CONTROL LINE AEROBATICS U month Ill talk about problems can arise checking out new airplane engine used word because looking trouble attempt both same time Sure its done will future certainly isnt mostdesirable situation Use engine system whatever likeincluding engine propeller tank exhaust unit tuned muffledthat know checked out working reliably Having baseline will prevent situation cant recover such engine stopping attitude will cause untrimmed model crash Check out new engine proven airplane after have sufficient time test bench Its fun monitor engine just running vital establishing goodrunning fit Follow supplier/manufacturers instructions company knows engine careful use recommended fuel type mixture need engines comfort zone has printed before pilots create own issues following instructions using common sense airplane make sure set parameters can based designers recommendations before depart workshop basic procedure will save problems baseline have doubts recheck call someone trust Make sure have good conservative numbers can discuss results what airplane doing get better advice know what settings example check center gravity CG set right place adjustable leadouts should positioned per plan minimum slightly behind CG Spend some time getting good handle setting line adjustment get field recheck everything run engine briefly ensure system normal Set engine slightly rich get first flight fine trimming next baseline must establish order proceed have diligently worked through what Ive already discussed youve done gross trim No matter carefully skillfully have constructed aligned airplane chances good will have level wing extremely important must done before attempting proceed other trimming wing may fly level number reasons including twist construction control surface alignment top weight Leveling wing such important step because nonlevel wing will affect maneuver probably adversely have seen some fliers try trim other problems canying out balance trim wouldnt recommend Some fliers able level wing help Im can get close last look gives trouble Its best balancing good day light winds little turbulence hove changed trim after setting wing windy day cost weeks grief finally someone fly airplane took look myself easy after Before proceed have some observations nded critical designs might help long-wing models high-aspect-ratio scientifically minded out prefer critical leveling wing manifest problems out-of-trim condition much noticeably have narrow range trim should especially true design has equal-span panels fad years ago related so-called barbell effect leverage 132 Model Aviation snt 1948its VSC 1998 Shown Bill Netzebands rendition Davy Slagles Nats winner Checkala Roma Curt Contratas original paint layout isnt paint Over white base detailed ink lightness Its effective Continued page 135 Bill Werwage gets ready launch Old-Time Frisky Pete Bob Hunt very light model flies well Fox 19 Cyclon engine 1992 broke Spanish record 291 km/h 182 mph Barcelona 1993 purchased Profi engine turned 299 km/h 187 mph 1994 Luiss next challenge attain 300 km/h worked friends Lluis Roger Jaume Porta Jordi Fout Eduard Giro obtained information books such Two Stroke Performance Tuning Graham Bell Motorcycle Tuning Two Stroke Engines John Robinson especially Design Simulation Two Stroke Engines Gordon Blair sources Luis used computing programs thermodynamic simulations other programs Lluis Roger propeller design model design CL cable flying wire leading addition mathematical calculations tested models wind tunnel Salvador Gonzalez Barcelona Engineering School tested engines dyno bench GP Development measured power torque versus rpm head exhaust temperatures exhaust head crankcase pressures transducers also ran metallographic analysis surface treatment analysis Luiss sidewinder airplane has traditional metal pan long almost onemeter aluminum inner wing does use wood fiberglass carbon fiber body tail used extruded polymethacrylate foam called Rohacell unaffected vibration comes various densities 35 kg/m3 foam used stab 50 kg/m3 used tailboom body wing has symmetrical airfoil tip swept back front flying wire 26 mm behind Center Gravity CG line rake compensates wire drag allows model fly tangent circle minimum drag model weighed 420 g engine pipe being 205 g Profi engine manufactured Ukraine powerful Speed engines available rather typical frontintake rear-exhaust ABC type couple interesting internal modifications has two ball bearings crankshaft engines rear doesnt have internal race balls run groove ground crankshaft ball retainer external race complete bearing Im interpreting letter correctly sleeve chrome-plated beryllium copper piston typical 24% silicon aluminum alloy Luis made few other modifications such changing valve timing 2300 boring crank 9 mm ID boring venturi 95 mm modifying transfer ports making head hemispherical chamber great deal work put crankshaft ball bearing assembly achieve perfect lowfriction fit 05 mm axial clearance front bearing Luiss propeller carbon-fiber-andresin single-blade also obtained Ukraine 742 mm radius 64 inches pitch dimensions metric except propeller pitch have no idea could because past winners have used inches top speed tip velocity approximately 1067 km/h 667 mph Mach 87 prop modified dimensions simulations computing program made Lluis Roger World Championships held July 22-29 1996 Swedish town Norrkoping unused airbase After some problems officials first flight Luis turned speed 304 km/h second flight became world champion third flight 3112 km/h 1945 mph hope has given some idea what takes world champion just difficult class since flying against best modelers world 4CL AerobaticslMcMillan Continued page 132 longer wings can exert However long-wing models fly well once trim Its easier set wings level lower aspect ratio designs seem less reactive turbulence Youve got model up air safely engine mnning reliably wing seems reasonably level outside circle appears riding inboard-wing-low adjustment time observe looking slight adjustment dont tweak things yet small increase tip weight might thing required case Depending design some models very sensitive tip weight add some point want reaction try half-ounce weight fly again close preflight settings will get you need condition looking should have equalright side up invertedif tmly tip weight added weight did level wingsor went past neutral opposite conditionand same nght side up inverted did have pure tip-weight problem adding tip weight exacerbated problem direction hurt other primarily flap tweak problem Cut back about half added weight wing went inboard-low slightly inboard-high soon wing still tends inboard-low after adding still weight need consider flap tweak tab Right now preference would tweak flaps times adjustment fraught chasing-the-tail syndrometoo much time too little next An adjustable tab part flap area very nice feature have can try go back-and-forth until have arrived good setting destroying best imtial alignment indication consider flap tweak/tab adjustment roll inside control opposite roll other control instance situation discussed previously inboard low upright up control would cause airplane roll down control would cause roll outside Make adjustment small increments case slight inboard flap down tab outboard wing tab up Fly again observe adjustment should start see airplanes reactions become linear rolling diminish Continue until wings level observed outside circle point can start looking tip weight see wing moving hard corner some have called hinging Think excess weight enough energy carry tip established line rather smoothly executing commanded tarn some models especially really light built-up wing designs tip weight overall will less will differential weight affects hinging Typically Ive seen about /2-ounce final tip weight little gram two showing hinging point lines diameter length type have signfi cant effect final trim Again leveling wings extremely important Dont hurry shotgun bunch changes until get right some other factors affect rolling after have achieved wings level Differential area flaps comes mind still heatedly argued day currently successful designs use slightly wider flap /32 inch outboard tip Its good number know works Others use tabs added outboard flap make adjustment thats another column Ive some good feedback previous column regarding effects pitch stability hard corners Well-known Nationals competitor Windy Urtnowski wrote thought last columnengine unloading higher rpm added GP stability lower pitchthis phenomenon especially true Big Jim setup using cut down 14 x 5 rev-ups pronounced 4-B carbon blades lower pitch rpmlots GP stabilityIve found true time go direction ie 6 pitch 55 4 etc assuming weight prop same Alsoa slightly higher comp will same thing rpmgood thoughts thanks detailing outmay help some guys understand whats happening out nose ember 1998 135
Edition: Model Aviation - 1998/09
Page Numbers: 132, 135
Edition: Model Aviation - 1998/09
Page Numbers: 132, 135
CONTROL LINE AEROBATICS U month Ill talk about problems can arise checking out new airplane engine used word because looking trouble attempt both same time Sure its done will future certainly isnt mostdesirable situation Use engine system whatever likeincluding engine propeller tank exhaust unit tuned muffledthat know checked out working reliably Having baseline will prevent situation cant recover such engine stopping attitude will cause untrimmed model crash Check out new engine proven airplane after have sufficient time test bench Its fun monitor engine just running vital establishing goodrunning fit Follow supplier/manufacturers instructions company knows engine careful use recommended fuel type mixture need engines comfort zone has printed before pilots create own issues following instructions using common sense airplane make sure set parameters can based designers recommendations before depart workshop basic procedure will save problems baseline have doubts recheck call someone trust Make sure have good conservative numbers can discuss results what airplane doing get better advice know what settings example check center gravity CG set right place adjustable leadouts should positioned per plan minimum slightly behind CG Spend some time getting good handle setting line adjustment get field recheck everything run engine briefly ensure system normal Set engine slightly rich get first flight fine trimming next baseline must establish order proceed have diligently worked through what Ive already discussed youve done gross trim No matter carefully skillfully have constructed aligned airplane chances good will have level wing extremely important must done before attempting proceed other trimming wing may fly level number reasons including twist construction control surface alignment top weight Leveling wing such important step because nonlevel wing will affect maneuver probably adversely have seen some fliers try trim other problems canying out balance trim wouldnt recommend Some fliers able level wing help Im can get close last look gives trouble Its best balancing good day light winds little turbulence hove changed trim after setting wing windy day cost weeks grief finally someone fly airplane took look myself easy after Before proceed have some observations nded critical designs might help long-wing models high-aspect-ratio scientifically minded out prefer critical leveling wing manifest problems out-of-trim condition much noticeably have narrow range trim should especially true design has equal-span panels fad years ago related so-called barbell effect leverage 132 Model Aviation snt 1948its VSC 1998 Shown Bill Netzebands rendition Davy Slagles Nats winner Checkala Roma Curt Contratas original paint layout isnt paint Over white base detailed ink lightness Its effective Continued page 135 Bill Werwage gets ready launch Old-Time Frisky Pete Bob Hunt very light model flies well Fox 19 Cyclon engine 1992 broke Spanish record 291 km/h 182 mph Barcelona 1993 purchased Profi engine turned 299 km/h 187 mph 1994 Luiss next challenge attain 300 km/h worked friends Lluis Roger Jaume Porta Jordi Fout Eduard Giro obtained information books such Two Stroke Performance Tuning Graham Bell Motorcycle Tuning Two Stroke Engines John Robinson especially Design Simulation Two Stroke Engines Gordon Blair sources Luis used computing programs thermodynamic simulations other programs Lluis Roger propeller design model design CL cable flying wire leading addition mathematical calculations tested models wind tunnel Salvador Gonzalez Barcelona Engineering School tested engines dyno bench GP Development measured power torque versus rpm head exhaust temperatures exhaust head crankcase pressures transducers also ran metallographic analysis surface treatment analysis Luiss sidewinder airplane has traditional metal pan long almost onemeter aluminum inner wing does use wood fiberglass carbon fiber body tail used extruded polymethacrylate foam called Rohacell unaffected vibration comes various densities 35 kg/m3 foam used stab 50 kg/m3 used tailboom body wing has symmetrical airfoil tip swept back front flying wire 26 mm behind Center Gravity CG line rake compensates wire drag allows model fly tangent circle minimum drag model weighed 420 g engine pipe being 205 g Profi engine manufactured Ukraine powerful Speed engines available rather typical frontintake rear-exhaust ABC type couple interesting internal modifications has two ball bearings crankshaft engines rear doesnt have internal race balls run groove ground crankshaft ball retainer external race complete bearing Im interpreting letter correctly sleeve chrome-plated beryllium copper piston typical 24% silicon aluminum alloy Luis made few other modifications such changing valve timing 2300 boring crank 9 mm ID boring venturi 95 mm modifying transfer ports making head hemispherical chamber great deal work put crankshaft ball bearing assembly achieve perfect lowfriction fit 05 mm axial clearance front bearing Luiss propeller carbon-fiber-andresin single-blade also obtained Ukraine 742 mm radius 64 inches pitch dimensions metric except propeller pitch have no idea could because past winners have used inches top speed tip velocity approximately 1067 km/h 667 mph Mach 87 prop modified dimensions simulations computing program made Lluis Roger World Championships held July 22-29 1996 Swedish town Norrkoping unused airbase After some problems officials first flight Luis turned speed 304 km/h second flight became world champion third flight 3112 km/h 1945 mph hope has given some idea what takes world champion just difficult class since flying against best modelers world 4CL AerobaticslMcMillan Continued page 132 longer wings can exert However long-wing models fly well once trim Its easier set wings level lower aspect ratio designs seem less reactive turbulence Youve got model up air safely engine mnning reliably wing seems reasonably level outside circle appears riding inboard-wing-low adjustment time observe looking slight adjustment dont tweak things yet small increase tip weight might thing required case Depending design some models very sensitive tip weight add some point want reaction try half-ounce weight fly again close preflight settings will get you need condition looking should have equalright side up invertedif tmly tip weight added weight did level wingsor went past neutral opposite conditionand same nght side up inverted did have pure tip-weight problem adding tip weight exacerbated problem direction hurt other primarily flap tweak problem Cut back about half added weight wing went inboard-low slightly inboard-high soon wing still tends inboard-low after adding still weight need consider flap tweak tab Right now preference would tweak flaps times adjustment fraught chasing-the-tail syndrometoo much time too little next An adjustable tab part flap area very nice feature have can try go back-and-forth until have arrived good setting destroying best imtial alignment indication consider flap tweak/tab adjustment roll inside control opposite roll other control instance situation discussed previously inboard low upright up control would cause airplane roll down control would cause roll outside Make adjustment small increments case slight inboard flap down tab outboard wing tab up Fly again observe adjustment should start see airplanes reactions become linear rolling diminish Continue until wings level observed outside circle point can start looking tip weight see wing moving hard corner some have called hinging Think excess weight enough energy carry tip established line rather smoothly executing commanded tarn some models especially really light built-up wing designs tip weight overall will less will differential weight affects hinging Typically Ive seen about /2-ounce final tip weight little gram two showing hinging point lines diameter length type have signfi cant effect final trim Again leveling wings extremely important Dont hurry shotgun bunch changes until get right some other factors affect rolling after have achieved wings level Differential area flaps comes mind still heatedly argued day currently successful designs use slightly wider flap /32 inch outboard tip Its good number know works Others use tabs added outboard flap make adjustment thats another column Ive some good feedback previous column regarding effects pitch stability hard corners Well-known Nationals competitor Windy Urtnowski wrote thought last columnengine unloading higher rpm added GP stability lower pitchthis phenomenon especially true Big Jim setup using cut down 14 x 5 rev-ups pronounced 4-B carbon blades lower pitch rpmlots GP stabilityIve found true time go direction ie 6 pitch 55 4 etc assuming weight prop same Alsoa slightly higher comp will same thing rpmgood thoughts thanks detailing outmay help some guys understand whats happening out nose ember 1998 135
