M. K. Bengtson Sopwith Pup 40 User manual

SopwithPup40”
Copyright©2005‐11M.K.BengtsonAllRightsReservedRev09/11
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SopwithPup40”1/8thScale
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R/CScaleModelInstructions
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CONTACTINFORMATION
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TheSopwithPupwasdesignedby
M.K.Bengtson
PrototypebyChrisGoodchild
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ManufacturedandDistributedby:
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BengtsonCompany
e‐mail:[email protected]
WebSite:www.aerodromerc.com

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Copyright©2005‐11M.K.BengtsonAllRightsReservedRev09/11
SopwithPup
Thankyouforpurchasingthe1/8thscaleSopwithPup
modelforelectricflight.
THEMODEL
AsemiscaleadaptationoftheSopwithPup,thismodelis
designedtobeeasytobuildandexcitingtofly.
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SopwithPupFinishedModel
ModelSpecifications
Scale:  1/8
Channels: R/E/A/T
Wingspan: 40ʺ
WingArea: 550sqin
Weight: 30ozreadytofly
PowerSystem:AXI2217/20
Prop:  10x7
Wheels: Balsa&plywood,Neoprenefoamtires
AirfoilType: Flatbottomed
Cowl:  Builtupbalsaandplywood
Covering: LitespanorPolyspan
Decals: Availableonthewebsite
BUILDINGTHEMODEL
BeforeStarting
Anoteaboutthephotos:Thephotosweretakenofan
earlierversionprototypeandthepartssuppliedmaylook
slightlydifferentfromthem.Alsothemodelhasbeen
upgradedtoincludeadummymotortohouseabrushless
outrunner.However,theconceptsillustratedarethe
same.
COWLING
ThecowlingisofbuiltupconstructionusingC1andC2.
AssembletheCowling
ConstructfrontcowlringbywrappingC1’swith1/32”
thickplywood.Thegrainintheplywoodshouldbe
paralleltotheshortaxis.Toreduceweight,theinnerC1
maybeshavedorsandeddownaftercowlconstructionis
finished.Aligntheinsideofthepartsforproper
construction.GluetwoC2sinthreepairsandlaminate
together.ThengluethemtothepreviouslyassembledC1s
andplywood.SandtheC2balsatoshape.
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CowlAssemblyDetail
Thecowlshouldnowbesealed,sandedandprimeduntil
nowoodgrainisleftshowing.Baby(Talcum)powderin
cleardopemakesanexcellentbalsasealer.Talcum
powdermixedinwhitegluemakesexcellentfillerfor
gapsorgouges.Sanddownfillerafterithasdried.
WINGS
WingConstruction
Pindown,overtheplan,thet/e,sparsandwingtip,
gluingasrequired.
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TopWingCenterSection

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TopRightWingPanel
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BottomLeftWing
Addthewingtipsandalignthefronttipalongthecenter
oftheleadingedge.Sandtheleadingedgestocktobe
roundedandmeettheribs.
Theleadingedgeoftheaileronisroundedoverwith
sandpapertomaketheaileronmovablewithaminimum
gap.Thetrailingedgeofthewinginthatsectionisleft
flat.
FUSELAGECONSTRUCTION
Thefuselageisbuiltastwoseparateboxstructures,the
frontsheetareaandtherearbuiltupsection,whichare
thenjoinedovertheplan.Thissystemnotonlykeepseach
stagesimple,butitalsohelpstoensureastraight
fuselage.
BuildingtheAftSectionoftheFuselage
Beginbybuildingtworearfuselageframesovertheplan.
Selecthardbalsaorlaminatedbalsaforthelongerons.
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BuildtheTwoRearFuselageFramesOverthePlan
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JointheTwoFramesoverthePlan
Jointhetwoframesovertheplanwithcrossbracesand
thetailskidmount.Check,checkandcheckagainthat
thisandALLotherstructuresremainperfectlystraight
andsquare.
BuildingtheFrontSectionoftheFuselage
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FrontBoxDetail
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BasicFrameComplete
Thefrontboxismadefrom1/8”balsasidesreinforcedby
aninternal1/32”plywooddoubler.
AddingtheDecking
Addallthedeckingandformers,andcarefullytrimto
sizeandfit1/16”sheeting.Smallpiecesof1/8”balsaare
addednexttothecabanestrutsbeforecovering.
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FuselageSideFairings
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DeckingDetail
CabaneStruts
Thecabanestrutsarefashionedusingbalsafairingson
lasercut1/8”thickplywoodformers.Theformersare
designedtomakealignmentofthetopwingeasy.Thetop
ofthecabanesformsabarthatfitsintoslotsinthewing.
Balsa,bassorscrapplywoodcanbeusedtofairthe
cabanes.
AddingtheUndercarriageMounts
TheundercarriageismountedusingKevlar™threadand
epoxy.Lasercutplywoodundercarriagemountsare
gluedintothebottomofthefuselage.
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UndercarriageDetail
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TAILSURFACES
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Layoutandgluepartsofthetailsurfacesontheplans.
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VerticalStabilizerandRudderPinnedforGluing
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ElevatorandHorizontalStabilizerPinnedforGluing
Sandthetailparts,roundingoffalledges.Don’taddthe
hornsorhingethesurfacesuntilaftercoveringis
complete.
LANDINGGEAR
ThelandinggearisfashionedfromCAhardened1/8”
plywood.Sand,soakwiththinCAandthen,securely,
epoxythegeartothemodel.0.045”musicwire.Use
Kevlar™threadorstrongcarpetthreadandsecurethe
wirealongthegear.CAglueinplace.AddingKevlar™
crossriggingwilldramaticallystrengthenthelanding
gear.
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CompletedUndercarriage
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COVERING
Anylightweightcoveringmaterialcanbeused.Polyspan
withdopeorMinwaxPolycrylicmakeagoodchoice.
Litespanisalsopopular.
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CoveringtheTailFeathers
Decaloutlinesforthismodelareavailableon
www.aerodromerc.com/decalsinAdobe®Acrobatpdf
formatforprintingondecalpaper.

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WHEELS
Gluingtheplysidesonthe3/8”balsacoremakesthebasis
forthewheels.Usethebrasshubforalignment.Epoxythe
hubsinplaceandaddasufficientamountofepoxy
aroundthebaseofthehubtoreinforcetheconnectionof
thehubtotheply.Plywoodreinforcinghubsareprovided
thataretoslipoverthebrasstubingasshown.Next,CA
gluetheneoprenecordingtogethertofroma“tire”.Use
thinCAsparinglyastheCAbondsveryaggressivelyto
therubber.PresstheCAwettedendstogetherforan
instantbond.Thebestwaytoaligntheendsistoglue
themwhiletheyareinplaceonthewheel.Thenattachthe
tirestothewheelsandCAinplace.AthinbeadofCA
aroundtherimmakesforasecuretire.
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WheelConstructionDetail
Paperconesarecutout.Useaballpointpentoscoreeach
lineonthebacktomakeanimpressionof“spokes”Itis
helpfultodothisoperationonapapertabletsothatthe
penmakesagoodcrease.Foldthepaperalongthecrease
linestoexaggeratetheraisedlines.Oneofthesections
formingawedgeiscutout.Makecutstothecenterofthe
circlealongapairofthespokes.Closethepapercutoutto
formaconeandtapethejointinsidethecone.
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WheelAssemblyDetail
Theinsideconesmaynowbeattachedtothewheels.The
outsideconesmaybeattachedatthispointifwheel
collarsaretobeused.Alternatively,afterinstallingthe
wheelsonthelandinggear,awashermaybesolderedto
holdthewheelinplaceandthentheconeisattached.This
methodmakesaverynicescaleappearance.
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INSTALLINGTHERADIOCONTROLGEAR
ServoBay
GettheR/Cgearfittedatthisstage,andalsothemotor.
AileronServos
Aileronservosaremountedinwingandattachedwith
shortthreadedrodstotheailerons.Usea“Y”wiring
harnessconnectortowiretheservostoasingleradio
connection.Alternatively,twoRCchannelscanbeused
whenmixedelectronically.Ifdifferentialaileronthrows
aredesired,rotateeachservohornforwardabout20
degrees,whilemaintainingtheneutralpositionofthe
aileron.Thisshouldcounteranyadverseaileronyaw.
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AileronServosaremountedinWing
BatteryTray
Afteralltheabovehasbeenplaced,mountthebattery
traymadefrom1/8”balsaandusethebatterypositionto
balancethemodelasshownontheplan.
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ASSEMBLY
FittingTailSurfaces
Attachtheruddertotheverticalstabilizerusing1/8”
stripsofCAhinges.Similarly,attachtheelevatortothe

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horizontalstabilizer.Gluethehorizontalstab/elevator
assemblyontothefuselage.Ifusingpushrods,slipthe
elevatorcontrolhornontothewirepushrodendand,with
theservoandtheelevatorcentered,gluethehornintothe
slot.Thengluetheverticalstabilizerandrudderassembly
intotheslotinthehorizontalstabilizer.Inasimilar
fashionastheelevator,sliptheruddercontrolhornonto
thewirepushrodendand,withtheservoandtherudder
centered,gluetheruddercontrolhornintotheslot.

Pull‐PullElevatorSetUp
FittingtheRiggingWires
UsestrongthreadorKevlar™fishinglineorelastic
beadingcordingtosimulateriggingwires.Usesmall
screws,fishinghookeyes,straightpinheadsorsmall
eyeletstoattachthelines.These“wires”canaddadegree
ofstrengthtoyourmodel.
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RiggingWireandPilotDetail
WindsockDatafile“SopwithPup“publicationhasdetails
onplacementandmarkings.
Availableat
http://www.byrdaviationbooks.com/
Batteryhatch
Fashionabatteryhatchfrom1/32”plywood

BalancingTheModel
Balancethemodelatthepointshown.Itisbesttoposition
thebatterytodothisoperation.
FLYING
ChrisGoodchild’soriginalmaidenreportusingprevious
versionʹspowersystem:

“Justashortnotefornowtoletyouknowthatthis
eveningtherewasaSopwithPuponduskpatroloverour
localschoolplayingfield!
YESSHEHASFLOWN!!!!!!
Iflewhermyself,onmyownsounfortunatelynoflying
picsatthemomentbutsheflewbeautifully!Thisisthe
firstmodelIhavebuiltwhereIhavenothadtodialin
ANYclicksoftrim.Ihad3flightsintotalusing2950mah
KANpacksandfeltverycomfortablewithherbytheend.
Itooksomefinalphotosatthefieldʹjustincaseʹandthen
wentthroughmyfinalchecklistbeforedecidingtotrya
quicktesthoptogetthefeelofthings.So,Ipointedher
intotheverygentlybreezeandgraduallypushedthe
throttleforwardwhilstholdinginsomeupelevatorto
keepthetaildown.Shepickedupspeedquitequickly
andonlyneededatouchofruddertocorrectherline
beforesheroseofftheground.Icutthethrottleandshe
toucheddownandgentlynosedoverontothecowl
mainlyduetothegrassbeingatadtoolong.Shehad
committedaviation!

Nowtore‐gathermycomposure,settlethenervesdown
andprepareforaʹrealʹflight.Againsheheadedoffagreat
paceandwasintheairinnexttonotime.FirstthingI
noticedwasthatshewastrackingstraightandtrueinthe
airwithouttheneedforevenoneclickoftrimonany
controlsurface!(Thatʹsafirstforme!).Shewasflying
beautifullyandIthrottledbacktoabout1/3tomaintain
altitudewhileIdidafewcircuitstogetthefeelofher.The
480motorina4:1gearboxand10x7APCslow‐flyprop
wereprovidingʹbagsʹofpower.Igottoareasonable
heightandtriedsomestalltest,whichwereveryun‐
dramaticwithnosignsofdroppingawing.Ithencutthe
powertoseehowrapidthedecentwas,welloneword
saysit‐‐GLIDER!Sheliterallyglidesataveryshallow

SopwithPup40”Page7

Copyright©2005‐11M.K.BengtsonAllRightsReservedRev09/11
angleandremainsutterlycontrollable.Iwasexpectinga
fairlyrapiddecentbutnotatall,great!
Idecidedtotryacoupleofpracticeapproachesand
eventuallysettledherdownonthegroundagainwithjust
agentlenoseover,whichIbegantofeelIcouldcontrol
withmoreelevatorinthefinaltouchdownstages.I
reckonedIwasabout4‐5min’sintothepackwhich
seemedtohaveplentyleftsoIdidanothertakeoffanda
fewmorecircuitsbeforefeelingtheedgehadgonefrom
thebatteryandbringingherbackdowntochangetopack
2.Thislandingdidendinanoseoveragainbutwaseven
gentlerandverynearlydidnʹtgooveratall.

Ontopack2.TakeoffwaseasyagainandIwasreally
gettingthefeelofthingsnow.Iwasevenbraveenoughto
trymyfirstloopwithhersouptoasafeheightandput
herintoaslightdivetopickupsomespeedwhenallofa
suddenthebatteryhatchdecidedtopartcompanyand
flutterdowntotheground.Nevermind,letstrythat
again,backaround,backintoashallowdiveandovershe
goes,beautifulandwithplentyofpowerinreserve.Iflew
aroundformaybe8minutesorso(Iforgottotakemy
timer)anddidsomelovelylowslowfly‐byswhiles
wishingIhadsomeonetophotograph/videothem.Thenit
wastimetoprepareforthelastlandingoftheday.This
timeIconcentratedhardonmyelevatorcontroland
managedaperfect3pointerwithagentlerollout,Iwas
grinninglikeaCheshirecat.

WhenhomeIrechargedthepacks,whichtookabout
650maand750marespectively,whichmeantIwasinthe
rightballparkforbringherin.NowIcan’twaittogofly
heragainandhopefullyIwillbeabletogetacamera
personalongtosharethespectacleofaSopwithPupon
duskpatrol.

Thisisagreatkitfromagreatdesignerandonethatflies
beautifully.“

ThemodelshouldROGongrass,pavementorhard
surfaces.Themodelmayrequirecoordinatedturns
usingbothaileronsandruddercontrol.Thisisdueto
adverseyaw.Halvingtheailerondownthrowmay
reducetheyaw.Thiseffectcanbeaccomplishedby
rotatingthecontrolarmoftheaileronservoforward
about20degrees.

Letthemodelgainaltitudeslowlyofftherunway.
Applyingtoomuchupelevatoratslowspeedsrisksa
stall.Makeyourturnsgentlyastightturnsrisktip
stallinginanymodel.Don’texpecttheelevatortomake
themodelclimb.Thinkoftheelevatorasadeviceto
changetheattitudeofthemodel.Thewingandairspeed
ultimatelymakethemodelclimb.Oftendownelevator
appliedatstallingcanavoidamajorcrash.Themost
importantdetailsforproperflightoperationsare:

1)CGlocation.Tailheavymodelsneverflywellorat
all.
2)Downandrightthrust
3)Straightandnonwarpedwings


FinishedModel

CONTACTINFORMATION
Distributedby:

BengtsonCompany
e‐mail:[email protected]
WebSite:www.aerodromerc.com
