Rubber - All You Need to Know

IN previous article development several new types excellent quality rubber described Laboratory tests field tests models have demonstrated new rubber types equivalent quality pre-1973 Pirelli Since 1973 Pirelli company reorganized disrupted supply rubber used contestants no consistent supply good rubber strip model airplanes until 1976 InthatyearFAlrubberappeared little later Sig Vintage Aero rubber similar properties 1978 Pirelli arrived back scene new Pirelli especially made model fliers new Pirelli yellow-brown almost translucent whereas Filati dark brown opaque excellent quality new types rubber according Mike Dikovitzky has Put fun back flying rubber powered models Table gives characteristics typical batch ofFAl rubber Table II gives characteristics batch 1978 new Pirelli FAI rubber thicker Pirelli Typically 14 Strands FAI equivalent 16 Strands Pirelli stretchiness rubber will valy considerably batch batch closely correlated capability take turns Good rubber varies maximum stretch terms original length 73 81 suspicious rubber less stretchiness figures Prank Parmenter winding Charisma Wake field using protective tube fuse lageandan extension onwinder permittingthe removai tube Protection isa must big rubber models because broken motor whiie winding wiii have catastrophic results less 73 probably old can brittle above 82 can undervulcanized too soft Undervulcan ized rubber has torque curve drops off rapidly good rubber gives trimming problems leads mushing stalls shortly after launch although power towards end motor run holds up very well Expect find differences batch batch both good types rubber inferior types rubber Tests Pirelli 1958 1972 ranged stretch 74 84 energy ranged 2940 3525 Current tests FAI rubber indicate wide range properties encountered Pirelli average energy good pre-1973 Pirelli time writing experience new Pirelli limited batch superior energy previously tested rubber giving 3725 foot-pounds per pound rubber gave significant increase duration demonstrated down 4-minute rounds 1978 Taft Wakefield Elimi nations Although new Pirelli obvious choice cool early morning flying few fliers supplies scarce new product experienced difficulty later day Pirelli tended blow up temperatures got over 900F led both Pirelli FAI switch FAI rubber much less likely blow-up leads another topic What effect does ambient temperature have ability rubber store energy Ambient Temperature Effect higher ambient temperature energy can stored addition shape power curve better higher temperature Fig 6 shows change power curve energy knee power curve energy knee airplane will perform better through period few seconds after launch stalls likely present writer has limited amount temperature effect data Fig 7 presents picture Both FAI Pirelli have about 5% energy 900F 750F Below 750F charac teristics diverge Pirelli rate change remains about same athighertemper ature FAI declines rapidly being down perhaps 20% 400F thought figures vary batch batch Waiter Erbach discussed tempera ture effect excellent report Energy Storage Rubber Filaments published 1971 NFFS Symposium Since rubber stores energy gets hotter try keep rubber hot possible being 68 Model Aviation AIIYou coverage discusses handling optimum resultsE Fred Pearce Won testing programand its no findings Concluding two-part wound sun exposed rubber gets significantly hotter ambient tem perature Experience indicates above 950F winding sun much likely break motor So careful trying take advantage rubbers capability store energy wanner cold weather much advantage use Pirelli FAI Maximum Turns Tables II give maximum turns several skein sizes FAI new Pirelli specific batch numbers derive actual winding experience batches Different batches course will vary number maximum turns formula maximum turns Turns max riginal Length m ] [Original Length IWeight oz J constant K varies stretchiness rubber can approximated formula K 75 [Maximum Stretched Length] Original Length J know maximum turns given size motor specific batch can solve K first formula TABLE Motor Characteristics March 1977 FAI Rubber * DryOriginalBroken-inMax TypeWeightStrandsLengthLengthTurns Wakefield388 gin10 x1/4228239530 12 x1/4190199403 14 xA163171320 16 x1/4~143150263 Coupe dHiver 97 gin10 x1/8114120375 6 x/951998286 * Energy 3450 foot pounds per pound maximum stretch 76 times original length Turns constant K TABLE II Motor Characteristics 1978 New Pirelli Rubber * DryOriginalBroken-inMax TypeWeightStrandsLengthLengthTurns Wakefield388 gin10 x260270686 12 x1/4~217226523 14 x1/4~186193415 16 x1/4163170341 Coupe dHiver 97 gin10 x1/8129134480 6 X1075112365 14 x1/8927963293 * Energy 3725 foot pounds per pound maximum stretch 81 times original length Turns constant K 606 compute turns size motor batch K two batches tables given bottom table Strand Size Does width rubber affect energy storage Would get less energy using equivalent skein smaller strands has hypothesized larger number smaller strands same cross-section area would enable store energy since tensile stress across narrow strands would have less gradient question intriguing enough induce Bob Champine conduct test Pirelli about 15 years ago divided sample er two halves stripped half 1/10 wide strand Both motors made up equivalent cross-section Energy stor age tests performed using torsion method unwinding torques vs turns recorded No appreciable difference torque energy storage evidenced Thus trade-off using different widths rubber other get proper cross-section smaller sizes tie easier knots also offer edges skein get frayed Tying-up Skein Table will found useful sizing skeins desired Special care must taken tying knot because smooth surface strip Wetting ends dusting extra talcum powder helps make secure knot will slip square knot topped single granny works well Saliva generously ap plied aids tying knots Breaking-in lubricated motors should broken stretching prior use force 7 pounds pull per strand ested 98 pounds 14-strand motor amount pull will stretch motor between 7 8 times its original length April 1979 69 Last month author reported Rubber-holding stirrups enabling detach ment prop assembly winding Top Wakefield bottom coupe 3400 33000 3200 z w 3100 Fig 4 0510520 MINUTES OF HOLDING several minutes pull motors twice oOnce very quickly 7 lb/strand relaxing immediately second time holding motor 5 minutes important have secure anchor point second anchor point end pull equally j - important Inspect re-tie slipped n knots measuring pull force z impractical stretch least 7 W times original length hold 5 ELminutes 60 z w 0 aLubrication A green soap glycerine mixture recommended green soap hard find although can occasionally found one-pound jars resembles brown grease form often tincture green soap available alcohol must boiled out tincture 2530very corrosive rubber prepare lubricant boil 8 ounces tincture sauce pan low heat After boils about 20 minutes add about 3 ounces glycerine boil another 20 minutes low heat Adjust viscosity thin honey adding glycerine after Fig 4 Energy loss time holding fully wound motor front end pulled out show way stirrup holds rubber _________ IS 16 IA 12 U 0 z nIC 0 0 Li 0 0 Li 8 6 4 2 0 1DEC 1976 FAI RUBBERI SAMPLES 395 gins X 1305I I I I ZERO HOLD ENERGY 3380 20 MINUTE HOLD ENERGY 3110 73o/o LOSS 02040 Fig 5 60 80100 STRETCH INCHES Fig 5 Comparison energy before after holding wound up motor 20 mm 70 Model Aviation Propeller assembly showing aluminum stirrup prop shaft stirrup enables propeller assembly detached safety winding cools careful getting lubricant evenly distributed Lubricate motors before breaking Smooth rubber inclined squeeze itself dry wound prevent breakage redistribute lubricant evenly after winding Table allows 12 grams lubricant bring rubber up weight Wakefield-size motor Winding sturdy winder good bear ings helpful winding author converted large hand-drill winder installing thrust bearing take pull motor adding additional leverage crank See photograph Several supply sources sell winders Begin stretching motor about 4 times its length point wind 50 55% maximum turns Continue winding slowly way full count Bunching around front hook bobbin aggravated stopping winding several inches nose coming rest way winding author uses special bobbin tube assembly shown photographs array permits winding propel ler removed aluminum protec tive tube fuselage prevent damage broken motors Remember caution about redistributing lubricant between windings dont redistribute tearing will take place dry spots Holding Wound Motor An important quality factor rubber strip its ability maintain its energy storage being held fully wound contest frequently necessary wait minutes thermal Rubber does decline rapidly stored energy great asset under conditions FAI rubber exceptionally good its capability hold energy Figure 4 shows decline stored energy rubber holding time loses power rather linear manner 5% loss after 11 minutes 10% loss 30 minutes Jon Davis 1971 NFFS Symposium article reported Pirelli found declined much rapidly FAI rubber Pirelli tests indicated 15% loss six minutes Figure 5 shows change power curve holding fully wound FAI rubber motor 20 minutes rubberlost73% ofits energy chiefly knee curvecorre sponding first 5 seconds motor run highly probable capability hold energy varies significantly batch batch ambient temperature Comments Taft holding quality new Pirelli good FAI holding its energy Few Closing Comments author found extremely beneficial have winder thrust take pull force low-friction winder can feel torque motor can maintain continued page 119 18 6 14 12 z n 0 a 10 lii C- LL 6 4 DECEMBER 1976 FAI RUBBER 44gm SAMPLES TEMP 9I0F ENERGY 3380 0 20 Fig 6 4060 STRETCH INCH ES 80 100 April1979 71 Fig 6 Effect ambient temperature energy Motor winding gear Winder coverted high quality hand drill Bob Wilder torque meter atached winder well aluminum rod rod enables removal protective aluminum tube inside fuselage after windingwith propeller detached safety Frank Parmenter near completion winding Charismaagain prop detached safety Winding began motor stretched out nose four motor lengths Bill Shaw holds aid Ia steel rod through /4 aluminum motoranchor Long rod attached winder enables removal 1 4 protective aluminum tube inside fuselage after motor has wound subjects landing gear length prime factor ridiculous Are building flying scale takeoff scale models An excellent method hand-launching proposed Ken Hamilton has noticed otherwise accomplished scale modelers launching excessive speed and/or nose-up angles hand moving through arc model says Ken should projected .along straight line desired flight path means arm motion involving both shoulder elbow joints arm moves hand straight line can match flying speed expected model excess lift produced nose-up hurling will minimized Sort ofjust let fly out hand Ken top men aircraft industry Sabreliner project before retirement adds Real aircraft docile within design speed envelope become unruly pushed outside too months TWA comes Dick Seifried Curtiss XP-37 pic Jan MA lost 1978 Flightmasters Annual three flights about minute final awe-inspiring 14 minutes QOS 22 span one-ounce model built la Earl Stahl clamshell construction flew six strands X 22 Sig contest rubber one-minute motor runs model did best calm air trouble ground turbulence due low power Dick feels shorter powerful motor would get up out problem reduction motor run 35/40 seconds Dick offers loan photo negative making own plans address R Seifried Jr 13022 Barto Dr Granada Hills CA 91344 readers have sent recommenda tions best buy year gold rubber-scale plans reduced catalogue Golden Age Reproductions POBox #13 Braintree MA 02184 Put out Joe Fitzgibbon book shows plans can order him full size collection 150 vintage drawings worth price catalogue Send along $5 wont regret Keep great hints tips TWAs 5 X 7 B/Ws coming Bill Warner 432C San Vicente Blvd Santa Monica CA 90402 Rubber/Pearce continued page 71 closer control winding maximum turns great priviledge wind knowing blow-up motor model fuselage will survive author achieved protective tube system shown photographs Others have constructed fuselages layers balsa fiberglass can contain broken motor Experience new Pirelli limited small quantities single batch source US Pirelli established written Sep tember 1978 perfect product has bad spots edge defects does FAI 110 N 0 WI 100 H C' 90 zW W- HZ 80 ZW wcr OW 70 aAr rubber choice between Pirelli FAI simple choice Both have virtues Although Pirelli has about 9% energy 750F FAL retains its energy better hold waiting good air hold over five minutes PIRELLI FAI 40 50 60 70 80 90 AMBIENT TEMP 0F 100 Fig 7 Energy storage variation temperature April1979 119 JLL-SIZE PLANNo 256 Fairchild FC-2$1 200 RC Clapps great Sport Scale Fairchild Two big sheetsfor60 No 257Astron$200 RC Bill Evans X-wing tailless biplane aerobatic 19s No 258Martin MO-i$275 CL Hazens highly competitive Profile Carrier Fox 36 etc No 259Chambermaid$200 FF Bill Henns superlative rubber-powered scale winner Kioud King 1519 RC Old-Timer Free Flight based upon 1938 record breaker FF $400 Wiley Post Biplane Petite durable scale design foreither rubber ortail waggerlpulse rudder $225 GollyGeeWhiz Dan Rutherfords simple Half-A powered Combat job turns dime $150 Gremlin Sturdy aerobatic RC biplane flies well 35s up 60s$300 4-Bits 40-powered RC 500 Club Racer has winning ways Good sport too$400 Semi-Pro Contest-winning HL glider has pop-up tail dethermalizer$100 Halt-Korda rubber John Oldenkamps 1/2-size all-balsa Old-Timer$175 Gee Bee Model Y 40-powered RC stand-off scale great Old-time racers $500 Fieseler Storch RC scale model 2345 5-channel has both slots flaps $400 QuickSilver RC 1/2A Pylon Racer incorporates latest techniques$200 comedian RC fun-fly aerobatic biplane good looker 40 60 -$400 Tercel Keith Trostles 1/2A CL Stunt ship flies excellent pattern- -$200 Midget Mustang CL 19751976 Nats winning Goodyear John Ballard $200 Nothing Fancy RC biplane 35 engines pretty handles beautifully-$825 Simitar RC spectacular flying wing 15 nose-mounted tractor$300 Dennyplane RC version famed cabin model kit trom 1937 192S$400 Zonker RC canard has pattern capability 40 power$300 country Boy FF Jim Clem thoroughbred 1 /2A -$300 Bed check charlie RC Scale model Russian PT trainer 09/15.$300 Seville RC Sport low-wing sailplane 80 wing has eacellent performance$350 Stiletto CL stunt model McDonald winner 1976 FAI World Champs-$375 Vol Libre FF rubber-powered Wakefield Bob White Great winner$275 Hatz Biplane RC aerobatic scale job takes 40/50 built-in muffler$475 Sportster RC deBolt wing choice aerobatics/racing- -$375 FokkerD-VIII RCfor45 60 Two sheets 2-1/2 scale$900 Hot Rock RC aerobatics 19-40 engines Simple tail-dragger$350 Livesey DL 5 RC English homebuilt 3-chan. 15s Exotic easy Good flier- $500 Miss America RC Antique famous historic model 2 big sheets 35 40. $925 Windlord Ken Bates RC flying wing sailplane highly competitive$550 Mustang Al Meyers lovely CL P-Si 35 46 Sport Scale Stunt-$400 Rc Fairchild Ranger 24 AMA Sport Scale 2 big sheets$1000 FF Fokker universal Jumbo-sized rubber scale model Bill Noonan $500 cL Bobcat John Kilsdonks Slow Ratlatest state art$1SO Winterhawk RC standard class sailplane rugged excellent soarer $350 Fly Baby CL Scale model Pete Bowers homebuilttor 3540 RC engine$375 Ole Reliable RC 70 version 38 oldtimer REM controls 1925$425 Spitfire CL profile 2 versionsbuilt-up solid stunter 35$450 AG-i Agrivation RC 4-chan. 2540 realistic trike gear low wing$400 Solution RC competitive pattern deBolt 40 power$475 Tiny White Mouse CL 1/2A powered mouse racer frequent big time winner$1SO Sport 40 RC 4-chan trike-gear shoulder-wing 40$425 Typhoon CL profile 15 WW II fighter Paul Schasi-$300 Mentor FF very nice 40 towliner small fields$300 Dasher RC combo racing pattern characteristics 151025$300 Stits Jr CL worlds smallest plane good flier 25 35$300 Wildcat RC Ace pulse rudder 02 Grumman fighter Bowers Srull . $17S Blue Birds RC Ken Willards formation plane 4-ch. 10$375 Miaflit RC Classy shoulder wing sport 4 ch. 15 power$400 Ace-Dart RC Scale-up Ehling Dart Pulse rudder Pee Wee 02$17S Dakota FF Scale-up famous Dakota bipe great sport 049$275 Super Burp CL Record jet speed model 1/2 size plan details full$1SO Spirit Springs RC sport racer REM 0915 also 1/4 Midget$250 Whip control Bagle CL Profile F-iS fighter easy build fun fly$1SO T-craft RC nice flying pulse rudder scale 02 electric$250 Wright Flyer Authentic plans real plane Harry Robinson 3 sheets . . $300 Pitcairn Maitwing RC Beautiful classic bipe 60 etc Two plan sheets . $750 Zilch Doc Mathews updates Jim Saftigs great stunter 35 $350 Hiperbipe FF Nats scale winner dramatic homebuilt 049 $350 Snowbird RC Delightful powered soarer cabin 049 mounted pylon $350 Little Devil FF Rubber-powered P-30 rules tubular wing pylon $17S Mitchell B-25 RC 4-ft i/2A twin Ace foam panels Well behaved $350 Aetos CL Sporty superlative flying built-up profile Fon 25 etc $350 ciklon FF WC Silver Medalist FAI 15automatics include tilt wing $325 103104 131136146149159165 181184193194195198 216218 219 220 234235 245246 256257 222 236 247 258 223 237 248 259 Circle numbers plans wish order 121123124 168169177 205207212 226227229 125 178 215 230231233 239240241242243244 249250251252253254255 Please print carefully Enclosed Price includes first-class postage Send Check money order payable Mode/Aviation AMA 815 Fifteenth St. NW. Washington DC 20005 probable FAI will have energy since FAL loses energy much lower rate Pirelli despite its 9% higher energy storage proved treacherous very hot weather Taft frequent breaking encountered have experience batch new Pirelli knows what subsequent batches may like FAI rubber can obtained FAI Model Supply POBox 9778 Phoenix AZ 85068 new Pirelli can also obtained FAI Model Supply Oldtimer Models PO Box 18002 Mil waukee WI 53218 have questions news con cerning rubber please contact author Fred Pearce 5317 Blythewood St Houston TX 77021 ADVERTISERS INDEX Ace Radio Control99 Andrews Aircraft Model Co117 Richard C Barron112 Bavarian Precision Products Co103 Boyntonand Associates115 Cleveland Model & Supply Co108 Coverite28 Cox Hobbies IncInside Front Cover DGM Industries100 Du-Bro Products8 FAI Model Supply108 Fli-Shirts104 Flyline Models100 Fourmost Racing Products102 Four Js Enterprises110 Fox Mfg Co7 Gemini Models108 Carl Goldberg Models Inc5 Jim Gray100 Grish Brothers101 Hobby Capitol Dist114 K&B Manufacturing3 Kustom Kraftsmanship114 Logictrol International7 Model Merchant105 Model Rectifier Corp side Back Cover Modernistic Models116 Pactra Industries113 Peck-Polymers116 Pica Products106 Progress Mfg Co6 Quarter Headquarters112 Repla-Tech International Inc116 Sig Mfg Co1 Sterling Models Inc107 Swanson Associates114 Tower Hobbies Inc57 VaI0ir111 Viking Tension Products9 Charles Werle102 Williams Brothers118 World EnginesBack Cover 1 20 Model Aviation No103 No104 No118 No 121 No 123 No 124 No 125 No 131 No 136 No 146 No 14g No 159 No 165 No 166 No 168 No 169 No 177 No 178 No 181 No 184 No 193 No 194 No 195 No iga No 203 No 205 No 207 No 212 No 215 No 218 No 218 No 219 No 220 No 222 No 223 No 225 No 226 No 227 No 229 No 231 No 233 No 234 No 235 No 236 No 237 No 238 No 239 No 240 No 241 No 242 No 243 No 244 No 245 No 246 No 247 No 248 No 249 No 250 No 251 No 252 No 253 No 254 No 255 118 166 203 225 238 NAME STREET CITY STATE Full-Size Plan List Available complete listing plans pre viously published magazine through No 243 may obtained free charge writing enclose stamped self-addressed business-size envelope Model Aviation 815 15th St NW Washington DC 20005

IN previous article development several new types excellent quality rubber described Laboratory tests field tests models have demonstrated new rubber types equivalent quality pre-1973 Pirelli Since 1973 Pirelli company reorganized disrupted supply rubber used contestants no consistent supply good rubber strip model airplanes until 1976 InthatyearFAlrubberappeared little later Sig Vintage Aero rubber similar properties 1978 Pirelli arrived back scene new Pirelli especially made model fliers new Pirelli yellow-brown almost translucent whereas Filati dark brown opaque excellent quality new types rubber according Mike Dikovitzky has Put fun back flying rubber powered models Table gives characteristics typical batch ofFAl rubber Table II gives characteristics batch 1978 new Pirelli FAI rubber thicker Pirelli Typically 14 Strands FAI equivalent 16 Strands Pirelli stretchiness rubber will valy considerably batch batch closely correlated capability take turns Good rubber varies maximum stretch terms original length 73 81 suspicious rubber less stretchiness figures Prank Parmenter winding Charisma Wake field using protective tube fuse lageandan extension onwinder permittingthe removai tube Protection isa must big rubber models because broken motor whiie winding wiii have catastrophic results less 73 probably old can brittle above 82 can undervulcanized too soft Undervulcan ized rubber has torque curve drops off rapidly good rubber gives trimming problems leads mushing stalls shortly after launch although power towards end motor run holds up very well Expect find differences batch batch both good types rubber inferior types rubber Tests Pirelli 1958 1972 ranged stretch 74 84 energy ranged 2940 3525 Current tests FAI rubber indicate wide range properties encountered Pirelli average energy good pre-1973 Pirelli time writing experience new Pirelli limited batch superior energy previously tested rubber giving 3725 foot-pounds per pound rubber gave significant increase duration demonstrated down 4-minute rounds 1978 Taft Wakefield Elimi nations Although new Pirelli obvious choice cool early morning flying few fliers supplies scarce new product experienced difficulty later day Pirelli tended blow up temperatures got over 900F led both Pirelli FAI switch FAI rubber much less likely blow-up leads another topic What effect does ambient temperature have ability rubber store energy Ambient Temperature Effect higher ambient temperature energy can stored addition shape power curve better higher temperature Fig 6 shows change power curve energy knee power curve energy knee airplane will perform better through period few seconds after launch stalls likely present writer has limited amount temperature effect data Fig 7 presents picture Both FAI Pirelli have about 5% energy 900F 750F Below 750F charac teristics diverge Pirelli rate change remains about same athighertemper ature FAI declines rapidly being down perhaps 20% 400F thought figures vary batch batch Waiter Erbach discussed tempera ture effect excellent report Energy Storage Rubber Filaments published 1971 NFFS Symposium Since rubber stores energy gets hotter try keep rubber hot possible being 68 Model Aviation AIIYou coverage discusses handling optimum resultsE Fred Pearce Won testing programand its no findings Concluding two-part wound sun exposed rubber gets significantly hotter ambient tem perature Experience indicates above 950F winding sun much likely break motor So careful trying take advantage rubbers capability store energy wanner cold weather much advantage use Pirelli FAI Maximum Turns Tables II give maximum turns several skein sizes FAI new Pirelli specific batch numbers derive actual winding experience batches Different batches course will vary number maximum turns formula maximum turns Turns max riginal Length m ] [Original Length IWeight oz J constant K varies stretchiness rubber can approximated formula K 75 [Maximum Stretched Length] Original Length J know maximum turns given size motor specific batch can solve K first formula TABLE Motor Characteristics March 1977 FAI Rubber * DryOriginalBroken-inMax TypeWeightStrandsLengthLengthTurns Wakefield388 gin10 x1/4228239530 12 x1/4190199403 14 xA163171320 16 x1/4~143150263 Coupe dHiver 97 gin10 x1/8114120375 6 x/951998286 * Energy 3450 foot pounds per pound maximum stretch 76 times original length Turns constant K TABLE II Motor Characteristics 1978 New Pirelli Rubber * DryOriginalBroken-inMax TypeWeightStrandsLengthLengthTurns Wakefield388 gin10 x260270686 12 x1/4~217226523 14 x1/4~186193415 16 x1/4163170341 Coupe dHiver 97 gin10 x1/8129134480 6 X1075112365 14 x1/8927963293 * Energy 3725 foot pounds per pound maximum stretch 81 times original length Turns constant K 606 compute turns size motor batch K two batches tables given bottom table Strand Size Does width rubber affect energy storage Would get less energy using equivalent skein smaller strands has hypothesized larger number smaller strands same cross-section area would enable store energy since tensile stress across narrow strands would have less gradient question intriguing enough induce Bob Champine conduct test Pirelli about 15 years ago divided sample er two halves stripped half 1/10 wide strand Both motors made up equivalent cross-section Energy stor age tests performed using torsion method unwinding torques vs turns recorded No appreciable difference torque energy storage evidenced Thus trade-off using different widths rubber other get proper cross-section smaller sizes tie easier knots also offer edges skein get frayed Tying-up Skein Table will found useful sizing skeins desired Special care must taken tying knot because smooth surface strip Wetting ends dusting extra talcum powder helps make secure knot will slip square knot topped single granny works well Saliva generously ap plied aids tying knots Breaking-in lubricated motors should broken stretching prior use force 7 pounds pull per strand ested 98 pounds 14-strand motor amount pull will stretch motor between 7 8 times its original length April 1979 69 Last month author reported Rubber-holding stirrups enabling detach ment prop assembly winding Top Wakefield bottom coupe 3400 33000 3200 z w 3100 Fig 4 0510520 MINUTES OF HOLDING several minutes pull motors twice oOnce very quickly 7 lb/strand relaxing immediately second time holding motor 5 minutes important have secure anchor point second anchor point end pull equally j - important Inspect re-tie slipped n knots measuring pull force z impractical stretch least 7 W times original length hold 5 ELminutes 60 z w 0 aLubrication A green soap glycerine mixture recommended green soap hard find although can occasionally found one-pound jars resembles brown grease form often tincture green soap available alcohol must boiled out tincture 2530very corrosive rubber prepare lubricant boil 8 ounces tincture sauce pan low heat After boils about 20 minutes add about 3 ounces glycerine boil another 20 minutes low heat Adjust viscosity thin honey adding glycerine after Fig 4 Energy loss time holding fully wound motor front end pulled out show way stirrup holds rubber _________ IS 16 IA 12 U 0 z nIC 0 0 Li 0 0 Li 8 6 4 2 0 1DEC 1976 FAI RUBBERI SAMPLES 395 gins X 1305I I I I ZERO HOLD ENERGY 3380 20 MINUTE HOLD ENERGY 3110 73o/o LOSS 02040 Fig 5 60 80100 STRETCH INCHES Fig 5 Comparison energy before after holding wound up motor 20 mm 70 Model Aviation Propeller assembly showing aluminum stirrup prop shaft stirrup enables propeller assembly detached safety winding cools careful getting lubricant evenly distributed Lubricate motors before breaking Smooth rubber inclined squeeze itself dry wound prevent breakage redistribute lubricant evenly after winding Table allows 12 grams lubricant bring rubber up weight Wakefield-size motor Winding sturdy winder good bear ings helpful winding author converted large hand-drill winder installing thrust bearing take pull motor adding additional leverage crank See photograph Several supply sources sell winders Begin stretching motor about 4 times its length point wind 50 55% maximum turns Continue winding slowly way full count Bunching around front hook bobbin aggravated stopping winding several inches nose coming rest way winding author uses special bobbin tube assembly shown photographs array permits winding propel ler removed aluminum protec tive tube fuselage prevent damage broken motors Remember caution about redistributing lubricant between windings dont redistribute tearing will take place dry spots Holding Wound Motor An important quality factor rubber strip its ability maintain its energy storage being held fully wound contest frequently necessary wait minutes thermal Rubber does decline rapidly stored energy great asset under conditions FAI rubber exceptionally good its capability hold energy Figure 4 shows decline stored energy rubber holding time loses power rather linear manner 5% loss after 11 minutes 10% loss 30 minutes Jon Davis 1971 NFFS Symposium article reported Pirelli found declined much rapidly FAI rubber Pirelli tests indicated 15% loss six minutes Figure 5 shows change power curve holding fully wound FAI rubber motor 20 minutes rubberlost73% ofits energy chiefly knee curvecorre sponding first 5 seconds motor run highly probable capability hold energy varies significantly batch batch ambient temperature Comments Taft holding quality new Pirelli good FAI holding its energy Few Closing Comments author found extremely beneficial have winder thrust take pull force low-friction winder can feel torque motor can maintain continued page 119 18 6 14 12 z n 0 a 10 lii C- LL 6 4 DECEMBER 1976 FAI RUBBER 44gm SAMPLES TEMP 9I0F ENERGY 3380 0 20 Fig 6 4060 STRETCH INCH ES 80 100 April1979 71 Fig 6 Effect ambient temperature energy Motor winding gear Winder coverted high quality hand drill Bob Wilder torque meter atached winder well aluminum rod rod enables removal protective aluminum tube inside fuselage after windingwith propeller detached safety Frank Parmenter near completion winding Charismaagain prop detached safety Winding began motor stretched out nose four motor lengths Bill Shaw holds aid Ia steel rod through /4 aluminum motoranchor Long rod attached winder enables removal 1 4 protective aluminum tube inside fuselage after motor has wound subjects landing gear length prime factor ridiculous Are building flying scale takeoff scale models An excellent method hand-launching proposed Ken Hamilton has noticed otherwise accomplished scale modelers launching excessive speed and/or nose-up angles hand moving through arc model says Ken should projected .along straight line desired flight path means arm motion involving both shoulder elbow joints arm moves hand straight line can match flying speed expected model excess lift produced nose-up hurling will minimized Sort ofjust let fly out hand Ken top men aircraft industry Sabreliner project before retirement adds Real aircraft docile within design speed envelope become unruly pushed outside too months TWA comes Dick Seifried Curtiss XP-37 pic Jan MA lost 1978 Flightmasters Annual three flights about minute final awe-inspiring 14 minutes QOS 22 span one-ounce model built la Earl Stahl clamshell construction flew six strands X 22 Sig contest rubber one-minute motor runs model did best calm air trouble ground turbulence due low power Dick feels shorter powerful motor would get up out problem reduction motor run 35/40 seconds Dick offers loan photo negative making own plans address R Seifried Jr 13022 Barto Dr Granada Hills CA 91344 readers have sent recommenda tions best buy year gold rubber-scale plans reduced catalogue Golden Age Reproductions POBox #13 Braintree MA 02184 Put out Joe Fitzgibbon book shows plans can order him full size collection 150 vintage drawings worth price catalogue Send along $5 wont regret Keep great hints tips TWAs 5 X 7 B/Ws coming Bill Warner 432C San Vicente Blvd Santa Monica CA 90402 Rubber/Pearce continued page 71 closer control winding maximum turns great priviledge wind knowing blow-up motor model fuselage will survive author achieved protective tube system shown photographs Others have constructed fuselages layers balsa fiberglass can contain broken motor Experience new Pirelli limited small quantities single batch source US Pirelli established written Sep tember 1978 perfect product has bad spots edge defects does FAI 110 N 0 WI 100 H C' 90 zW W- HZ 80 ZW wcr OW 70 aAr rubber choice between Pirelli FAI simple choice Both have virtues Although Pirelli has about 9% energy 750F FAL retains its energy better hold waiting good air hold over five minutes PIRELLI FAI 40 50 60 70 80 90 AMBIENT TEMP 0F 100 Fig 7 Energy storage variation temperature April1979 119 JLL-SIZE PLANNo 256 Fairchild FC-2$1 200 RC Clapps great Sport Scale Fairchild Two big sheetsfor60 No 257Astron$200 RC Bill Evans X-wing tailless biplane aerobatic 19s No 258Martin MO-i$275 CL Hazens highly competitive Profile Carrier Fox 36 etc No 259Chambermaid$200 FF Bill Henns superlative rubber-powered scale winner Kioud King 1519 RC Old-Timer Free Flight based upon 1938 record breaker FF $400 Wiley Post Biplane Petite durable scale design foreither rubber ortail waggerlpulse rudder $225 GollyGeeWhiz Dan Rutherfords simple Half-A powered Combat job turns dime $150 Gremlin Sturdy aerobatic RC biplane flies well 35s up 60s$300 4-Bits 40-powered RC 500 Club Racer has winning ways Good sport too$400 Semi-Pro Contest-winning HL glider has pop-up tail dethermalizer$100 Halt-Korda rubber John Oldenkamps 1/2-size all-balsa Old-Timer$175 Gee Bee Model Y 40-powered RC stand-off scale great Old-time racers $500 Fieseler Storch RC scale model 2345 5-channel has both slots flaps $400 QuickSilver RC 1/2A Pylon Racer incorporates latest techniques$200 comedian RC fun-fly aerobatic biplane good looker 40 60 -$400 Tercel Keith Trostles 1/2A CL Stunt ship flies excellent pattern- -$200 Midget Mustang CL 19751976 Nats winning Goodyear John Ballard $200 Nothing Fancy RC biplane 35 engines pretty handles beautifully-$825 Simitar RC spectacular flying wing 15 nose-mounted tractor$300 Dennyplane RC version famed cabin model kit trom 1937 192S$400 Zonker RC canard has pattern capability 40 power$300 country Boy FF Jim Clem thoroughbred 1 /2A -$300 Bed check charlie RC Scale model Russian PT trainer 09/15.$300 Seville RC Sport low-wing sailplane 80 wing has eacellent performance$350 Stiletto CL stunt model McDonald winner 1976 FAI World Champs-$375 Vol Libre FF rubber-powered Wakefield Bob White Great winner$275 Hatz Biplane RC aerobatic scale job takes 40/50 built-in muffler$475 Sportster RC deBolt wing choice aerobatics/racing- -$375 FokkerD-VIII RCfor45 60 Two sheets 2-1/2 scale$900 Hot Rock RC aerobatics 19-40 engines Simple tail-dragger$350 Livesey DL 5 RC English homebuilt 3-chan. 15s Exotic easy Good flier- $500 Miss America RC Antique famous historic model 2 big sheets 35 40. $925 Windlord Ken Bates RC flying wing sailplane highly competitive$550 Mustang Al Meyers lovely CL P-Si 35 46 Sport Scale Stunt-$400 Rc Fairchild Ranger 24 AMA Sport Scale 2 big sheets$1000 FF Fokker universal Jumbo-sized rubber scale model Bill Noonan $500 cL Bobcat John Kilsdonks Slow Ratlatest state art$1SO Winterhawk RC standard class sailplane rugged excellent soarer $350 Fly Baby CL Scale model Pete Bowers homebuilttor 3540 RC engine$375 Ole Reliable RC 70 version 38 oldtimer REM controls 1925$425 Spitfire CL profile 2 versionsbuilt-up solid stunter 35$450 AG-i Agrivation RC 4-chan. 2540 realistic trike gear low wing$400 Solution RC competitive pattern deBolt 40 power$475 Tiny White Mouse CL 1/2A powered mouse racer frequent big time winner$1SO Sport 40 RC 4-chan trike-gear shoulder-wing 40$425 Typhoon CL profile 15 WW II fighter Paul Schasi-$300 Mentor FF very nice 40 towliner small fields$300 Dasher RC combo racing pattern characteristics 151025$300 Stits Jr CL worlds smallest plane good flier 25 35$300 Wildcat RC Ace pulse rudder 02 Grumman fighter Bowers Srull . $17S Blue Birds RC Ken Willards formation plane 4-ch. 10$375 Miaflit RC Classy shoulder wing sport 4 ch. 15 power$400 Ace-Dart RC Scale-up Ehling Dart Pulse rudder Pee Wee 02$17S Dakota FF Scale-up famous Dakota bipe great sport 049$275 Super Burp CL Record jet speed model 1/2 size plan details full$1SO Spirit Springs RC sport racer REM 0915 also 1/4 Midget$250 Whip control Bagle CL Profile F-iS fighter easy build fun fly$1SO T-craft RC nice flying pulse rudder scale 02 electric$250 Wright Flyer Authentic plans real plane Harry Robinson 3 sheets . . $300 Pitcairn Maitwing RC Beautiful classic bipe 60 etc Two plan sheets . $750 Zilch Doc Mathews updates Jim Saftigs great stunter 35 $350 Hiperbipe FF Nats scale winner dramatic homebuilt 049 $350 Snowbird RC Delightful powered soarer cabin 049 mounted pylon $350 Little Devil FF Rubber-powered P-30 rules tubular wing pylon $17S Mitchell B-25 RC 4-ft i/2A twin Ace foam panels Well behaved $350 Aetos CL Sporty superlative flying built-up profile Fon 25 etc $350 ciklon FF WC Silver Medalist FAI 15automatics include tilt wing $325 103104 131136146149159165 181184193194195198 216218 219 220 234235 245246 256257 222 236 247 258 223 237 248 259 Circle numbers plans wish order 121123124 168169177 205207212 226227229 125 178 215 230231233 239240241242243244 249250251252253254255 Please print carefully Enclosed Price includes first-class postage Send Check money order payable Mode/Aviation AMA 815 Fifteenth St. NW. Washington DC 20005 probable FAI will have energy since FAL loses energy much lower rate Pirelli despite its 9% higher energy storage proved treacherous very hot weather Taft frequent breaking encountered have experience batch new Pirelli knows what subsequent batches may like FAI rubber can obtained FAI Model Supply POBox 9778 Phoenix AZ 85068 new Pirelli can also obtained FAI Model Supply Oldtimer Models PO Box 18002 Mil waukee WI 53218 have questions news con cerning rubber please contact author Fred Pearce 5317 Blythewood St Houston TX 77021 ADVERTISERS INDEX Ace Radio Control99 Andrews Aircraft Model Co117 Richard C Barron112 Bavarian Precision Products Co103 Boyntonand Associates115 Cleveland Model & Supply Co108 Coverite28 Cox Hobbies IncInside Front Cover DGM Industries100 Du-Bro Products8 FAI Model Supply108 Fli-Shirts104 Flyline Models100 Fourmost Racing Products102 Four Js Enterprises110 Fox Mfg Co7 Gemini Models108 Carl Goldberg Models Inc5 Jim Gray100 Grish Brothers101 Hobby Capitol Dist114 K&B Manufacturing3 Kustom Kraftsmanship114 Logictrol International7 Model Merchant105 Model Rectifier Corp side Back Cover Modernistic Models116 Pactra Industries113 Peck-Polymers116 Pica Products106 Progress Mfg Co6 Quarter Headquarters112 Repla-Tech International Inc116 Sig Mfg Co1 Sterling Models Inc107 Swanson Associates114 Tower Hobbies Inc57 VaI0ir111 Viking Tension Products9 Charles Werle102 Williams Brothers118 World EnginesBack Cover 1 20 Model Aviation No103 No104 No118 No 121 No 123 No 124 No 125 No 131 No 136 No 146 No 14g No 159 No 165 No 166 No 168 No 169 No 177 No 178 No 181 No 184 No 193 No 194 No 195 No iga No 203 No 205 No 207 No 212 No 215 No 218 No 218 No 219 No 220 No 222 No 223 No 225 No 226 No 227 No 229 No 231 No 233 No 234 No 235 No 236 No 237 No 238 No 239 No 240 No 241 No 242 No 243 No 244 No 245 No 246 No 247 No 248 No 249 No 250 No 251 No 252 No 253 No 254 No 255 118 166 203 225 238 NAME STREET CITY STATE Full-Size Plan List Available complete listing plans pre viously published magazine through No 243 may obtained free charge writing enclose stamped self-addressed business-size envelope Model Aviation 815 15th St NW Washington DC 20005