffener to top ofbulkhead, in m

s : spacing of vertical stiffeners, in m

S : aggregate span of vertical stiffeners.

The connection of the bulkhead to planking is to be effectedon grown or laminated frames, and provided with water-tight packing where necessary.

Bulkheads are to be caulked or made watertight by meansof suitable gaskets. On completion, any watertight bulk-heads and doors are to be tested using a strong jet of water.

3 Internal lining of hull and drainage

3.1

3.1.1 Where ceilings or internal linings are arranged, theyare to be fitted so as to be, as far as practicable, easilyremovable for maintenance and painting of the underlyingstructures. Linings are to allow sufficient ventilation of airspaces between them and planking.

Limber holes are to be provided in the bottom structuressuch as to allow the drainage of bilge liquids into suctionwells.

4 Machinery space structures

4.1

4.1.1 The scantlings of floors, web frames and foundationgirders are to be adequate for the weight, power and type ofmachinery; their suitability and that of associated connec-tions is to be satisfactory with particular regard to enginerunning and navigation tests when required by these Rule.Z 4 2, 4h+( )s S2⋅=


Pt B, Ch 5, Sec 6

Table 1 : Watertight steel bulkheads

Height of bulkheadmm

Spacing of vertical stiffenersmm

Thickness of lower strakemm

Thickness of other strakesmm

≤2,40 2,60 2,80 3,00 3,20 3,40 3,60 3,80 4,00 4,20 4,40 4,60 4,80 5,00

375390410425440460475490510525540560575590

455

5,55,55,56666

6,56,56,56,5

3,54,54,5555

5,55,55,55,56666


partb

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