model pt boat
DESCRIPTION
Model PT BoatTRANSCRIPT
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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 1/11
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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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 2/11
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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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 3/11
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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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 4/11
Sandthechineedgetomeetthehullbottomshape.
Oncethesidesareplankedandedgesanded,startonthebottomplanking,againIstartedfromthelongestpiecesnearthebowandworkedforwardsandthenaft.
IamveryhappywiththestrengthandtheshapeofHull2,it'salreadylookingfabulous!
Asyougetfurtheraftitbecomesapparentthatsandingthefirstsideplankingofftothekeelangleisnotgoingtoworkontheaftendduetotheshallowanglesinvolvedsoafterabouttherib25positionIstartedsawingtheplanksthroughusingapencillineandahobbysawandthenusingtheremainingplankhalfon
theotherbottomside,ifsawnthroughcarefullytheresultingbuttjoinisaperfectangle
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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 5/11
Forwardofrib25sandtheplankingofftothekeelshapeandoverlapthekeeljoin.
Asyoupassthevariouskeelcutoutsforpropshaftsandruddersetc.cutsmallerholesoutoftheplankingsothatyouknowwheretheyarelater.Cutthepropshaftholesmoretosternthanyouthinkortheywillbetoofarforward.
Onceyouhavefinishedbothsidesandbottomplanking,trim,fileandsandalltheedgestothehullshape.Don'troundtheedges,keepthemreallysharp,particularlythekeelatthebowaswehavetoputonmoreplankingyet.Ifiledoffoneflatsideofacorksandingblockasaprogressivecurveandthensuper
gluedsomefairlyroughsandpapertoittomakeasandingblockasimilarshapetothebowshape.Iamreallypleasedwiththishull!
Oncethetransomissandedapplyplankingreallyneatly,buttjoinedattheangleshown,Therewillbeonlyonelayerofplankinghereasthereisnoneedfortwolayersduetothesolidwaterprooftransom.Cutouttheexhaustpipeholesasyougowithascalpel,littlecutsatatime.
LayerTwo
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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 6/11
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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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 7/11
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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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 8/11
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!
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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 9/11
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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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 10/11
anangleoneachsidetomaketheshapeofthekeel.
17thJune2005Hull2Inthepoolwith3AXIBrushlessmotors
That'ssomeseriouswater
TheseshotsarewiththreeAXI282010brushlessmotors,two40mm3bladeLHpropsandone40mm4bladeRHprop,twoJiaBao40AbrushlesscontrollersandoneKontronic40Acontroller,sonoreverseyet.
Iamverypleased,thisboatisveryhardtoholdandIhaveafeelingitisgoingtogolikeabatoutofhell!!!Thatroostertailistwiceashighastheboatandittookmeawhiletomopupthemess!
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5/8/2015 ModelHull2
http://www.ptboat.com/Hull2/Hull2.html 11/11
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