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HOWTO V O L U M EON E


INTRODUCTION Tothoseof usinvolved in R/Csailing, Lloyd"Swede" Johnson is legendary forthemany contributions hehasmadeto theevolution of remote control sailing.Recognized asoneof the foremost innovaton in hulldesign, sailsandhowtheyarerigged, rigdesign andliterarily hundreds of littleoddsandendsthatcontribute to making a boatsimple, efficient andfast. Several of the boats Swede hasdesigned andmanyof histheories of "whatcanI doto makea boatgofaster"have playeda majorrolein theevolution of R/Csailingoverthepastthirtyyears.Foranyone whohashad thepleasure of meeting Swede knows thatwhatmakes himtrulya remarkable designer andinnovator goesfar beyond theboaBthatheput inthewater.Hiswillingness to sharehisvastwealthof knowledge withotherdesigners, buildenandskippers is whatmakes Swede Johnson trulyanR/C sailing treasure. Thiscollection "HowTo", editedby Dennis of Swede's Desprois, is notonlyintended forthe serious designer/builders butalsoforthoseskippen whosimply wantto betterunderstand how partsof anR/Cyachtaremadeandwhytheydowhattheydo. different

GOODSAILING !

Dennis Desprois March 2000


LLOYD F.'SWEDE" JOHNSON Lloyd"Swede" Johnson, therenown sailmaker andremote control sailinginnovator fromCosta Mesa, Califomia wasbornin Pomona, Califomia in 1919.In 1985,in recognition of hisou6tanding contdbution to settingfor oceanracingfor localyachtclubs,Swede wasawarded the Edward F. Kennedy Memorial Newport HarborYach8man of theYearTrophy.Swede setthemarkforsuch prestigious races astheGovernor Cupin 1979,81and1984,the FinnNationals in 1980and theSix MeterNationals in 1981.In 1981,82and83,Swede setthecouses fortheU.S.Y.R.U. 0lympiE classes. In 1985hesetthecourses fortheEtchells 22Worlds, 5.5WorldChampionship andthe Scandinavian GOLD CUP.Whenthe)filll Olympic Games werein LosAngeles in .1984, Swede not onlywasthesailmeasure forthe470Class, heatsodesigned andbuilttheinflatable markthatwere usedonthecourse.Swede wasdeservedly elected to theBalboa YachtClub'sHallof Fame in t gg8. Thelonglistof successful R/Csailboatsdesigned (for0range bySwede include theORCo County), theSKlNfrff Marblehead andtheORCO HOTDOG. Inthe36/600andoneMeterClasses, Swedehasdesigned the ORCO FIAIRBOW, the SKINNY andthetorpedoshapedORCO 90 all of which havewonACCR',s. Swede's latestbutcertainly nothislast35/600design istheoRCoMILLENNIUM.


MODET DESIGN It seems thetrendof modeldesign isto makethemlookliketheirfullsizecounter parBwith fineends,overhangs andevenwingsonthekeels.Theendresuhisa modelthatlaclathestability to standupto a tenknotwind. Manyof ourAMYAclassmodels, suchasthesoling,EastCoast Twelve Meter,SantaBarbara and''6specially theVitoriaandFainrind(notyetanAMYAcertified class)have theshapeandproportion butNOTtheperformance parb. These of theirlargercounter designs make theaesthetics a priorityoverperformance. Ofcou6e,it isdesirable to havea onedesignclassthat notonlyloob appealing withrulesthatallowanequalchance at winningduringa competitioRtirr Thelogistia,however, dictatethatthistypeof modelcouldhavebeenmadeto bea much higherperformer withnoaddition of costto themanufacture or builder simplybyconsidering the scaling effecgincurred withtheproportions whenmaking a smaller boat. Myintentisn'tto advocate andchanges in existing classrulesor to criticize thedesigners of theabovementioned boatsbutto possibly influence thosepenons endeavoring to design newmodel boatsbyexplaining thephenomenon: ASA BOAT DECREASES lNSIZE, PROPORTIONS DONOT DECREASE EQUALLY. Forexample, let's"take anffCHELL a highlysuccessful 30.5footracing class sailboat and scaleit downto onetenthor a thirty-six inchmodel. ETCHEI.I LENGTH OVER ALL: SAIL AREA SQ.FT.: WATERLINE LENGTH: BEAM: DRAFI : DISPLACEMENT CU/ff.: DISPIACEMENT LBS.

MODEL 30'.5" 291 22'.0 7'.0 4'.5" 51.17 3275.0

3' .05 2.91(DOWN BYTHESQUARE) z'..2u .7u

.45' (DOWN .05117 BYTHE CUBE) 3.194(DOWN BYTHECUBE) Page3


MAST HEfGHT: HEEL| NGARMFT.: RIGHTING ARMff.:

35'.0 15.6 2.55

3'.5r', 1.56 .255

Theheelingarmisdistance fromthecenterof thesailareato thecenterof underwater lateral plane.Therightingarmisthedistance fromthevefticalcentero1buoyancy to thevefticalcenterof gravlty.Thewindpressure persquarfootof sailareaat 8 milesis .25pounds fromMartin's formula: P:.004X velocity squared. Tocalculate theheeling anglein 8 milesof windusingtheDellenbaugh formula: 57.3X sailareaX heeling armX windpressure persquare foot Righting armX displacement in pound ETCHELL

MODEL did..

57.3 X 291X 15.6X .25

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57.3Xz.glx 1.56X .25 -7 .75 dggfges

2.56X 3275

------------------------------r-o-or 79.5 degfges

255X 3.194(downbythe4* power)

Asyouansee,thedisplacement hasscaled downfaster thanthesailareaandthestability has scaled downfasterthanthedisplacement. Thenumben clearly illustrate thatwhi6theFICHELL is barely heeling, themodelisflatonit,sear! Thecorrection wouldbeto addweightdownlowandincrease thehulldisplacement to compensate orto lowerthecenter ofthesailareaor both.Obviously, byputtingtheweightdeeper willgivetherighting armmoreleverage withoutadding (providing to thedisplacement thepondis deepenough). Thereduction of weftedsurface will alsoincrease theperformance. Thetateralplanecanbe aslittleas1/25thof thesailarea.These twothingswill notdistract fromtheboat'saesthetics and will lookmuchbetterasit sailsstanding upto thewindrather thanoveronit'ssideandrounding up. Modelboassailin proportionately stronger windsthantheirlargercounterparts andareat hullspeedmuchof thetime.A modelthatisfa in themiddleandhasfineendsandoverhangs hasa Page4


in the middlewherethe hullhasit's tendency to createsteepbow andsternwaveswith a depression whichdoesn'thelp the hullto dropin orderto get it's buoyancy greatest Thiscauses displacement. in loweringthe centerof Also,keepingthe lessweightalofthelpconsiderably it'sperformance. {or a smallamountof weightaddedto the gravity.lt takesa lot of weightin thekeelto compensate masthead. in designing and buildinga modelyachtanda little All of thesefactonshouldbeconsidered excellent of the modelboat. Thereareseveral research will helpin addingto the sailingperformance whichwill provide OFYACHT ELEMENTS DESIGN, boolaon full sizeyachtdesign,suchasSKENE'S theoverall andunderstanding formulas of calculation. A littletimespenton research and methods in designing modelyachtswill be rewardedmanytimes concept of whatyouaretryingto accomplish over.

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CALCUTATING THESTABILIWOFA TVIODEL YACHT ln thetwo abovedrawings, notethefourovalswhichdiagrammatically represent four "numbers". Whenthenumben inthefourovalsareknown, thevelocity ofthewind,in milesper hour,thatit takesto heela boat20degrees canbefoundby usingtheformula: V=i sin20 degrees X rightingarm

0.004

METACENTRIC (orG.M.)lsthe intersection HEIGHT of theVERTICAL CENTER OFBUOYANCy andthe andthecenterline of theboat. VERTICAL GENTER oF BAIANCE (seedemonstration drawing) isthepointwheretheboatbalances onthefinwhentheboatishorizontal. CENTER oF TATERAL PIANEisthevertical centerofthesideviewof theunderwater profile. CENTER OFSAILAREAisthevertical center of thetotalsaitarea."SailArea"isdefined asthetotal area,in squarefeet,including theroach. Tofindwindvelocity foranother angle, insert theSineandCosine figures forthatangleintothe formula. Windpressure is basedon MARTIN'S FORMULA: Sine20degrees - 0.3429

: 0.9397 Cosine 20degrees

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Gut trrp block out of clear soft gfai:eed wood strch as rn redwood, poplar, red cedar, alder or. whlte pbe r:slng t!.e z Ereasur€me:tts g[ven. Cf r euggest usirlg a sbarp band saw and a twelve 1ncb, dlsc sa,ad.er. smooth t'be two top crrrred surfaces so there ar€ no buraps or trollows as if tb.e ehaFe would slmulate two strips of sheet metal curved ln one dj:sestlon with no twist. The two wood sr:rfaces can be painted or flber. glassed to make a banrler gmoother surface Tb.e end w-lth the most sr::nre is for tbe hrff end of th,e sea"n and the flatter end, is for tJre leactr end of the

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Rrt tJre lower Sall p:nel on tJre block 16ltb the ed6e overlappin€l the center of tbe btock about one eightb incb and put s rnark on the block where you bave tJre ]uff end- Tlris will be used to position tb,e luff of aII of tbe searrrs. secrre t'be panel to the bl0ck with paper tape lrttn no wyil]<les. Appiy tbe double sided paper back tape, I su€gest tr?aylock one quart€r inch tape #966, to the ed,ge -tb.e of tb.e panel. Ptrt the next panel on block Jr-rst overlapping t'he paper backed tape and secr:re to block llke y9u_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 tJre rrff end for fuller sa,i1s closer to tbe leaclr end, for flatter gai'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 rnils

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WHERE TOPUTTHINGS Forexperienced andnovice buildenalike,oneof thefirstquestions thathasto beanswered is wheredothekeelfin,bulb,rudder andmastgo. Because theboat(hull)hasto floatwithallof this stuff,it'simportant thatit havetheproper displacement. Place thefinished hullin a filledbathtub or swimming poolandplaceallofthecomponents inside thehullin theirapproximate positions and addingextraweightto equalthemastandtheradioequipment. Thiswill bringthehulltoit,s approximate waterline. Since thebulbistheheaviest partof theboat,position it to wheretheboag waterline isconect.Boththebowandtransom shouldbeslightly abovethe water.Once thehullis properly balanced, marktheposition of thebutbonthehult.Straight downfromthismar( at the proper depth,iswherethebulbshouldbe. Younowhavedetermined wheretheweightof theboat isgoingto belocated. There is a degree of latitude intheshape of configuration of thefin. lt canbesloping, completely vertical, fonrardor aftof thebulb. Because thefin isthegreatest partof the lateralplane it will influence theposition of thesailarea.lf youdesire thesailareaforward, havethefin area forward.lf youwantthesailareaaft,thenhavethefin areaaft. Personally, I preferthefin vertical andinthecenter ofthebulb. placing I suggest therudder asfaraftastheclassrulesallowto getmoreturningleverage withlessdrag.Withthekeelfinandrudderinstalled, position therudderamidship, floattheboatin waterdeepenough to accommodate thelengthof thefin andgentlypushtheboatsideways with yourfinger.Whenyouhavefoundthespotonthehullwheretheboatmoves youhave straight foundthecenter of lateral resistance orthecenter of thelateralplane.Fromthispoint,measure forward tenpercent of thewaterlengthto tocate wherethecenter of thesailareawill be. Themast position canthenbelocated bythedistance fromthecenter of themastfromthecenter of thesail area.Thetenpercent istheleadof thesailareaforwardof thelateral plane.lf thisdisanceistoo greatit will produce lessleehelm(boatturnsawayfromthewind)andit istoosmallit will produce weather helm(boatturnsintothewind)causing stalling.Thetenpercent figureisaboutaverage and should beusedasa starting point. I hopethatyournewboatsailswell.

Page8


TIMESAVING TIPONDESIGNING A HUIL Thecubicinchdisplacement of theboatbelowthewaterline, timestheweightof waterper cubicinchwillequalte all upweightof theboa. Fresh waterweighs.03G1 percubicinch I pounds andseawaterweighs.37037pounds percubicinch.Theallupweightof alltheparaof theboat mustbeascertained byactualweighing or calculations. Thetip to savetimeisthatinstead of drawingallof thestations andthencalculating the displacement usingSimpson's rule,isto usetheoptimum prismatic coefficient of .52in drawing stationnumber fiveof a tenstationdrawing. FOR EXAMPLE: a 35/500thatyouwantto weighsixpounds witha watertine of 3Gincfeswill needa cubicinchdisplacement of 166.15435 belowthewaterline. Theprismistheshape and volumeof theareabelowthewaterline of stationfiveorthelargeststationstretched outto 35 inches. Theprismatic coefficient isthe ratioof the volumeof the hullto the volumeof the prism.Fiftytwo percent isabouttheoptimum. Thinkof theprismasa tankwiththehullinside occupying fiftytwopercent ofthetank.Tofindtheprism divide166.1 5435by.52whichis319.52759. Tofindtheareaforstation number fivebelowthewaterline divide319.52759 by36whichis 8.8757563. Remember, if youareusinghalfstations, a goodwayto beginyourdrawing, thisnumber wouldhaveto behalfof thearea.Drawtheshapeof stationnumber fiveandadjustuntilit'sareais 8.87square inches thencontinue drawing allof thestations andlines.Thedisplacement shouldbe around thedesired sixpounds. REMEMBER: THEERASER SHOUI"D OUTWTTHEPENcIt! HAVEFUII.

HOWTOMAKEAN ORCO RUDDER Page9


Forthemold,maketwotriangles of aluminum theheightandwidthof therudder youw6hto make'useabout.030T-6aluminum (spring). waxthesurface andlayuponelayerof aboutfour ouncewovenglassor carbon cloth.Wetoutwithepoy or polyester resin.Whencured, trimoffthe excess around theedges, beingcareful notto pullthefabricoffof thealuminum. putthetwo halves together andtapearound theedges of thefonrard,aftandendedges.Insefta rudder shaftwiththe sidessfightlyflattened wereit ente6between thefabric.Theshaftshouldbeabout25o/o altofthe leading edge.Pourresinintothevoidbetween thetwosides.whencured,remove thealuminum platesandtrimtherudder to thedesired shape.I suggest 1/8stainless or 3/15T-5aluminum rodfor theshaft.

HoWTotvlAKE ANoRcocURvED BooM A lightweight,curved boomcaneasilybemadewitha balsacorecovered withwovencarbon tubing'Tomakethebalsacore,laminate thinbalsastripsbyglueing themovera formof thedesired curve'Thesoftbalsacanthenbesanded roundor ellipticalas desired. Thewovencarbon tubingcan beobtained in different sizes to accommodate thesizeof thelaminated core.Thecarbon tubecanbe expanded andslipped overthebalsacoreandconstriaed bypullinglengthwise likea Chinese finger puzzle'0ncetheclothisstretched overthebalsacore,wetoutwithpolyester or eporyresin. wovencarbon fibertubingcanbeobtained from:AERospAcE coMp0slrEpRoDUCrS.

SANDCASTING A LEADBULB sandcasting isfun,rewarding andeasier thanyouthinkthoughit doesrequire somebasic equipment' Youwill needa patternof whatit isyouwantto cast,a flashflat board,a taperedspue, a tamp,talcumanda leadpotandheater.Sandis reallymislabeled sinceit isa mixture of veryfine sedimentary silicaandclay.Thecomposition is suchthatwhencompressed inyourhandit maintains theshape andtexture of yourhands andfingen.Thismolding sandcanbepurchased froma foundry Pagel0


supply, usually listedintheyellowpages.Thecostisminimal andthesandcanbeusedrepeatedly. l geta goodmolding sandfromthebackbayat NewportBeach. A goodmolding sandmusthave andwill require someporosity somemoisture fiomtimeto time. Iheflask knownasthecopanddrag(l don'tknowwhichiswhich)istheboxyoutampthe sandin overthepattem.Theboxshouldbelargeenough to haveat leastaninchanda halfof sand between theboxandthepatternbothveftically andhorizontally. lf possible, it shouldalsohavemore thananinchanda halfabove thepattern wherethespueor pouring holeislocated.Thiswillgive morepressure onthemoltenleadin thecavity.Leadshrinlsasit coolssoit'simportant to havethe molten leadfillthecavitycompletely. Theflaskcanbemadeof woodasa rectangle andthenrippedona tablesawto maketwo rectangles withnotopsor bottoms.Putline-uppinsin oneboxandalinetheholessotherectangles willstack together in perfect alinement.

PATTERNS It'seasyto makea splitpatternfor a keelbulbbyroughing outtwo pieces of woodlonger thanthepattern andclamping themtogether withhoseclamps ontheends.Thenturnthemajor poftionin a latheandtrueuptheendsbyhand.Finally, center thepinsareto bein onehatfof the pattern andmatching holesin theotherhalfol thepatternto keepthemin perfect alinement.

SETTI NGUP Thehalfof thepattemwithoutthe pinsis placedontheboardandpowdered whhtalcumto keepthesandfromsticking to thepatternandtheboard.Thepin-less halfof theboxisthenplaced overthepattern andtheboxfilledwithscreened sand.Tampthesandin untilit'slevelfullin thebox PageI I


andturntheboxoverontheboard.Next,thepinnedhalfof tnelattem is placedontheotherhalfof thepattern, covered withtalcandthepinnedhalfof theboxis putontop. Talcum will alsokeepthe separation between thetop andthebottomsand.Theriseror spueis placed onthepattemandthe top boxfilledwithscreened sandandtamped.Thespueisthenremoved, theflaskopenedandthe patterncarefully removed.Whentheflaskis reassembled, it'sreadyfor pouring.lt'sadvisable to weightthetopto prevent thetop halffromfloatingandreleasing mohenlead.Aftercooling, theriser canberemoved fromthecasting bybandsaw. Theimperfections canberemoved bya blockplaneor file. A cuttingliquidis recommended whencuttingordrillingleadto prevent theleadfrombui6ing up(galling) in thesawbladeor drillbit.

ANTIMONY Addingantimony to theleadwill makethecasting muchharder andlessbendable, however, it willraisethemelting pointof theleadslightly.Leadmelgat a temperature of G21degrees andit canbemeltedin a castironfryingpanona gasstove.Mohenleadis ilffREMELy dangerous and mustbehandled withcare. WHYNOTGETTHELEADOUTANDTRYSANDCASTINGIII

SCHOONER RIBS Foramodelboatthatrequires ribsandplanking, theribscanbecutfromplywood, natural grainwood,steambentWhiteoalganhydrous curved ammonia treated wood(though not recommended) or laminated wood.Laminating seems to betheeasiest, strongest andmostaccurate. lf youaregoingto laminate, Whiteoakisthebestchoiceof woodto use. For114', sguare ribs,cutpieces 1/15"X 3/4"making ceftain thatyoumakethema fewinches longer thanwhatis required fortheboatkeelto rail. Thefirstthingisto makea formto shapethelaminations. 3/4,' Page12


scrapplywoodwork wellforthisasit allowsforthethickness of tf,. planking andthe3/4"wide rib. Glueupfourlayeso{theoakandclampto theformleavingexcess laminated fortrimwherethe ribsfastento the keel. The3/4"widelaminated ribwill cutin two makinganidentical pairof ribsforthatstation.A floortimbergluestheribstogether whichwillfit overthekeei.the upperendsof theribsshouldbe fastened to a temporary spreader alinedsecurely to thecenterline. Thegoodpartof thistypeof ribbingisthattheywill conform to thecontour of theplanking withnohumpsor hollowsandtheyareeasyto clamponto. Building a schooner isanendeavor thathasmanyrewards in theshopandonthewater. Have fun!

NOTES:

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May,2007 C{JRVED BOOMS WHY The classrules dictatewhethera curvedboomcan be usedor no! and for the classesthat allow curvedboomsit canbe an advant4geasin u3 one meterand Marbleheadand36-600.. Draggingthe main clew on a broadreachdoesnot help the boat speedor steeringandby raising the clew with a curvedboomwilt tessenthis probtem.If you will noticeasthe clew is laised,the LP measurement goes up with it and effectively raisesthe sail area.This is * ua"*t"jr i" fig,1 weather. The rules for US onemeterandMarbleheadand36-600sailsallow a one inch roachon the foot of both main andjib andwhenthe boornis curvedthe sail can fit this curve andhavelessspaci betweenthe sail and boomth"t"by usingthe boom and sail moreeffectively by letting lessair going through this slot. The main boom when curvedcan allow the tack to be loweredandto sbme extent' closeoffthe areabetweenboomand deck in the lower forward part of the main. I learnedhow importantthis areais from SteveDashewin the C classCatamaran.He designedandbuilt the Beowolfttrat held the speed recordfor a long tirne. I madethe sails for him and saileda few times checkingout the sails.On the measuredmile a coupleof times he hadme closethe areaunderthe boomwith my body and liie preserversasbestI could. He said, " swede" it madea difference,a liule faster. Curvedboomsare an advantage. SwedeJohnson,amya lgTS



Swede Johnson's HOW TO Vol 1