Radio Control Scale Bob Dolly Wischer SCALE MATH Scale modelers build kits havesome questions answered designer manufacturer expected weight model suggested range engine sizes given drawing instruction booklet Scratch-builders ask searching questions such important matters projected estimate model weight engine requirements answer really needed early stages design Once model size has decided upon wing span area straightforward function scale ratio number represents dif ference between full-size aircraft model simply divide prototypes span scale ratio determine models span find models wing area divide area prototype wing square scale ratio example Y4-scale model has scale ratio 4 42 16 prototype wing area 146 sq ft 146/16 sq ft 1314 sq easy part What scratch-builder really needs know early design stages approximate weight model what engine size will best scalelike flight Since now con sidering mass rather simple linear dimen sions areas divide weight pro totype cube scale ratio previous example ratio 4 43 rototype lightplane weighing 670 lb fuel passengers 670/64 lb projected model weight base calculations airplane weight passengers because full-size airplane flight characteristics will vary widely between light heavy loads typical ultralight can carry its own weight payload lightplane about half its empty weight passengers does 1046 lb compare /4-scale model ready flight Using Y4-scale Aeronca K model 670-lb weight example model weighs 115 lb fuel ready fly weight bit heavy side about pound scalelike flight lightly-loaded aircraft comparing scale another larger model has advantage because on-board RC equipment weight approximately same both hypothetical model designer also would like know engine should power model rough estimate again use cube scale ratio division factor Aeronca K engine rather low-powered 40 hp Dividing horsepower cube scale ratio 40/64 625 tells us 60-size two-stroke engine would provide model scalelike flight 105 lb model actually powered 05 120 Gemini fourstroke has about twice power neces sary explains reason models angle climb about 200 compared 30 40 prototype passenger best source model engine horsepower statistics Peter Chinns series reviews Model Airplane News Overpowering model permissible within reason must kept mind Dormoy Bathtub L work Dow Davison Engine isa Saito FA-30 fourstroker Charles Bybee scratch-built SE5-A R Bill Effingets WE Technical Services plans Quadra 35 powers Weight 22 lb Finish Chevron paint over Super Coverite Don Rathbuns Corben Baby Ace L originated Great Planes kit Power OS 120 four-stroker weight 115 lb Covering Solartex polyurethane paint R isa seldom-modeled Slemens-SchuketI D-3 scratch-built Wylam plans Carl Harris 1/-scalO uses Zenoah 38 cu engine weighs 20 lb its ornate camouflage part latex part K&B epoxy over Coverite 52 Model Aviation Larry Gordons well-detailed Grumman F4F-3 Wildcat 1/5-scale spans 915 weighs 24 lb uses Quadra power Color markings Butch OHares plane too heavy engine could increase wing load ing small model Underpowered models usually go back workshop basket Now know models wing area its approximate weight simple matter extrapolate projected wing loading Since wing loading model airplanes ordinarily expressed ounces per square foot first convert its pro jected weight ounces divide area square feet find wing loading Aeronca example 2368 oz/9125 sq ft oz per sq ft loading reality because model came out slightly heavier expected added weighty dummy pilot its wing loading 22 oz per sq ft fuel calculation particular value deter mination whether model will manageable flight Experience says 30 oz per sq ft considered about upper limit smaller models 60-size engines Giant Scale airplanes can go high 45 oz variation result change Reynolds numbers due size series calculations supposed kept simple course simplified calculations can go seriously awry applied some aircraft such overpowered heavy types intended car rying great loads part flight Carrying heavy bomb fuel load military aircraft has no counterpart Scale modeling models weight varies little flights beginning end useful calculations must tempered reason Fuel loads models dont approach full-size aircraft may half gross weight world-circling airliners Calculations power requirements based takeoff horsepower can also lead us astray High-powered aircraft use full output short duration Starting empty weight Douglas A-20G attack bomber 17000 lb scale ratio 196 766-in-span model would have calculated weight 19 lb Its actual weight 14 lb because all-out weight reduction effort construction weight its wing loading astounding 44 oz per sq ft its handling air bit precarious climb glide speeds about equal 1275-horsepower Wright radials power engine calculates 14 horsepower HP 40 engines model will peak 12 acceptable 14-lb weight Douglas Mailplane has scale ratio 6857 694-in span Its weight calculations full-size included half ton fuel would have brought projected model weight up 154 lb Its actual measurement 12 lb wing loading 22 oz because model will never expected lift /3 its weight fuel load Power requirements calculated 400-hp Liberty engine prototype divided 6857 3224 about 12 hp adequately supplied its Enya 120 four-stroke Because model doesnt carry equivalent ton fuel mail load calculations cannot really begin published figures gross weight calculations provide some figures aid scratch-builder getting started along de sign route system seems its best calculations involving standard passengercarrying aircraft can use Ryan SCW example scale ratio 565 model weight should 1025 lb almost exactly correct Horsepower requirements should about 8 standard 60 engine would suffice Super Tigre 60 model rated well over horsepower able use larger-diameter prop greater efficiency around radial engine cowl wing loading Continued page 151 00 DGA Designs go DGA Designs co OGA Designs ec DGA Designs . OGA Designs 0 *DARNED GOOD AIRMEN 21 Lightest weight Pilots Availablea a BODY PILOT KIT L e keVnv ae ubberparts Easy assemble finish Kit contains Pilot head hands boots helmet0 cap goggles full templates easy instructions Fully positionable too.0 Height- WeIght- NEW Low Phsee No206 1/6 Scale ils 2 ozS 7j0 No205 /5 Scale 14d 3 oz55aa SPORTSMAN OAPNSTORMES FULL SODY BUST or0 ONo204-1/4 Scale 173a 40zS 5 No203 13 Scale 23s 6oz 0 0 0 0 Cs *60, sImple sewinga Ineqalreat0 0 0 0 0 *BU5T PILOT KIT Lifelike iflyl lilfyt rubbe part, K, canajns PIlot head helmet sport cap 909950 Jacket Easy asselnhlc fjnhh -Height WeIght Low P1100 No lOG 1 khcalo 3-18 34oc 5h 00 Shhdle 3-Cs -fdO S SSh V9No log dScdIe 4-30 f-i 20 5 No lOS ale S-3d 2-140 sl4 24. . Astosanding net attoinoblo plastIcs.. 0 ODoe hell extreme light weight ho oomplothd full hotly Ol p101 0hoOtS mdl haoe lIttle no effehl hdllnch OtyOo-airCl-dff. 0 Send 5100 Catalog New York State Resotents add 70 Sales teo BOnd 055k MO --caD-s.Allow 3 weeks tor 8500k 010cr 5 DGA Designs . DA o DGA Designs 1hLe~ RETRACTABLE ITOW HOOK RELEASE Price S 990 KI Simpiest reiiabie device avaiiabie After iine released hook retracts body unit ieaving SMOOTH surface bottom aircraft No speciai attachments required N eight oz OTHER FOURMOST PRODUCTS 049105 /2 REDUCES DRAG VIBRATION FREE PRICE $300 40 AIRFLO ENGINE MOUNT IDEAL FOR QUICKY 500 PRICE $630 Fuei Fitting Sets Fuei Shut Off Fuel Manifold Gapless Hinges Gapiess Hinge Slotter Strut Fairings Cockpit Coaming Send SASE Complete Information FOURMOST p4040 24th Ave Forest Grove OR 97116 RODUCTS Phone 503 357-2732 July1987 53 Winning Ideas FOURT lOST AIRFLO ENGINE MOUNT excellent candidate especially YS engine flies FAI pattern extremely well Since ARF Almost Ready Fly flying charac teristics likely consistent aircraft aircraft arent cheap event like would need major sponsor obviously things would have considered before fair test piloting ability would possible such setup wouldnt great watch best country/world compete nobody un fair advantage/liability Ron Van Pune 111 Sleepy Oaks Rd Ft Wal ton Beach FL 32548 RC Scale/Wischers Continued page 53 calculations indicated about 236 oz per sq ft model actually 259 Everything indi cated would good flying model always pleasantly surprised after model finished closely agrees mathe matical projection Estimated values quickly acquiredand just quickly discarded fall outside expectations Control weight during design construction difficult tasks scratchbuilder Having made some calculations deter estimated wing loading example builder now faced serious problem selecting material placement strengthening structural members avoid exceeding desired maximum weight choice made has always strict policy choose lighter material grounds crashed model will have come apart badly regardless built-in strengthening Wide variations strength also avoided example strong fuselage can survive bad landing due stall weak wing structure shattered stall occurred result overweight condi tion heavy fuselage may well have contributing factor cant build protection against pilot error As preferred construction method weight reduction ease building Scale mod eling must come conclusion dont have fact no two models have built alike duplicating older model wings open structure com mon framework leading edge trailing edge spars ribs has variations new Douglas Mailplane has solid-balsaplank leading edges partially shaped circular saw minimize carving sanding afterward Advantage No spars near leading edge spar near trailing edge good airfoil shape retention Disadvantage style construction expensive could con tribute heavy weight unless special care taken selecting light balsa solid leading edges wings completely sheet-covered have tried foam well conventional rib construction found no appreciable difference final weight strength building time electronic calculator has taken sweat out plotting airfoils tapered wings dozen rib positions Starting Handbook Airfoil Sections Light Aircraft MS Rice airfoil can plotted drawn size matter minutes repetition tapered wing rib positions may become monotonous no worse cutting later balsa sheet Some older Scale models non-scale airfoils seem fly just well later ones true scale shapes Maintaining true airfoil shape fabric-covered wings partially successful due fabric sag between ribs both models full-size planes good reason use scale airfoil appearance de pends upon critical eye viewer use Scale airfoil shapes probably has greater effect flight larger models flat-bottomed airfoil may acceptable Schoolyard Scale would hesitate use small Pylon Racer Building fuselage meet low weight projec tions becomes less difficult model size creases Its small model suffers too-high wing loading Building excess strength fuselage temptation re sisted After bad landing strong fuselage merely has larger pieces summarize scratch-designer can make some fairly accurate estimates design parame ters doubt concerning engine size choose larger displacement take advantage using larger-diameter propellers engine exhaust will less noisy prop will efficient because its tips will working outside cowl front-face area fuel consumption should reduced have no problems over heating large slow-turning props engines seem wear forever Excessive engine wear can traced overheating due lean needle settings inadequate ventilation conditions can exist regardless prop size larger prop may scale diame ter appearance definitely improved scratch-builder has positive control over center-of-gravity location Light balsa aft fuselage tail surfaces can help move all-important balance point comfortable 25% position wing chord first flights Having early estimate total weight observing nose tail moments can definite aid material selection Bob Dolly Wiseher 5-22 1 Lapham Peak Rd Delafleld WI 53018 RC Old-Timers/Mathews Continued page 55 kitted after war Scorpion rate very attractive design available version difficult wing construction size suitable 25-size two-cycle engines 30/40 four-strokers span 66 thereabouts making anything bigger excessive Although writer has never seen Ben Buckle kit certainly several interesting designs line Id appreciate hearing com ments have built Buckle kits lament lost skills David Evans letter mentions 24-year-old working PhD English literature University Virginia Some favorite RC memories spring building flying both Quaker 54 Air Trails Sportster teenager Both flew beautifully old 05 15 surprises somewhat few young people build fly Old-Timers satisfaction great hottest hotshots seem really love putting around sky Powerhouse some such Perhaps immediate generation last came model aviation directly through Comet Guil lows rubber kitswhich make transition stick-built Oldies pretty easy Bill Northrop Model Builder Maga zine has often expressed same concerns GATOR RIC PRODUCTS TIGER TAIL 45 DELUX ALL BALSA KIT An new Tiger Tail 120 four strokes piped 60 two strokes beautiful performer competition just showing offl balsa kit machined wood parts complete hardware package includes plug-in adjustable stab parts new wing mounts Wing Span -72 inWing Area 860 sq complete Delux KitS 15995 PLUG-IN ADJUSTABLE STAB KIT last can optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matching phenolic socket TRANSMITTER CASE An inexpensive rugged molded case protect expensive transmitter both two stick rngle s5ck transmitters Brown ather grain aluminum trim locking clasp S 1895 WING TUBE & SOCKETS Aluminum alloy tubing plug-In wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2t 895 diax25 995 1 diax352495 feather Ilte glass cloth 7 ozlsq yd est weave Fastest Filling est Finished Weight Big 3 Sq Yard Pkg Detailed Instructions 5895 ENGINE SLEEVE & BEARING PULLER Pull tight sleeves bearings easily out damage new 60s 17MM rear bearings Sleeve Puller5 795 Searing Puller5 695 ForS1395 IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure wJfl aileron elevator rudder throw Takes guess work out trimming out airplane quality tool complete instrtatkons log book tarrying caseS 795 NEWI WING MOUTifING SET wing mounting system developed Ron chidgey fast neat accurate stays tight Three nylon brackets screws machined wood wing blocks included 5595 See Dealer Order Direct Include S2 Per item UPS GATOR RIC PRODUCTS 3713 Pompano Dr acola Pt 32514 1 476-8639 July1987 151
Edition: Model Aviation - 1987/07
Page Numbers: 52, 53, 151
Radio Control Scale Bob Dolly Wischer SCALE MATH Scale modelers build kits havesome questions answered designer manufacturer expected weight model suggested range engine sizes given drawing instruction booklet Scratch-builders ask searching questions such important matters projected estimate model weight engine requirements answer really needed early stages design Once model size has decided upon wing span area straightforward function scale ratio number represents dif ference between full-size aircraft model simply divide prototypes span scale ratio determine models span find models wing area divide area prototype wing square scale ratio example Y4-scale model has scale ratio 4 42 16 prototype wing area 146 sq ft 146/16 sq ft 1314 sq easy part What scratch-builder really needs know early design stages approximate weight model what engine size will best scalelike flight Since now con sidering mass rather simple linear dimen sions areas divide weight pro totype cube scale ratio previous example ratio 4 43 rototype lightplane weighing 670 lb fuel passengers 670/64 lb projected model weight base calculations airplane weight passengers because full-size airplane flight characteristics will vary widely between light heavy loads typical ultralight can carry its own weight payload lightplane about half its empty weight passengers does 1046 lb compare /4-scale model ready flight Using Y4-scale Aeronca K model 670-lb weight example model weighs 115 lb fuel ready fly weight bit heavy side about pound scalelike flight lightly-loaded aircraft comparing scale another larger model has advantage because on-board RC equipment weight approximately same both hypothetical model designer also would like know engine should power model rough estimate again use cube scale ratio division factor Aeronca K engine rather low-powered 40 hp Dividing horsepower cube scale ratio 40/64 625 tells us 60-size two-stroke engine would provide model scalelike flight 105 lb model actually powered 05 120 Gemini fourstroke has about twice power neces sary explains reason models angle climb about 200 compared 30 40 prototype passenger best source model engine horsepower statistics Peter Chinns series reviews Model Airplane News Overpowering model permissible within reason must kept mind Dormoy Bathtub L work Dow Davison Engine isa Saito FA-30 fourstroker Charles Bybee scratch-built SE5-A R Bill Effingets WE Technical Services plans Quadra 35 powers Weight 22 lb Finish Chevron paint over Super Coverite Don Rathbuns Corben Baby Ace L originated Great Planes kit Power OS 120 four-stroker weight 115 lb Covering Solartex polyurethane paint R isa seldom-modeled Slemens-SchuketI D-3 scratch-built Wylam plans Carl Harris 1/-scalO uses Zenoah 38 cu engine weighs 20 lb its ornate camouflage part latex part K&B epoxy over Coverite 52 Model Aviation Larry Gordons well-detailed Grumman F4F-3 Wildcat 1/5-scale spans 915 weighs 24 lb uses Quadra power Color markings Butch OHares plane too heavy engine could increase wing load ing small model Underpowered models usually go back workshop basket Now know models wing area its approximate weight simple matter extrapolate projected wing loading Since wing loading model airplanes ordinarily expressed ounces per square foot first convert its pro jected weight ounces divide area square feet find wing loading Aeronca example 2368 oz/9125 sq ft oz per sq ft loading reality because model came out slightly heavier expected added weighty dummy pilot its wing loading 22 oz per sq ft fuel calculation particular value deter mination whether model will manageable flight Experience says 30 oz per sq ft considered about upper limit smaller models 60-size engines Giant Scale airplanes can go high 45 oz variation result change Reynolds numbers due size series calculations supposed kept simple course simplified calculations can go seriously awry applied some aircraft such overpowered heavy types intended car rying great loads part flight Carrying heavy bomb fuel load military aircraft has no counterpart Scale modeling models weight varies little flights beginning end useful calculations must tempered reason Fuel loads models dont approach full-size aircraft may half gross weight world-circling airliners Calculations power requirements based takeoff horsepower can also lead us astray High-powered aircraft use full output short duration Starting empty weight Douglas A-20G attack bomber 17000 lb scale ratio 196 766-in-span model would have calculated weight 19 lb Its actual weight 14 lb because all-out weight reduction effort construction weight its wing loading astounding 44 oz per sq ft its handling air bit precarious climb glide speeds about equal 1275-horsepower Wright radials power engine calculates 14 horsepower HP 40 engines model will peak 12 acceptable 14-lb weight Douglas Mailplane has scale ratio 6857 694-in span Its weight calculations full-size included half ton fuel would have brought projected model weight up 154 lb Its actual measurement 12 lb wing loading 22 oz because model will never expected lift /3 its weight fuel load Power requirements calculated 400-hp Liberty engine prototype divided 6857 3224 about 12 hp adequately supplied its Enya 120 four-stroke Because model doesnt carry equivalent ton fuel mail load calculations cannot really begin published figures gross weight calculations provide some figures aid scratch-builder getting started along de sign route system seems its best calculations involving standard passengercarrying aircraft can use Ryan SCW example scale ratio 565 model weight should 1025 lb almost exactly correct Horsepower requirements should about 8 standard 60 engine would suffice Super Tigre 60 model rated well over horsepower able use larger-diameter prop greater efficiency around radial engine cowl wing loading Continued page 151 00 DGA Designs go DGA Designs co OGA Designs ec DGA Designs . OGA Designs 0 *DARNED GOOD AIRMEN 21 Lightest weight Pilots Availablea a BODY PILOT KIT L e keVnv ae ubberparts Easy assemble finish Kit contains Pilot head hands boots helmet0 cap goggles full templates easy instructions Fully positionable too.0 Height- WeIght- NEW Low Phsee No206 1/6 Scale ils 2 ozS 7j0 No205 /5 Scale 14d 3 oz55aa SPORTSMAN OAPNSTORMES FULL SODY BUST or0 ONo204-1/4 Scale 173a 40zS 5 No203 13 Scale 23s 6oz 0 0 0 0 Cs *60, sImple sewinga Ineqalreat0 0 0 0 0 *BU5T PILOT KIT Lifelike iflyl lilfyt rubbe part, K, canajns PIlot head helmet sport cap 909950 Jacket Easy asselnhlc fjnhh -Height WeIght Low P1100 No lOG 1 khcalo 3-18 34oc 5h 00 Shhdle 3-Cs -fdO S SSh V9No log dScdIe 4-30 f-i 20 5 No lOS ale S-3d 2-140 sl4 24. . Astosanding net attoinoblo plastIcs.. 0 ODoe hell extreme light weight ho oomplothd full hotly Ol p101 0hoOtS mdl haoe lIttle no effehl hdllnch OtyOo-airCl-dff. 0 Send 5100 Catalog New York State Resotents add 70 Sales teo BOnd 055k MO --caD-s.Allow 3 weeks tor 8500k 010cr 5 DGA Designs . DA o DGA Designs 1hLe~ RETRACTABLE ITOW HOOK RELEASE Price S 990 KI Simpiest reiiabie device avaiiabie After iine released hook retracts body unit ieaving SMOOTH surface bottom aircraft No speciai attachments required N eight oz OTHER FOURMOST PRODUCTS 049105 /2 REDUCES DRAG VIBRATION FREE PRICE $300 40 AIRFLO ENGINE MOUNT IDEAL FOR QUICKY 500 PRICE $630 Fuei Fitting Sets Fuei Shut Off Fuel Manifold Gapless Hinges Gapiess Hinge Slotter Strut Fairings Cockpit Coaming Send SASE Complete Information FOURMOST p4040 24th Ave Forest Grove OR 97116 RODUCTS Phone 503 357-2732 July1987 53 Winning Ideas FOURT lOST AIRFLO ENGINE MOUNT excellent candidate especially YS engine flies FAI pattern extremely well Since ARF Almost Ready Fly flying charac teristics likely consistent aircraft aircraft arent cheap event like would need major sponsor obviously things would have considered before fair test piloting ability would possible such setup wouldnt great watch best country/world compete nobody un fair advantage/liability Ron Van Pune 111 Sleepy Oaks Rd Ft Wal ton Beach FL 32548 RC Scale/Wischers Continued page 53 calculations indicated about 236 oz per sq ft model actually 259 Everything indi cated would good flying model always pleasantly surprised after model finished closely agrees mathe matical projection Estimated values quickly acquiredand just quickly discarded fall outside expectations Control weight during design construction difficult tasks scratchbuilder Having made some calculations deter estimated wing loading example builder now faced serious problem selecting material placement strengthening structural members avoid exceeding desired maximum weight choice made has always strict policy choose lighter material grounds crashed model will have come apart badly regardless built-in strengthening Wide variations strength also avoided example strong fuselage can survive bad landing due stall weak wing structure shattered stall occurred result overweight condi tion heavy fuselage may well have contributing factor cant build protection against pilot error As preferred construction method weight reduction ease building Scale mod eling must come conclusion dont have fact no two models have built alike duplicating older model wings open structure com mon framework leading edge trailing edge spars ribs has variations new Douglas Mailplane has solid-balsaplank leading edges partially shaped circular saw minimize carving sanding afterward Advantage No spars near leading edge spar near trailing edge good airfoil shape retention Disadvantage style construction expensive could con tribute heavy weight unless special care taken selecting light balsa solid leading edges wings completely sheet-covered have tried foam well conventional rib construction found no appreciable difference final weight strength building time electronic calculator has taken sweat out plotting airfoils tapered wings dozen rib positions Starting Handbook Airfoil Sections Light Aircraft MS Rice airfoil can plotted drawn size matter minutes repetition tapered wing rib positions may become monotonous no worse cutting later balsa sheet Some older Scale models non-scale airfoils seem fly just well later ones true scale shapes Maintaining true airfoil shape fabric-covered wings partially successful due fabric sag between ribs both models full-size planes good reason use scale airfoil appearance de pends upon critical eye viewer use Scale airfoil shapes probably has greater effect flight larger models flat-bottomed airfoil may acceptable Schoolyard Scale would hesitate use small Pylon Racer Building fuselage meet low weight projec tions becomes less difficult model size creases Its small model suffers too-high wing loading Building excess strength fuselage temptation re sisted After bad landing strong fuselage merely has larger pieces summarize scratch-designer can make some fairly accurate estimates design parame ters doubt concerning engine size choose larger displacement take advantage using larger-diameter propellers engine exhaust will less noisy prop will efficient because its tips will working outside cowl front-face area fuel consumption should reduced have no problems over heating large slow-turning props engines seem wear forever Excessive engine wear can traced overheating due lean needle settings inadequate ventilation conditions can exist regardless prop size larger prop may scale diame ter appearance definitely improved scratch-builder has positive control over center-of-gravity location Light balsa aft fuselage tail surfaces can help move all-important balance point comfortable 25% position wing chord first flights Having early estimate total weight observing nose tail moments can definite aid material selection Bob Dolly Wiseher 5-22 1 Lapham Peak Rd Delafleld WI 53018 RC Old-Timers/Mathews Continued page 55 kitted after war Scorpion rate very attractive design available version difficult wing construction size suitable 25-size two-cycle engines 30/40 four-strokers span 66 thereabouts making anything bigger excessive Although writer has never seen Ben Buckle kit certainly several interesting designs line Id appreciate hearing com ments have built Buckle kits lament lost skills David Evans letter mentions 24-year-old working PhD English literature University Virginia Some favorite RC memories spring building flying both Quaker 54 Air Trails Sportster teenager Both flew beautifully old 05 15 surprises somewhat few young people build fly Old-Timers satisfaction great hottest hotshots seem really love putting around sky Powerhouse some such Perhaps immediate generation last came model aviation directly through Comet Guil lows rubber kitswhich make transition stick-built Oldies pretty easy Bill Northrop Model Builder Maga zine has often expressed same concerns GATOR RIC PRODUCTS TIGER TAIL 45 DELUX ALL BALSA KIT An new Tiger Tail 120 four strokes piped 60 two strokes beautiful performer competition just showing offl balsa kit machined wood parts complete hardware package includes plug-in adjustable stab parts new wing mounts Wing Span -72 inWing Area 860 sq complete Delux KitS 15995 PLUG-IN ADJUSTABLE STAB KIT last can optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matching phenolic socket TRANSMITTER CASE An inexpensive rugged molded case protect expensive transmitter both two stick rngle s5ck transmitters Brown ather grain aluminum trim locking clasp S 1895 WING TUBE & SOCKETS Aluminum alloy tubing plug-In wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2t 895 diax25 995 1 diax352495 feather Ilte glass cloth 7 ozlsq yd est weave Fastest Filling est Finished Weight Big 3 Sq Yard Pkg Detailed Instructions 5895 ENGINE SLEEVE & BEARING PULLER Pull tight sleeves bearings easily out damage new 60s 17MM rear bearings Sleeve Puller5 795 Searing Puller5 695 ForS1395 IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure wJfl aileron elevator rudder throw Takes guess work out trimming out airplane quality tool complete instrtatkons log book tarrying caseS 795 NEWI WING MOUTifING SET wing mounting system developed Ron chidgey fast neat accurate stays tight Three nylon brackets screws machined wood wing blocks included 5595 See Dealer Order Direct Include S2 Per item UPS GATOR RIC PRODUCTS 3713 Pompano Dr acola Pt 32514 1 476-8639 July1987 151
Edition: Model Aviation - 1987/07
Page Numbers: 52, 53, 151
Radio Control Scale Bob Dolly Wischer SCALE MATH Scale modelers build kits havesome questions answered designer manufacturer expected weight model suggested range engine sizes given drawing instruction booklet Scratch-builders ask searching questions such important matters projected estimate model weight engine requirements answer really needed early stages design Once model size has decided upon wing span area straightforward function scale ratio number represents dif ference between full-size aircraft model simply divide prototypes span scale ratio determine models span find models wing area divide area prototype wing square scale ratio example Y4-scale model has scale ratio 4 42 16 prototype wing area 146 sq ft 146/16 sq ft 1314 sq easy part What scratch-builder really needs know early design stages approximate weight model what engine size will best scalelike flight Since now con sidering mass rather simple linear dimen sions areas divide weight pro totype cube scale ratio previous example ratio 4 43 rototype lightplane weighing 670 lb fuel passengers 670/64 lb projected model weight base calculations airplane weight passengers because full-size airplane flight characteristics will vary widely between light heavy loads typical ultralight can carry its own weight payload lightplane about half its empty weight passengers does 1046 lb compare /4-scale model ready flight Using Y4-scale Aeronca K model 670-lb weight example model weighs 115 lb fuel ready fly weight bit heavy side about pound scalelike flight lightly-loaded aircraft comparing scale another larger model has advantage because on-board RC equipment weight approximately same both hypothetical model designer also would like know engine should power model rough estimate again use cube scale ratio division factor Aeronca K engine rather low-powered 40 hp Dividing horsepower cube scale ratio 40/64 625 tells us 60-size two-stroke engine would provide model scalelike flight 105 lb model actually powered 05 120 Gemini fourstroke has about twice power neces sary explains reason models angle climb about 200 compared 30 40 prototype passenger best source model engine horsepower statistics Peter Chinns series reviews Model Airplane News Overpowering model permissible within reason must kept mind Dormoy Bathtub L work Dow Davison Engine isa Saito FA-30 fourstroker Charles Bybee scratch-built SE5-A R Bill Effingets WE Technical Services plans Quadra 35 powers Weight 22 lb Finish Chevron paint over Super Coverite Don Rathbuns Corben Baby Ace L originated Great Planes kit Power OS 120 four-stroker weight 115 lb Covering Solartex polyurethane paint R isa seldom-modeled Slemens-SchuketI D-3 scratch-built Wylam plans Carl Harris 1/-scalO uses Zenoah 38 cu engine weighs 20 lb its ornate camouflage part latex part K&B epoxy over Coverite 52 Model Aviation Larry Gordons well-detailed Grumman F4F-3 Wildcat 1/5-scale spans 915 weighs 24 lb uses Quadra power Color markings Butch OHares plane too heavy engine could increase wing load ing small model Underpowered models usually go back workshop basket Now know models wing area its approximate weight simple matter extrapolate projected wing loading Since wing loading model airplanes ordinarily expressed ounces per square foot first convert its pro jected weight ounces divide area square feet find wing loading Aeronca example 2368 oz/9125 sq ft oz per sq ft loading reality because model came out slightly heavier expected added weighty dummy pilot its wing loading 22 oz per sq ft fuel calculation particular value deter mination whether model will manageable flight Experience says 30 oz per sq ft considered about upper limit smaller models 60-size engines Giant Scale airplanes can go high 45 oz variation result change Reynolds numbers due size series calculations supposed kept simple course simplified calculations can go seriously awry applied some aircraft such overpowered heavy types intended car rying great loads part flight Carrying heavy bomb fuel load military aircraft has no counterpart Scale modeling models weight varies little flights beginning end useful calculations must tempered reason Fuel loads models dont approach full-size aircraft may half gross weight world-circling airliners Calculations power requirements based takeoff horsepower can also lead us astray High-powered aircraft use full output short duration Starting empty weight Douglas A-20G attack bomber 17000 lb scale ratio 196 766-in-span model would have calculated weight 19 lb Its actual weight 14 lb because all-out weight reduction effort construction weight its wing loading astounding 44 oz per sq ft its handling air bit precarious climb glide speeds about equal 1275-horsepower Wright radials power engine calculates 14 horsepower HP 40 engines model will peak 12 acceptable 14-lb weight Douglas Mailplane has scale ratio 6857 694-in span Its weight calculations full-size included half ton fuel would have brought projected model weight up 154 lb Its actual measurement 12 lb wing loading 22 oz because model will never expected lift /3 its weight fuel load Power requirements calculated 400-hp Liberty engine prototype divided 6857 3224 about 12 hp adequately supplied its Enya 120 four-stroke Because model doesnt carry equivalent ton fuel mail load calculations cannot really begin published figures gross weight calculations provide some figures aid scratch-builder getting started along de sign route system seems its best calculations involving standard passengercarrying aircraft can use Ryan SCW example scale ratio 565 model weight should 1025 lb almost exactly correct Horsepower requirements should about 8 standard 60 engine would suffice Super Tigre 60 model rated well over horsepower able use larger-diameter prop greater efficiency around radial engine cowl wing loading Continued page 151 00 DGA Designs go DGA Designs co OGA Designs ec DGA Designs . OGA Designs 0 *DARNED GOOD AIRMEN 21 Lightest weight Pilots Availablea a BODY PILOT KIT L e keVnv ae ubberparts Easy assemble finish Kit contains Pilot head hands boots helmet0 cap goggles full templates easy instructions Fully positionable too.0 Height- WeIght- NEW Low Phsee No206 1/6 Scale ils 2 ozS 7j0 No205 /5 Scale 14d 3 oz55aa SPORTSMAN OAPNSTORMES FULL SODY BUST or0 ONo204-1/4 Scale 173a 40zS 5 No203 13 Scale 23s 6oz 0 0 0 0 Cs *60, sImple sewinga Ineqalreat0 0 0 0 0 *BU5T PILOT KIT Lifelike iflyl lilfyt rubbe part, K, canajns PIlot head helmet sport cap 909950 Jacket Easy asselnhlc fjnhh -Height WeIght Low P1100 No lOG 1 khcalo 3-18 34oc 5h 00 Shhdle 3-Cs -fdO S SSh V9No log dScdIe 4-30 f-i 20 5 No lOS ale S-3d 2-140 sl4 24. . Astosanding net attoinoblo plastIcs.. 0 ODoe hell extreme light weight ho oomplothd full hotly Ol p101 0hoOtS mdl haoe lIttle no effehl hdllnch OtyOo-airCl-dff. 0 Send 5100 Catalog New York State Resotents add 70 Sales teo BOnd 055k MO --caD-s.Allow 3 weeks tor 8500k 010cr 5 DGA Designs . DA o DGA Designs 1hLe~ RETRACTABLE ITOW HOOK RELEASE Price S 990 KI Simpiest reiiabie device avaiiabie After iine released hook retracts body unit ieaving SMOOTH surface bottom aircraft No speciai attachments required N eight oz OTHER FOURMOST PRODUCTS 049105 /2 REDUCES DRAG VIBRATION FREE PRICE $300 40 AIRFLO ENGINE MOUNT IDEAL FOR QUICKY 500 PRICE $630 Fuei Fitting Sets Fuei Shut Off Fuel Manifold Gapless Hinges Gapiess Hinge Slotter Strut Fairings Cockpit Coaming Send SASE Complete Information FOURMOST p4040 24th Ave Forest Grove OR 97116 RODUCTS Phone 503 357-2732 July1987 53 Winning Ideas FOURT lOST AIRFLO ENGINE MOUNT excellent candidate especially YS engine flies FAI pattern extremely well Since ARF Almost Ready Fly flying charac teristics likely consistent aircraft aircraft arent cheap event like would need major sponsor obviously things would have considered before fair test piloting ability would possible such setup wouldnt great watch best country/world compete nobody un fair advantage/liability Ron Van Pune 111 Sleepy Oaks Rd Ft Wal ton Beach FL 32548 RC Scale/Wischers Continued page 53 calculations indicated about 236 oz per sq ft model actually 259 Everything indi cated would good flying model always pleasantly surprised after model finished closely agrees mathe matical projection Estimated values quickly acquiredand just quickly discarded fall outside expectations Control weight during design construction difficult tasks scratchbuilder Having made some calculations deter estimated wing loading example builder now faced serious problem selecting material placement strengthening structural members avoid exceeding desired maximum weight choice made has always strict policy choose lighter material grounds crashed model will have come apart badly regardless built-in strengthening Wide variations strength also avoided example strong fuselage can survive bad landing due stall weak wing structure shattered stall occurred result overweight condi tion heavy fuselage may well have contributing factor cant build protection against pilot error As preferred construction method weight reduction ease building Scale mod eling must come conclusion dont have fact no two models have built alike duplicating older model wings open structure com mon framework leading edge trailing edge spars ribs has variations new Douglas Mailplane has solid-balsaplank leading edges partially shaped circular saw minimize carving sanding afterward Advantage No spars near leading edge spar near trailing edge good airfoil shape retention Disadvantage style construction expensive could con tribute heavy weight unless special care taken selecting light balsa solid leading edges wings completely sheet-covered have tried foam well conventional rib construction found no appreciable difference final weight strength building time electronic calculator has taken sweat out plotting airfoils tapered wings dozen rib positions Starting Handbook Airfoil Sections Light Aircraft MS Rice airfoil can plotted drawn size matter minutes repetition tapered wing rib positions may become monotonous no worse cutting later balsa sheet Some older Scale models non-scale airfoils seem fly just well later ones true scale shapes Maintaining true airfoil shape fabric-covered wings partially successful due fabric sag between ribs both models full-size planes good reason use scale airfoil appearance de pends upon critical eye viewer use Scale airfoil shapes probably has greater effect flight larger models flat-bottomed airfoil may acceptable Schoolyard Scale would hesitate use small Pylon Racer Building fuselage meet low weight projec tions becomes less difficult model size creases Its small model suffers too-high wing loading Building excess strength fuselage temptation re sisted After bad landing strong fuselage merely has larger pieces summarize scratch-designer can make some fairly accurate estimates design parame ters doubt concerning engine size choose larger displacement take advantage using larger-diameter propellers engine exhaust will less noisy prop will efficient because its tips will working outside cowl front-face area fuel consumption should reduced have no problems over heating large slow-turning props engines seem wear forever Excessive engine wear can traced overheating due lean needle settings inadequate ventilation conditions can exist regardless prop size larger prop may scale diame ter appearance definitely improved scratch-builder has positive control over center-of-gravity location Light balsa aft fuselage tail surfaces can help move all-important balance point comfortable 25% position wing chord first flights Having early estimate total weight observing nose tail moments can definite aid material selection Bob Dolly Wiseher 5-22 1 Lapham Peak Rd Delafleld WI 53018 RC Old-Timers/Mathews Continued page 55 kitted after war Scorpion rate very attractive design available version difficult wing construction size suitable 25-size two-cycle engines 30/40 four-strokers span 66 thereabouts making anything bigger excessive Although writer has never seen Ben Buckle kit certainly several interesting designs line Id appreciate hearing com ments have built Buckle kits lament lost skills David Evans letter mentions 24-year-old working PhD English literature University Virginia Some favorite RC memories spring building flying both Quaker 54 Air Trails Sportster teenager Both flew beautifully old 05 15 surprises somewhat few young people build fly Old-Timers satisfaction great hottest hotshots seem really love putting around sky Powerhouse some such Perhaps immediate generation last came model aviation directly through Comet Guil lows rubber kitswhich make transition stick-built Oldies pretty easy Bill Northrop Model Builder Maga zine has often expressed same concerns GATOR RIC PRODUCTS TIGER TAIL 45 DELUX ALL BALSA KIT An new Tiger Tail 120 four strokes piped 60 two strokes beautiful performer competition just showing offl balsa kit machined wood parts complete hardware package includes plug-in adjustable stab parts new wing mounts Wing Span -72 inWing Area 860 sq complete Delux KitS 15995 PLUG-IN ADJUSTABLE STAB KIT last can optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matching phenolic socket TRANSMITTER CASE An inexpensive rugged molded case protect expensive transmitter both two stick rngle s5ck transmitters Brown ather grain aluminum trim locking clasp S 1895 WING TUBE & SOCKETS Aluminum alloy tubing plug-In wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2t 895 diax25 995 1 diax352495 feather Ilte glass cloth 7 ozlsq yd est weave Fastest Filling est Finished Weight Big 3 Sq Yard Pkg Detailed Instructions 5895 ENGINE SLEEVE & BEARING PULLER Pull tight sleeves bearings easily out damage new 60s 17MM rear bearings Sleeve Puller5 795 Searing Puller5 695 ForS1395 IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure wJfl aileron elevator rudder throw Takes guess work out trimming out airplane quality tool complete instrtatkons log book tarrying caseS 795 NEWI WING MOUTifING SET wing mounting system developed Ron chidgey fast neat accurate stays tight Three nylon brackets screws machined wood wing blocks included 5595 See Dealer Order Direct Include S2 Per item UPS GATOR RIC PRODUCTS 3713 Pompano Dr acola Pt 32514 1 476-8639 July1987 151