TRUE DYNAMIC THERE HAVE BEEN numerous articles writ ten subject scaling down full-size aircraft RC model size authors have often presented certain rule-of-thumb formulas graphs allow designer determine what weight power goals should set model flyable Note said flyable fly reason stems fact aflyable model will have much severe constraints placed must simply fly flyable RC model will required take off reasonable distance land reasonable speed whereas airplane launch-assisted has parachute recovery capability will have constraints placed upon will still fly latter case true flight characteristics full-size airplane can almost always scaled accordance certain physical laws laws lead formulas called rules True Dynamic Scale rules presented article compared generally agreed upon rules thumb ensure model will flyable think youll surprised results comparison applied some full-size air planes interesting results some airplanes can scaled fly precisely way full-size counterpart does also satis flyability criteria comparsion also reveals desirable scale factor associated airplane particular scale compromises true dynamic scale flyability constraints meaningful SCifLIIIG has quarter scale Maule Lunar Rocket de signed Don Palumbo built Don Myron Pickard STOL performance ofthefull size aircraft duplicated model very close dynamic scale construction article will appear future issue art producinga Scale model involves just get ting dimen sions right Weve heard scale speed like series articles practical method calculat ing true scale flight characteristics isnt complicated might think Part 1 Dominic J Palumbo fashion Methods determine also discussed article will three parts article first part rules true dynamic scale will presented formulas graphs second part will consist general comparison rules flyability constraints RC models final part three specific airplanes will used illustrate application rules flyability constraints determining optimal scale factor Principles dynamic scale Dynamic scale term used describe miniaturization airplanes motion word dynamic im mediately implies motion opposed word static Static scaling simply application scale factor airplanes dimen sions generate corresponding model dimen sions example scale factor 6 used model airplane having wingspan of3O ft will result model has span 30/6 other airplane dimensions would reduced same factor leading model has precisely same proportions full-size airplane Sometimes cheat little increas ing horizontal stab area tail moment order enhance models stability we no longer have exact static scale model call Sport Scale Standoff Scale Dynamic scaling quite different little complicated desire model exhibit identical motion full-size 32 Model Aviation 150 FIgure 1 D44-T / ML \ R tL# T 4 w 125 N 100 0 D II 0 0 / 75 5025 050100ISO200 AIRPLANE SPEED V M illustrated forces considered scaling flight characteristics aircraft weight model operate different directions depending models attitude 70 1 7777 z 4-4 #-- f-60 yyfj 7 ,I ~ I // 4C 30 20 I0 LL1L 10 15 20 25 30 35 40 45 50 55 FULL SIZE WING LOADING LBSISQFTJ Figure 3 Shown above relationship between wing loading model prototype depending scale factor used airplane flight must ensure parameters affect motion scaled accordance static scale factor used generate models dimensions course numerous parameters affect motion airplane flight will suffice consider have significant influence forces acting Figure 2 graph shows relationship between speed model speed prototype different scale factors cj -j liJ 0 0 60 50 4 II 40 r0 30 20 t410 IC C 0 2000 4000 6000 8000 10000 12000 FULL SIZE AIRPLANE WEIGHT LBS Figure 4 Relationships between model weight prototype weight different scale factors shown charts can used determine appropriate scale factor given model subject See text airplane flightthrust gravi ty aero-dynamic forces Maneuver forces must con sidered because wants model perform within scaled airspace places tighter constraint upon model simply requiring perform maneuvers full-size airplane capable because defines maneuver envelope close look dynamic equations governing motion airplane reveals necessary consider absoulte magnitude of forces merely consider ratio aerodynamic thrust maneuver forces force due gravity weight Aircraft having identical ratios thrust weight T/W aerodynamic force weightAIW maneuver force weight MIW will exhibit identical motion ratios proportions provide basis laws dynamic scaling will now examine ratios related static scale factor laws dynamic scale Lets take look ratio maneuver force weight consider simple inside loop shown Fig 1 becomes obvious dominant maneuver Continued page 115 August1981 33 4 4 250300 6 C C N CD z 0 1 CD z -J w 0 0 05 Machine-shaped balsa plywood hardwood Die-cut ribs constant chord wing Dursi main landing gear tricycle gear Hardware package nuts bolts control RAPIER s nose-gear bearing Fuel tank size 10 oz 12 oz Flying weight 6 lb Wingspan 57 Wing area 752 sq Wing chord 13 SPECIFICATIONSFuselage 48 Build 15 hours gentle tlyer wIth a40 great sport tlyer a60 Semi-symmetrical wing long moment big plane responsive tlyer tully aerobatic Four-channel radio engine elevator rudder Complete building instruction booklet Basic materials balsa plywood2657 N 6 188th Street selected hardwoodsMam Ftoda 33180 TelepSone 935-1436 wider flywheel would great would just engine size Quadra 24 Kioritz engine comes larger Kioritz professional chainsaws Roush brothers have done beautiful job converting aircraft use understand inquiries about other large engines coming people building micro-lights powered hang gliders Roush can supply engines up 5 6 dil reason have little operational data engine difficulty getting run engine has fairly high compression starting procedure somewhat different what have using first session engine resulted run mainly because werent doing things right next weekend little luck getting started first time ran some ignition problems decided hold off until could get ourselves sorted out reporting what can now will add operating data get interested using engine selves impressed Like Kioritz products very high quality conversion work match consider start ing problems due own lack familiarity level engine size wish thank following firms assistance part Big Banger project GB Associates Inc 21658 Cloud Way Hay ward CA 94545 Kawasaki Dynathrust Props Inc 2541 NE 11th Ct, Pompano Beach FL 33062 Giezendanner USA P0 Box 818 Pottatown PA 19464 Grish Bros St John IN 46373 Homer Sales Inc 300 Dixie Hwy Beecher IL 60401 Roper JC Enterprises 2251 SW 28th Terrace Ft Lauderdale FL 33312 Husky Mag-Aero Mfg Co P0 Box 490 Freeland WA 98249 Roush Mfg P0 Box 251 Sandyville OH 44671 Kioritz Top Flite Models Inc 1901 Narragansett Ave Chicago IL 60639 J & Z Products 25029 S Vermont Ave Harbor City CA 90710 Zinger SAFE FLYING IS NO ACCIDENT Scaling Palumbo Continued page 33 force centrifugal force Centrifugal force will exist model moving along straight flight path magnitude centrifugal force equal weightW times velocity V squared divided radius R maneuver times earths gravitational acceleration g32 ft/sec/sec math ematical formula maneuver force therefore WV2 M gR Equation 1 ratio M W simply V2/gR use lower-case letters denote models velocity maneuver radius ratio v2/gr model Equating full-size airplanes ratio models ratio MIW m/w obtain V2_ v2 R r Equation 2 because g common both Now lets assume models scale factor number denoted N model manuever within scale airspace must maneuver within scale its dimensions Hence maneuver radius model should scaled accordance models scale factor mathematically means r Substituting R Equation 2 gives V Equation 3 establishes relationship between models speed speed full-size airplane necessary ensure model will perform within scale airspace Note since distance has scaled directly N velocity distance divided time can now seen full-size airplanes time frame stretched square root N compared models time frame As example full-size airplane performing 600-ft diameter loop average speed 150 mph would scale 1/6-size model performing 100-ft diameter loop average speed 61 mph would take 86 seconds full-size airplane complete loop 35 seconds model complete itslp formula Eq 3 presented graphically Fig 2 variety scale factors mathematically inclined aerodynamic forces airplane lift drag direct proportion air density wing area square velocity proportionality constant called force coefficient Mathematically CA$V2S August1981 115 h-L1~at KIORITZ ENiINES BY GIBBS HOBBY & RESEAI Original Developer Factory Trained Authorized Master Service Dealer Year Limited LnlJ Pre-Onhied Props Avail Ask About Custom- Built KIORITZ Engines Deep Fins Optimum Cooling 21/4 Flywheel Small Magneto 1 5/am Six Bolt Aluminum Hub Carb Needles &Throttle Accessible Engine Running IDon Godfrey 722-1765 Points Sealed Rear Housing $19995 pay shIp pre-pald orders Mufflers Now Availablel DEALERS WELCOME SPECIFICATIONS 242 Co 397ccWalbro Potnp CabSaii Reanogs Crank 32HP t 8000 ~3 Ring PistonCaged Rollers Rod Piston Pin Weight 64 lb GIBBS HOBBY & RESEARCH 6195 Hillfield St NW N CANTON OHIO 44720 Phone 216 499-8854 after 600 PM STOP-A-PROP BRAKES GEE BEE Z T-SHIRTA-ATDBrakeKltno 1O1$275 Attractive Black OnFAI CABBrake Kit no 102 $325 Yellow Poly/CottonB ke Kit no 103 Se Sizes SML1 ea size $8503 FAI size $850 Thsnd$1 PostAdaptor Kit$150 force coefficients themselves related other parameters may vary scale such Reynolds number Mach number disregard variations also disregard effect altitude air density can relate models ratio Ww full-size airplanes ratio NW through formula VS quation 4 Ww models wing loading can related full-size airplane directly through use formula information concerning ratio maneuver force weight ratio see Eq 3 w WV2 LW EquationS Sv2 NS Noting now S N2s just due static scaiing model weight full-size weight realted other via formula wN3 WEquation 6 Eq 5 presented graphically Fig 3 Eq 6 Fig 4 Equations 3 and6 relate speed weight model speed weight full-size airplane true dynamic scaie modeL will now consider final force ratio namely thrust/weight simplest ratios because must require models thrust/weight equal full-size airplanes thrust/weight leads simple formula wW combined Eq 6 models thrust full-size airplanes thrust related through equation 1 N3 T next series three articles laws dynamic scale will compared flyable K/C model constraints determine general relationships between two get feel types airplanes suitable candidates true dynamic scale models RC Scale/Wischers Continued page 37 tonal control nose begins wander side model may near stall point nose should lowered Sudden application throttle stall point avoided can precipitate fatal snap roll due engine torque Lowering nose will add bit speed after small increase throttle can used regain height lost due close appraoach stall Opening throttle first will merely reduce rate descent little effect impending stall predictable approach path best obtained using DOWN elevator trim keep speed well above stalling Large amounts UP elevator must reserved instant needed landing flare Too early will kill off speed required reach ground safely landing under windy conditions little additional speed recommended keep glide path being upset due turbulence can also predicted wind speed will constant way down surface Expect lessening wind caused friction earth obstructions Keep little extra speed avoid situation bottom drops out suddenlyjust model about flare its landing classic example Scale model accident snap roll takeoff Best insurance against often-fatal mishap control angle attack using bit DOWN elevator trim let model gather adequate speed before lifting off just touch UP elevator prepared release elevator instant nodel breaks surface lifts off too early two ingredients snap roll present low airspeed UP elevator As landing experience needed judging airspeed keep takeoff straight line prefer stand behind model point easy judge speed nosewheel model predictable takeoff run permits pilot stand side better observation acceleration third element surprise snap roll takeoff tail heaviness Check center gravity location carefully follow example other Scale modelers use much weight necessary place center proper location An error nose-heavy side preferred Planies Toledo As past years centers attention Toledo exhibit Jim Funduk year F4U Corsair threeyear project air-operated folding wings attracted constant interest plane numer ous other features some hidden Jim com bined two Dooling 61 engines connected in-line using Webra carburetor basic fuselage fiberglass 006-in aluminum cover Rudder elevator silk covered Trim tabs flaps operational hatches wings opened expose machine guns Best-of-show first place Precision Scale awards won George Rose well known Curtiss Hawk P-6E same plane has doing well contest circuit including second place recent World Championship Ottawa Georges first attendance Toledo prototype Hawk located Daytons Air Force Museum five-year-old model looks better ever refreshing see well-flown model winner Toledo Expo non-flying types radio installed have too often taken top prizes Second place Precision Scale won Weldon Smiths Bell RP-63GKingcobra target plane Now retired airline captain Weldon flown prototype ferry pilot 1944 Buffalo NY factory Texas Several hun dred target planes built guns omitted ton armor added protect against fire gunners simulated attacks air combat Thats right live ammunition fired plane live pilot visitor show Art Johnson pilots fly missions Art will remembered modeler flies P-38 P-40 P-82 Nats other events Weldon Art introduced spent happy half-hour listening stories about plane Art told RP-63G could withstand 30 caliber fire tried rifle denting surface finding soft spot penetrating through windshield remembers bullets finding way inside including cockpit well some rattled around inside air intakes wing root plane lights would flash target hit Getting back Weldons model plane quite large 84-in wingspan has Supertigre 60 engine mounted scale location mid ship 24 functional exhaust pipes leading its mufflers long shaft scale location extends nose 25-to-i reduction lowers prop speed Weldon now has Rossi 90 ready installation 60 proves insufficient Continued page 120 116 Model Aviation
Edition: Model Aviation - 1981/08
Page Numbers: 32, 33, 115, 116
TRUE DYNAMIC THERE HAVE BEEN numerous articles writ ten subject scaling down full-size aircraft RC model size authors have often presented certain rule-of-thumb formulas graphs allow designer determine what weight power goals should set model flyable Note said flyable fly reason stems fact aflyable model will have much severe constraints placed must simply fly flyable RC model will required take off reasonable distance land reasonable speed whereas airplane launch-assisted has parachute recovery capability will have constraints placed upon will still fly latter case true flight characteristics full-size airplane can almost always scaled accordance certain physical laws laws lead formulas called rules True Dynamic Scale rules presented article compared generally agreed upon rules thumb ensure model will flyable think youll surprised results comparison applied some full-size air planes interesting results some airplanes can scaled fly precisely way full-size counterpart does also satis flyability criteria comparsion also reveals desirable scale factor associated airplane particular scale compromises true dynamic scale flyability constraints meaningful SCifLIIIG has quarter scale Maule Lunar Rocket de signed Don Palumbo built Don Myron Pickard STOL performance ofthefull size aircraft duplicated model very close dynamic scale construction article will appear future issue art producinga Scale model involves just get ting dimen sions right Weve heard scale speed like series articles practical method calculat ing true scale flight characteristics isnt complicated might think Part 1 Dominic J Palumbo fashion Methods determine also discussed article will three parts article first part rules true dynamic scale will presented formulas graphs second part will consist general comparison rules flyability constraints RC models final part three specific airplanes will used illustrate application rules flyability constraints determining optimal scale factor Principles dynamic scale Dynamic scale term used describe miniaturization airplanes motion word dynamic im mediately implies motion opposed word static Static scaling simply application scale factor airplanes dimen sions generate corresponding model dimen sions example scale factor 6 used model airplane having wingspan of3O ft will result model has span 30/6 other airplane dimensions would reduced same factor leading model has precisely same proportions full-size airplane Sometimes cheat little increas ing horizontal stab area tail moment order enhance models stability we no longer have exact static scale model call Sport Scale Standoff Scale Dynamic scaling quite different little complicated desire model exhibit identical motion full-size 32 Model Aviation 150 FIgure 1 D44-T / ML \ R tL# T 4 w 125 N 100 0 D II 0 0 / 75 5025 050100ISO200 AIRPLANE SPEED V M illustrated forces considered scaling flight characteristics aircraft weight model operate different directions depending models attitude 70 1 7777 z 4-4 #-- f-60 yyfj 7 ,I ~ I // 4C 30 20 I0 LL1L 10 15 20 25 30 35 40 45 50 55 FULL SIZE WING LOADING LBSISQFTJ Figure 3 Shown above relationship between wing loading model prototype depending scale factor used airplane flight must ensure parameters affect motion scaled accordance static scale factor used generate models dimensions course numerous parameters affect motion airplane flight will suffice consider have significant influence forces acting Figure 2 graph shows relationship between speed model speed prototype different scale factors cj -j liJ 0 0 60 50 4 II 40 r0 30 20 t410 IC C 0 2000 4000 6000 8000 10000 12000 FULL SIZE AIRPLANE WEIGHT LBS Figure 4 Relationships between model weight prototype weight different scale factors shown charts can used determine appropriate scale factor given model subject See text airplane flightthrust gravi ty aero-dynamic forces Maneuver forces must con sidered because wants model perform within scaled airspace places tighter constraint upon model simply requiring perform maneuvers full-size airplane capable because defines maneuver envelope close look dynamic equations governing motion airplane reveals necessary consider absoulte magnitude of forces merely consider ratio aerodynamic thrust maneuver forces force due gravity weight Aircraft having identical ratios thrust weight T/W aerodynamic force weightAIW maneuver force weight MIW will exhibit identical motion ratios proportions provide basis laws dynamic scaling will now examine ratios related static scale factor laws dynamic scale Lets take look ratio maneuver force weight consider simple inside loop shown Fig 1 becomes obvious dominant maneuver Continued page 115 August1981 33 4 4 250300 6 C C N CD z 0 1 CD z -J w 0 0 05 Machine-shaped balsa plywood hardwood Die-cut ribs constant chord wing Dursi main landing gear tricycle gear Hardware package nuts bolts control RAPIER s nose-gear bearing Fuel tank size 10 oz 12 oz Flying weight 6 lb Wingspan 57 Wing area 752 sq Wing chord 13 SPECIFICATIONSFuselage 48 Build 15 hours gentle tlyer wIth a40 great sport tlyer a60 Semi-symmetrical wing long moment big plane responsive tlyer tully aerobatic Four-channel radio engine elevator rudder Complete building instruction booklet Basic materials balsa plywood2657 N 6 188th Street selected hardwoodsMam Ftoda 33180 TelepSone 935-1436 wider flywheel would great would just engine size Quadra 24 Kioritz engine comes larger Kioritz professional chainsaws Roush brothers have done beautiful job converting aircraft use understand inquiries about other large engines coming people building micro-lights powered hang gliders Roush can supply engines up 5 6 dil reason have little operational data engine difficulty getting run engine has fairly high compression starting procedure somewhat different what have using first session engine resulted run mainly because werent doing things right next weekend little luck getting started first time ran some ignition problems decided hold off until could get ourselves sorted out reporting what can now will add operating data get interested using engine selves impressed Like Kioritz products very high quality conversion work match consider start ing problems due own lack familiarity level engine size wish thank following firms assistance part Big Banger project GB Associates Inc 21658 Cloud Way Hay ward CA 94545 Kawasaki Dynathrust Props Inc 2541 NE 11th Ct, Pompano Beach FL 33062 Giezendanner USA P0 Box 818 Pottatown PA 19464 Grish Bros St John IN 46373 Homer Sales Inc 300 Dixie Hwy Beecher IL 60401 Roper JC Enterprises 2251 SW 28th Terrace Ft Lauderdale FL 33312 Husky Mag-Aero Mfg Co P0 Box 490 Freeland WA 98249 Roush Mfg P0 Box 251 Sandyville OH 44671 Kioritz Top Flite Models Inc 1901 Narragansett Ave Chicago IL 60639 J & Z Products 25029 S Vermont Ave Harbor City CA 90710 Zinger SAFE FLYING IS NO ACCIDENT Scaling Palumbo Continued page 33 force centrifugal force Centrifugal force will exist model moving along straight flight path magnitude centrifugal force equal weightW times velocity V squared divided radius R maneuver times earths gravitational acceleration g32 ft/sec/sec math ematical formula maneuver force therefore WV2 M gR Equation 1 ratio M W simply V2/gR use lower-case letters denote models velocity maneuver radius ratio v2/gr model Equating full-size airplanes ratio models ratio MIW m/w obtain V2_ v2 R r Equation 2 because g common both Now lets assume models scale factor number denoted N model manuever within scale airspace must maneuver within scale its dimensions Hence maneuver radius model should scaled accordance models scale factor mathematically means r Substituting R Equation 2 gives V Equation 3 establishes relationship between models speed speed full-size airplane necessary ensure model will perform within scale airspace Note since distance has scaled directly N velocity distance divided time can now seen full-size airplanes time frame stretched square root N compared models time frame As example full-size airplane performing 600-ft diameter loop average speed 150 mph would scale 1/6-size model performing 100-ft diameter loop average speed 61 mph would take 86 seconds full-size airplane complete loop 35 seconds model complete itslp formula Eq 3 presented graphically Fig 2 variety scale factors mathematically inclined aerodynamic forces airplane lift drag direct proportion air density wing area square velocity proportionality constant called force coefficient Mathematically CA$V2S August1981 115 h-L1~at KIORITZ ENiINES BY GIBBS HOBBY & RESEAI Original Developer Factory Trained Authorized Master Service Dealer Year Limited LnlJ Pre-Onhied Props Avail Ask About Custom- Built KIORITZ Engines Deep Fins Optimum Cooling 21/4 Flywheel Small Magneto 1 5/am Six Bolt Aluminum Hub Carb Needles &Throttle Accessible Engine Running IDon Godfrey 722-1765 Points Sealed Rear Housing $19995 pay shIp pre-pald orders Mufflers Now Availablel DEALERS WELCOME SPECIFICATIONS 242 Co 397ccWalbro Potnp CabSaii Reanogs Crank 32HP t 8000 ~3 Ring PistonCaged Rollers Rod Piston Pin Weight 64 lb GIBBS HOBBY & RESEARCH 6195 Hillfield St NW N CANTON OHIO 44720 Phone 216 499-8854 after 600 PM STOP-A-PROP BRAKES GEE BEE Z T-SHIRTA-ATDBrakeKltno 1O1$275 Attractive Black OnFAI CABBrake Kit no 102 $325 Yellow Poly/CottonB ke Kit no 103 Se Sizes SML1 ea size $8503 FAI size $850 Thsnd$1 PostAdaptor Kit$150 force coefficients themselves related other parameters may vary scale such Reynolds number Mach number disregard variations also disregard effect altitude air density can relate models ratio Ww full-size airplanes ratio NW through formula VS quation 4 Ww models wing loading can related full-size airplane directly through use formula information concerning ratio maneuver force weight ratio see Eq 3 w WV2 LW EquationS Sv2 NS Noting now S N2s just due static scaiing model weight full-size weight realted other via formula wN3 WEquation 6 Eq 5 presented graphically Fig 3 Eq 6 Fig 4 Equations 3 and6 relate speed weight model speed weight full-size airplane true dynamic scaie modeL will now consider final force ratio namely thrust/weight simplest ratios because must require models thrust/weight equal full-size airplanes thrust/weight leads simple formula wW combined Eq 6 models thrust full-size airplanes thrust related through equation 1 N3 T next series three articles laws dynamic scale will compared flyable K/C model constraints determine general relationships between two get feel types airplanes suitable candidates true dynamic scale models RC Scale/Wischers Continued page 37 tonal control nose begins wander side model may near stall point nose should lowered Sudden application throttle stall point avoided can precipitate fatal snap roll due engine torque Lowering nose will add bit speed after small increase throttle can used regain height lost due close appraoach stall Opening throttle first will merely reduce rate descent little effect impending stall predictable approach path best obtained using DOWN elevator trim keep speed well above stalling Large amounts UP elevator must reserved instant needed landing flare Too early will kill off speed required reach ground safely landing under windy conditions little additional speed recommended keep glide path being upset due turbulence can also predicted wind speed will constant way down surface Expect lessening wind caused friction earth obstructions Keep little extra speed avoid situation bottom drops out suddenlyjust model about flare its landing classic example Scale model accident snap roll takeoff Best insurance against often-fatal mishap control angle attack using bit DOWN elevator trim let model gather adequate speed before lifting off just touch UP elevator prepared release elevator instant nodel breaks surface lifts off too early two ingredients snap roll present low airspeed UP elevator As landing experience needed judging airspeed keep takeoff straight line prefer stand behind model point easy judge speed nosewheel model predictable takeoff run permits pilot stand side better observation acceleration third element surprise snap roll takeoff tail heaviness Check center gravity location carefully follow example other Scale modelers use much weight necessary place center proper location An error nose-heavy side preferred Planies Toledo As past years centers attention Toledo exhibit Jim Funduk year F4U Corsair threeyear project air-operated folding wings attracted constant interest plane numer ous other features some hidden Jim com bined two Dooling 61 engines connected in-line using Webra carburetor basic fuselage fiberglass 006-in aluminum cover Rudder elevator silk covered Trim tabs flaps operational hatches wings opened expose machine guns Best-of-show first place Precision Scale awards won George Rose well known Curtiss Hawk P-6E same plane has doing well contest circuit including second place recent World Championship Ottawa Georges first attendance Toledo prototype Hawk located Daytons Air Force Museum five-year-old model looks better ever refreshing see well-flown model winner Toledo Expo non-flying types radio installed have too often taken top prizes Second place Precision Scale won Weldon Smiths Bell RP-63GKingcobra target plane Now retired airline captain Weldon flown prototype ferry pilot 1944 Buffalo NY factory Texas Several hun dred target planes built guns omitted ton armor added protect against fire gunners simulated attacks air combat Thats right live ammunition fired plane live pilot visitor show Art Johnson pilots fly missions Art will remembered modeler flies P-38 P-40 P-82 Nats other events Weldon Art introduced spent happy half-hour listening stories about plane Art told RP-63G could withstand 30 caliber fire tried rifle denting surface finding soft spot penetrating through windshield remembers bullets finding way inside including cockpit well some rattled around inside air intakes wing root plane lights would flash target hit Getting back Weldons model plane quite large 84-in wingspan has Supertigre 60 engine mounted scale location mid ship 24 functional exhaust pipes leading its mufflers long shaft scale location extends nose 25-to-i reduction lowers prop speed Weldon now has Rossi 90 ready installation 60 proves insufficient Continued page 120 116 Model Aviation
Edition: Model Aviation - 1981/08
Page Numbers: 32, 33, 115, 116
TRUE DYNAMIC THERE HAVE BEEN numerous articles writ ten subject scaling down full-size aircraft RC model size authors have often presented certain rule-of-thumb formulas graphs allow designer determine what weight power goals should set model flyable Note said flyable fly reason stems fact aflyable model will have much severe constraints placed must simply fly flyable RC model will required take off reasonable distance land reasonable speed whereas airplane launch-assisted has parachute recovery capability will have constraints placed upon will still fly latter case true flight characteristics full-size airplane can almost always scaled accordance certain physical laws laws lead formulas called rules True Dynamic Scale rules presented article compared generally agreed upon rules thumb ensure model will flyable think youll surprised results comparison applied some full-size air planes interesting results some airplanes can scaled fly precisely way full-size counterpart does also satis flyability criteria comparsion also reveals desirable scale factor associated airplane particular scale compromises true dynamic scale flyability constraints meaningful SCifLIIIG has quarter scale Maule Lunar Rocket de signed Don Palumbo built Don Myron Pickard STOL performance ofthefull size aircraft duplicated model very close dynamic scale construction article will appear future issue art producinga Scale model involves just get ting dimen sions right Weve heard scale speed like series articles practical method calculat ing true scale flight characteristics isnt complicated might think Part 1 Dominic J Palumbo fashion Methods determine also discussed article will three parts article first part rules true dynamic scale will presented formulas graphs second part will consist general comparison rules flyability constraints RC models final part three specific airplanes will used illustrate application rules flyability constraints determining optimal scale factor Principles dynamic scale Dynamic scale term used describe miniaturization airplanes motion word dynamic im mediately implies motion opposed word static Static scaling simply application scale factor airplanes dimen sions generate corresponding model dimen sions example scale factor 6 used model airplane having wingspan of3O ft will result model has span 30/6 other airplane dimensions would reduced same factor leading model has precisely same proportions full-size airplane Sometimes cheat little increas ing horizontal stab area tail moment order enhance models stability we no longer have exact static scale model call Sport Scale Standoff Scale Dynamic scaling quite different little complicated desire model exhibit identical motion full-size 32 Model Aviation 150 FIgure 1 D44-T / ML \ R tL# T 4 w 125 N 100 0 D II 0 0 / 75 5025 050100ISO200 AIRPLANE SPEED V M illustrated forces considered scaling flight characteristics aircraft weight model operate different directions depending models attitude 70 1 7777 z 4-4 #-- f-60 yyfj 7 ,I ~ I // 4C 30 20 I0 LL1L 10 15 20 25 30 35 40 45 50 55 FULL SIZE WING LOADING LBSISQFTJ Figure 3 Shown above relationship between wing loading model prototype depending scale factor used airplane flight must ensure parameters affect motion scaled accordance static scale factor used generate models dimensions course numerous parameters affect motion airplane flight will suffice consider have significant influence forces acting Figure 2 graph shows relationship between speed model speed prototype different scale factors cj -j liJ 0 0 60 50 4 II 40 r0 30 20 t410 IC C 0 2000 4000 6000 8000 10000 12000 FULL SIZE AIRPLANE WEIGHT LBS Figure 4 Relationships between model weight prototype weight different scale factors shown charts can used determine appropriate scale factor given model subject See text airplane flightthrust gravi ty aero-dynamic forces Maneuver forces must con sidered because wants model perform within scaled airspace places tighter constraint upon model simply requiring perform maneuvers full-size airplane capable because defines maneuver envelope close look dynamic equations governing motion airplane reveals necessary consider absoulte magnitude of forces merely consider ratio aerodynamic thrust maneuver forces force due gravity weight Aircraft having identical ratios thrust weight T/W aerodynamic force weightAIW maneuver force weight MIW will exhibit identical motion ratios proportions provide basis laws dynamic scaling will now examine ratios related static scale factor laws dynamic scale Lets take look ratio maneuver force weight consider simple inside loop shown Fig 1 becomes obvious dominant maneuver Continued page 115 August1981 33 4 4 250300 6 C C N CD z 0 1 CD z -J w 0 0 05 Machine-shaped balsa plywood hardwood Die-cut ribs constant chord wing Dursi main landing gear tricycle gear Hardware package nuts bolts control RAPIER s nose-gear bearing Fuel tank size 10 oz 12 oz Flying weight 6 lb Wingspan 57 Wing area 752 sq Wing chord 13 SPECIFICATIONSFuselage 48 Build 15 hours gentle tlyer wIth a40 great sport tlyer a60 Semi-symmetrical wing long moment big plane responsive tlyer tully aerobatic Four-channel radio engine elevator rudder Complete building instruction booklet Basic materials balsa plywood2657 N 6 188th Street selected hardwoodsMam Ftoda 33180 TelepSone 935-1436 wider flywheel would great would just engine size Quadra 24 Kioritz engine comes larger Kioritz professional chainsaws Roush brothers have done beautiful job converting aircraft use understand inquiries about other large engines coming people building micro-lights powered hang gliders Roush can supply engines up 5 6 dil reason have little operational data engine difficulty getting run engine has fairly high compression starting procedure somewhat different what have using first session engine resulted run mainly because werent doing things right next weekend little luck getting started first time ran some ignition problems decided hold off until could get ourselves sorted out reporting what can now will add operating data get interested using engine selves impressed Like Kioritz products very high quality conversion work match consider start ing problems due own lack familiarity level engine size wish thank following firms assistance part Big Banger project GB Associates Inc 21658 Cloud Way Hay ward CA 94545 Kawasaki Dynathrust Props Inc 2541 NE 11th Ct, Pompano Beach FL 33062 Giezendanner USA P0 Box 818 Pottatown PA 19464 Grish Bros St John IN 46373 Homer Sales Inc 300 Dixie Hwy Beecher IL 60401 Roper JC Enterprises 2251 SW 28th Terrace Ft Lauderdale FL 33312 Husky Mag-Aero Mfg Co P0 Box 490 Freeland WA 98249 Roush Mfg P0 Box 251 Sandyville OH 44671 Kioritz Top Flite Models Inc 1901 Narragansett Ave Chicago IL 60639 J & Z Products 25029 S Vermont Ave Harbor City CA 90710 Zinger SAFE FLYING IS NO ACCIDENT Scaling Palumbo Continued page 33 force centrifugal force Centrifugal force will exist model moving along straight flight path magnitude centrifugal force equal weightW times velocity V squared divided radius R maneuver times earths gravitational acceleration g32 ft/sec/sec math ematical formula maneuver force therefore WV2 M gR Equation 1 ratio M W simply V2/gR use lower-case letters denote models velocity maneuver radius ratio v2/gr model Equating full-size airplanes ratio models ratio MIW m/w obtain V2_ v2 R r Equation 2 because g common both Now lets assume models scale factor number denoted N model manuever within scale airspace must maneuver within scale its dimensions Hence maneuver radius model should scaled accordance models scale factor mathematically means r Substituting R Equation 2 gives V Equation 3 establishes relationship between models speed speed full-size airplane necessary ensure model will perform within scale airspace Note since distance has scaled directly N velocity distance divided time can now seen full-size airplanes time frame stretched square root N compared models time frame As example full-size airplane performing 600-ft diameter loop average speed 150 mph would scale 1/6-size model performing 100-ft diameter loop average speed 61 mph would take 86 seconds full-size airplane complete loop 35 seconds model complete itslp formula Eq 3 presented graphically Fig 2 variety scale factors mathematically inclined aerodynamic forces airplane lift drag direct proportion air density wing area square velocity proportionality constant called force coefficient Mathematically CA$V2S August1981 115 h-L1~at KIORITZ ENiINES BY GIBBS HOBBY & RESEAI Original Developer Factory Trained Authorized Master Service Dealer Year Limited LnlJ Pre-Onhied Props Avail Ask About Custom- Built KIORITZ Engines Deep Fins Optimum Cooling 21/4 Flywheel Small Magneto 1 5/am Six Bolt Aluminum Hub Carb Needles &Throttle Accessible Engine Running IDon Godfrey 722-1765 Points Sealed Rear Housing $19995 pay shIp pre-pald orders Mufflers Now Availablel DEALERS WELCOME SPECIFICATIONS 242 Co 397ccWalbro Potnp CabSaii Reanogs Crank 32HP t 8000 ~3 Ring PistonCaged Rollers Rod Piston Pin Weight 64 lb GIBBS HOBBY & RESEARCH 6195 Hillfield St NW N CANTON OHIO 44720 Phone 216 499-8854 after 600 PM STOP-A-PROP BRAKES GEE BEE Z T-SHIRTA-ATDBrakeKltno 1O1$275 Attractive Black OnFAI CABBrake Kit no 102 $325 Yellow Poly/CottonB ke Kit no 103 Se Sizes SML1 ea size $8503 FAI size $850 Thsnd$1 PostAdaptor Kit$150 force coefficients themselves related other parameters may vary scale such Reynolds number Mach number disregard variations also disregard effect altitude air density can relate models ratio Ww full-size airplanes ratio NW through formula VS quation 4 Ww models wing loading can related full-size airplane directly through use formula information concerning ratio maneuver force weight ratio see Eq 3 w WV2 LW EquationS Sv2 NS Noting now S N2s just due static scaiing model weight full-size weight realted other via formula wN3 WEquation 6 Eq 5 presented graphically Fig 3 Eq 6 Fig 4 Equations 3 and6 relate speed weight model speed weight full-size airplane true dynamic scaie modeL will now consider final force ratio namely thrust/weight simplest ratios because must require models thrust/weight equal full-size airplanes thrust/weight leads simple formula wW combined Eq 6 models thrust full-size airplanes thrust related through equation 1 N3 T next series three articles laws dynamic scale will compared flyable K/C model constraints determine general relationships between two get feel types airplanes suitable candidates true dynamic scale models RC Scale/Wischers Continued page 37 tonal control nose begins wander side model may near stall point nose should lowered Sudden application throttle stall point avoided can precipitate fatal snap roll due engine torque Lowering nose will add bit speed after small increase throttle can used regain height lost due close appraoach stall Opening throttle first will merely reduce rate descent little effect impending stall predictable approach path best obtained using DOWN elevator trim keep speed well above stalling Large amounts UP elevator must reserved instant needed landing flare Too early will kill off speed required reach ground safely landing under windy conditions little additional speed recommended keep glide path being upset due turbulence can also predicted wind speed will constant way down surface Expect lessening wind caused friction earth obstructions Keep little extra speed avoid situation bottom drops out suddenlyjust model about flare its landing classic example Scale model accident snap roll takeoff Best insurance against often-fatal mishap control angle attack using bit DOWN elevator trim let model gather adequate speed before lifting off just touch UP elevator prepared release elevator instant nodel breaks surface lifts off too early two ingredients snap roll present low airspeed UP elevator As landing experience needed judging airspeed keep takeoff straight line prefer stand behind model point easy judge speed nosewheel model predictable takeoff run permits pilot stand side better observation acceleration third element surprise snap roll takeoff tail heaviness Check center gravity location carefully follow example other Scale modelers use much weight necessary place center proper location An error nose-heavy side preferred Planies Toledo As past years centers attention Toledo exhibit Jim Funduk year F4U Corsair threeyear project air-operated folding wings attracted constant interest plane numer ous other features some hidden Jim com bined two Dooling 61 engines connected in-line using Webra carburetor basic fuselage fiberglass 006-in aluminum cover Rudder elevator silk covered Trim tabs flaps operational hatches wings opened expose machine guns Best-of-show first place Precision Scale awards won George Rose well known Curtiss Hawk P-6E same plane has doing well contest circuit including second place recent World Championship Ottawa Georges first attendance Toledo prototype Hawk located Daytons Air Force Museum five-year-old model looks better ever refreshing see well-flown model winner Toledo Expo non-flying types radio installed have too often taken top prizes Second place Precision Scale won Weldon Smiths Bell RP-63GKingcobra target plane Now retired airline captain Weldon flown prototype ferry pilot 1944 Buffalo NY factory Texas Several hun dred target planes built guns omitted ton armor added protect against fire gunners simulated attacks air combat Thats right live ammunition fired plane live pilot visitor show Art Johnson pilots fly missions Art will remembered modeler flies P-38 P-40 P-82 Nats other events Weldon Art introduced spent happy half-hour listening stories about plane Art told RP-63G could withstand 30 caliber fire tried rifle denting surface finding soft spot penetrating through windshield remembers bullets finding way inside including cockpit well some rattled around inside air intakes wing root plane lights would flash target hit Getting back Weldons model plane quite large 84-in wingspan has Supertigre 60 engine mounted scale location mid ship 24 functional exhaust pipes leading its mufflers long shaft scale location extends nose 25-to-i reduction lowers prop speed Weldon now has Rossi 90 ready installation 60 proves insufficient Continued page 120 116 Model Aviation
Edition: Model Aviation - 1981/08
Page Numbers: 32, 33, 115, 116
TRUE DYNAMIC THERE HAVE BEEN numerous articles writ ten subject scaling down full-size aircraft RC model size authors have often presented certain rule-of-thumb formulas graphs allow designer determine what weight power goals should set model flyable Note said flyable fly reason stems fact aflyable model will have much severe constraints placed must simply fly flyable RC model will required take off reasonable distance land reasonable speed whereas airplane launch-assisted has parachute recovery capability will have constraints placed upon will still fly latter case true flight characteristics full-size airplane can almost always scaled accordance certain physical laws laws lead formulas called rules True Dynamic Scale rules presented article compared generally agreed upon rules thumb ensure model will flyable think youll surprised results comparison applied some full-size air planes interesting results some airplanes can scaled fly precisely way full-size counterpart does also satis flyability criteria comparsion also reveals desirable scale factor associated airplane particular scale compromises true dynamic scale flyability constraints meaningful SCifLIIIG has quarter scale Maule Lunar Rocket de signed Don Palumbo built Don Myron Pickard STOL performance ofthefull size aircraft duplicated model very close dynamic scale construction article will appear future issue art producinga Scale model involves just get ting dimen sions right Weve heard scale speed like series articles practical method calculat ing true scale flight characteristics isnt complicated might think Part 1 Dominic J Palumbo fashion Methods determine also discussed article will three parts article first part rules true dynamic scale will presented formulas graphs second part will consist general comparison rules flyability constraints RC models final part three specific airplanes will used illustrate application rules flyability constraints determining optimal scale factor Principles dynamic scale Dynamic scale term used describe miniaturization airplanes motion word dynamic im mediately implies motion opposed word static Static scaling simply application scale factor airplanes dimen sions generate corresponding model dimen sions example scale factor 6 used model airplane having wingspan of3O ft will result model has span 30/6 other airplane dimensions would reduced same factor leading model has precisely same proportions full-size airplane Sometimes cheat little increas ing horizontal stab area tail moment order enhance models stability we no longer have exact static scale model call Sport Scale Standoff Scale Dynamic scaling quite different little complicated desire model exhibit identical motion full-size 32 Model Aviation 150 FIgure 1 D44-T / ML \ R tL# T 4 w 125 N 100 0 D II 0 0 / 75 5025 050100ISO200 AIRPLANE SPEED V M illustrated forces considered scaling flight characteristics aircraft weight model operate different directions depending models attitude 70 1 7777 z 4-4 #-- f-60 yyfj 7 ,I ~ I // 4C 30 20 I0 LL1L 10 15 20 25 30 35 40 45 50 55 FULL SIZE WING LOADING LBSISQFTJ Figure 3 Shown above relationship between wing loading model prototype depending scale factor used airplane flight must ensure parameters affect motion scaled accordance static scale factor used generate models dimensions course numerous parameters affect motion airplane flight will suffice consider have significant influence forces acting Figure 2 graph shows relationship between speed model speed prototype different scale factors cj -j liJ 0 0 60 50 4 II 40 r0 30 20 t410 IC C 0 2000 4000 6000 8000 10000 12000 FULL SIZE AIRPLANE WEIGHT LBS Figure 4 Relationships between model weight prototype weight different scale factors shown charts can used determine appropriate scale factor given model subject See text airplane flightthrust gravi ty aero-dynamic forces Maneuver forces must con sidered because wants model perform within scaled airspace places tighter constraint upon model simply requiring perform maneuvers full-size airplane capable because defines maneuver envelope close look dynamic equations governing motion airplane reveals necessary consider absoulte magnitude of forces merely consider ratio aerodynamic thrust maneuver forces force due gravity weight Aircraft having identical ratios thrust weight T/W aerodynamic force weightAIW maneuver force weight MIW will exhibit identical motion ratios proportions provide basis laws dynamic scaling will now examine ratios related static scale factor laws dynamic scale Lets take look ratio maneuver force weight consider simple inside loop shown Fig 1 becomes obvious dominant maneuver Continued page 115 August1981 33 4 4 250300 6 C C N CD z 0 1 CD z -J w 0 0 05 Machine-shaped balsa plywood hardwood Die-cut ribs constant chord wing Dursi main landing gear tricycle gear Hardware package nuts bolts control RAPIER s nose-gear bearing Fuel tank size 10 oz 12 oz Flying weight 6 lb Wingspan 57 Wing area 752 sq Wing chord 13 SPECIFICATIONSFuselage 48 Build 15 hours gentle tlyer wIth a40 great sport tlyer a60 Semi-symmetrical wing long moment big plane responsive tlyer tully aerobatic Four-channel radio engine elevator rudder Complete building instruction booklet Basic materials balsa plywood2657 N 6 188th Street selected hardwoodsMam Ftoda 33180 TelepSone 935-1436 wider flywheel would great would just engine size Quadra 24 Kioritz engine comes larger Kioritz professional chainsaws Roush brothers have done beautiful job converting aircraft use understand inquiries about other large engines coming people building micro-lights powered hang gliders Roush can supply engines up 5 6 dil reason have little operational data engine difficulty getting run engine has fairly high compression starting procedure somewhat different what have using first session engine resulted run mainly because werent doing things right next weekend little luck getting started first time ran some ignition problems decided hold off until could get ourselves sorted out reporting what can now will add operating data get interested using engine selves impressed Like Kioritz products very high quality conversion work match consider start ing problems due own lack familiarity level engine size wish thank following firms assistance part Big Banger project GB Associates Inc 21658 Cloud Way Hay ward CA 94545 Kawasaki Dynathrust Props Inc 2541 NE 11th Ct, Pompano Beach FL 33062 Giezendanner USA P0 Box 818 Pottatown PA 19464 Grish Bros St John IN 46373 Homer Sales Inc 300 Dixie Hwy Beecher IL 60401 Roper JC Enterprises 2251 SW 28th Terrace Ft Lauderdale FL 33312 Husky Mag-Aero Mfg Co P0 Box 490 Freeland WA 98249 Roush Mfg P0 Box 251 Sandyville OH 44671 Kioritz Top Flite Models Inc 1901 Narragansett Ave Chicago IL 60639 J & Z Products 25029 S Vermont Ave Harbor City CA 90710 Zinger SAFE FLYING IS NO ACCIDENT Scaling Palumbo Continued page 33 force centrifugal force Centrifugal force will exist model moving along straight flight path magnitude centrifugal force equal weightW times velocity V squared divided radius R maneuver times earths gravitational acceleration g32 ft/sec/sec math ematical formula maneuver force therefore WV2 M gR Equation 1 ratio M W simply V2/gR use lower-case letters denote models velocity maneuver radius ratio v2/gr model Equating full-size airplanes ratio models ratio MIW m/w obtain V2_ v2 R r Equation 2 because g common both Now lets assume models scale factor number denoted N model manuever within scale airspace must maneuver within scale its dimensions Hence maneuver radius model should scaled accordance models scale factor mathematically means r Substituting R Equation 2 gives V Equation 3 establishes relationship between models speed speed full-size airplane necessary ensure model will perform within scale airspace Note since distance has scaled directly N velocity distance divided time can now seen full-size airplanes time frame stretched square root N compared models time frame As example full-size airplane performing 600-ft diameter loop average speed 150 mph would scale 1/6-size model performing 100-ft diameter loop average speed 61 mph would take 86 seconds full-size airplane complete loop 35 seconds model complete itslp formula Eq 3 presented graphically Fig 2 variety scale factors mathematically inclined aerodynamic forces airplane lift drag direct proportion air density wing area square velocity proportionality constant called force coefficient Mathematically CA$V2S August1981 115 h-L1~at KIORITZ ENiINES BY GIBBS HOBBY & RESEAI Original Developer Factory Trained Authorized Master Service Dealer Year Limited LnlJ Pre-Onhied Props Avail Ask About Custom- Built KIORITZ Engines Deep Fins Optimum Cooling 21/4 Flywheel Small Magneto 1 5/am Six Bolt Aluminum Hub Carb Needles &Throttle Accessible Engine Running IDon Godfrey 722-1765 Points Sealed Rear Housing $19995 pay shIp pre-pald orders Mufflers Now Availablel DEALERS WELCOME SPECIFICATIONS 242 Co 397ccWalbro Potnp CabSaii Reanogs Crank 32HP t 8000 ~3 Ring PistonCaged Rollers Rod Piston Pin Weight 64 lb GIBBS HOBBY & RESEARCH 6195 Hillfield St NW N CANTON OHIO 44720 Phone 216 499-8854 after 600 PM STOP-A-PROP BRAKES GEE BEE Z T-SHIRTA-ATDBrakeKltno 1O1$275 Attractive Black OnFAI CABBrake Kit no 102 $325 Yellow Poly/CottonB ke Kit no 103 Se Sizes SML1 ea size $8503 FAI size $850 Thsnd$1 PostAdaptor Kit$150 force coefficients themselves related other parameters may vary scale such Reynolds number Mach number disregard variations also disregard effect altitude air density can relate models ratio Ww full-size airplanes ratio NW through formula VS quation 4 Ww models wing loading can related full-size airplane directly through use formula information concerning ratio maneuver force weight ratio see Eq 3 w WV2 LW EquationS Sv2 NS Noting now S N2s just due static scaiing model weight full-size weight realted other via formula wN3 WEquation 6 Eq 5 presented graphically Fig 3 Eq 6 Fig 4 Equations 3 and6 relate speed weight model speed weight full-size airplane true dynamic scaie modeL will now consider final force ratio namely thrust/weight simplest ratios because must require models thrust/weight equal full-size airplanes thrust/weight leads simple formula wW combined Eq 6 models thrust full-size airplanes thrust related through equation 1 N3 T next series three articles laws dynamic scale will compared flyable K/C model constraints determine general relationships between two get feel types airplanes suitable candidates true dynamic scale models RC Scale/Wischers Continued page 37 tonal control nose begins wander side model may near stall point nose should lowered Sudden application throttle stall point avoided can precipitate fatal snap roll due engine torque Lowering nose will add bit speed after small increase throttle can used regain height lost due close appraoach stall Opening throttle first will merely reduce rate descent little effect impending stall predictable approach path best obtained using DOWN elevator trim keep speed well above stalling Large amounts UP elevator must reserved instant needed landing flare Too early will kill off speed required reach ground safely landing under windy conditions little additional speed recommended keep glide path being upset due turbulence can also predicted wind speed will constant way down surface Expect lessening wind caused friction earth obstructions Keep little extra speed avoid situation bottom drops out suddenlyjust model about flare its landing classic example Scale model accident snap roll takeoff Best insurance against often-fatal mishap control angle attack using bit DOWN elevator trim let model gather adequate speed before lifting off just touch UP elevator prepared release elevator instant nodel breaks surface lifts off too early two ingredients snap roll present low airspeed UP elevator As landing experience needed judging airspeed keep takeoff straight line prefer stand behind model point easy judge speed nosewheel model predictable takeoff run permits pilot stand side better observation acceleration third element surprise snap roll takeoff tail heaviness Check center gravity location carefully follow example other Scale modelers use much weight necessary place center proper location An error nose-heavy side preferred Planies Toledo As past years centers attention Toledo exhibit Jim Funduk year F4U Corsair threeyear project air-operated folding wings attracted constant interest plane numer ous other features some hidden Jim com bined two Dooling 61 engines connected in-line using Webra carburetor basic fuselage fiberglass 006-in aluminum cover Rudder elevator silk covered Trim tabs flaps operational hatches wings opened expose machine guns Best-of-show first place Precision Scale awards won George Rose well known Curtiss Hawk P-6E same plane has doing well contest circuit including second place recent World Championship Ottawa Georges first attendance Toledo prototype Hawk located Daytons Air Force Museum five-year-old model looks better ever refreshing see well-flown model winner Toledo Expo non-flying types radio installed have too often taken top prizes Second place Precision Scale won Weldon Smiths Bell RP-63GKingcobra target plane Now retired airline captain Weldon flown prototype ferry pilot 1944 Buffalo NY factory Texas Several hun dred target planes built guns omitted ton armor added protect against fire gunners simulated attacks air combat Thats right live ammunition fired plane live pilot visitor show Art Johnson pilots fly missions Art will remembered modeler flies P-38 P-40 P-82 Nats other events Weldon Art introduced spent happy half-hour listening stories about plane Art told RP-63G could withstand 30 caliber fire tried rifle denting surface finding soft spot penetrating through windshield remembers bullets finding way inside including cockpit well some rattled around inside air intakes wing root plane lights would flash target hit Getting back Weldons model plane quite large 84-in wingspan has Supertigre 60 engine mounted scale location mid ship 24 functional exhaust pipes leading its mufflers long shaft scale location extends nose 25-to-i reduction lowers prop speed Weldon now has Rossi 90 ready installation 60 proves insufficient Continued page 120 116 Model Aviation