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HOWTOVOLUME ONE

INTRODUCTION

To those of us involved in R/C sailing, Lloyd "Swede" Johnson is legendary for the many

contributions he has made to the evolution of remote control sailing. Recognized as one of the

foremost innovaton in hull design, sails and how they are rigged, rig design and literarily hundreds of

little odds and ends that contribute to making a boat simple, efficient and fast. Several of the boats

Swede has designed and many of his theories of "what can I do to make a boat go faster" have

played a major role in the evolution of R/C sailing over the past thirty years. For anyone who has had

the pleasure of meeting Swede knows that what makes him truly a remarkable designer and innovator

goes far beyond the boaB that he put in the water. His willingness to share his vast wealth of

knowledge with other designers, builden and skippers is what makes Swede Johnson truly an R/C

sailing treasure.

This collection of Swede's "How To" , edited by Dennis Desprois, is not only intended for the

serious designer/builders but also for those skippen who simply want to better understand how

different parts of an R/C yacht are made and why they do what they do.

GOOD SAILING !

Dennis Desprois

March 2000

LLOYD F.'SWEDE" JOHNSON

Lloyd "Swede" Johnson, the renown sailmaker and remote control sailing innovator from CostaMesa, Califomia was born in Pomona, Califomia in 1919. In 1985, in recognition of his ou6tandingcontdbution to setting for ocean racing for local yacht clubs, Swede was awarded the Edward F.Kennedy Memorial Newport HarborYach8man of the Year Trophy. Swede set the mark for suchprestigious races as the Governor Cup in 1979, 81 and 1984, the Finn Nationals in 1980 and the SixMeter Nationals in 1981. In 1981, 82 and 83, Swede set the couses for the U.S.Y.R.U. 0lympiEclasses. In 1985 he set the courses for the Etchells 22 Worlds, 5.5 World Championship and theScandinavian GOLD CUP. When the )filll Olympic Games were in Los Angeles in .1984, Swede notonly was the sail measure for the 470 Class, he atso designed and built the inflatable mark that wereused on the course. Swede was deservedly elected to the Balboa Yacht Club's Hall of Fame in t gg8.

The long list of successful R/C sail boats designed by Swede include the ORCo (for 0rangeCounty), the SKlNfrff Marblehead and the ORCO HOTDOG. In the 36/600 and one Meter Classes,Swede has designed the ORCO FIAIRBOW, the SKINNY and the torpedo shaped ORCO 90 all of whichhave won ACCR',s. Swede's latest but certainly not his last 35/600 design is the oRCo MILLENNIUM.

MODET DESIGN

It seems the trend of model design is to make them look like their full size counter parB with

fine ends, overhangs and even wings on the keels. The end resuh is a model that lacla the stability to

stand up to a ten knot wind. Many of our AMYA class models, such as the soling, East Coast Twelve

Meter, Santa Barbara and''6specially the Vitoria and Fainrind (not yet an AMYA certified class) have

the shape and proportion but NOT the performance of their larger counter parb. These designs make

the aesthetics a priority over performance. Of cou6e, it is desirable to have a one design class that

not only loob appealing with rules that allow an equal chance at winning during a competitioRtirr

The logistia, however, dictate that this type of model could have been made to be a much

higher performer with no addition of cost to the manufacture or builder simply by considering the

scaling effecg incurred with the proportions when making a smaller boat.

My intent isn't to advocate and changes in existing class rules or to criticize the designers of

the above mentioned boats but to possibly influence those penons endeavoring to design new model

boats by explaining the phenomenon: AS A BOAT DECREASES lN SIZE, PROPORTIONS DO NOT

DECREASE EQUALLY.

For example, let's"take an ffCHELL a highly successful 30.5 foot racing class sailboat and

scale it down to one tenth or a thirty-six inch model.

ETCHEI.I

LENGTH OVER ALL: 30'.5"SAIL AREA SQ. FT.: 291WATERLINE LENGTH: 22'.0BEAM: 7'.0DRAFI : 4'.5"DISPLACEMENT CU/ff.: 51 .17DISPIACEMENT LBS. 3275.0

MODEL

3' .052.91 (DOWN BY THE SQUARE)z'..2u.7u.45'.05117 (DOWN BY THE CUBE)3.194 (DOWN BY THE CUBE)

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MAST HEfGHT: 35'.0HEEL| NG ARM FT.: 15.6RIGHTING ARM ff.: 2.55

3'.5r',1.56.255

The heeling arm is distance from the center of the sail area to the center of underwater lateralplane. The righting arm is the distance from the veftical center o1 buoyancy to the veftical center ofgravlty. The wind pressure per squar foot of sail area at 8 miles is .25 pounds from Martin's formula:P:.004 X velocity squared.

To calculate the heeling angle in 8 miles of wind using the Dellenbaugh formula:

57.3 X sail area X heeling arm X wind pressure per square foot

ETCHELL

57 .3 X 291 X 15.6 X .25

2.56 X 3275

Righting arm X displacement in pound

MODELdid. . .

57.3 Xz.gl x 1.56 X .25-7 .7 5 dggfges ------------------------------r-o-or 79.5 degfges

255 X 3.194 (down by the 4* power)

As you an see, the displacement has scaled down faster than the sail area and the stability hasscaled down faster than the displacement. The numben clearly illustrate that whi6 the FICHELL isbarely heeling, the model is flat on it,s ear!

The correction would be to add weight down low and increase the hull displacement tocompensate or to lower the center of the sail area or both. Obviously, by putting the weight deeperwill give the righting arm more leverage without adding to the displacement (providing the pond isdeep enough).

The reduction of wefted surface will also increase the performance. The tateral plane can beas little as 1/25th of the sail area. These two things will not distract from the boat's aesthetics andwill look much better as it sails standing up to the wind rather than over on it's side and rounding up.

Model boas sail in proportionately stronger winds than their larger counterparts and are athull speed much of the time. A model that is fa in the middle and has fine ends and overhangs has a

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tendency to create steep bow and stern waves with a depression in the middle where the hull has it's

greatest displacement. This causes the hull to drop in order to get it's buoyancy which doesn't help

it's performance. Also, keeping the less weight aloft help considerably in lowering the center of

gravity. lt takes a lot of weight in the keel to compensate {or a small amount of weight added to the

masthead.

All of these facton should be considered in designing and building a model yacht and a little

research will help in adding to the sailing performance of the model boat. There are several excellent

boola on full size yacht design, such as SKENE'S ELEMENTS OF YACHT DESIGN, which will provide

formulas and methods of calculation. A little time spent on research and understanding the overall

concept of what you are trying to accomplish in designing model yachts will be rewarded many times

over.

TO FI ND THE STABILITY OFA MODELYACHT

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CALCUTATING THE STABILIW OF A TVIODEL YACHT

ln the two above drawings, note the four ovals which diagrammatically represent four"numbers". When the numben in the four ovals are known, the velocity of the wind, in miles perhour, that it takes to heel a boat 20 degrees can be found by using the formula:

V=i sin 20 degrees X righting arm

0.004

METACENTRIC HEIGHT (or G.M.) ls the intersection of the VERTICAL CENTER OF BUOYANCy and theand the centerline of the boat.

VERTICAL GENTER oF BAIANCE (see demonstration drawing) is the point where the boat balanceson the fin when the boat is horizontal.

CENTER oF TATERAL PIANE is the vertical center of the side view of the underwater profile.CENTER OF SAIL AREA is the vertical center of the total sait area. "Sail Area" is defined as the totalarea, in square feet, including the roach.To find wind velocity for another angle, insert the Sine and Cosine figures for that angle into theformula.

Wind pressure is based on MARTIN'S FORMULA:

Sine 20 degrees - 0.3429 Cosine 20 degrees : 0.9397

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TEIE BLOCKFOR BROADS G SAILS

Gut trrp block out of clear soft gfai:eed wood strch asredwood, poplar, red cedar, alder or. whlte pbe r:slng t!.eEreasur€me:tts g[ven.r euggest usirlg a sbarp band saw and a twelve 1ncb, dlscsa,ad.er. smooth t'be two top crrrred surfaces so there ar€no buraps or trollows as if tb.e ehaFe would slmulate twostrips of sheet metal curved ln one dj:sestlon with no twist.The two wood sr:rfaces can be painted or flber. glassed tomake a banrler gmoother surfaceTb.e end w-lth the most sr::nre is for tbe hrff end of th,esea"n and the flatter end, is for tJre leactr end of thesgern.Rrt tJre lower Sall p:nel on tJre block 16ltb the ed6eoverlappin€l the center of tbe btock about one eightb incband put s rnark on the block where you bave tJre ]uffend- Tlris will be used to position tb,e luff of aII of tbesearrrs. secrre t'be panel to the bl0ck with paper tape lrttnno wyil]<les. Appiy tbe double sided paper back tape, Isu€gest tr?aylock one quart€r inch tape #966, to the ed,geof tb.e panel. Ptrt the next panel on

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overlapping t'he paper backed tape and secr:re to block llkey9u_did w-itb the otJrer Fanel. Carrefr:tly r€rnove tb,e bactri-€of tJre adhesive tape end bur:rlsb tbe !e"t,.TIre luff stafi,iDg mark on the block can be close to tJrerrff end for fuller sa,i1s closer to tbe leaclr end, for flattergai'l< and. mOre SeF"n< vrllf make firller ga{.ls. Matertals f91,se.ils can be mqtar frrcm tr?ayloc and polyester Film.,Melllnex, fiom Ptasttc suppllers about one to gpe rnilsf.higf,.

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WHERE TO PUT THINGSFor experienced and novice builden alike, one of the first questions that has to be answered is

where do the keel fin, bulb, rudder and mast go. Because the boat (hull) has to float with all of thisstuff, it's important that it have the proper displacement. Place the finished hull in a filled bathtub orswimming pool and place all of the components inside the hull in their approximate positions andadding extra weight to equalthe mast and the radio equipment. This will bring the hullto it,sapproximate waterline. Since the bulb is the heaviest part of the boat, position it to where the boagwaterline is conect. Both the bow and transom should be slightly above the water. Once the hull isproperly balanced, mark the position of the butb on the hult. Straight down from this mar( at theproper depth, is where the bulb should be. You now have determined where the weight of the boatis going to be located.

There is a degree of latitude in the shape of configuration of the fin. lt can be sloping,completely vertical, fonrard or aft of the bulb. Because the fin is the greatest part of the lateral planeit will influence the position of the sail area. lf you desire the sail area forward, have the fin areaforward. lf you want the sail area aft, then have the fin area aft. Personally, I prefer the fin verticaland in the center of the bulb.

I suggest placing the rudder as far aft as the class rules allow to get more turning leveragewith less drag. With the keelfin and rudder installed, position the rudder amidship, float the boat inwater deep enough to accommodate the length of the fin and gently push the boat sideways withyour finger. When you have found the spot on the hull where the boat moves straight you havefound the center of lateral resistance or the center of the lateral plane. From this point, measureforward ten percent of the water length to tocate where the center of the sail area will be. The mastposition can then be located by the distance from the center of the mast from the center of the sailarea. The ten percent is the lead of the sail area forward of the lateral plane. lf this disance is toogreat it will produce less lee helm (boat turns away from the wind) and it is too small it will produceweather helm (boat turns into the wind) causing stalling. The ten percent figure is about average andshould be used as a starting point. I hope that your new boat sails well.

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TIME SAVING TIP ON DESIGNING A HUIL

The cubic inch displacement of the boat below the waterline, times the weight of water per

cubic inch will equal te all up weight of the boa. Fresh water weighs .03G1 I pounds per cubic inchand sea water weighs .37037 pounds per cubic inch. The all up weight of all the para of the boatmust be ascertained by actual weighing or calculations.

The tip to save time is that instead of drawing all of the stations and then calculating thedisplacement using Simpson's rule, is to use the optimum prismatic coefficient of .52 in drawingstation number five of a ten station drawing.

FOR EXAMPLE: a 35/500 that you want to weigh six pounds with a watertine of 3G incfes willneed a cubic inch displacement of 166.15435 below the waterline. The prism is the shape andvolume of the area below the waterline of station five or the largest station stretched out to 35 inches.

The prismatic coefficient is the ratio of the volume of the hull to the volume of the prism. Fifty-two percent is about the optimum. Think of the prism as a tank with the hull inside occupying fifty-two percent of the tank. To find the prism divide 166.1 5435 by.52 which is 319.52759.

To find the area for station number five below the waterline divide 319.52759 by 36 which is8.8757563. Remember, if you are using half stations, a good way to begin your drawing, this numberwould have to be half of the area. Draw the shape of station number five and adjust until it's area is8.87 square inches then continue drawing all of the stations and lines. The displacement should bearound the desired six pounds.

REMEMBER: THE ERASER SHOUI"D OUTWT THE PENcIt! HAVE FUII.

HOW TO MAKE AN ORCO RUDDER

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For the mold, make two triangles of aluminum the height and width of the rudder you w6h tomake' use about .030 T-6 aluminum (spring). wax the surface and lay up one layer of about fourounce woven glass or carbon cloth. Wet out with epoy or polyester resin. When cured, trim off theexcess around the edges, being careful not to pull the fabric off of the aluminum. put the two halvestogether and tape around the edges of the fonrard, aft and end edges. Inseft a rudder shaft with thesides sfightly flattened were it ente6 between the fabric. The shaft should be about 25o/o altof theleading edge. Pour resin into the void between the two sides. when cured, remove the aluminumplates and trim the rudder to the desired shape. I suggest 1/8 stainless or 3/15 T-5 aluminum rod forthe shaft.

HoW To tvlAKE AN oRco cURvED BooM

A light weight, curved boom can easily be made with a balsa core covered with woven carbontubing' To make the balsa core, laminate thin balsa strips by glueing them over a form of the desiredcurve' The soft balsa can then be sanded round or ellipticalas desired. The woven carbon tubing canbe obtained in different sizes to accommodate the size of the laminated core. The carbon tube can beexpanded and slipped over the balsa core and constriaed by pulling lengthwise like a Chinese fingerpuzzle' 0nce the cloth is stretched over the balsa core, wet out with polyester or epory resin.

woven carbon fiber tubing can be obtained from: AERospAcE coMp0slrE pRoDUCrS.

SAND CASTING A LEAD BULB

sand casting is fun, rewarding and easier than you think though it does require some basicequipment' You will need a pattern of what it is you want to cast, a flash flat board, a tapered spue,a tamp, talcum and a lead pot and heater. Sand is really mislabeled since it is a mixture of very finesedimentary silica and clay. The composition is such that when compressed in your hand it maintainsthe shape and texture of your hands and fingen. This molding sand can be purchased from a foundry

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supply, usually listed in the yellow pages. The cost is minimal and the sand can be used repeatedly. l

get a good molding sand from the back bay at Newport Beach. A good molding sand must have

some porosity and will require some moisture fiom time to time.

Ihe flask known as the cop and drag (l don't know which is which) is the box you tamp the

sand in over the pattem. The box should be large enough to have at least an inch and a half of sand

between the box and the pattern both veftically and horizontally. lf possible, it should also have more

than an inch and a half above the pattern where the spue or pouring hole is located. This will give

more pressure on the molten lead in the cavity. Lead shrinls as it cools so it's important to have the

molten lead fillthe cavity completely.

The flask can be made of wood as a rectangle and then ripped on a table saw to make two

rectangles with no tops or bottoms. Put line-up pins in one box and aline the holes so the rectangles

will stack together in perfect alinement.

PATTERNSIt's easy to make a split pattern for a keel bulb by roughing out two pieces of wood longer

than the pattern and clamping them together with hose clamps on the ends. Then turn the majorcenter poftion in a lathe and true up the ends by hand. Finally, the pins are to be in one hatf of thepattern and matching holes in the other half ol the pattern to keep them in perfect alinement.

SETTI NG UP

The half of the pattem without the pins is placed on the board and powdered whh talcum tokeep the sand from sticking to the pattern and the board. The pin-less half of the box is then placed

over the pattern and the box filled with screened sand. Tamp the sand in until it's level full in the box

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and turn the box over on the board. Next, the pinned half of tne lattem is placed on the other half ofthe pattern, covered with talc and the pinned half of the box is put on top. Talcum will also keep theseparation between the top and the bottom sand. The riser or spue is placed on the pattem and thetop box filled with screened sand and tamped. The spue is then removed, the flask opened and thepattern carefully removed. When the flask is reassembled, it's ready for pouring. lt's advisable toweight the top to prevent the top half from floating and releasing mohen lead. After cooling, the risercan be removed from the casting by bandsaw. The imperfections can be removed by a block plane orfile. A cutting liquid is recommended when cutting or drilling lead to prevent the lead from bui6ingup (galling) in the saw blade or drill bit.

ANTIMONY

Adding antimony to the lead will make the casting much harder and less bendable, however,it will raise the melting point of the lead slightly. Lead melg at a temperature of G21 degrees and itcan be melted in a cast iron frying pan on a gas stove. Mohen lead is ilffREMELy dangerous andmust be handled with care.

WHY NOT GET THE LEAD OUT AND TRY SAND CASTINGIII

SCHOONER RIBS

Fora model boat that requires ribs and planking, the ribs can be cut from plywood, naturalcurved grain wood, steam bent White oalg anhydrous ammonia treated wood (though notrecommended) or laminated wood. Laminating seems to be the easiest, strongest and most accurate.

lf you are going to laminate, White oak is the best choice of wood to use. For 114', sguareribs, cut pieces 1/15" X 3/4" making ceftain that you make them a few inches longer than what isrequired for the boat keel to rail. The first thing is to make a form to shape the laminations. 3/4,'

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scrap plywood work well forthis as it allows forthe thickness of tf,. planking and the 3/4" wide

laminated rib. Glue up four layes o{ the oak and clamp to the form leaving excess for trim where the

ribs fasten to the keel.

The 3/4" wide laminated rib will cut in two making an identical pair of ribs for that station. A

floor timber glues the ribs together which will fit over the keei. the upper ends of the ribs should be

fastened to a temporary spreader alined securely to the centerline.

The good part of this type of ribbing is that they will conform to the contour of the planking

with no humps or hollows and they are easy to clamp onto.

Building a schooner is an endeavor that has many rewards in the shop and on the water.

Have fun!

NOTES:

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May,2007

C{JRVED BOOMSWHY

The class rules dictate whether a curved boom can be used or no! and forthe classes that allow curved booms it can be an advant4ge as in u3 onemeter and Marblehead and 36-600..Dragging the main clew on a broad reach does not help the boat speed or

steering and by raising the clew with a curved boom wilt tessen thisprobtem. If you will notice as the clew is laised, the LP measurement goesup with it and effectively raises the sail area. This is * ua"*t"jr i" fig,1weather.The rules for US one meter and Marblehead and 36-600 sails allow a one

inch roach on the foot of both main and jib and when the boorn is curved thesail can fit this curve and have less spaci between the sail and boom th"t"byusing the boom and sail more effectively by letting less air going throughthis slot.The main boom when curved can allow the tack to be lowered and to sbme

extent' close offthe area between boom and deck in the lower forward partof the main. I learned how important this area is from Steve Dashew in the Cclass Catamaran. He designed and built the Beowolfttrat held the speedrecord for a long tirne. I made the sails for him and sailed a few timeschecking out the sails. On the measured mile a couple of times he had meclose the area under the boom with my body and liie preservers as best Icould. He said, " swede" it made a difference, a liule faster.Curved booms are an advantage.

Swede Johnson, amya lgTS