Notes Pattern Aircraft Design comes areas proportions scratch builders up tree useful data will dispel aura mystery Richard C Scamehorn SCRATCH DESIGN criteria isnt much available Its thing scratch build plans. its another thing design yourself plane general criteria full-scale aircraft design holds true RC aircraft design Basic aircraft design begins trying answer question What will gross weight plane Gross mean ing all-up weight RC terms article will deal RC planes understand rationale full-scale de sign can better understand princi ples application RC design Anyhow gross weight established two basic reasons 1 ensure can carry enough passengers cargo mission 2 give us basis designing sufficient wing area RC design latter far important can short-cut step use accompanying RC chart Various performance lines plotted against wing area sq also en gine displacement first RC design choice type plane want Lets say want stunt plane also want retracts wed better select 60 engine because starting add weight plane chart find stunt pat tern plane 60 engine should have 650 sq wing whats span chord Taper Airfoil selection Well might sound silly airfoil selection least important According KW Woods Aircraft Design Since costs vary widely time time place place follows best-design wing criterion also variable may cover wide range dimensions materials also follows number widely varying designs may nearly good best Also FE Weick Piper Corp states thing looks like wing will fly nearly well best wing Well may shatter confidence next time take family vacation air travel thats just about scien tific some things seem general wing thickness should vary depending type service intended plane High-lift wings flaps have thickness 14%-18% chord high drag also Moderate per formance lift wings run thickness l0%-13% chord thickness have lower co-efficient lift must take off land much faster high-lift wings also have much less drag can fly faster. can fly land flaps theres high-speed wings have thickness 6%-9% chord low lift low drag need flaps take-off especially landing Toads wing thickness 12-1/2% chord pattern plane ought have 10% 13% thickness-to-chord ratio because want retracts well go thick wing use 15% Thus far have decided design pattern plane using 60 engine 650 sq wing thickness 15% chord wing could 650 span 1 chord 10 span 65 chord thicknesses respectively 015 ft 9-3/4 Neither very practical either span chord thick ness considerations So decide span chord dimen sions thus thickness need intro duce concept aspect ratio As equal wing span b squared di vided wing area s A5 s Some full Scale planes aspect ratios Type Plane Supersonic Fighters05 acers4 II Fighters Small Private Planes Gliders Sailplanes As might apparent above A5 increases lift increases drag creases almost fast So youre too much worried about high speed because high drag will limit choose high As really want high speed choose low A5 sure youve got big pow erplant cause low As also has low lift unless really get going pattern plane well choose As 56 68 9 3 16 June1976 11 Dale Adams white hat has help buddies checking out Webra Speed Utopiadesigner George Aibright right Rom-Air retracts Kavan muffler 117 3/4 Rev-Up prop Pattern Aircraft Design will work nice later its medium hot range isnt out sight like racer So following A5 formula A5 5538 50 X 650 3600 span 0 Now also know span 60 area 650 sq average chord 10-27/32 650 divided 60 7/32 Also chosen thick ness 15% chord average thickness 15 X 10-27/32 average thickness 8 well get signifi cance average later So little design knowledge few decisions weve designed following criteria 1 Mission 2 Power 3 Wingarea 4 Wing thickness 5 Aspect ratio 6 Wing span 7 Wing chord 8 Wing thickness pattern plane 60 650 sq 15% 5538 60 10-27/32 average 1-5/8 average Now thats quite few factors weve resolved long way start ing cut balsa foam Next need consider control sur faces often think control sur faces portion moved servos entire horizontal tail stab ator vertical fin fin er consid ered control surface Aileron control area should 9%-l0% wing area horizontal tail 16%-20% vertical tail 75%-85% Because going pat tern work plane can go low range vertical tail needed stall turns well go high side ailerons horizontal tail So well mul tiply wing area factors get Aileron area X 10% q Horizontal tail 20% sq Vertical tail X 75% q As vertical tail should 10-18 horizontal tail 35 45 Remem bering A5 vertical tail span height using A5 -1/4 average chord will 7-27/32 Using As 40 hori zontal tail span 22-7/8 aver age chord 5-5/8 Now need 65 sq aileron area want ailerons start 1/4 way wing centerline out tip thats 3/4 wing spanor 45 So chord aileron 65 sq divided 45 1-7/16 So preliminary data now WingSpan 60 Chord 10-27/32in avg Aileron Chord 3/4 span 1-7/16 avg Thickness 1-5/8 avg Horizontal TailSpan 22-7/8 Chord 5-5/8 avg Elevator Chord 2-13/16 avg Vertical TailHeight 6-1/4 Chord 7-27/32 avg Rudder Chord 3-15/16 avg Its pretty easy conclude both vertical horizontal tail could 15% thickness chord ratio 15% vertical chord 1-11/64 15% 10-27/32 1626 could change 15/8 convenient Well getting closer theres still way go brings us wing taper explains used average chord constant chord 10-27/32 can improve performance some appearance lot introducing taper wingand well taper vertical horizontal tail also visual consistency horizontal tail create anti-rudder lock fin vertical tail Tapering wing does several things 1 Slightly increases lift* 2 Slightly reduces drag* 3 Makes wing slightly stall-prone 4 Moves semi-wing CG slightly closer fuse 5 Makes wing root thicker hold retracts *Note very few design changes can make simultaneously increases lift decreases drag best planform taper purely elliptical wing Supermarine Spitfire next best semi-elliptical wing Thunderbolt Problem both very costly full-scale somewhat difficult build RC So com ENGINE DISPLACEMENT VS WING AREA 70 60___ __/ t 40_____ 30-- __ 20 10 J7 0200 12 Model Aviation 7 /7 // sand 300 400 500 600 700 800 900 000 promise made shown semi span Some German fighters WW II another compromise designers used constant chord 1/3 semispan taper out-board 2/3 semi-span sketch above diagram youll see closely approaches elliptical wing does tapered wing Well weve decided taper wing too much written about selection wing taper ratio chord root divided chord tip RC building con sideration make tip too thin thin construction becomes unneces sarily difficult Also wing tip too thin will prone break hit tip rough landing general taper ratio 31 pretty hot around 21 medium go much below 151 might well forget taper-related decision have left apply taper going eliminate swept-back wing design configuration because its too stallprone dont want forward sweep either choices 1 Constant straight leading edge gives us least increase both lift drag least stall prone 2 Constant straight trailing edge gives us increase lift slight increase drag three choices stall-prone 3 compromise equal taper angle both leading trailing edgeyielding moderate lift increases too much stall propensity Well use plane taper horizontal vertical tail should have constant trailing edge both easier construction stick 21 taper ratio horizontal tail chord will 7-1/2 root 3-3/4 tip constant straight trailing edge Experience tells us preliminary data elevator chord 2-13/16 neces sary well change based upon experi ence 1-1/2 elevator chord same aileron Well also use 21 taper constant TE vertical tail Now will yield root chord 10-7/16 tip chord 5-7/32 Once again well use 1-1/2 chord last airfoil decisions about over still need design some dihedral Throw out full-scale rule book build scale RC model plans call about half less full-scale plane So again well rely experience use 1-1/2 dihedral under wing tip Now virtually done except weve got choose NACA series looking lift drag charts youll much likely accept advicesome tried-and-true airfoil line old saying Let buyer beware say let designer beware number factors -- used design decisions Most ex tremes would make plane hot cool make design decisions choose variable hot side well have plane will go like bat out hell providing someone knows take-off fly land bat out hell An example use high taper ratio get thickness wing root enough hold retracts use little higher aspect ratio youre building stubby-winged thing real low aspect ratio pick cooler wing thick ness ratio 18%-20% Some hot cool decisions 1 Wing area engine see chart 2 Wing thickness ratio 3 Aspect ratio 4 Taper ratio 5 Control surface area 6 Aileron area Good designing June1976 13 N C G LOCATIONS 32 I Constant Chord J 2- Compromise Taper / 3 - Ellipse Trouble Too neme Tony Bonetti gave 74 Nats entry very maneuverable design shown free-style demonstration Semi-Span 30 14 1/271/4 II F 7 1/2I 1/2 VerticalHorizontal Tail TailI, 10 7/16 57/327l/11/2T yi1 __ 33/4 ___ /32SemiSpan II 7/16
Edition: Model Aviation - 1976/06
Page Numbers: 11, 12, 13
Notes Pattern Aircraft Design comes areas proportions scratch builders up tree useful data will dispel aura mystery Richard C Scamehorn SCRATCH DESIGN criteria isnt much available Its thing scratch build plans. its another thing design yourself plane general criteria full-scale aircraft design holds true RC aircraft design Basic aircraft design begins trying answer question What will gross weight plane Gross mean ing all-up weight RC terms article will deal RC planes understand rationale full-scale de sign can better understand princi ples application RC design Anyhow gross weight established two basic reasons 1 ensure can carry enough passengers cargo mission 2 give us basis designing sufficient wing area RC design latter far important can short-cut step use accompanying RC chart Various performance lines plotted against wing area sq also en gine displacement first RC design choice type plane want Lets say want stunt plane also want retracts wed better select 60 engine because starting add weight plane chart find stunt pat tern plane 60 engine should have 650 sq wing whats span chord Taper Airfoil selection Well might sound silly airfoil selection least important According KW Woods Aircraft Design Since costs vary widely time time place place follows best-design wing criterion also variable may cover wide range dimensions materials also follows number widely varying designs may nearly good best Also FE Weick Piper Corp states thing looks like wing will fly nearly well best wing Well may shatter confidence next time take family vacation air travel thats just about scien tific some things seem general wing thickness should vary depending type service intended plane High-lift wings flaps have thickness 14%-18% chord high drag also Moderate per formance lift wings run thickness l0%-13% chord thickness have lower co-efficient lift must take off land much faster high-lift wings also have much less drag can fly faster. can fly land flaps theres high-speed wings have thickness 6%-9% chord low lift low drag need flaps take-off especially landing Toads wing thickness 12-1/2% chord pattern plane ought have 10% 13% thickness-to-chord ratio because want retracts well go thick wing use 15% Thus far have decided design pattern plane using 60 engine 650 sq wing thickness 15% chord wing could 650 span 1 chord 10 span 65 chord thicknesses respectively 015 ft 9-3/4 Neither very practical either span chord thick ness considerations So decide span chord dimen sions thus thickness need intro duce concept aspect ratio As equal wing span b squared di vided wing area s A5 s Some full Scale planes aspect ratios Type Plane Supersonic Fighters05 acers4 II Fighters Small Private Planes Gliders Sailplanes As might apparent above A5 increases lift increases drag creases almost fast So youre too much worried about high speed because high drag will limit choose high As really want high speed choose low A5 sure youve got big pow erplant cause low As also has low lift unless really get going pattern plane well choose As 56 68 9 3 16 June1976 11 Dale Adams white hat has help buddies checking out Webra Speed Utopiadesigner George Aibright right Rom-Air retracts Kavan muffler 117 3/4 Rev-Up prop Pattern Aircraft Design will work nice later its medium hot range isnt out sight like racer So following A5 formula A5 5538 50 X 650 3600 span 0 Now also know span 60 area 650 sq average chord 10-27/32 650 divided 60 7/32 Also chosen thick ness 15% chord average thickness 15 X 10-27/32 average thickness 8 well get signifi cance average later So little design knowledge few decisions weve designed following criteria 1 Mission 2 Power 3 Wingarea 4 Wing thickness 5 Aspect ratio 6 Wing span 7 Wing chord 8 Wing thickness pattern plane 60 650 sq 15% 5538 60 10-27/32 average 1-5/8 average Now thats quite few factors weve resolved long way start ing cut balsa foam Next need consider control sur faces often think control sur faces portion moved servos entire horizontal tail stab ator vertical fin fin er consid ered control surface Aileron control area should 9%-l0% wing area horizontal tail 16%-20% vertical tail 75%-85% Because going pat tern work plane can go low range vertical tail needed stall turns well go high side ailerons horizontal tail So well mul tiply wing area factors get Aileron area X 10% q Horizontal tail 20% sq Vertical tail X 75% q As vertical tail should 10-18 horizontal tail 35 45 Remem bering A5 vertical tail span height using A5 -1/4 average chord will 7-27/32 Using As 40 hori zontal tail span 22-7/8 aver age chord 5-5/8 Now need 65 sq aileron area want ailerons start 1/4 way wing centerline out tip thats 3/4 wing spanor 45 So chord aileron 65 sq divided 45 1-7/16 So preliminary data now WingSpan 60 Chord 10-27/32in avg Aileron Chord 3/4 span 1-7/16 avg Thickness 1-5/8 avg Horizontal TailSpan 22-7/8 Chord 5-5/8 avg Elevator Chord 2-13/16 avg Vertical TailHeight 6-1/4 Chord 7-27/32 avg Rudder Chord 3-15/16 avg Its pretty easy conclude both vertical horizontal tail could 15% thickness chord ratio 15% vertical chord 1-11/64 15% 10-27/32 1626 could change 15/8 convenient Well getting closer theres still way go brings us wing taper explains used average chord constant chord 10-27/32 can improve performance some appearance lot introducing taper wingand well taper vertical horizontal tail also visual consistency horizontal tail create anti-rudder lock fin vertical tail Tapering wing does several things 1 Slightly increases lift* 2 Slightly reduces drag* 3 Makes wing slightly stall-prone 4 Moves semi-wing CG slightly closer fuse 5 Makes wing root thicker hold retracts *Note very few design changes can make simultaneously increases lift decreases drag best planform taper purely elliptical wing Supermarine Spitfire next best semi-elliptical wing Thunderbolt Problem both very costly full-scale somewhat difficult build RC So com ENGINE DISPLACEMENT VS WING AREA 70 60___ __/ t 40_____ 30-- __ 20 10 J7 0200 12 Model Aviation 7 /7 // sand 300 400 500 600 700 800 900 000 promise made shown semi span Some German fighters WW II another compromise designers used constant chord 1/3 semispan taper out-board 2/3 semi-span sketch above diagram youll see closely approaches elliptical wing does tapered wing Well weve decided taper wing too much written about selection wing taper ratio chord root divided chord tip RC building con sideration make tip too thin thin construction becomes unneces sarily difficult Also wing tip too thin will prone break hit tip rough landing general taper ratio 31 pretty hot around 21 medium go much below 151 might well forget taper-related decision have left apply taper going eliminate swept-back wing design configuration because its too stallprone dont want forward sweep either choices 1 Constant straight leading edge gives us least increase both lift drag least stall prone 2 Constant straight trailing edge gives us increase lift slight increase drag three choices stall-prone 3 compromise equal taper angle both leading trailing edgeyielding moderate lift increases too much stall propensity Well use plane taper horizontal vertical tail should have constant trailing edge both easier construction stick 21 taper ratio horizontal tail chord will 7-1/2 root 3-3/4 tip constant straight trailing edge Experience tells us preliminary data elevator chord 2-13/16 neces sary well change based upon experi ence 1-1/2 elevator chord same aileron Well also use 21 taper constant TE vertical tail Now will yield root chord 10-7/16 tip chord 5-7/32 Once again well use 1-1/2 chord last airfoil decisions about over still need design some dihedral Throw out full-scale rule book build scale RC model plans call about half less full-scale plane So again well rely experience use 1-1/2 dihedral under wing tip Now virtually done except weve got choose NACA series looking lift drag charts youll much likely accept advicesome tried-and-true airfoil line old saying Let buyer beware say let designer beware number factors -- used design decisions Most ex tremes would make plane hot cool make design decisions choose variable hot side well have plane will go like bat out hell providing someone knows take-off fly land bat out hell An example use high taper ratio get thickness wing root enough hold retracts use little higher aspect ratio youre building stubby-winged thing real low aspect ratio pick cooler wing thick ness ratio 18%-20% Some hot cool decisions 1 Wing area engine see chart 2 Wing thickness ratio 3 Aspect ratio 4 Taper ratio 5 Control surface area 6 Aileron area Good designing June1976 13 N C G LOCATIONS 32 I Constant Chord J 2- Compromise Taper / 3 - Ellipse Trouble Too neme Tony Bonetti gave 74 Nats entry very maneuverable design shown free-style demonstration Semi-Span 30 14 1/271/4 II F 7 1/2I 1/2 VerticalHorizontal Tail TailI, 10 7/16 57/327l/11/2T yi1 __ 33/4 ___ /32SemiSpan II 7/16
Edition: Model Aviation - 1976/06
Page Numbers: 11, 12, 13
Notes Pattern Aircraft Design comes areas proportions scratch builders up tree useful data will dispel aura mystery Richard C Scamehorn SCRATCH DESIGN criteria isnt much available Its thing scratch build plans. its another thing design yourself plane general criteria full-scale aircraft design holds true RC aircraft design Basic aircraft design begins trying answer question What will gross weight plane Gross mean ing all-up weight RC terms article will deal RC planes understand rationale full-scale de sign can better understand princi ples application RC design Anyhow gross weight established two basic reasons 1 ensure can carry enough passengers cargo mission 2 give us basis designing sufficient wing area RC design latter far important can short-cut step use accompanying RC chart Various performance lines plotted against wing area sq also en gine displacement first RC design choice type plane want Lets say want stunt plane also want retracts wed better select 60 engine because starting add weight plane chart find stunt pat tern plane 60 engine should have 650 sq wing whats span chord Taper Airfoil selection Well might sound silly airfoil selection least important According KW Woods Aircraft Design Since costs vary widely time time place place follows best-design wing criterion also variable may cover wide range dimensions materials also follows number widely varying designs may nearly good best Also FE Weick Piper Corp states thing looks like wing will fly nearly well best wing Well may shatter confidence next time take family vacation air travel thats just about scien tific some things seem general wing thickness should vary depending type service intended plane High-lift wings flaps have thickness 14%-18% chord high drag also Moderate per formance lift wings run thickness l0%-13% chord thickness have lower co-efficient lift must take off land much faster high-lift wings also have much less drag can fly faster. can fly land flaps theres high-speed wings have thickness 6%-9% chord low lift low drag need flaps take-off especially landing Toads wing thickness 12-1/2% chord pattern plane ought have 10% 13% thickness-to-chord ratio because want retracts well go thick wing use 15% Thus far have decided design pattern plane using 60 engine 650 sq wing thickness 15% chord wing could 650 span 1 chord 10 span 65 chord thicknesses respectively 015 ft 9-3/4 Neither very practical either span chord thick ness considerations So decide span chord dimen sions thus thickness need intro duce concept aspect ratio As equal wing span b squared di vided wing area s A5 s Some full Scale planes aspect ratios Type Plane Supersonic Fighters05 acers4 II Fighters Small Private Planes Gliders Sailplanes As might apparent above A5 increases lift increases drag creases almost fast So youre too much worried about high speed because high drag will limit choose high As really want high speed choose low A5 sure youve got big pow erplant cause low As also has low lift unless really get going pattern plane well choose As 56 68 9 3 16 June1976 11 Dale Adams white hat has help buddies checking out Webra Speed Utopiadesigner George Aibright right Rom-Air retracts Kavan muffler 117 3/4 Rev-Up prop Pattern Aircraft Design will work nice later its medium hot range isnt out sight like racer So following A5 formula A5 5538 50 X 650 3600 span 0 Now also know span 60 area 650 sq average chord 10-27/32 650 divided 60 7/32 Also chosen thick ness 15% chord average thickness 15 X 10-27/32 average thickness 8 well get signifi cance average later So little design knowledge few decisions weve designed following criteria 1 Mission 2 Power 3 Wingarea 4 Wing thickness 5 Aspect ratio 6 Wing span 7 Wing chord 8 Wing thickness pattern plane 60 650 sq 15% 5538 60 10-27/32 average 1-5/8 average Now thats quite few factors weve resolved long way start ing cut balsa foam Next need consider control sur faces often think control sur faces portion moved servos entire horizontal tail stab ator vertical fin fin er consid ered control surface Aileron control area should 9%-l0% wing area horizontal tail 16%-20% vertical tail 75%-85% Because going pat tern work plane can go low range vertical tail needed stall turns well go high side ailerons horizontal tail So well mul tiply wing area factors get Aileron area X 10% q Horizontal tail 20% sq Vertical tail X 75% q As vertical tail should 10-18 horizontal tail 35 45 Remem bering A5 vertical tail span height using A5 -1/4 average chord will 7-27/32 Using As 40 hori zontal tail span 22-7/8 aver age chord 5-5/8 Now need 65 sq aileron area want ailerons start 1/4 way wing centerline out tip thats 3/4 wing spanor 45 So chord aileron 65 sq divided 45 1-7/16 So preliminary data now WingSpan 60 Chord 10-27/32in avg Aileron Chord 3/4 span 1-7/16 avg Thickness 1-5/8 avg Horizontal TailSpan 22-7/8 Chord 5-5/8 avg Elevator Chord 2-13/16 avg Vertical TailHeight 6-1/4 Chord 7-27/32 avg Rudder Chord 3-15/16 avg Its pretty easy conclude both vertical horizontal tail could 15% thickness chord ratio 15% vertical chord 1-11/64 15% 10-27/32 1626 could change 15/8 convenient Well getting closer theres still way go brings us wing taper explains used average chord constant chord 10-27/32 can improve performance some appearance lot introducing taper wingand well taper vertical horizontal tail also visual consistency horizontal tail create anti-rudder lock fin vertical tail Tapering wing does several things 1 Slightly increases lift* 2 Slightly reduces drag* 3 Makes wing slightly stall-prone 4 Moves semi-wing CG slightly closer fuse 5 Makes wing root thicker hold retracts *Note very few design changes can make simultaneously increases lift decreases drag best planform taper purely elliptical wing Supermarine Spitfire next best semi-elliptical wing Thunderbolt Problem both very costly full-scale somewhat difficult build RC So com ENGINE DISPLACEMENT VS WING AREA 70 60___ __/ t 40_____ 30-- __ 20 10 J7 0200 12 Model Aviation 7 /7 // sand 300 400 500 600 700 800 900 000 promise made shown semi span Some German fighters WW II another compromise designers used constant chord 1/3 semispan taper out-board 2/3 semi-span sketch above diagram youll see closely approaches elliptical wing does tapered wing Well weve decided taper wing too much written about selection wing taper ratio chord root divided chord tip RC building con sideration make tip too thin thin construction becomes unneces sarily difficult Also wing tip too thin will prone break hit tip rough landing general taper ratio 31 pretty hot around 21 medium go much below 151 might well forget taper-related decision have left apply taper going eliminate swept-back wing design configuration because its too stallprone dont want forward sweep either choices 1 Constant straight leading edge gives us least increase both lift drag least stall prone 2 Constant straight trailing edge gives us increase lift slight increase drag three choices stall-prone 3 compromise equal taper angle both leading trailing edgeyielding moderate lift increases too much stall propensity Well use plane taper horizontal vertical tail should have constant trailing edge both easier construction stick 21 taper ratio horizontal tail chord will 7-1/2 root 3-3/4 tip constant straight trailing edge Experience tells us preliminary data elevator chord 2-13/16 neces sary well change based upon experi ence 1-1/2 elevator chord same aileron Well also use 21 taper constant TE vertical tail Now will yield root chord 10-7/16 tip chord 5-7/32 Once again well use 1-1/2 chord last airfoil decisions about over still need design some dihedral Throw out full-scale rule book build scale RC model plans call about half less full-scale plane So again well rely experience use 1-1/2 dihedral under wing tip Now virtually done except weve got choose NACA series looking lift drag charts youll much likely accept advicesome tried-and-true airfoil line old saying Let buyer beware say let designer beware number factors -- used design decisions Most ex tremes would make plane hot cool make design decisions choose variable hot side well have plane will go like bat out hell providing someone knows take-off fly land bat out hell An example use high taper ratio get thickness wing root enough hold retracts use little higher aspect ratio youre building stubby-winged thing real low aspect ratio pick cooler wing thick ness ratio 18%-20% Some hot cool decisions 1 Wing area engine see chart 2 Wing thickness ratio 3 Aspect ratio 4 Taper ratio 5 Control surface area 6 Aileron area Good designing June1976 13 N C G LOCATIONS 32 I Constant Chord J 2- Compromise Taper / 3 - Ellipse Trouble Too neme Tony Bonetti gave 74 Nats entry very maneuverable design shown free-style demonstration Semi-Span 30 14 1/271/4 II F 7 1/2I 1/2 VerticalHorizontal Tail TailI, 10 7/16 57/327l/11/2T yi1 __ 33/4 ___ /32SemiSpan II 7/16