model pt boat

5/8/2015 ModelHull2

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Hull21/20thSkeletonKit

1/20thscale(4')topand1/35thscale(27.5")modelssidebyside.

Hull2SkeletonKitisnowavailableagaininboth1/20thscale(4'long)and1/35thscale(27"long)versions.

IhavefinishedthedesignoftheHull21/20thscaleHullskeletonkitandIhavealsofinishedthe9pagesofinstructionswithlotsofphoto'sabouthowtobuildit,Ihaveincreasedthenumberofpartsto122seethepricelistfordetails.

Basedonmyyearsofresearch,manybooks,photographsandthefewavailableoriginaldrawingsthatIhavemanagedtogetholdofIspentmanythousandsofhoursrecreatingandredrawingtheoriginalboatplans(whichisanongoingproject)andbasedontheseplansIhavedevelopedthenew,moreaccurate,1/20thscale(4'or1220mmlong)andthe1/35thscale(27.4"or697mmlong)modelhullsavailableaslasercutribsetsofapproximately122pieces.Please

don'taskmeforAutocadfilesasrefusalsometimesoffends!

Thelasercut1/20thscalekitincludes20ribs,transom,laminatedmainkeel,laminatedwingpropshaftsandseparaterudderkeels,breakawaylaminateddeckrunnerswhichincludesthedeckopeningupstand,motormounts,servomounts,alargebatteryboxandalaminatedstand.Thesepartsarecutfromveryfinegrade2mm(5/64")thickGL3BirchplyfromUPMinFinlandandaresuppliedon8separatesheetsthatare300mmx400mm(1'x1'4"),thismakesa16mm(5/8")thickstackthatcanbeshippedasaflatcardboardboxbyairmailandwillweigharound1.3Kg(3pounds).ThisisanimportantconsiderationasIamin

Australia!

Thelongkeelswhenmadeup,arelaminatedas4thicknessesof2mmplywith6thicknessesatthepropshaftsandrudders,thedeckrunnersare2thicknesses,theindividualshortpiecesarefittedtogetherendtoendwithstaggeredjigsawlikejoints.Allindividualkitpartsjointogetherintoslotsorrecessesandmakeforaverystrongbutlightweighthullframethatisfairlyeasytobuild.ThemotormountingboardisdesignedtotakeeverytypeofmotorthatIcurrentlyhave

orhavepreviouslyusedinHull1andcanbesetupaseitheragearedordirectdrivearrangement.

Youwillneedtosupplythelongchineandgunwaletimbersandthehullcoveringmaterialsaswellastherunninggear.Thechineandgunwaleare4mm(5/32")squaresectionmaterialasfulllengths(1200mmplusor4'plus)ofbalsaorharderwoodsuchasRaminorSpruceandyoucancoverthehullin

whateveryoulike,Iamusing2layersof0.8mm(1/32")BirchplywhichIhavelasercutinto1/20thscale6"wideplanks,justliketherealthingwhichwascoveredintwolayersof1/2"Mahoganyplankswithwaterproofedmuslinclothbetweenthelayers.

ModelHull2variesfromModelHull1inthefollowingways:

1.Themotorsaremountedclosetotheoriginallocationandaremuchfurtheraft(rearward)thaninHull1,thismeansthatthepropshaftsaremuchshorterandcanbeboughtascomplete8"typesratherthanhavingtomakethemupyourself.Ihaveallowedforboth6.35mm(1/4")or8mmoutsidediameterprop

shafts.Movingthemotorsmeansthattheboatwillbebalancedbetterasthebatterieswillbefurtherforwardinfrontofthemotors.

2.Thehull2shapehasamuchmoreconcaveprofileinthesidesandbottomwhichisasclosetotheoriginalElcoPT103class80'hulldrawingsasIcangetit.

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3.ThepropellershaftsareparalleltoeachotherliketheoriginalfullsizeboatandnottaperedoutwardslikeHull1whichgivesmoreroomforlargermotorsuptoSpeed700/775size.Seethiscurrentarticleonmotors:www.rcboatmodeler.com/pdf/MEGA_MOTOR_GUIDE.pdf

4.ThewingruddersaresplayedoutwardsattheafthullbottomangleliketheoriginalElcoboats,thisshouldhelptheboatturnbetterbyhelpingthebowtonot"digin"orhavethesterntryingtoliftwiththeparallelruddersinatightturnduetotheangleofthehullinthewaterasitleansintotheturn.

5.Hull2isveryaccuratelylasercutsothereisaheaplessdrudgeworkinvolvedinbuildingit,forthosethathavenotbuiltHull1thereisaLOTofworkjustcuttingoutribsandmakingupthepropshafts,gearboxetcandtheendresultshouldbeamuchmoreaccuratelighterand"tighter"hull.ThewholeHull2

skeletoncanbeputtogetherinacoupleofdays!

Iamworkingonthesuperstructurekit(s)currentlyandrevisingthetorpedorolloffrackkitwhichwillalsobeavailableshortly.

Iwilldoanextrememodelsoonish(butpleasedon'tholdyourbreath).Thismodelwillhaveall69+1ribswithVeedrivegearboxesandPackardenginesbutImayproduceitasahalfhulltoshowofftheinterior.

Thisisanexampleofthelayoutofthelasercutskeletonkitforthenew'Hull2'at1/20thscale.

(ThereisstillquitealotofwastematerialleftsoIamaddingextrapiecesthatIcanincludethatcanalsobecutfrom2mmply.)

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Thisisthe1/20thSkeletonkitfinished,sandedandreadyforplanking.

FinishingtheSkeletonKitintoaboat

IlookedattheavailableplankingmaterialsandthepriceandIdecidedtomakeupsome1/20thscale6"planking(7.62mmwide)usingthelasercutter,Iwasgoingtousescale0.6mmbirchplybutit'sjustalittlebittooflimsysoIsettledon0.8mmwhichifscaleduptothefullsizeboatwouldmaketheoverall

coveringthickness(twolayers)32mmorabout11/4"thick,whichifyouconsidertheoriginalboathadtwolayersof1/2"plankingandalayerofmuslinclothandglueinbetweenitwouldhavecomeoutthickerthan1"anywayandwithsomesandingthecoveringwillgetsomewhatthinner.Iget39stripsoutofa300x400mmsheetandeachstripisaprettygoodlengthtodotwostripsat45degreesorsoonthehullsurfaces,that'sabout15linealmetresor50linealfeetof

plankingpersheet.Iusedabout8sheetstodotheentirecoveringintwolayers.

TheFirstLayer

Plankonesidestartingnearthebow,whereitmeetsthechine,gluetheplankstotheribsandchinetimbersbutNOTtoeachotheronthefirstlayer,thiswillleavesomeflexibilityfortheplankstomoveinbetweentheribswhenthesecondlayerisaddedlaterattheoppositeangle.Generallyitworksbesttoplank"upwards"sothatthegluerunsdownonthelastplanksostartnearabottomcornerbutyoudon'twanttostartrightattheboworalloftheafttimberswill

wanttobebenttofitagainstthelastoneasthetwistintheplanksatthehollowbowmakesthemiddleoftheplankseemfatter.Itdoesn'treallymatterifyoucanseedaylightbetweentheplanksonthefirstlayerjustallowtheplankstofindtheirowncurve.Icuttheexcessplankingoffatthechinewithagoodpairofsidecutters(nailclippersshouldworkalso).Thereshouldbeabout110stripspersidedependingontheangle,Iendedupwith3or4moreononeside,notimportantontheinnerlayers.IletthehullshapechoosetheanglewherethewoodwantedtogonearthebowandthenmadesurethatIcouldgettwostripsoutofeachlengthofplankingwithouttoomuchwaste.Iftheangleischosencorrectlythestripswillbefairlystraightendtoendwithjustatwisttotakeupthehullshape.Thenfileorsandoffthechinetothebottomshape,thebowtotheoppositesideshapeandthetransomflush.Thevariouslayersofplankingwillalternatelyoverlapatthejoinededgesmakingforverystrongjoints.Iusedmediumsuperglueandpressurefrom4or5fingerstoholdtheplankingin

place.ThereisaLOToftimerequiredherebutveryrelaxing!

Andrememberifyoudon'tglueyourfingerstothehullinlotsofplaces,you'reprobablynotusingenoughglue!

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Sandthechineedgetomeetthehullbottomshape.

Oncethesidesareplankedandedgesanded,startonthebottomplanking,againIstartedfromthelongestpiecesnearthebowandworkedforwardsandthenaft.

IamveryhappywiththestrengthandtheshapeofHull2,it'salreadylookingfabulous!

Asyougetfurtheraftitbecomesapparentthatsandingthefirstsideplankingofftothekeelangleisnotgoingtoworkontheaftendduetotheshallowanglesinvolvedsoafterabouttherib25positionIstartedsawingtheplanksthroughusingapencillineandahobbysawandthenusingtheremainingplankhalfon

theotherbottomside,ifsawnthroughcarefullytheresultingbuttjoinisaperfectangle

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Forwardofrib25sandtheplankingofftothekeelshapeandoverlapthekeeljoin.

Asyoupassthevariouskeelcutoutsforpropshaftsandruddersetc.cutsmallerholesoutoftheplankingsothatyouknowwheretheyarelater.Cutthepropshaftholesmoretosternthanyouthinkortheywillbetoofarforward.

Onceyouhavefinishedbothsidesandbottomplanking,trim,fileandsandalltheedgestothehullshape.Don'troundtheedges,keepthemreallysharp,particularlythekeelatthebowaswehavetoputonmoreplankingyet.Ifiledoffoneflatsideofacorksandingblockasaprogressivecurveandthensuper

gluedsomefairlyroughsandpapertoittomakeasandingblockasimilarshapetothebowshape.Iamreallypleasedwiththishull!

Oncethetransomissandedapplyplankingreallyneatly,buttjoinedattheangleshown,Therewillbeonlyonelayerofplankinghereasthereisnoneedfortwolayersduetothesolidwaterprooftransom.Cutouttheexhaustpipeholesasyougowithascalpel,littlecutsatatime.

LayerTwo

5/8/2015 ModelHull2

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Oncethebottomandtransomarecoveredwithonelayerofplankingandsandedoffstartonlayertwoonthesides.Startattherearfulllengthandworkbacktothetransomandthenplankforwards.IchosetheplankanglebasedonacoupleofpicturesthatIhaveinbooksandthemovie"GiantKillers",whichisamovieoftheElcoboatconstructionin1943,anditisalsobasedoneachfullstripbeingabouthalfthelength(~200mm)ofthelasercutstripsthatImadesothatthereisverylittlewastage.Thiscomesoutveryclosetotheoriginalboatplankingangle.Runalineofgluedowntheedgeofthelastplankandanother

linejustinfromwherethenewplankwillendandalongthechinejoinline.

Thisisthebowwithbothsidesdoubleplanked,theplankingangleisnotbadbutifthestripswerelongeritwouldhavebeenmoreaccurateatthebow.

Oncethesidesaresandedofftothechineedgeyoucanstartonthesecondlayerofbottomplanking,againIstartedwitha"half'lengthofplanking(~200mm)nearthebowandIwillplanktothebowandthentothestern.

Thisisthehullalldoubleplankedwithjustalightsand.

Thereareapproximately110stripspersurfaceand25stripsonthetransomsoallupthereareinexcessof900stripsofplankingand2x2ozbottlesof"Flash"mediumcyanoacrylatesuperglue(NHP322)..

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InordertofillupmostofthegapsbetweentheplanksandregluetheoddstripthatwasalittlelooseononesideImadeupaverythin5050solutionofPVAwoodglueandwaterandpaintedthewholesurfaceofthehull,thissolutionsoaksrightinbetweenthestripsofwood,Ithenmadeupaslightlythicker

solutionandpaintedittwicemore,aboutadayaparttoletthepreviouscoatdryfully.Oncedrythehullcanbesandedagainandthenpainted.Iwillprobablypaintthishull'ForestGreen'asIintendtomakeitintoPT109.IwanttoleavesomeevidenceoftheplankingsoIdon'twantthesurfaceperfectlysmooth,Iwanttobeabletoseetheplankjoinsbutitdoesneedtobewaterproofobviously!Ifyouwantamoresmoothfinishyoucouldmixsomesandingsawdustin

withthefinalPVAsolutionwhichwillactasafiller.

Thisisthehullfilledandsandedandremovedfromtheassemblyboard(left,inmydiningroom)comparedtopicturesoftheoriginalhull(right,inElco'sFactory)fromVictorChun'sbookandItriedrealhardtogettheperspective,anglesandlightingthesame.BasedonthesecomparisonsIreckontheoriginalplankingwasprobably5"wideandnot6"wide.Itrimmedupthesideplankingaroundthedecklevelwithathincuttingbladeina"Dremel"andthensanded

flushwiththeribtops.Anadvantageoflasercuttingisthatitleavestheedgesbrownsoyoucanseeyou'vesanded.

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Thesetwopicturesshowthebuildingrunnersstrippedoffleavingtheupstandsectionthroughthecenteroftheboat,thedeckingwillgoaroundtheupstandwhichistheretoprovideabasetoholdthesuperstructureonandtostopwatergettingintothehullwhenunderway.

Thisisthe8"propshaftandtheuniversalcouplingsthatIwillbeusinginthe1/20thscaleHull2,thebrasspartsofthecouplingsareavailableineverysizeyoumightneedtosuitanymotororpropshaftsize,shownhereare4mm,5mmand3.18mm(1/8")Ibelievetheseareavailableallovertheworldandare

brandedas"RadioActive"inAustralia.

Propshafts,newcaststrutsandcastruddersfitted,therewillbethreemorestrutsfurtheruptheshafts,fittedlater.Icutthepropshaftoutertubesdownto110mm(4.33")long,droveoutthebearingfromtheshortleftoverendusingthebluntendofadrillbitthatjustfittedtheinsideofthetubeandpresseditintothenewshortertube.Iwasgoingtomountthemwiththepropshafttubeendsstickingoutoftheboatwithsquarecutendsandnotfittheextrastrutsbutthendecidedthatthatwouldlookcrap,soIthenpushedthebearingsfurtherupthetubesandcutthetubesatanangletomatchthehullopeningssothatthebrasstubewouldbeflushwiththehull,easierthanIthoughtactually.IthenfittedthestrutsandtubesoneatatimeusingAralditeandinsertedalongpieceof4mm

diameterstainlesssteelpianowiretolineupthestrut,shafttubeandthroughthemotormounttokeepitallinlinewhilethegluecured.Thecentrestrutneededalittle"fitting"intothehullasitsanglewithrespecttothehullisveryslightlydifferenttotheoutsidestruts.

Makesureyoudon'tepoxythetemporary4mmshaft!!!

YoumayalsonoticethatIhavethreedifferentpropellersfitted,twodifferentshape35mmtypesanda40mm,allRaboesch,IhavefittedthemwithalocknutastheyarealllefthandpropellersbutonceIhavedecidedonthetypetouseIwilluseananaerobicgluetolockthemontotheshaftsandgetridofthenutas

itjustdoesn'tlookright.

Ihaveboughtsomenew40mmprops,twomoreofthe15606whichistheclosestshapetotheoriginalboat,a4bladedtypewhichRaboeschrecommendforfastboatswhichisaRHtypeasIwanttotrythecenterproprotatingintheoppositedirectiontotheoutsidepropsandIalsofoundacutelittle4bladed20mmpropforthe1/35thHull2modelwhichhasanM3thread,thereisalsoa3bladedversionbutthebladearealookedabittinysoIwilltrythreeofthesefirst!

5/8/2015 ModelHull2

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ThehullcoveringhasbeenslightlycountersunkandthenrepaintedattherudderholesastheruddertubeshaveOringsthatIwantedtokeepinplacebetterthanjustsquashingthemoutofshape,particularlythemiddleoneonthemainkeel..

Testmotorsanduniversalsfitted,threedifferentmotors,twobrushlessandone700sizebrushmotor.

Allthreeruddersfittedwithtillerarmsconnectedwithuniversalcouplings,threadedrodandadualballcouplingatthecentrearm.Istillneedtocoupletheservototherudderlinkageanditwouldbereallyhelpfulifthetillerarmshada'T"shape,ImayhavetomakeupsomethingasIdidinboat1.

Adrawingandphoto'softhepropshaft,Imademinefromthe8"long"RadioActive"onesthatIbought(photodoesnotshowthecorrectlength,justatrial).ThebrasstubeMUSTcomeoutthroughthehullplankingsotheopeningcanbesealedproperly,fromasandingandfinishingperspectivethebrassis

probablyeasiertosandthanthebirchply,soitcanbesandedflushoryoucanfillthegapifitisslightlybelowthesurface.Thecentretubeneedstobefiledto

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anangleoneachsidetomaketheshapeofthekeel.

17thJune2005Hull2Inthepoolwith3AXIBrushlessmotors

That'ssomeseriouswater

TheseshotsarewiththreeAXI282010brushlessmotors,two40mm3bladeLHpropsandone40mm4bladeRHprop,twoJiaBao40AbrushlesscontrollersandoneKontronic40Acontroller,sonoreverseyet.

Iamverypleased,thisboatisveryhardtoholdandIhaveafeelingitisgoingtogolikeabatoutofhell!!!Thatroostertailistwiceashighastheboatandittookmeawhiletomopupthemess!

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Thisiswhatmadeallthemess,Imadeafanononeofthemotorsbuttheydon'tseemtogethotanyway!

BobKoskisentmeapictureofhisfullyplankedHull2beingthoroughlyscrutinisedbyhismarineinspector"Mippsey"

BobisintheUSandforcoveringhebought0.8mmFinnishBirchPlyfrom"AircraftSpruceandSpecialties"andusedastandardBalsasplitterwitha#11ExactoBladetomakethestrips,heglueditwithmediumCAandalsousedanoldmonokotehotirononmediumheattoirontheplyintoshapewhichhesaid

relaxesthewoodandallowsittofiteasierandkeepsmuchoftheglueoffyourfingers.

Nowthedecktoplankornottoplank?TheElcomovie"GiantKillers"oftheoriginalconstructionshowsafullhalfwidth,80'lengthofscarfjoinedplysheetbeingbroughtinbyoveradozenmenandlaiddownontheboatsdeckandthenscrewedintoplacewithmanythousandsofscrewsbutmanyphoto'softheboat'sdeck'sshowlineslikeplanking.AlsothereisapictureinVictorChun'sbookthatseemstoshowplankingonan80'boat.Wasthedeckplankedover

theplymaybe?

(C)Copyright2004,2005JohnDrain