20.11.2013

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High Speed Crafts

What is High Speed Craft?

High-speed craft is a craft capable of a

maximum speed in meters per second (m/s)

equal to or exceeding:

Vmax = 3.7 0.1667

where:

= displacement volume corresponding to the design waterline (m3).

Prof. Metin Taylan

20.11.2013

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High Speed Craft

A high-speed vessel is generally defined as crafts operating with Froude number (Fn) larger than about 0.5.

Generally speaking, the buoyancy force dominates relative to the hydrodynamic force effect when Fn is less than approximately 0.5.

When Fn>1.0, the hydrodynamic force mainly carries the weight, and the vessel is called a planing vessel.

Semi-displacement Vessel

In general, vessels operating with maximum speed in the range

0.5 < Fn < 1.0

are called semi-displacement vessels

Prof. Metin Taylan

20.11.2013

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Graphical Definition

Design Parameters

Empirical evidence has shown that two important relations in the design of high speed hulls are;

Prof. Metin Taylan

20.11.2013

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Design Parameters

Means of Support Systems

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20.11.2013

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Air Cushion Vehicle

Surface Effect Ship (SES)

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20.11.2013

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Bow Seal

Static Equilibrium at Zero Speed

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20.11.2013

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Air Cushion Reduces GM

Disadvantages of SES

Strength/weight (all high-speed vessels)

Propulsion/machinery

Wear of skirts

Ride control of cobblestone effect

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20.11.2013

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Seakeeping of SES

Cobblestone oscillations

-small sea states

-automatic control

-scaling of model tests

Ventilation of water jet inlet in waves -Automatic control of propulsion system

Speed loss in waves -Sufficient fan power

Cobblestone Effect

Prof. Metin Taylan

20.11.2013

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Automatic Control System

Ventilation of Waterjet Inlet

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Speed Range Comparison

Air Cushion Support During Take-off

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Hydrofoil Vessels

Free Surface Piercing Foils

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Fully Submerged Foil System

Foil Systems

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Sailing Catamaran with Foils

Hydrofoil vessels

Cavitation and ventilation limits the speed

Sufficient power during lift to foilborne condition

Automatic motion control for submerged foil system

Submerged foil system gives very good seakeeping behaviour

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20.11.2013

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Important Aspects

Maintenance of directional and roll stability

Stable recovery when a foil comes out of the water (broaches)

Graceful deterioration of performance in severe seas

Safety

Maneuvering

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20.11.2013

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Side Force Coefficient on Strut used as Rudder (Model Tests)

Automatic Control System

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Automatic Control

Foil Interaction

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Downwash at Aft Foil Due to Forward Foils

Birds in V-Form

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Birds in V-Form

Flap Effect

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Flap Action

Semi-Displacement Vessels

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SWATH Ships

Wave-Piercing Catamarans

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Trimaran

Pentamaran

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T-Foil

Americas Cup

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Trim Tab Installation

Interceptor and High-speed Rudder

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Anti-roll Damping Fins

Resistance

Spray resistance

Air resistance

Viscous resistance

Form factors

Flow separation at transom stern

Wave resistance

Wash

Wave decay of wave systems

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20.11.2013

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Resistance and Propulsion of Sea Animals

Spray Resistance

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Air Resistance and Flow

Kelvin Waves

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Kelvin Waves

HSC Wave System Near Critical Speed

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Wave Pattern at Critical Speed

Wave Pattern at Super-critical Speed

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Waterjet Propulsion

Deck (Bow) Diving of High Speed Catamaran in Following Waves

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Steady Roll Stability as a Function of Speed

Roll Stability

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Global Wave Loads

Local and Global Slamming Effects

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Slamming Drop Test

Stena Discovery Accident (1997)

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Global Slamming Effect

Green Water on Deck

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Green Water on Deck

Hammer Fist and Karate

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Stepped Planing Hull

SteamerDuck

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Porpoising in Nature and of Planing Vessels

General Types of Instability

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Spray Rails

A way to improve the lack of lift production associated with a deep V-shape is to add spray rails along the hull. When water flows sidewards it is forced to turn downwards by the rail and creates a lift force.

The flow generally runs sidewards along the forebody and more parallel towards the keel.

For this reason, spray rails may be cut towards the stern as they will increase resistance.

Spray Rails Spray rails should be used conservatively since if high lift is

developed when the forebody hits the waves, large accelerations may occur and reduce the positive effect of the V-shape.

Prof. Metin Taylan