ti7oIk vqbout wwq Brad Powers PROLOGUE In October issue arti cle consisted 20 questions airplane design As turns out got grade 90% missed P-factor result gave bad advice about propeller swing twin-engine designs During after WW 111939-1952 preliminary design engineer Con vair days P-factor unheard years later read brief de scription about flight manual simply dismissed simplistic explanation effects torque did appear aerodynamic texts aware nor old cohorts heard prob ably because days design ing large jet-powered aircraft P-factor consideration Since however engineer named Ribner NACA has shown P-factor valid notion after contributes ad ditionally yaw takeoff especially tail-draggers approaching stall does negate torque addition being true turns out propeller rotation acting down respect fuselage twin-engine designs preferable up out said will future article torque thus missed two own questions apologize readers giving wrong information thank politely pointed out error Lift Equation engineering pro fession certain hard criteria example electrical engineer expected least know Ohms Law expressed structural engineer should really familiar formula bending f same way aerodynamicist worth salt should have some awareness basic Lift Equation L Seriously though learn use equation can find answers sort problems follow will have understanding weight wing area speed etc interrelated some problems together answers end article will able check answers 1 Harry wants build Quarter Scale model will land slowly realistically about 25 mph figures will weigh 30 lb knows value CL 10 Information about lift coefficients use Lift Equa tion topics month Part 2 about best can expect What should wing area Answer 18 sq ft 2 Jim other hand interested speed Pylon Racer can fly CL 04 full power racer weighs five pounds has wing area 3125 sq ft fast will fly still air Answer 125 mph 3 Larry has designed airplane concerned about its weight wants land 25 mph less has wing area 6 sq ft has flaps allowing develop CL 15 much can airplane weigh Answer 144 lb 4 Gary intrigued MacCreadys Gos samer Condor wants build model having similar slow flight characteristics wants model cruise 15 mph CL 5 what should wing loading Answer 29 lb per sq ft about 46 oz per sq ft 5 If above problem Garys wing area 20 sq ft what must model weigh Answer 58 lb can seen achieve such slow flight model must very light indeed Perhaps Gary should contact MacCready about weightsaving featuressuch carbon-fiber spars etc 6 Assuming have adequate power wing area 6 sq ft weight 10 lb what speed will fly CL 3 CL 6 CL 9 Answers 3 ph 6 ph 9 27 mph 7 What angles attack speeds represent Answers 4 degrees 8 degrees 12 degrees 8 How much speed will gain per centage build new wing half U area weight remains same Answer 40% greater speed 9 As percentage what will doubling wing area speed no weight change Answer 70% fast 30% slower 10 reduce weight 20% what will landing speed Answer It will reduce landing speed 11% Fig 1 shows Lift Curve lift coefficient CL plotted against angle attack usually denoted Greek letter c alpha time time articles appear showing curves like rarely explained think readers havent faintest idea what lift coefficient perhaps should assume some least honestly curious about such things would like know about First lets rearrange equation put terms lift coefficient CL Doing becomes CLL q S Where CL pure number ratio L lift pounds q dynamic pressure pounds per square foot S for surface wing area square feet As fliers have learned lift af fected several things apply extra power increase speed airplane hut usually find ourselves applying control trim keep climbing too high So lift function airspeed land usually cut throttle increase angle attack maintain lift low speed Lift also function angle attack know given speed model large wing will develop lift small wing Lift function wing area cold dry weather takeoff runs gen erally shorter hot moist weather also shorter sea level Denver Mexico City Lift function air density Some thick highly-cambered airfoils de velop lift thin flat ones having same wing area use flaps will in40 Model Aviation qill El' crease lift wing considerably Lift function airfoil characteristics Other factors such altitude aspect ratio size also affect lift effects treated separately part Lift Equation itself Unless stated otherwise will assume models flown sea level have aspect ratios around 61 larger Quarter Scale dynamic pressure q pounds per square foot multiplied wing area square feet gives value total lift produced measure factors producing lift write saying CL CL qS Lift Factors Producing Lift lots lift needed CL must have large valuecorresponding high angle attack graph flaps high speeds angle attack small values CL low So can see CL might regarded percentage lift required given set conditions What dynamic pressure q about dynamic pressure depends both velocity air density Lets see can derive its value scaring anybody putting some sleep thing air has weight Thirteen cubic feet air weighs about pound volume air roughly size console TV set Since has weight air also has mass measure its inertia resistance acceleration Something heavy massive harder speed up accelerate something light airy Mass expressed W/gweight related acceleration due gravity 32 feet per second squared air has den sity 11n pound per cubic foot 076 pound per cubic foot has mass density 076/32or 002378 slugs per cubic foot slug unit mass order impart lift wing air must moving respect wing will have energy due motion energy called kinetic energy equal MV2or 002378 V 001 19V2 2 2 cubic foot air velocity V feet per second Since handier express velocity speed miles per hour rather feet per second multiply 1472 mile per hour 147 feet per second 001 19V2 becomes 00256V2 V2 391 value call q Thus lift equation expands read LCLqS CLV2S 391 20 18 16 14 12 10 6 4 2 FigI1ZZ17 I- ----7---------1-t- 4-II / 2 1Ctj7Q -K 1-- -----4-- # --- 4- 10 17/ --4----4~ I I7L V44. -.-4-4 - III - I- 1. .. 1- ----4- 1Iii -I14 .IUIULuIin --1i1I1i ~[it t { 111 J 0 4 8 12 16 20 oZ angle attack degrees level flight constant speed lift developed must equal weight lift exceeds weight airplane will climb weight exceeds lift airplane will descend equation lift equals weight L vel flight Now lets take equation rear range sequentially term 1 LiftL L V2 S 391 2Lift coefficient CL— 391 L V2 S 391W V2 S 3 Velocity V L — CLS 391 W CLS 4 Wing area 5391_L CLV2 CLV2 5 Wing loading W 2 5391 seen following rela tionships hold true 1 Lift varies directly CL wing area 5 varies square speed 2 lift coefficient CL varies versely square speed di rectly wing loading W/S 3 Speed velocity varies inversely square root CL directly square root wing loading 4 Wing area varies directly lift weight varies inversely square speed inversely CL 5 Wing loading W/S varies directly CL square speed Lets look Fig minute well check answers problems show two curves CL plotted against angle attack lower curve typical symmetrical airfoil angle zero lift zero angle attack upper curve shows lift developed wing Continued page 134 February 1984 41 related RC/WC will great help have several items three Rd WC events US plan send Bob have something youd like send him either mail Bob Skinner PO Box 31166 Braamfontein 2017 Johannesburg Republic South Africa send Ill see gets sounds like great project well worth support Ron Van Putte 111 Sleepy Oaks Rd Fort Walton Beach FL 32548 Design/Powers Continued naae 41 flap Since wing flap really same thing airfoil having very high J-5s DEEP SEA CRUISER Great sport boat just fun boating J-5s DEEP SEA CRUISER loves running 1 2 foot waves Speeds up 25-30 mph FULLSIZE PLANS Matched Sheets 42 3/32x4100 1/8x4108 3/16x4120 1/4x4131 36 NEW Basswood b Pine Sticks 114 Scale ALL SHEET ONE PIECE AAA GRADE KILN DRIED SANDED TO CLOSE TOLERANCES PED 100% 36Light 4-6lb361l8x3453/l6sq.173/8x11/2 33 1116x349 1116x448 lI4sq.26 1/2x2 40 3/32x356 3I32x456 114x31830 43 1I8x367 118x 466 3/8 sq.37 493116x37648 Sticks 561/4 x 385Add 40% 3l8x3115 37112x3139 44 54Balsa SheetsAa 621116x3 733I32x3 851/8x3 883/16x3 110114x3 1653t8x3 200l/2x3 581/16x4 703132x4 801/8x4 933/16x4 1101/4x4 1663/8x4 225 camber angle zero lift didnt show would shifted over left negative angle attack curve rises extending above the unflapped section Because Reynolds Number model wing can reach maximum CL value about 10 Flaps will increase about 15 other hand full-size wing can run up much higher lift coefficients Reynolds No R 0 x mph x chord feet model chord foot flying 50 mph operating Rey nolds No S00000indicated solid part curveswhile full-size airplane will operate values R way up millions depending size speed See Lets Talk About Reynolds Number February 1979 MA Suffice say low Reynolds Nos flow over wing breaks down readily wing stalls about 12 degrees depending 48 LOA x 181/2 beam x 11 deep Easy build mahogany plywood soft wood construction Designed tor hobby Quadra TML 35 gasoline engine Kit includes fullsize plan instructions $ 1795 46 70 BalsaTriangles 36 1/4x1/425 3/8x31830 1/2x1/235 3/453/445 lxi55 Lite Ply lilt n see flaps Harry will just get CL 10 Larry will get 15 using flaps Now lets check answers I We can find Harrys wing area using Equation 4 391W 391 x30 CLV210 x 25 x 25 1876 say 18 sq ft 2 Jims speed equation No 3 V391W CL found using 391x5 04 x 3125 12506 say 125 3 Larrys weight Equation No 1 WCLV2S l5x25x25x6 391 144 lb 4 From Equation 5 W — 5x15x15 5391 391 b per sq ft about 46 oz per sq ft W 5 If lb/sq ft S q ft W 20 58 lb 6V391W _391x10 CLS3x6 V21722 466 mph say 46 391x10 6 x 6 391 W CL S V 10861 mph say 33 391W391 x 10 CLS9x6 V 724 mph say 27 Continued page 138 134 Model Aviation RC Aerobatics/yen Puffs Continued Fmm ,nnn 131 6 aCCepi v1j88 PS Add *2 aspect ratio wing loading other factors KIT & DRIVE TRAIN $19350 J-5 ENTERPRISES KIT DRIVE TRAIN & ENGINE $32445 PO Box 82 Belmont Ontario NOL 180 Phone 1-519-644-0375 / IF YOU CAN BUILD KIT YOU CAN BUILD SCRAJCH-A-PLANE SCRATCH A-PLANE SION OF KEISER GRAPHICS U WI WI WHAT IS SCRATCH-A-PLANEiZ Professionally engineered designs accessories discriminating ler design tested top flight performance excellent parts fit Ij ease construction plans reproduced professionally inked mylars complete full size templates separate plans building instructions accessories heavy gauge plastic clean detail GUARANTEE IF YOU ARE NOT TOTALLY SATISFIED WITH PLANS EASE OF CONSTRUCTION AND QUALITY OF ACCESSORIES SHIP RACK TO US BY ZI RETURN MAIL FOR FuLl Rmrnin RIIV WITH CONFIDENCE!U -I U WI WI Ii ZI U I-I cc U WI WI SCALE CAP 21 CONSTRUCTION BALSA & LITE PLY Wing Span 80Wing Area 880 sq inWeight 15 lbs Engine 2 cubic inch Quadra Radio 4 Channel 5 Channel flaps Rolled Plan Pack $2495 Cowl canopy & wheelpants S3995 xl THIS CAP 21 15 DESIGNED TO BE BUILT PAST. THEN YOUR FUN JUST BEGINSI i CAPABLE OF ALL AEROBATIC MANEUVERS INCLUDING SQUARE LOOPS 8 POINT ROLLS i KNIFE EDGE LOOPS OUTSIDE SNAP ROLLS LOMCEVAKS AND INVERTED FLAT SPINS YET Icc ON TAKE OFFS NORMAL FLIGHTS AND LANDING SHES REAL PUSSY CATTI AEROBATICS ENDORSED BY WORLD FAMOUS AEROBATIC PILOT BOB SCHULTZ SCALE QUADRA POWER DESIGNSWI FOKKER DR-iWING SPAN 70WT 16 lbs WI FOKKER D VIIIWING SPAN 82WT 14 lbs z NIEUPORT 17WING SPAN 80WT 15 lbs cc ROLLED PLAN PACKS $2495COWLS $1195 la Cd 40 SIZE FOUR STROKE DESIGN de HAVILLAND LEOPARD MOTH WING SPAN 63 FLYING WT 6 lbs ROLLED PLAN PACK 31995COWL WHEELPANTS & CANOPY 314 5 ZI U 60 90 TWO STROKE DESIGN 1934 AVIA B534-IVBI-PLANE WING SPAN 62WING AREA 1140 sq inWT 9 lbs IU ROLLED PLAN PACK $2295COWL CANOPY & RADIATOR $1495 Gfli 4 1/4 SCALE VINTAGE FLOATSWI LENGTH 45MAX LOAD 30 lbs PLANS TEMPLATES & INSTRUCTIONS $895 ppd folded OR ORDER DIRESHIPPING CHARGE $300 COD ORDERS ACCEPTEDVISA & MASTtRCARD WELCOMtA 2080 ATHENS AVE REDDING CA 96001 -J 5-916241-4190 SCRATcH SRATH PIAjE SCRJTCH 138 Model Aviation Design/Powers Conhnued fmm flAflA 134 see V varies inversely square root ratio lift coef fiCients CL example CL 46 mpl 3 33mph 6 ratio 3 tc 6 re root 7 multiply 466 707 get 32 mph bothering solve other terms 7 We Can read answers directly Fig 8 in item 3 stated relation2 ships see speed varies directly square root wing loading W/S problem halving wing area doubling wing loading speed will increase factor equal square root 2 14 speed will 14 times greator 40% faster 9 Conversely doubling wing area cut wing loading W/S half speed will decrease factor equal square root 5 7 speed will 70% fastor 30% slower ever way wishes state 10 If reduce weight 80% its original value reducing wing loading W/S same proportion square root 80% 89% reducing safe landing speed 11% math wasnt com plicated mysterious future will try minimize math much possible some things difficult impossible express other way topic happens Anyway mathematics useful beautiful human accomplishment Without would back stone age wondering di vide three birds eggs among four people product review product review product review very accurate Cuts necessary youre building special new project TinyTools Tablesaw just ticket Ifs 1 2-volt powered tool thai gives full torque allow speeds 200 rpm speeds up 17000 rpm variable thrugh speed control transformer table saw slotted rip ping accommodates indexing mitre gauge up 45 can also used wet dry stained glass lapidary work product review product review product review 0 U U I. 0 4 4 U Id 5 0 z 4 U -4 0 U U 4 -J 5 U Id 0 U U Id U U 4 U 4 5 -J Id Id U Id 5 0 4 U TinyTools Tablesaw Byrom International Corp 117 South St. Box 246 Chardon OH 44024 tel 216/285-2341 Epilogue subject aerodynamics bit complex have tried make seem intention articles try expose reader subject rational light fashionyet giving some useful formulas relationships ex ample say CL 10 typical models quite true general way effects aspect ratio air foil selection etc can change some what some critics have loudly indicated such criticism must reply am trying take complicated subject put fairly simple terms can digested average reader hope discussion Lift Equation has interest want know about design Questions comments may ad dressed Brad Powers 5470 Castle Hills Dr San Diego CA 92109 RC Scale/Wischers Continued page 45 Light steel parts can brazed 23000 F flame either kind gas heavier metal such l/.in.diameter steel tube landing gears torch suitable use MAPP methyl acetylene pro padiene gas preferred Its flame tempera ture used appropriate torch such Master Mechanic Whirlwind $24 36000 F gas about three times expensive propane s2n3 New Standard Giant Models 28 HP Lbs Send $100 Catalog 149 Direct Sales Only PIns hippsg Work Horse rel7fl 96 IORITZ 2a4 32 HP 6A Lbs III Dealer Direct PIns sblppiq Now Distribute Sachs-Dolmar Engines Yeager Machines TO RUN INCLUDING 6 BOLT PROP HUB AVAILABLE AT EXTRA CHARGE Nm ___ ___ NGINERear 340w Cleveland Isve. SW EU EEECanton OH 44707I IC DIVISIONPhone 216484-6810 48443741 job finished time because intensely hot flame actual cost per joint remains about same /2-in -diameter 035-in -wall aircraft steel tube brought red heat ready brazing bronze rod about ten seconds out red heat steel brazed bronze rod brazing alloy will melt flow uniformly around joint Insufficient heat primary reason lack success brazing Whirlwind torch has pres sure adjustment permits its use propane butane gases lowertemperature brazing maximum joint strength brazing Continued page 142 VXPHONE 6194424838 -h/pates 469-8675 BOX 2498-MALA MESA CA 92041 1 Great Trainers Send $150 complete Kit Catalog p Midwest Products C. Inc 400 S Indiana St PO Box 564-T Hobart 46342 83 t03l February 1984 139 BL ILAP4 MAILABLE IN TWO 1/4 Scale 90 to2EngInes 1 60EngIne EOPWITH TABLOIDI/ASeal77 Span524OOppUSA EOPWlTI4 TABLOID2V —I64 Span$1BOOppUSA 016 TEXAN41101 Span$27tOppUSA POSKEB DRI27 I63 Trip$2SOOppUSA F4U COESAIB2 I93 Span$27tppUSA CUBTISS p402 I94 Span$27OOppUSA FM BEAECAT2 —196 Span$2700 ppUSA Fiberglass COwlingS & Canopies available Send Stamp detailed Brochures oar Giant Scale AccessarreS Forego Orders Please add 254 POstage & Handling Nick Ziroli 29 Edgar Drive Smlthtowfl NY 11787 USA Brazing heavy metals Use Whirlwind Torch L stank stabilized acetylene gas lighter work use Microfiame torch R butane oxidizer cylinders sliver solder C02 ENGINES WE NOW HAVE COMPLETE LINE OF BROWN TELCO DAVIS CO-2 ENGINES INCLUDING SPARE PARTS SERVICE IAOWNTEL LO A23 PEANUT $2996STANDARD TELCO$2400 CAMPUS BEE $2495TURBO 300092295 CAMPUS TWiN- $5995TURBO 800093900 SODACHARGER $1200 MVIS- COX 02 CONVERSION TO CO2$3900 NEWt C4T4LOG No 25 $150 Classic R/C Scale LAKES TH G4Qr Wing 15 25 Engines Dealers & Distributors Welcomed Phone 703 273-9593 FLYLINE MODELS INC PO Boa 2136 Pairfars VirginIa 22021 USA
Edition: Model Aviation - 1984/02
Page Numbers: 40, 41, 130, 134, 135
ti7oIk vqbout wwq Brad Powers PROLOGUE In October issue arti cle consisted 20 questions airplane design As turns out got grade 90% missed P-factor result gave bad advice about propeller swing twin-engine designs During after WW 111939-1952 preliminary design engineer Con vair days P-factor unheard years later read brief de scription about flight manual simply dismissed simplistic explanation effects torque did appear aerodynamic texts aware nor old cohorts heard prob ably because days design ing large jet-powered aircraft P-factor consideration Since however engineer named Ribner NACA has shown P-factor valid notion after contributes ad ditionally yaw takeoff especially tail-draggers approaching stall does negate torque addition being true turns out propeller rotation acting down respect fuselage twin-engine designs preferable up out said will future article torque thus missed two own questions apologize readers giving wrong information thank politely pointed out error Lift Equation engineering pro fession certain hard criteria example electrical engineer expected least know Ohms Law expressed structural engineer should really familiar formula bending f same way aerodynamicist worth salt should have some awareness basic Lift Equation L Seriously though learn use equation can find answers sort problems follow will have understanding weight wing area speed etc interrelated some problems together answers end article will able check answers 1 Harry wants build Quarter Scale model will land slowly realistically about 25 mph figures will weigh 30 lb knows value CL 10 Information about lift coefficients use Lift Equa tion topics month Part 2 about best can expect What should wing area Answer 18 sq ft 2 Jim other hand interested speed Pylon Racer can fly CL 04 full power racer weighs five pounds has wing area 3125 sq ft fast will fly still air Answer 125 mph 3 Larry has designed airplane concerned about its weight wants land 25 mph less has wing area 6 sq ft has flaps allowing develop CL 15 much can airplane weigh Answer 144 lb 4 Gary intrigued MacCreadys Gos samer Condor wants build model having similar slow flight characteristics wants model cruise 15 mph CL 5 what should wing loading Answer 29 lb per sq ft about 46 oz per sq ft 5 If above problem Garys wing area 20 sq ft what must model weigh Answer 58 lb can seen achieve such slow flight model must very light indeed Perhaps Gary should contact MacCready about weightsaving featuressuch carbon-fiber spars etc 6 Assuming have adequate power wing area 6 sq ft weight 10 lb what speed will fly CL 3 CL 6 CL 9 Answers 3 ph 6 ph 9 27 mph 7 What angles attack speeds represent Answers 4 degrees 8 degrees 12 degrees 8 How much speed will gain per centage build new wing half U area weight remains same Answer 40% greater speed 9 As percentage what will doubling wing area speed no weight change Answer 70% fast 30% slower 10 reduce weight 20% what will landing speed Answer It will reduce landing speed 11% Fig 1 shows Lift Curve lift coefficient CL plotted against angle attack usually denoted Greek letter c alpha time time articles appear showing curves like rarely explained think readers havent faintest idea what lift coefficient perhaps should assume some least honestly curious about such things would like know about First lets rearrange equation put terms lift coefficient CL Doing becomes CLL q S Where CL pure number ratio L lift pounds q dynamic pressure pounds per square foot S for surface wing area square feet As fliers have learned lift af fected several things apply extra power increase speed airplane hut usually find ourselves applying control trim keep climbing too high So lift function airspeed land usually cut throttle increase angle attack maintain lift low speed Lift also function angle attack know given speed model large wing will develop lift small wing Lift function wing area cold dry weather takeoff runs gen erally shorter hot moist weather also shorter sea level Denver Mexico City Lift function air density Some thick highly-cambered airfoils de velop lift thin flat ones having same wing area use flaps will in40 Model Aviation qill El' crease lift wing considerably Lift function airfoil characteristics Other factors such altitude aspect ratio size also affect lift effects treated separately part Lift Equation itself Unless stated otherwise will assume models flown sea level have aspect ratios around 61 larger Quarter Scale dynamic pressure q pounds per square foot multiplied wing area square feet gives value total lift produced measure factors producing lift write saying CL CL qS Lift Factors Producing Lift lots lift needed CL must have large valuecorresponding high angle attack graph flaps high speeds angle attack small values CL low So can see CL might regarded percentage lift required given set conditions What dynamic pressure q about dynamic pressure depends both velocity air density Lets see can derive its value scaring anybody putting some sleep thing air has weight Thirteen cubic feet air weighs about pound volume air roughly size console TV set Since has weight air also has mass measure its inertia resistance acceleration Something heavy massive harder speed up accelerate something light airy Mass expressed W/gweight related acceleration due gravity 32 feet per second squared air has den sity 11n pound per cubic foot 076 pound per cubic foot has mass density 076/32or 002378 slugs per cubic foot slug unit mass order impart lift wing air must moving respect wing will have energy due motion energy called kinetic energy equal MV2or 002378 V 001 19V2 2 2 cubic foot air velocity V feet per second Since handier express velocity speed miles per hour rather feet per second multiply 1472 mile per hour 147 feet per second 001 19V2 becomes 00256V2 V2 391 value call q Thus lift equation expands read LCLqS CLV2S 391 20 18 16 14 12 10 6 4 2 FigI1ZZ17 I- ----7---------1-t- 4-II / 2 1Ctj7Q -K 1-- -----4-- # --- 4- 10 17/ --4----4~ I I7L V44. -.-4-4 - III - I- 1. .. 1- ----4- 1Iii -I14 .IUIULuIin --1i1I1i ~[it t { 111 J 0 4 8 12 16 20 oZ angle attack degrees level flight constant speed lift developed must equal weight lift exceeds weight airplane will climb weight exceeds lift airplane will descend equation lift equals weight L vel flight Now lets take equation rear range sequentially term 1 LiftL L V2 S 391 2Lift coefficient CL— 391 L V2 S 391W V2 S 3 Velocity V L — CLS 391 W CLS 4 Wing area 5391_L CLV2 CLV2 5 Wing loading W 2 5391 seen following rela tionships hold true 1 Lift varies directly CL wing area 5 varies square speed 2 lift coefficient CL varies versely square speed di rectly wing loading W/S 3 Speed velocity varies inversely square root CL directly square root wing loading 4 Wing area varies directly lift weight varies inversely square speed inversely CL 5 Wing loading W/S varies directly CL square speed Lets look Fig minute well check answers problems show two curves CL plotted against angle attack lower curve typical symmetrical airfoil angle zero lift zero angle attack upper curve shows lift developed wing Continued page 134 February 1984 41 related RC/WC will great help have several items three Rd WC events US plan send Bob have something youd like send him either mail Bob Skinner PO Box 31166 Braamfontein 2017 Johannesburg Republic South Africa send Ill see gets sounds like great project well worth support Ron Van Putte 111 Sleepy Oaks Rd Fort Walton Beach FL 32548 Design/Powers Continued naae 41 flap Since wing flap really same thing airfoil having very high J-5s DEEP SEA CRUISER Great sport boat just fun boating J-5s DEEP SEA CRUISER loves running 1 2 foot waves Speeds up 25-30 mph FULLSIZE PLANS Matched Sheets 42 3/32x4100 1/8x4108 3/16x4120 1/4x4131 36 NEW Basswood b Pine Sticks 114 Scale ALL SHEET ONE PIECE AAA GRADE KILN DRIED SANDED TO CLOSE TOLERANCES PED 100% 36Light 4-6lb361l8x3453/l6sq.173/8x11/2 33 1116x349 1116x448 lI4sq.26 1/2x2 40 3/32x356 3I32x456 114x31830 43 1I8x367 118x 466 3/8 sq.37 493116x37648 Sticks 561/4 x 385Add 40% 3l8x3115 37112x3139 44 54Balsa SheetsAa 621116x3 733I32x3 851/8x3 883/16x3 110114x3 1653t8x3 200l/2x3 581/16x4 703132x4 801/8x4 933/16x4 1101/4x4 1663/8x4 225 camber angle zero lift didnt show would shifted over left negative angle attack curve rises extending above the unflapped section Because Reynolds Number model wing can reach maximum CL value about 10 Flaps will increase about 15 other hand full-size wing can run up much higher lift coefficients Reynolds No R 0 x mph x chord feet model chord foot flying 50 mph operating Rey nolds No S00000indicated solid part curveswhile full-size airplane will operate values R way up millions depending size speed See Lets Talk About Reynolds Number February 1979 MA Suffice say low Reynolds Nos flow over wing breaks down readily wing stalls about 12 degrees depending 48 LOA x 181/2 beam x 11 deep Easy build mahogany plywood soft wood construction Designed tor hobby Quadra TML 35 gasoline engine Kit includes fullsize plan instructions $ 1795 46 70 BalsaTriangles 36 1/4x1/425 3/8x31830 1/2x1/235 3/453/445 lxi55 Lite Ply lilt n see flaps Harry will just get CL 10 Larry will get 15 using flaps Now lets check answers I We can find Harrys wing area using Equation 4 391W 391 x30 CLV210 x 25 x 25 1876 say 18 sq ft 2 Jims speed equation No 3 V391W CL found using 391x5 04 x 3125 12506 say 125 3 Larrys weight Equation No 1 WCLV2S l5x25x25x6 391 144 lb 4 From Equation 5 W — 5x15x15 5391 391 b per sq ft about 46 oz per sq ft W 5 If lb/sq ft S q ft W 20 58 lb 6V391W _391x10 CLS3x6 V21722 466 mph say 46 391x10 6 x 6 391 W CL S V 10861 mph say 33 391W391 x 10 CLS9x6 V 724 mph say 27 Continued page 138 134 Model Aviation RC Aerobatics/yen Puffs Continued Fmm ,nnn 131 6 aCCepi v1j88 PS Add *2 aspect ratio wing loading other factors KIT & DRIVE TRAIN $19350 J-5 ENTERPRISES KIT DRIVE TRAIN & ENGINE $32445 PO Box 82 Belmont Ontario NOL 180 Phone 1-519-644-0375 / IF YOU CAN BUILD KIT YOU CAN BUILD SCRAJCH-A-PLANE SCRATCH A-PLANE SION OF KEISER GRAPHICS U WI WI WHAT IS SCRATCH-A-PLANEiZ Professionally engineered designs accessories discriminating ler design tested top flight performance excellent parts fit Ij ease construction plans reproduced professionally inked mylars complete full size templates separate plans building instructions accessories heavy gauge plastic clean detail GUARANTEE IF YOU ARE NOT TOTALLY SATISFIED WITH PLANS EASE OF CONSTRUCTION AND QUALITY OF ACCESSORIES SHIP RACK TO US BY ZI RETURN MAIL FOR FuLl Rmrnin RIIV WITH CONFIDENCE!U -I U WI WI Ii ZI U I-I cc U WI WI SCALE CAP 21 CONSTRUCTION BALSA & LITE PLY Wing Span 80Wing Area 880 sq inWeight 15 lbs Engine 2 cubic inch Quadra Radio 4 Channel 5 Channel flaps Rolled Plan Pack $2495 Cowl canopy & wheelpants S3995 xl THIS CAP 21 15 DESIGNED TO BE BUILT PAST. THEN YOUR FUN JUST BEGINSI i CAPABLE OF ALL AEROBATIC MANEUVERS INCLUDING SQUARE LOOPS 8 POINT ROLLS i KNIFE EDGE LOOPS OUTSIDE SNAP ROLLS LOMCEVAKS AND INVERTED FLAT SPINS YET Icc ON TAKE OFFS NORMAL FLIGHTS AND LANDING SHES REAL PUSSY CATTI AEROBATICS ENDORSED BY WORLD FAMOUS AEROBATIC PILOT BOB SCHULTZ SCALE QUADRA POWER DESIGNSWI FOKKER DR-iWING SPAN 70WT 16 lbs WI FOKKER D VIIIWING SPAN 82WT 14 lbs z NIEUPORT 17WING SPAN 80WT 15 lbs cc ROLLED PLAN PACKS $2495COWLS $1195 la Cd 40 SIZE FOUR STROKE DESIGN de HAVILLAND LEOPARD MOTH WING SPAN 63 FLYING WT 6 lbs ROLLED PLAN PACK 31995COWL WHEELPANTS & CANOPY 314 5 ZI U 60 90 TWO STROKE DESIGN 1934 AVIA B534-IVBI-PLANE WING SPAN 62WING AREA 1140 sq inWT 9 lbs IU ROLLED PLAN PACK $2295COWL CANOPY & RADIATOR $1495 Gfli 4 1/4 SCALE VINTAGE FLOATSWI LENGTH 45MAX LOAD 30 lbs PLANS TEMPLATES & INSTRUCTIONS $895 ppd folded OR ORDER DIRESHIPPING CHARGE $300 COD ORDERS ACCEPTEDVISA & MASTtRCARD WELCOMtA 2080 ATHENS AVE REDDING CA 96001 -J 5-916241-4190 SCRATcH SRATH PIAjE SCRJTCH 138 Model Aviation Design/Powers Conhnued fmm flAflA 134 see V varies inversely square root ratio lift coef fiCients CL example CL 46 mpl 3 33mph 6 ratio 3 tc 6 re root 7 multiply 466 707 get 32 mph bothering solve other terms 7 We Can read answers directly Fig 8 in item 3 stated relation2 ships see speed varies directly square root wing loading W/S problem halving wing area doubling wing loading speed will increase factor equal square root 2 14 speed will 14 times greator 40% faster 9 Conversely doubling wing area cut wing loading W/S half speed will decrease factor equal square root 5 7 speed will 70% fastor 30% slower ever way wishes state 10 If reduce weight 80% its original value reducing wing loading W/S same proportion square root 80% 89% reducing safe landing speed 11% math wasnt com plicated mysterious future will try minimize math much possible some things difficult impossible express other way topic happens Anyway mathematics useful beautiful human accomplishment Without would back stone age wondering di vide three birds eggs among four people product review product review product review very accurate Cuts necessary youre building special new project TinyTools Tablesaw just ticket Ifs 1 2-volt powered tool thai gives full torque allow speeds 200 rpm speeds up 17000 rpm variable thrugh speed control transformer table saw slotted rip ping accommodates indexing mitre gauge up 45 can also used wet dry stained glass lapidary work product review product review product review 0 U U I. 0 4 4 U Id 5 0 z 4 U -4 0 U U 4 -J 5 U Id 0 U U Id U U 4 U 4 5 -J Id Id U Id 5 0 4 U TinyTools Tablesaw Byrom International Corp 117 South St. Box 246 Chardon OH 44024 tel 216/285-2341 Epilogue subject aerodynamics bit complex have tried make seem intention articles try expose reader subject rational light fashionyet giving some useful formulas relationships ex ample say CL 10 typical models quite true general way effects aspect ratio air foil selection etc can change some what some critics have loudly indicated such criticism must reply am trying take complicated subject put fairly simple terms can digested average reader hope discussion Lift Equation has interest want know about design Questions comments may ad dressed Brad Powers 5470 Castle Hills Dr San Diego CA 92109 RC Scale/Wischers Continued page 45 Light steel parts can brazed 23000 F flame either kind gas heavier metal such l/.in.diameter steel tube landing gears torch suitable use MAPP methyl acetylene pro padiene gas preferred Its flame tempera ture used appropriate torch such Master Mechanic Whirlwind $24 36000 F gas about three times expensive propane s2n3 New Standard Giant Models 28 HP Lbs Send $100 Catalog 149 Direct Sales Only PIns hippsg Work Horse rel7fl 96 IORITZ 2a4 32 HP 6A Lbs III Dealer Direct PIns sblppiq Now Distribute Sachs-Dolmar Engines Yeager Machines TO RUN INCLUDING 6 BOLT PROP HUB AVAILABLE AT EXTRA CHARGE Nm ___ ___ NGINERear 340w Cleveland Isve. SW EU EEECanton OH 44707I IC DIVISIONPhone 216484-6810 48443741 job finished time because intensely hot flame actual cost per joint remains about same /2-in -diameter 035-in -wall aircraft steel tube brought red heat ready brazing bronze rod about ten seconds out red heat steel brazed bronze rod brazing alloy will melt flow uniformly around joint Insufficient heat primary reason lack success brazing Whirlwind torch has pres sure adjustment permits its use propane butane gases lowertemperature brazing maximum joint strength brazing Continued page 142 VXPHONE 6194424838 -h/pates 469-8675 BOX 2498-MALA MESA CA 92041 1 Great Trainers Send $150 complete Kit Catalog p Midwest Products C. Inc 400 S Indiana St PO Box 564-T Hobart 46342 83 t03l February 1984 139 BL ILAP4 MAILABLE IN TWO 1/4 Scale 90 to2EngInes 1 60EngIne EOPWITH TABLOIDI/ASeal77 Span524OOppUSA EOPWlTI4 TABLOID2V —I64 Span$1BOOppUSA 016 TEXAN41101 Span$27tOppUSA POSKEB DRI27 I63 Trip$2SOOppUSA F4U COESAIB2 I93 Span$27tppUSA CUBTISS p402 I94 Span$27OOppUSA FM BEAECAT2 —196 Span$2700 ppUSA Fiberglass COwlingS & Canopies available Send Stamp detailed Brochures oar Giant Scale AccessarreS Forego Orders Please add 254 POstage & Handling Nick Ziroli 29 Edgar Drive Smlthtowfl NY 11787 USA Brazing heavy metals Use Whirlwind Torch L stank stabilized acetylene gas lighter work use Microfiame torch R butane oxidizer cylinders sliver solder C02 ENGINES WE NOW HAVE COMPLETE LINE OF BROWN TELCO DAVIS CO-2 ENGINES INCLUDING SPARE PARTS SERVICE IAOWNTEL LO A23 PEANUT $2996STANDARD TELCO$2400 CAMPUS BEE $2495TURBO 300092295 CAMPUS TWiN- $5995TURBO 800093900 SODACHARGER $1200 MVIS- COX 02 CONVERSION TO CO2$3900 NEWt C4T4LOG No 25 $150 Classic R/C Scale LAKES TH G4Qr Wing 15 25 Engines Dealers & Distributors Welcomed Phone 703 273-9593 FLYLINE MODELS INC PO Boa 2136 Pairfars VirginIa 22021 USA
Edition: Model Aviation - 1984/02
Page Numbers: 40, 41, 130, 134, 135
ti7oIk vqbout wwq Brad Powers PROLOGUE In October issue arti cle consisted 20 questions airplane design As turns out got grade 90% missed P-factor result gave bad advice about propeller swing twin-engine designs During after WW 111939-1952 preliminary design engineer Con vair days P-factor unheard years later read brief de scription about flight manual simply dismissed simplistic explanation effects torque did appear aerodynamic texts aware nor old cohorts heard prob ably because days design ing large jet-powered aircraft P-factor consideration Since however engineer named Ribner NACA has shown P-factor valid notion after contributes ad ditionally yaw takeoff especially tail-draggers approaching stall does negate torque addition being true turns out propeller rotation acting down respect fuselage twin-engine designs preferable up out said will future article torque thus missed two own questions apologize readers giving wrong information thank politely pointed out error Lift Equation engineering pro fession certain hard criteria example electrical engineer expected least know Ohms Law expressed structural engineer should really familiar formula bending f same way aerodynamicist worth salt should have some awareness basic Lift Equation L Seriously though learn use equation can find answers sort problems follow will have understanding weight wing area speed etc interrelated some problems together answers end article will able check answers 1 Harry wants build Quarter Scale model will land slowly realistically about 25 mph figures will weigh 30 lb knows value CL 10 Information about lift coefficients use Lift Equa tion topics month Part 2 about best can expect What should wing area Answer 18 sq ft 2 Jim other hand interested speed Pylon Racer can fly CL 04 full power racer weighs five pounds has wing area 3125 sq ft fast will fly still air Answer 125 mph 3 Larry has designed airplane concerned about its weight wants land 25 mph less has wing area 6 sq ft has flaps allowing develop CL 15 much can airplane weigh Answer 144 lb 4 Gary intrigued MacCreadys Gos samer Condor wants build model having similar slow flight characteristics wants model cruise 15 mph CL 5 what should wing loading Answer 29 lb per sq ft about 46 oz per sq ft 5 If above problem Garys wing area 20 sq ft what must model weigh Answer 58 lb can seen achieve such slow flight model must very light indeed Perhaps Gary should contact MacCready about weightsaving featuressuch carbon-fiber spars etc 6 Assuming have adequate power wing area 6 sq ft weight 10 lb what speed will fly CL 3 CL 6 CL 9 Answers 3 ph 6 ph 9 27 mph 7 What angles attack speeds represent Answers 4 degrees 8 degrees 12 degrees 8 How much speed will gain per centage build new wing half U area weight remains same Answer 40% greater speed 9 As percentage what will doubling wing area speed no weight change Answer 70% fast 30% slower 10 reduce weight 20% what will landing speed Answer It will reduce landing speed 11% Fig 1 shows Lift Curve lift coefficient CL plotted against angle attack usually denoted Greek letter c alpha time time articles appear showing curves like rarely explained think readers havent faintest idea what lift coefficient perhaps should assume some least honestly curious about such things would like know about First lets rearrange equation put terms lift coefficient CL Doing becomes CLL q S Where CL pure number ratio L lift pounds q dynamic pressure pounds per square foot S for surface wing area square feet As fliers have learned lift af fected several things apply extra power increase speed airplane hut usually find ourselves applying control trim keep climbing too high So lift function airspeed land usually cut throttle increase angle attack maintain lift low speed Lift also function angle attack know given speed model large wing will develop lift small wing Lift function wing area cold dry weather takeoff runs gen erally shorter hot moist weather also shorter sea level Denver Mexico City Lift function air density Some thick highly-cambered airfoils de velop lift thin flat ones having same wing area use flaps will in40 Model Aviation qill El' crease lift wing considerably Lift function airfoil characteristics Other factors such altitude aspect ratio size also affect lift effects treated separately part Lift Equation itself Unless stated otherwise will assume models flown sea level have aspect ratios around 61 larger Quarter Scale dynamic pressure q pounds per square foot multiplied wing area square feet gives value total lift produced measure factors producing lift write saying CL CL qS Lift Factors Producing Lift lots lift needed CL must have large valuecorresponding high angle attack graph flaps high speeds angle attack small values CL low So can see CL might regarded percentage lift required given set conditions What dynamic pressure q about dynamic pressure depends both velocity air density Lets see can derive its value scaring anybody putting some sleep thing air has weight Thirteen cubic feet air weighs about pound volume air roughly size console TV set Since has weight air also has mass measure its inertia resistance acceleration Something heavy massive harder speed up accelerate something light airy Mass expressed W/gweight related acceleration due gravity 32 feet per second squared air has den sity 11n pound per cubic foot 076 pound per cubic foot has mass density 076/32or 002378 slugs per cubic foot slug unit mass order impart lift wing air must moving respect wing will have energy due motion energy called kinetic energy equal MV2or 002378 V 001 19V2 2 2 cubic foot air velocity V feet per second Since handier express velocity speed miles per hour rather feet per second multiply 1472 mile per hour 147 feet per second 001 19V2 becomes 00256V2 V2 391 value call q Thus lift equation expands read LCLqS CLV2S 391 20 18 16 14 12 10 6 4 2 FigI1ZZ17 I- ----7---------1-t- 4-II / 2 1Ctj7Q -K 1-- -----4-- # --- 4- 10 17/ --4----4~ I I7L V44. -.-4-4 - III - I- 1. .. 1- ----4- 1Iii -I14 .IUIULuIin --1i1I1i ~[it t { 111 J 0 4 8 12 16 20 oZ angle attack degrees level flight constant speed lift developed must equal weight lift exceeds weight airplane will climb weight exceeds lift airplane will descend equation lift equals weight L vel flight Now lets take equation rear range sequentially term 1 LiftL L V2 S 391 2Lift coefficient CL— 391 L V2 S 391W V2 S 3 Velocity V L — CLS 391 W CLS 4 Wing area 5391_L CLV2 CLV2 5 Wing loading W 2 5391 seen following rela tionships hold true 1 Lift varies directly CL wing area 5 varies square speed 2 lift coefficient CL varies versely square speed di rectly wing loading W/S 3 Speed velocity varies inversely square root CL directly square root wing loading 4 Wing area varies directly lift weight varies inversely square speed inversely CL 5 Wing loading W/S varies directly CL square speed Lets look Fig minute well check answers problems show two curves CL plotted against angle attack lower curve typical symmetrical airfoil angle zero lift zero angle attack upper curve shows lift developed wing Continued page 134 February 1984 41 related RC/WC will great help have several items three Rd WC events US plan send Bob have something youd like send him either mail Bob Skinner PO Box 31166 Braamfontein 2017 Johannesburg Republic South Africa send Ill see gets sounds like great project well worth support Ron Van Putte 111 Sleepy Oaks Rd Fort Walton Beach FL 32548 Design/Powers Continued naae 41 flap Since wing flap really same thing airfoil having very high J-5s DEEP SEA CRUISER Great sport boat just fun boating J-5s DEEP SEA CRUISER loves running 1 2 foot waves Speeds up 25-30 mph FULLSIZE PLANS Matched Sheets 42 3/32x4100 1/8x4108 3/16x4120 1/4x4131 36 NEW Basswood b Pine Sticks 114 Scale ALL SHEET ONE PIECE AAA GRADE KILN DRIED SANDED TO CLOSE TOLERANCES PED 100% 36Light 4-6lb361l8x3453/l6sq.173/8x11/2 33 1116x349 1116x448 lI4sq.26 1/2x2 40 3/32x356 3I32x456 114x31830 43 1I8x367 118x 466 3/8 sq.37 493116x37648 Sticks 561/4 x 385Add 40% 3l8x3115 37112x3139 44 54Balsa SheetsAa 621116x3 733I32x3 851/8x3 883/16x3 110114x3 1653t8x3 200l/2x3 581/16x4 703132x4 801/8x4 933/16x4 1101/4x4 1663/8x4 225 camber angle zero lift didnt show would shifted over left negative angle attack curve rises extending above the unflapped section Because Reynolds Number model wing can reach maximum CL value about 10 Flaps will increase about 15 other hand full-size wing can run up much higher lift coefficients Reynolds No R 0 x mph x chord feet model chord foot flying 50 mph operating Rey nolds No S00000indicated solid part curveswhile full-size airplane will operate values R way up millions depending size speed See Lets Talk About Reynolds Number February 1979 MA Suffice say low Reynolds Nos flow over wing breaks down readily wing stalls about 12 degrees depending 48 LOA x 181/2 beam x 11 deep Easy build mahogany plywood soft wood construction Designed tor hobby Quadra TML 35 gasoline engine Kit includes fullsize plan instructions $ 1795 46 70 BalsaTriangles 36 1/4x1/425 3/8x31830 1/2x1/235 3/453/445 lxi55 Lite Ply lilt n see flaps Harry will just get CL 10 Larry will get 15 using flaps Now lets check answers I We can find Harrys wing area using Equation 4 391W 391 x30 CLV210 x 25 x 25 1876 say 18 sq ft 2 Jims speed equation No 3 V391W CL found using 391x5 04 x 3125 12506 say 125 3 Larrys weight Equation No 1 WCLV2S l5x25x25x6 391 144 lb 4 From Equation 5 W — 5x15x15 5391 391 b per sq ft about 46 oz per sq ft W 5 If lb/sq ft S q ft W 20 58 lb 6V391W _391x10 CLS3x6 V21722 466 mph say 46 391x10 6 x 6 391 W CL S V 10861 mph say 33 391W391 x 10 CLS9x6 V 724 mph say 27 Continued page 138 134 Model Aviation RC Aerobatics/yen Puffs Continued Fmm ,nnn 131 6 aCCepi v1j88 PS Add *2 aspect ratio wing loading other factors KIT & DRIVE TRAIN $19350 J-5 ENTERPRISES KIT DRIVE TRAIN & ENGINE $32445 PO Box 82 Belmont Ontario NOL 180 Phone 1-519-644-0375 / IF YOU CAN BUILD KIT YOU CAN BUILD SCRAJCH-A-PLANE SCRATCH A-PLANE SION OF KEISER GRAPHICS U WI WI WHAT IS SCRATCH-A-PLANEiZ Professionally engineered designs accessories discriminating ler design tested top flight performance excellent parts fit Ij ease construction plans reproduced professionally inked mylars complete full size templates separate plans building instructions accessories heavy gauge plastic clean detail GUARANTEE IF YOU ARE NOT TOTALLY SATISFIED WITH PLANS EASE OF CONSTRUCTION AND QUALITY OF ACCESSORIES SHIP RACK TO US BY ZI RETURN MAIL FOR FuLl Rmrnin RIIV WITH CONFIDENCE!U -I U WI WI Ii ZI U I-I cc U WI WI SCALE CAP 21 CONSTRUCTION BALSA & LITE PLY Wing Span 80Wing Area 880 sq inWeight 15 lbs Engine 2 cubic inch Quadra Radio 4 Channel 5 Channel flaps Rolled Plan Pack $2495 Cowl canopy & wheelpants S3995 xl THIS CAP 21 15 DESIGNED TO BE BUILT PAST. THEN YOUR FUN JUST BEGINSI i CAPABLE OF ALL AEROBATIC MANEUVERS INCLUDING SQUARE LOOPS 8 POINT ROLLS i KNIFE EDGE LOOPS OUTSIDE SNAP ROLLS LOMCEVAKS AND INVERTED FLAT SPINS YET Icc ON TAKE OFFS NORMAL FLIGHTS AND LANDING SHES REAL PUSSY CATTI AEROBATICS ENDORSED BY WORLD FAMOUS AEROBATIC PILOT BOB SCHULTZ SCALE QUADRA POWER DESIGNSWI FOKKER DR-iWING SPAN 70WT 16 lbs WI FOKKER D VIIIWING SPAN 82WT 14 lbs z NIEUPORT 17WING SPAN 80WT 15 lbs cc ROLLED PLAN PACKS $2495COWLS $1195 la Cd 40 SIZE FOUR STROKE DESIGN de HAVILLAND LEOPARD MOTH WING SPAN 63 FLYING WT 6 lbs ROLLED PLAN PACK 31995COWL WHEELPANTS & CANOPY 314 5 ZI U 60 90 TWO STROKE DESIGN 1934 AVIA B534-IVBI-PLANE WING SPAN 62WING AREA 1140 sq inWT 9 lbs IU ROLLED PLAN PACK $2295COWL CANOPY & RADIATOR $1495 Gfli 4 1/4 SCALE VINTAGE FLOATSWI LENGTH 45MAX LOAD 30 lbs PLANS TEMPLATES & INSTRUCTIONS $895 ppd folded OR ORDER DIRESHIPPING CHARGE $300 COD ORDERS ACCEPTEDVISA & MASTtRCARD WELCOMtA 2080 ATHENS AVE REDDING CA 96001 -J 5-916241-4190 SCRATcH SRATH PIAjE SCRJTCH 138 Model Aviation Design/Powers Conhnued fmm flAflA 134 see V varies inversely square root ratio lift coef fiCients CL example CL 46 mpl 3 33mph 6 ratio 3 tc 6 re root 7 multiply 466 707 get 32 mph bothering solve other terms 7 We Can read answers directly Fig 8 in item 3 stated relation2 ships see speed varies directly square root wing loading W/S problem halving wing area doubling wing loading speed will increase factor equal square root 2 14 speed will 14 times greator 40% faster 9 Conversely doubling wing area cut wing loading W/S half speed will decrease factor equal square root 5 7 speed will 70% fastor 30% slower ever way wishes state 10 If reduce weight 80% its original value reducing wing loading W/S same proportion square root 80% 89% reducing safe landing speed 11% math wasnt com plicated mysterious future will try minimize math much possible some things difficult impossible express other way topic happens Anyway mathematics useful beautiful human accomplishment Without would back stone age wondering di vide three birds eggs among four people product review product review product review very accurate Cuts necessary youre building special new project TinyTools Tablesaw just ticket Ifs 1 2-volt powered tool thai gives full torque allow speeds 200 rpm speeds up 17000 rpm variable thrugh speed control transformer table saw slotted rip ping accommodates indexing mitre gauge up 45 can also used wet dry stained glass lapidary work product review product review product review 0 U U I. 0 4 4 U Id 5 0 z 4 U -4 0 U U 4 -J 5 U Id 0 U U Id U U 4 U 4 5 -J Id Id U Id 5 0 4 U TinyTools Tablesaw Byrom International Corp 117 South St. Box 246 Chardon OH 44024 tel 216/285-2341 Epilogue subject aerodynamics bit complex have tried make seem intention articles try expose reader subject rational light fashionyet giving some useful formulas relationships ex ample say CL 10 typical models quite true general way effects aspect ratio air foil selection etc can change some what some critics have loudly indicated such criticism must reply am trying take complicated subject put fairly simple terms can digested average reader hope discussion Lift Equation has interest want know about design Questions comments may ad dressed Brad Powers 5470 Castle Hills Dr San Diego CA 92109 RC Scale/Wischers Continued page 45 Light steel parts can brazed 23000 F flame either kind gas heavier metal such l/.in.diameter steel tube landing gears torch suitable use MAPP methyl acetylene pro padiene gas preferred Its flame tempera ture used appropriate torch such Master Mechanic Whirlwind $24 36000 F gas about three times expensive propane s2n3 New Standard Giant Models 28 HP Lbs Send $100 Catalog 149 Direct Sales Only PIns hippsg Work Horse rel7fl 96 IORITZ 2a4 32 HP 6A Lbs III Dealer Direct PIns sblppiq Now Distribute Sachs-Dolmar Engines Yeager Machines TO RUN INCLUDING 6 BOLT PROP HUB AVAILABLE AT EXTRA CHARGE Nm ___ ___ NGINERear 340w Cleveland Isve. SW EU EEECanton OH 44707I IC DIVISIONPhone 216484-6810 48443741 job finished time because intensely hot flame actual cost per joint remains about same /2-in -diameter 035-in -wall aircraft steel tube brought red heat ready brazing bronze rod about ten seconds out red heat steel brazed bronze rod brazing alloy will melt flow uniformly around joint Insufficient heat primary reason lack success brazing Whirlwind torch has pres sure adjustment permits its use propane butane gases lowertemperature brazing maximum joint strength brazing Continued page 142 VXPHONE 6194424838 -h/pates 469-8675 BOX 2498-MALA MESA CA 92041 1 Great Trainers Send $150 complete Kit Catalog p Midwest Products C. Inc 400 S Indiana St PO Box 564-T Hobart 46342 83 t03l February 1984 139 BL ILAP4 MAILABLE IN TWO 1/4 Scale 90 to2EngInes 1 60EngIne EOPWITH TABLOIDI/ASeal77 Span524OOppUSA EOPWlTI4 TABLOID2V —I64 Span$1BOOppUSA 016 TEXAN41101 Span$27tOppUSA POSKEB DRI27 I63 Trip$2SOOppUSA F4U COESAIB2 I93 Span$27tppUSA CUBTISS p402 I94 Span$27OOppUSA FM BEAECAT2 —196 Span$2700 ppUSA Fiberglass COwlingS & Canopies available Send Stamp detailed Brochures oar Giant Scale AccessarreS Forego Orders Please add 254 POstage & Handling Nick Ziroli 29 Edgar Drive Smlthtowfl NY 11787 USA Brazing heavy metals Use Whirlwind Torch L stank stabilized acetylene gas lighter work use Microfiame torch R butane oxidizer cylinders sliver solder C02 ENGINES WE NOW HAVE COMPLETE LINE OF BROWN TELCO DAVIS CO-2 ENGINES INCLUDING SPARE PARTS SERVICE IAOWNTEL LO A23 PEANUT $2996STANDARD TELCO$2400 CAMPUS BEE $2495TURBO 300092295 CAMPUS TWiN- $5995TURBO 800093900 SODACHARGER $1200 MVIS- COX 02 CONVERSION TO CO2$3900 NEWt C4T4LOG No 25 $150 Classic R/C Scale LAKES TH G4Qr Wing 15 25 Engines Dealers & Distributors Welcomed Phone 703 273-9593 FLYLINE MODELS INC PO Boa 2136 Pairfars VirginIa 22021 USA
Edition: Model Aviation - 1984/02
Page Numbers: 40, 41, 130, 134, 135
ti7oIk vqbout wwq Brad Powers PROLOGUE In October issue arti cle consisted 20 questions airplane design As turns out got grade 90% missed P-factor result gave bad advice about propeller swing twin-engine designs During after WW 111939-1952 preliminary design engineer Con vair days P-factor unheard years later read brief de scription about flight manual simply dismissed simplistic explanation effects torque did appear aerodynamic texts aware nor old cohorts heard prob ably because days design ing large jet-powered aircraft P-factor consideration Since however engineer named Ribner NACA has shown P-factor valid notion after contributes ad ditionally yaw takeoff especially tail-draggers approaching stall does negate torque addition being true turns out propeller rotation acting down respect fuselage twin-engine designs preferable up out said will future article torque thus missed two own questions apologize readers giving wrong information thank politely pointed out error Lift Equation engineering pro fession certain hard criteria example electrical engineer expected least know Ohms Law expressed structural engineer should really familiar formula bending f same way aerodynamicist worth salt should have some awareness basic Lift Equation L Seriously though learn use equation can find answers sort problems follow will have understanding weight wing area speed etc interrelated some problems together answers end article will able check answers 1 Harry wants build Quarter Scale model will land slowly realistically about 25 mph figures will weigh 30 lb knows value CL 10 Information about lift coefficients use Lift Equa tion topics month Part 2 about best can expect What should wing area Answer 18 sq ft 2 Jim other hand interested speed Pylon Racer can fly CL 04 full power racer weighs five pounds has wing area 3125 sq ft fast will fly still air Answer 125 mph 3 Larry has designed airplane concerned about its weight wants land 25 mph less has wing area 6 sq ft has flaps allowing develop CL 15 much can airplane weigh Answer 144 lb 4 Gary intrigued MacCreadys Gos samer Condor wants build model having similar slow flight characteristics wants model cruise 15 mph CL 5 what should wing loading Answer 29 lb per sq ft about 46 oz per sq ft 5 If above problem Garys wing area 20 sq ft what must model weigh Answer 58 lb can seen achieve such slow flight model must very light indeed Perhaps Gary should contact MacCready about weightsaving featuressuch carbon-fiber spars etc 6 Assuming have adequate power wing area 6 sq ft weight 10 lb what speed will fly CL 3 CL 6 CL 9 Answers 3 ph 6 ph 9 27 mph 7 What angles attack speeds represent Answers 4 degrees 8 degrees 12 degrees 8 How much speed will gain per centage build new wing half U area weight remains same Answer 40% greater speed 9 As percentage what will doubling wing area speed no weight change Answer 70% fast 30% slower 10 reduce weight 20% what will landing speed Answer It will reduce landing speed 11% Fig 1 shows Lift Curve lift coefficient CL plotted against angle attack usually denoted Greek letter c alpha time time articles appear showing curves like rarely explained think readers havent faintest idea what lift coefficient perhaps should assume some least honestly curious about such things would like know about First lets rearrange equation put terms lift coefficient CL Doing becomes CLL q S Where CL pure number ratio L lift pounds q dynamic pressure pounds per square foot S for surface wing area square feet As fliers have learned lift af fected several things apply extra power increase speed airplane hut usually find ourselves applying control trim keep climbing too high So lift function airspeed land usually cut throttle increase angle attack maintain lift low speed Lift also function angle attack know given speed model large wing will develop lift small wing Lift function wing area cold dry weather takeoff runs gen erally shorter hot moist weather also shorter sea level Denver Mexico City Lift function air density Some thick highly-cambered airfoils de velop lift thin flat ones having same wing area use flaps will in40 Model Aviation qill El' crease lift wing considerably Lift function airfoil characteristics Other factors such altitude aspect ratio size also affect lift effects treated separately part Lift Equation itself Unless stated otherwise will assume models flown sea level have aspect ratios around 61 larger Quarter Scale dynamic pressure q pounds per square foot multiplied wing area square feet gives value total lift produced measure factors producing lift write saying CL CL qS Lift Factors Producing Lift lots lift needed CL must have large valuecorresponding high angle attack graph flaps high speeds angle attack small values CL low So can see CL might regarded percentage lift required given set conditions What dynamic pressure q about dynamic pressure depends both velocity air density Lets see can derive its value scaring anybody putting some sleep thing air has weight Thirteen cubic feet air weighs about pound volume air roughly size console TV set Since has weight air also has mass measure its inertia resistance acceleration Something heavy massive harder speed up accelerate something light airy Mass expressed W/gweight related acceleration due gravity 32 feet per second squared air has den sity 11n pound per cubic foot 076 pound per cubic foot has mass density 076/32or 002378 slugs per cubic foot slug unit mass order impart lift wing air must moving respect wing will have energy due motion energy called kinetic energy equal MV2or 002378 V 001 19V2 2 2 cubic foot air velocity V feet per second Since handier express velocity speed miles per hour rather feet per second multiply 1472 mile per hour 147 feet per second 001 19V2 becomes 00256V2 V2 391 value call q Thus lift equation expands read LCLqS CLV2S 391 20 18 16 14 12 10 6 4 2 FigI1ZZ17 I- ----7---------1-t- 4-II / 2 1Ctj7Q -K 1-- -----4-- # --- 4- 10 17/ --4----4~ I I7L V44. -.-4-4 - III - I- 1. .. 1- ----4- 1Iii -I14 .IUIULuIin --1i1I1i ~[it t { 111 J 0 4 8 12 16 20 oZ angle attack degrees level flight constant speed lift developed must equal weight lift exceeds weight airplane will climb weight exceeds lift airplane will descend equation lift equals weight L vel flight Now lets take equation rear range sequentially term 1 LiftL L V2 S 391 2Lift coefficient CL— 391 L V2 S 391W V2 S 3 Velocity V L — CLS 391 W CLS 4 Wing area 5391_L CLV2 CLV2 5 Wing loading W 2 5391 seen following rela tionships hold true 1 Lift varies directly CL wing area 5 varies square speed 2 lift coefficient CL varies versely square speed di rectly wing loading W/S 3 Speed velocity varies inversely square root CL directly square root wing loading 4 Wing area varies directly lift weight varies inversely square speed inversely CL 5 Wing loading W/S varies directly CL square speed Lets look Fig minute well check answers problems show two curves CL plotted against angle attack lower curve typical symmetrical airfoil angle zero lift zero angle attack upper curve shows lift developed wing Continued page 134 February 1984 41 related RC/WC will great help have several items three Rd WC events US plan send Bob have something youd like send him either mail Bob Skinner PO Box 31166 Braamfontein 2017 Johannesburg Republic South Africa send Ill see gets sounds like great project well worth support Ron Van Putte 111 Sleepy Oaks Rd Fort Walton Beach FL 32548 Design/Powers Continued naae 41 flap Since wing flap really same thing airfoil having very high J-5s DEEP SEA CRUISER Great sport boat just fun boating J-5s DEEP SEA CRUISER loves running 1 2 foot waves Speeds up 25-30 mph FULLSIZE PLANS Matched Sheets 42 3/32x4100 1/8x4108 3/16x4120 1/4x4131 36 NEW Basswood b Pine Sticks 114 Scale ALL SHEET ONE PIECE AAA GRADE KILN DRIED SANDED TO CLOSE TOLERANCES PED 100% 36Light 4-6lb361l8x3453/l6sq.173/8x11/2 33 1116x349 1116x448 lI4sq.26 1/2x2 40 3/32x356 3I32x456 114x31830 43 1I8x367 118x 466 3/8 sq.37 493116x37648 Sticks 561/4 x 385Add 40% 3l8x3115 37112x3139 44 54Balsa SheetsAa 621116x3 733I32x3 851/8x3 883/16x3 110114x3 1653t8x3 200l/2x3 581/16x4 703132x4 801/8x4 933/16x4 1101/4x4 1663/8x4 225 camber angle zero lift didnt show would shifted over left negative angle attack curve rises extending above the unflapped section Because Reynolds Number model wing can reach maximum CL value about 10 Flaps will increase about 15 other hand full-size wing can run up much higher lift coefficients Reynolds No R 0 x mph x chord feet model chord foot flying 50 mph operating Rey nolds No S00000indicated solid part curveswhile full-size airplane will operate values R way up millions depending size speed See Lets Talk About Reynolds Number February 1979 MA Suffice say low Reynolds Nos flow over wing breaks down readily wing stalls about 12 degrees depending 48 LOA x 181/2 beam x 11 deep Easy build mahogany plywood soft wood construction Designed tor hobby Quadra TML 35 gasoline engine Kit includes fullsize plan instructions $ 1795 46 70 BalsaTriangles 36 1/4x1/425 3/8x31830 1/2x1/235 3/453/445 lxi55 Lite Ply lilt n see flaps Harry will just get CL 10 Larry will get 15 using flaps Now lets check answers I We can find Harrys wing area using Equation 4 391W 391 x30 CLV210 x 25 x 25 1876 say 18 sq ft 2 Jims speed equation No 3 V391W CL found using 391x5 04 x 3125 12506 say 125 3 Larrys weight Equation No 1 WCLV2S l5x25x25x6 391 144 lb 4 From Equation 5 W — 5x15x15 5391 391 b per sq ft about 46 oz per sq ft W 5 If lb/sq ft S q ft W 20 58 lb 6V391W _391x10 CLS3x6 V21722 466 mph say 46 391x10 6 x 6 391 W CL S V 10861 mph say 33 391W391 x 10 CLS9x6 V 724 mph say 27 Continued page 138 134 Model Aviation RC Aerobatics/yen Puffs Continued Fmm ,nnn 131 6 aCCepi v1j88 PS Add *2 aspect ratio wing loading other factors KIT & DRIVE TRAIN $19350 J-5 ENTERPRISES KIT DRIVE TRAIN & ENGINE $32445 PO Box 82 Belmont Ontario NOL 180 Phone 1-519-644-0375 / IF YOU CAN BUILD KIT YOU CAN BUILD SCRAJCH-A-PLANE SCRATCH A-PLANE SION OF KEISER GRAPHICS U WI WI WHAT IS SCRATCH-A-PLANEiZ Professionally engineered designs accessories discriminating ler design tested top flight performance excellent parts fit Ij ease construction plans reproduced professionally inked mylars complete full size templates separate plans building instructions accessories heavy gauge plastic clean detail GUARANTEE IF YOU ARE NOT TOTALLY SATISFIED WITH PLANS EASE OF CONSTRUCTION AND QUALITY OF ACCESSORIES SHIP RACK TO US BY ZI RETURN MAIL FOR FuLl Rmrnin RIIV WITH CONFIDENCE!U -I U WI WI Ii ZI U I-I cc U WI WI SCALE CAP 21 CONSTRUCTION BALSA & LITE PLY Wing Span 80Wing Area 880 sq inWeight 15 lbs Engine 2 cubic inch Quadra Radio 4 Channel 5 Channel flaps Rolled Plan Pack $2495 Cowl canopy & wheelpants S3995 xl THIS CAP 21 15 DESIGNED TO BE BUILT PAST. THEN YOUR FUN JUST BEGINSI i CAPABLE OF ALL AEROBATIC MANEUVERS INCLUDING SQUARE LOOPS 8 POINT ROLLS i KNIFE EDGE LOOPS OUTSIDE SNAP ROLLS LOMCEVAKS AND INVERTED FLAT SPINS YET Icc ON TAKE OFFS NORMAL FLIGHTS AND LANDING SHES REAL PUSSY CATTI AEROBATICS ENDORSED BY WORLD FAMOUS AEROBATIC PILOT BOB SCHULTZ SCALE QUADRA POWER DESIGNSWI FOKKER DR-iWING SPAN 70WT 16 lbs WI FOKKER D VIIIWING SPAN 82WT 14 lbs z NIEUPORT 17WING SPAN 80WT 15 lbs cc ROLLED PLAN PACKS $2495COWLS $1195 la Cd 40 SIZE FOUR STROKE DESIGN de HAVILLAND LEOPARD MOTH WING SPAN 63 FLYING WT 6 lbs ROLLED PLAN PACK 31995COWL WHEELPANTS & CANOPY 314 5 ZI U 60 90 TWO STROKE DESIGN 1934 AVIA B534-IVBI-PLANE WING SPAN 62WING AREA 1140 sq inWT 9 lbs IU ROLLED PLAN PACK $2295COWL CANOPY & RADIATOR $1495 Gfli 4 1/4 SCALE VINTAGE FLOATSWI LENGTH 45MAX LOAD 30 lbs PLANS TEMPLATES & INSTRUCTIONS $895 ppd folded OR ORDER DIRESHIPPING CHARGE $300 COD ORDERS ACCEPTEDVISA & MASTtRCARD WELCOMtA 2080 ATHENS AVE REDDING CA 96001 -J 5-916241-4190 SCRATcH SRATH PIAjE SCRJTCH 138 Model Aviation Design/Powers Conhnued fmm flAflA 134 see V varies inversely square root ratio lift coef fiCients CL example CL 46 mpl 3 33mph 6 ratio 3 tc 6 re root 7 multiply 466 707 get 32 mph bothering solve other terms 7 We Can read answers directly Fig 8 in item 3 stated relation2 ships see speed varies directly square root wing loading W/S problem halving wing area doubling wing loading speed will increase factor equal square root 2 14 speed will 14 times greator 40% faster 9 Conversely doubling wing area cut wing loading W/S half speed will decrease factor equal square root 5 7 speed will 70% fastor 30% slower ever way wishes state 10 If reduce weight 80% its original value reducing wing loading W/S same proportion square root 80% 89% reducing safe landing speed 11% math wasnt com plicated mysterious future will try minimize math much possible some things difficult impossible express other way topic happens Anyway mathematics useful beautiful human accomplishment Without would back stone age wondering di vide three birds eggs among four people product review product review product review very accurate Cuts necessary youre building special new project TinyTools Tablesaw just ticket Ifs 1 2-volt powered tool thai gives full torque allow speeds 200 rpm speeds up 17000 rpm variable thrugh speed control transformer table saw slotted rip ping accommodates indexing mitre gauge up 45 can also used wet dry stained glass lapidary work product review product review product review 0 U U I. 0 4 4 U Id 5 0 z 4 U -4 0 U U 4 -J 5 U Id 0 U U Id U U 4 U 4 5 -J Id Id U Id 5 0 4 U TinyTools Tablesaw Byrom International Corp 117 South St. Box 246 Chardon OH 44024 tel 216/285-2341 Epilogue subject aerodynamics bit complex have tried make seem intention articles try expose reader subject rational light fashionyet giving some useful formulas relationships ex ample say CL 10 typical models quite true general way effects aspect ratio air foil selection etc can change some what some critics have loudly indicated such criticism must reply am trying take complicated subject put fairly simple terms can digested average reader hope discussion Lift Equation has interest want know about design Questions comments may ad dressed Brad Powers 5470 Castle Hills Dr San Diego CA 92109 RC Scale/Wischers Continued page 45 Light steel parts can brazed 23000 F flame either kind gas heavier metal such l/.in.diameter steel tube landing gears torch suitable use MAPP methyl acetylene pro padiene gas preferred Its flame tempera ture used appropriate torch such Master Mechanic Whirlwind $24 36000 F gas about three times expensive propane s2n3 New Standard Giant Models 28 HP Lbs Send $100 Catalog 149 Direct Sales Only PIns hippsg Work Horse rel7fl 96 IORITZ 2a4 32 HP 6A Lbs III Dealer Direct PIns sblppiq Now Distribute Sachs-Dolmar Engines Yeager Machines TO RUN INCLUDING 6 BOLT PROP HUB AVAILABLE AT EXTRA CHARGE Nm ___ ___ NGINERear 340w Cleveland Isve. SW EU EEECanton OH 44707I IC DIVISIONPhone 216484-6810 48443741 job finished time because intensely hot flame actual cost per joint remains about same /2-in -diameter 035-in -wall aircraft steel tube brought red heat ready brazing bronze rod about ten seconds out red heat steel brazed bronze rod brazing alloy will melt flow uniformly around joint Insufficient heat primary reason lack success brazing Whirlwind torch has pres sure adjustment permits its use propane butane gases lowertemperature brazing maximum joint strength brazing Continued page 142 VXPHONE 6194424838 -h/pates 469-8675 BOX 2498-MALA MESA CA 92041 1 Great Trainers Send $150 complete Kit Catalog p Midwest Products C. Inc 400 S Indiana St PO Box 564-T Hobart 46342 83 t03l February 1984 139 BL ILAP4 MAILABLE IN TWO 1/4 Scale 90 to2EngInes 1 60EngIne EOPWITH TABLOIDI/ASeal77 Span524OOppUSA EOPWlTI4 TABLOID2V —I64 Span$1BOOppUSA 016 TEXAN41101 Span$27tOppUSA POSKEB DRI27 I63 Trip$2SOOppUSA F4U COESAIB2 I93 Span$27tppUSA CUBTISS p402 I94 Span$27OOppUSA FM BEAECAT2 —196 Span$2700 ppUSA Fiberglass COwlingS & Canopies available Send Stamp detailed Brochures oar Giant Scale AccessarreS Forego Orders Please add 254 POstage & Handling Nick Ziroli 29 Edgar Drive Smlthtowfl NY 11787 USA Brazing heavy metals Use Whirlwind Torch L stank stabilized acetylene gas lighter work use Microfiame torch R butane oxidizer cylinders sliver solder C02 ENGINES WE NOW HAVE COMPLETE LINE OF BROWN TELCO DAVIS CO-2 ENGINES INCLUDING SPARE PARTS SERVICE IAOWNTEL LO A23 PEANUT $2996STANDARD TELCO$2400 CAMPUS BEE $2495TURBO 300092295 CAMPUS TWiN- $5995TURBO 800093900 SODACHARGER $1200 MVIS- COX 02 CONVERSION TO CO2$3900 NEWt C4T4LOG No 25 $150 Classic R/C Scale LAKES TH G4Qr Wing 15 25 Engines Dealers & Distributors Welcomed Phone 703 273-9593 FLYLINE MODELS INC PO Boa 2136 Pairfars VirginIa 22021 USA
Edition: Model Aviation - 1984/02
Page Numbers: 40, 41, 130, 134, 135
ti7oIk vqbout wwq Brad Powers PROLOGUE In October issue arti cle consisted 20 questions airplane design As turns out got grade 90% missed P-factor result gave bad advice about propeller swing twin-engine designs During after WW 111939-1952 preliminary design engineer Con vair days P-factor unheard years later read brief de scription about flight manual simply dismissed simplistic explanation effects torque did appear aerodynamic texts aware nor old cohorts heard prob ably because days design ing large jet-powered aircraft P-factor consideration Since however engineer named Ribner NACA has shown P-factor valid notion after contributes ad ditionally yaw takeoff especially tail-draggers approaching stall does negate torque addition being true turns out propeller rotation acting down respect fuselage twin-engine designs preferable up out said will future article torque thus missed two own questions apologize readers giving wrong information thank politely pointed out error Lift Equation engineering pro fession certain hard criteria example electrical engineer expected least know Ohms Law expressed structural engineer should really familiar formula bending f same way aerodynamicist worth salt should have some awareness basic Lift Equation L Seriously though learn use equation can find answers sort problems follow will have understanding weight wing area speed etc interrelated some problems together answers end article will able check answers 1 Harry wants build Quarter Scale model will land slowly realistically about 25 mph figures will weigh 30 lb knows value CL 10 Information about lift coefficients use Lift Equa tion topics month Part 2 about best can expect What should wing area Answer 18 sq ft 2 Jim other hand interested speed Pylon Racer can fly CL 04 full power racer weighs five pounds has wing area 3125 sq ft fast will fly still air Answer 125 mph 3 Larry has designed airplane concerned about its weight wants land 25 mph less has wing area 6 sq ft has flaps allowing develop CL 15 much can airplane weigh Answer 144 lb 4 Gary intrigued MacCreadys Gos samer Condor wants build model having similar slow flight characteristics wants model cruise 15 mph CL 5 what should wing loading Answer 29 lb per sq ft about 46 oz per sq ft 5 If above problem Garys wing area 20 sq ft what must model weigh Answer 58 lb can seen achieve such slow flight model must very light indeed Perhaps Gary should contact MacCready about weightsaving featuressuch carbon-fiber spars etc 6 Assuming have adequate power wing area 6 sq ft weight 10 lb what speed will fly CL 3 CL 6 CL 9 Answers 3 ph 6 ph 9 27 mph 7 What angles attack speeds represent Answers 4 degrees 8 degrees 12 degrees 8 How much speed will gain per centage build new wing half U area weight remains same Answer 40% greater speed 9 As percentage what will doubling wing area speed no weight change Answer 70% fast 30% slower 10 reduce weight 20% what will landing speed Answer It will reduce landing speed 11% Fig 1 shows Lift Curve lift coefficient CL plotted against angle attack usually denoted Greek letter c alpha time time articles appear showing curves like rarely explained think readers havent faintest idea what lift coefficient perhaps should assume some least honestly curious about such things would like know about First lets rearrange equation put terms lift coefficient CL Doing becomes CLL q S Where CL pure number ratio L lift pounds q dynamic pressure pounds per square foot S for surface wing area square feet As fliers have learned lift af fected several things apply extra power increase speed airplane hut usually find ourselves applying control trim keep climbing too high So lift function airspeed land usually cut throttle increase angle attack maintain lift low speed Lift also function angle attack know given speed model large wing will develop lift small wing Lift function wing area cold dry weather takeoff runs gen erally shorter hot moist weather also shorter sea level Denver Mexico City Lift function air density Some thick highly-cambered airfoils de velop lift thin flat ones having same wing area use flaps will in40 Model Aviation qill El' crease lift wing considerably Lift function airfoil characteristics Other factors such altitude aspect ratio size also affect lift effects treated separately part Lift Equation itself Unless stated otherwise will assume models flown sea level have aspect ratios around 61 larger Quarter Scale dynamic pressure q pounds per square foot multiplied wing area square feet gives value total lift produced measure factors producing lift write saying CL CL qS Lift Factors Producing Lift lots lift needed CL must have large valuecorresponding high angle attack graph flaps high speeds angle attack small values CL low So can see CL might regarded percentage lift required given set conditions What dynamic pressure q about dynamic pressure depends both velocity air density Lets see can derive its value scaring anybody putting some sleep thing air has weight Thirteen cubic feet air weighs about pound volume air roughly size console TV set Since has weight air also has mass measure its inertia resistance acceleration Something heavy massive harder speed up accelerate something light airy Mass expressed W/gweight related acceleration due gravity 32 feet per second squared air has den sity 11n pound per cubic foot 076 pound per cubic foot has mass density 076/32or 002378 slugs per cubic foot slug unit mass order impart lift wing air must moving respect wing will have energy due motion energy called kinetic energy equal MV2or 002378 V 001 19V2 2 2 cubic foot air velocity V feet per second Since handier express velocity speed miles per hour rather feet per second multiply 1472 mile per hour 147 feet per second 001 19V2 becomes 00256V2 V2 391 value call q Thus lift equation expands read LCLqS CLV2S 391 20 18 16 14 12 10 6 4 2 FigI1ZZ17 I- ----7---------1-t- 4-II / 2 1Ctj7Q -K 1-- -----4-- # --- 4- 10 17/ --4----4~ I I7L V44. -.-4-4 - III - I- 1. .. 1- ----4- 1Iii -I14 .IUIULuIin --1i1I1i ~[it t { 111 J 0 4 8 12 16 20 oZ angle attack degrees level flight constant speed lift developed must equal weight lift exceeds weight airplane will climb weight exceeds lift airplane will descend equation lift equals weight L vel flight Now lets take equation rear range sequentially term 1 LiftL L V2 S 391 2Lift coefficient CL— 391 L V2 S 391W V2 S 3 Velocity V L — CLS 391 W CLS 4 Wing area 5391_L CLV2 CLV2 5 Wing loading W 2 5391 seen following rela tionships hold true 1 Lift varies directly CL wing area 5 varies square speed 2 lift coefficient CL varies versely square speed di rectly wing loading W/S 3 Speed velocity varies inversely square root CL directly square root wing loading 4 Wing area varies directly lift weight varies inversely square speed inversely CL 5 Wing loading W/S varies directly CL square speed Lets look Fig minute well check answers problems show two curves CL plotted against angle attack lower curve typical symmetrical airfoil angle zero lift zero angle attack upper curve shows lift developed wing Continued page 134 February 1984 41 related RC/WC will great help have several items three Rd WC events US plan send Bob have something youd like send him either mail Bob Skinner PO Box 31166 Braamfontein 2017 Johannesburg Republic South Africa send Ill see gets sounds like great project well worth support Ron Van Putte 111 Sleepy Oaks Rd Fort Walton Beach FL 32548 Design/Powers Continued naae 41 flap Since wing flap really same thing airfoil having very high J-5s DEEP SEA CRUISER Great sport boat just fun boating J-5s DEEP SEA CRUISER loves running 1 2 foot waves Speeds up 25-30 mph FULLSIZE PLANS Matched Sheets 42 3/32x4100 1/8x4108 3/16x4120 1/4x4131 36 NEW Basswood b Pine Sticks 114 Scale ALL SHEET ONE PIECE AAA GRADE KILN DRIED SANDED TO CLOSE TOLERANCES PED 100% 36Light 4-6lb361l8x3453/l6sq.173/8x11/2 33 1116x349 1116x448 lI4sq.26 1/2x2 40 3/32x356 3I32x456 114x31830 43 1I8x367 118x 466 3/8 sq.37 493116x37648 Sticks 561/4 x 385Add 40% 3l8x3115 37112x3139 44 54Balsa SheetsAa 621116x3 733I32x3 851/8x3 883/16x3 110114x3 1653t8x3 200l/2x3 581/16x4 703132x4 801/8x4 933/16x4 1101/4x4 1663/8x4 225 camber angle zero lift didnt show would shifted over left negative angle attack curve rises extending above the unflapped section Because Reynolds Number model wing can reach maximum CL value about 10 Flaps will increase about 15 other hand full-size wing can run up much higher lift coefficients Reynolds No R 0 x mph x chord feet model chord foot flying 50 mph operating Rey nolds No S00000indicated solid part curveswhile full-size airplane will operate values R way up millions depending size speed See Lets Talk About Reynolds Number February 1979 MA Suffice say low Reynolds Nos flow over wing breaks down readily wing stalls about 12 degrees depending 48 LOA x 181/2 beam x 11 deep Easy build mahogany plywood soft wood construction Designed tor hobby Quadra TML 35 gasoline engine Kit includes fullsize plan instructions $ 1795 46 70 BalsaTriangles 36 1/4x1/425 3/8x31830 1/2x1/235 3/453/445 lxi55 Lite Ply lilt n see flaps Harry will just get CL 10 Larry will get 15 using flaps Now lets check answers I We can find Harrys wing area using Equation 4 391W 391 x30 CLV210 x 25 x 25 1876 say 18 sq ft 2 Jims speed equation No 3 V391W CL found using 391x5 04 x 3125 12506 say 125 3 Larrys weight Equation No 1 WCLV2S l5x25x25x6 391 144 lb 4 From Equation 5 W — 5x15x15 5391 391 b per sq ft about 46 oz per sq ft W 5 If lb/sq ft S q ft W 20 58 lb 6V391W _391x10 CLS3x6 V21722 466 mph say 46 391x10 6 x 6 391 W CL S V 10861 mph say 33 391W391 x 10 CLS9x6 V 724 mph say 27 Continued page 138 134 Model Aviation RC Aerobatics/yen Puffs Continued Fmm ,nnn 131 6 aCCepi v1j88 PS Add *2 aspect ratio wing loading other factors KIT & DRIVE TRAIN $19350 J-5 ENTERPRISES KIT DRIVE TRAIN & ENGINE $32445 PO Box 82 Belmont Ontario NOL 180 Phone 1-519-644-0375 / IF YOU CAN BUILD KIT YOU CAN BUILD SCRAJCH-A-PLANE SCRATCH A-PLANE SION OF KEISER GRAPHICS U WI WI WHAT IS SCRATCH-A-PLANEiZ Professionally engineered designs accessories discriminating ler design tested top flight performance excellent parts fit Ij ease construction plans reproduced professionally inked mylars complete full size templates separate plans building instructions accessories heavy gauge plastic clean detail GUARANTEE IF YOU ARE NOT TOTALLY SATISFIED WITH PLANS EASE OF CONSTRUCTION AND QUALITY OF ACCESSORIES SHIP RACK TO US BY ZI RETURN MAIL FOR FuLl Rmrnin RIIV WITH CONFIDENCE!U -I U WI WI Ii ZI U I-I cc U WI WI SCALE CAP 21 CONSTRUCTION BALSA & LITE PLY Wing Span 80Wing Area 880 sq inWeight 15 lbs Engine 2 cubic inch Quadra Radio 4 Channel 5 Channel flaps Rolled Plan Pack $2495 Cowl canopy & wheelpants S3995 xl THIS CAP 21 15 DESIGNED TO BE BUILT PAST. THEN YOUR FUN JUST BEGINSI i CAPABLE OF ALL AEROBATIC MANEUVERS INCLUDING SQUARE LOOPS 8 POINT ROLLS i KNIFE EDGE LOOPS OUTSIDE SNAP ROLLS LOMCEVAKS AND INVERTED FLAT SPINS YET Icc ON TAKE OFFS NORMAL FLIGHTS AND LANDING SHES REAL PUSSY CATTI AEROBATICS ENDORSED BY WORLD FAMOUS AEROBATIC PILOT BOB SCHULTZ SCALE QUADRA POWER DESIGNSWI FOKKER DR-iWING SPAN 70WT 16 lbs WI FOKKER D VIIIWING SPAN 82WT 14 lbs z NIEUPORT 17WING SPAN 80WT 15 lbs cc ROLLED PLAN PACKS $2495COWLS $1195 la Cd 40 SIZE FOUR STROKE DESIGN de HAVILLAND LEOPARD MOTH WING SPAN 63 FLYING WT 6 lbs ROLLED PLAN PACK 31995COWL WHEELPANTS & CANOPY 314 5 ZI U 60 90 TWO STROKE DESIGN 1934 AVIA B534-IVBI-PLANE WING SPAN 62WING AREA 1140 sq inWT 9 lbs IU ROLLED PLAN PACK $2295COWL CANOPY & RADIATOR $1495 Gfli 4 1/4 SCALE VINTAGE FLOATSWI LENGTH 45MAX LOAD 30 lbs PLANS TEMPLATES & INSTRUCTIONS $895 ppd folded OR ORDER DIRESHIPPING CHARGE $300 COD ORDERS ACCEPTEDVISA & MASTtRCARD WELCOMtA 2080 ATHENS AVE REDDING CA 96001 -J 5-916241-4190 SCRATcH SRATH PIAjE SCRJTCH 138 Model Aviation Design/Powers Conhnued fmm flAflA 134 see V varies inversely square root ratio lift coef fiCients CL example CL 46 mpl 3 33mph 6 ratio 3 tc 6 re root 7 multiply 466 707 get 32 mph bothering solve other terms 7 We Can read answers directly Fig 8 in item 3 stated relation2 ships see speed varies directly square root wing loading W/S problem halving wing area doubling wing loading speed will increase factor equal square root 2 14 speed will 14 times greator 40% faster 9 Conversely doubling wing area cut wing loading W/S half speed will decrease factor equal square root 5 7 speed will 70% fastor 30% slower ever way wishes state 10 If reduce weight 80% its original value reducing wing loading W/S same proportion square root 80% 89% reducing safe landing speed 11% math wasnt com plicated mysterious future will try minimize math much possible some things difficult impossible express other way topic happens Anyway mathematics useful beautiful human accomplishment Without would back stone age wondering di vide three birds eggs among four people product review product review product review very accurate Cuts necessary youre building special new project TinyTools Tablesaw just ticket Ifs 1 2-volt powered tool thai gives full torque allow speeds 200 rpm speeds up 17000 rpm variable thrugh speed control transformer table saw slotted rip ping accommodates indexing mitre gauge up 45 can also used wet dry stained glass lapidary work product review product review product review 0 U U I. 0 4 4 U Id 5 0 z 4 U -4 0 U U 4 -J 5 U Id 0 U U Id U U 4 U 4 5 -J Id Id U Id 5 0 4 U TinyTools Tablesaw Byrom International Corp 117 South St. Box 246 Chardon OH 44024 tel 216/285-2341 Epilogue subject aerodynamics bit complex have tried make seem intention articles try expose reader subject rational light fashionyet giving some useful formulas relationships ex ample say CL 10 typical models quite true general way effects aspect ratio air foil selection etc can change some what some critics have loudly indicated such criticism must reply am trying take complicated subject put fairly simple terms can digested average reader hope discussion Lift Equation has interest want know about design Questions comments may ad dressed Brad Powers 5470 Castle Hills Dr San Diego CA 92109 RC Scale/Wischers Continued page 45 Light steel parts can brazed 23000 F flame either kind gas heavier metal such l/.in.diameter steel tube landing gears torch suitable use MAPP methyl acetylene pro padiene gas preferred Its flame tempera ture used appropriate torch such Master Mechanic Whirlwind $24 36000 F gas about three times expensive propane s2n3 New Standard Giant Models 28 HP Lbs Send $100 Catalog 149 Direct Sales Only PIns hippsg Work Horse rel7fl 96 IORITZ 2a4 32 HP 6A Lbs III Dealer Direct PIns sblppiq Now Distribute Sachs-Dolmar Engines Yeager Machines TO RUN INCLUDING 6 BOLT PROP HUB AVAILABLE AT EXTRA CHARGE Nm ___ ___ NGINERear 340w Cleveland Isve. SW EU EEECanton OH 44707I IC DIVISIONPhone 216484-6810 48443741 job finished time because intensely hot flame actual cost per joint remains about same /2-in -diameter 035-in -wall aircraft steel tube brought red heat ready brazing bronze rod about ten seconds out red heat steel brazed bronze rod brazing alloy will melt flow uniformly around joint Insufficient heat primary reason lack success brazing Whirlwind torch has pres sure adjustment permits its use propane butane gases lowertemperature brazing maximum joint strength brazing Continued page 142 VXPHONE 6194424838 -h/pates 469-8675 BOX 2498-MALA MESA CA 92041 1 Great Trainers Send $150 complete Kit Catalog p Midwest Products C. Inc 400 S Indiana St PO Box 564-T Hobart 46342 83 t03l February 1984 139 BL ILAP4 MAILABLE IN TWO 1/4 Scale 90 to2EngInes 1 60EngIne EOPWITH TABLOIDI/ASeal77 Span524OOppUSA EOPWlTI4 TABLOID2V —I64 Span$1BOOppUSA 016 TEXAN41101 Span$27tOppUSA POSKEB DRI27 I63 Trip$2SOOppUSA F4U COESAIB2 I93 Span$27tppUSA CUBTISS p402 I94 Span$27OOppUSA FM BEAECAT2 —196 Span$2700 ppUSA Fiberglass COwlingS & Canopies available Send Stamp detailed Brochures oar Giant Scale AccessarreS Forego Orders Please add 254 POstage & Handling Nick Ziroli 29 Edgar Drive Smlthtowfl NY 11787 USA Brazing heavy metals Use Whirlwind Torch L stank stabilized acetylene gas lighter work use Microfiame torch R butane oxidizer cylinders sliver solder C02 ENGINES WE NOW HAVE COMPLETE LINE OF BROWN TELCO DAVIS CO-2 ENGINES INCLUDING SPARE PARTS SERVICE IAOWNTEL LO A23 PEANUT $2996STANDARD TELCO$2400 CAMPUS BEE $2495TURBO 300092295 CAMPUS TWiN- $5995TURBO 800093900 SODACHARGER $1200 MVIS- COX 02 CONVERSION TO CO2$3900 NEWt C4T4LOG No 25 $150 Classic R/C Scale LAKES TH G4Qr Wing 15 25 Engines Dealers & Distributors Welcomed Phone 703 273-9593 FLYLINE MODELS INC PO Boa 2136 Pairfars VirginIa 22021 USA