QSpIa1 '77 childs understand/ ing natural laws / can give us power less noise U Duane Gall RC FLIERS especially Racing Pattern fliers have problem noise No Im going discuss detail fact problem much noise intolerance sport nonpartici pants Nor will say much about men tally debilitating effects staring dB meter too long will simply say standard including dB use muffled tuned pipe significantly im proves noise situation no power loss Tuned pipes both muffled nonmuf fled have around since 1960s use muffled pipes now commonplace RC Pattern muffled pipe ap propriate header can found fit virtu ally two-stroke engine now mar ket modern Schnuerle-ported engine designs benefit use pipe much benefit can expected Ex perimenting Picco 40-powered Scat Cat racer measured drop over 11 dB simply fitting stock MACS #1240 muf fled pipe over open end header same time gained over 1000 rpm significant either changes however change sound qualitythe pipe changed sound raspy drag racer snarl pleasant Saab turbo-style whoosh contrast muffler came engine reduced b dB about half much no no ticeable effect rpm did nothing smooth out sound quality Im convinced complaints about noise have nothing dB rather quality sound mod els make else nonmodeler neighbors tolerate lawn mowers motorcy cles full-size aircraft vastly exceed sound levels model aircraft else Giant Scale models often granted unofficial exemption dB limits flying fields have such limits digress Suffice say use muf fled tuned pipe gives least much reduc tion noise dB meter would indi cateand probably much morewithout sacrificing power Ill now explain can get benefits little no tinker ing fliers think tuned pipe cy lindrical chamber filled voodoo magic Theyre scared use because think need PhD understand Bal derdash youve ever seen six-year-old take bath already know pipe works Just watch kid sits tub leans forward little back little forward again small wave starts traveling end tub other back forth kid soon discovers wave always goes same speed rocking faster doesnt help along rocking just right speed kid adds little energy time wave passes building up real tsunami slams end tub spraying water everywhere fun doesnt end until tub empty adult comes room whichever happens first tuned pipe bathtub above ex ample engine kid goal find point Maximum Splat varying length tub speed kid both length tub pipe determines its resonant frequency speed kid engine needs go achieve Maximum Splat beauty tuned pipe takes otherwise wasted portion engines energyie noiseand returns some engine stroke piston shock wave little burp exhaust travels down diverging cone pipe see sketch gaining mo mentum pulling spent fuel/air mixturethe exhaustbehind out engine same time its also pulling some fresh fuel/air mixture completely through engine carburetor part shock wave hits con verging cone far end pipe reflected back toward engine re 34 Model Aviation 1 flected wave actually pushes some fresh fuel/air mixture upstream ex haust port just before closes packing fresh charge combus tion chamber would otherwise result like supercharging no moving parts small weight penalty addition secondary expansion chamber see sketch diffuses exhaust stream reducing noise further doesnt interfere supercharging ef fect contrast ordinary untuned expan sion chamber muffler simply absorbs diffuses engines sonic energy its equivalent covering bathtub examplekid allwith large plastic bag its just about healthy engine bag kid find point Maximum Splat Start mounting pipe header sans pipe engine Put normal-size propeller front fire up Dont forget ear plugs Needle peak rpm back off slightly rich Shut en gine down Now add pipe pipe generally taches header using short piece neoprene tubing allowing overall length adjusted over range 1 now keep longdont insert metal parts way neoprene tubing can use pair small automotive hose clamps stops set length sembly see sketch Start up engine low throttle ad vance high throttle As engine rpm ap proaches pipes resonant frequency will start come pipe Youll no tice very definite boost power Splat begins doesnt either propel ler too big pipe too short Switch lighter prop eg 10 x 6 9 x 6 10 x 5 try again Manufacturers generally make pipes headers about right anything little long should able get nice boost too much fiddling next step push ends pipe header together until touch side neoprene coupler shortens pipe little Now see engine still comes pipe sitting ground go back original length Set needle valve rich can noticeably reducing rpm ensures engine wont run ning lean air pipe wont hear sag until its very overlean Fly airplane comes off pipe top loops vertical climbs youre sure its because overlean mixturego smaller propeller hear waffling warbling dives youre sure its because overly rich mixturego bigger prop start shortening header % time using saw tubing cutter After cut sure blow out metal shavings before running engine again pumping ac tion pipe will inject right exhaust port Once sounds happy air youre ba sically done During flight testing may NEOPRENE ORDIVERGING SILICONE eSUPLER HEAOER TO CONTROL LENGT4 COUPLER have shortened pipe point wont always come sitting Continued page 182 CONVERGING TAILPIPE RIrv CONE iIOIINING I SECONDAR EXPANSION CI4AIIEER LJTN INTEPMAL BAFFLES SJ4GCIC WAVE ACCELERATIWG IN DIVERGING CONE 7- COMPACTED IJI CYUOJDESPEJT GASES r CTAILPIPE tuned pipe action top drawing depicts typical tuned pipe installation show ing coupler clamps allow minor adjustments overall length tailpipe mount ing bracket cutaway view muffled pipe interior drawing engine has fired releasing spent gases header shock wave travels down pipes diverg ing cone creating partial vacuum carrying spent gases drawing B process has drawn some fresh fuel/air mixture completely through engine header same time reflected shock wave develops far end pipe begins move upstream drawing C reflected wave has supercharged engine fresh fuel/air mixture just before exhaust port closes Any spent gases remain ing pipe will pushed out cycle starts again refer back drawing August 1990 35 authors Scat Cat demonstrates typical tuned pipe installation Its completely stock MACS #1 240 pipe hooked up Picco 40 engine Picco header swinging 9 x 7 Rev-Up propeller engine/header/pipe combo operates about 17000 rpm ground Note pressure line running widest point pipe pressure greatest constant simple twist tie secures aft end pipe MACS nylon fitting total length pipe exhaust port widest point about 12 Cross-Country clarification February column said Great Race put Chicagos SOAR club granddaddy CrossCountry races said because believed guess oldest X-C race still ing conducted having started 1976 Bicen tennial tribute Jerry Krainock Dave Peltz wrote point out Great Race first X C race Jerry San Fernando Valley Silent Flyers clubmates organized first X-C race fall 1975 SFVSF ran contest until about 1987 Jerry goes back much farther X C having set FM-recognized distance records 1972 1974 Dave said Jerry co authors FAT F3H X-C rules hope sets record straight Max Splat/Gall Continued page 35 ground OK engine generally un loads 10-20% air ground rpm may well below pipes resonant frequency though system works Well air want highest possible power output such FAI racing competition theres factor consider engine has rpm rangethe power band peak rpm produces power Manufactur ers often include information instruc tion sheet comes engine Ha threw away didnt case trick have Maxi mum Splat occur have occur engines power band air Recall Maximum Splat depends two factors pipe length engine rpm know engines peak rpm can make ourselves bench prop will spin about speed simulate con ditions air allows us control other factor pipe length gradually cutting pipe header shorter until rings happily target rpm always balance propeller always wear eye protection As zero target rpm bench prop may spin little too fast due assistance pipe Also inevitable result cutting pipe match specific rpm last cut will actually go little too far Its like helpful lady bus says Oh know stop Just watch get off stop before So its best start bench prop little large say 2000 rpm below target rpm have target rpm itself little low say 1000 rpm below engines actual peak time go over target rpm make slightly larger bench prop Shorten pipe time until rpm no longer increases witl cut done whittle new prop i turns 80-90% engines peak rpm ac count 15% unloading alr Fly tht plane using trial error outlined above t find exactly right ground rpm Muffled tuned pipes may cure ills solve elegant fashion twin problems insufficient muffling power needed insufficient power muffling needed modelers used readily available devices perhaps could quil bickering about noise get real bus iness sport hobby enjoy May Splat Giants/de Vries Continued page 41 Japanese Zero Platt kit en tered Precision William Carper Jackson OH Precision Scale model turned everybodys head Frank Mizers Westland Lysander its fully detailed scale interiorincluding such niceties trim wheels complete crew safety harnesses epitomized art Precision Scale functional metal leading etlge slats scale paint job scale Hercules engine frosting cake Giant Scale birds also evident nonscale judging categories black-and-gold Ray Ban special Weeks biplane entered Sport Biplane Big birds invaded OldTimer category well Boehie Giant looked must have taken weeks pro duction Top Flites transparent Mono Kote cover huge wide-angle camera lens couldnt capture stalwart wasnt content just dis play model Upon returning under ground parking garage next hotel Friday afternoon heard unmistakable sound RC engine parked car walked toward engines hum Sure enough flying RC Heli copter goodan opinion confirmed three municipal employ ees formed audience As 1989 RC helium balloonsI counted nine various timesflittered above crowd arena Pickup bal loon races arranged radio prob lems hanging power cables frustrated would-be Phineas Foggs 1990 Giant year Toledo show Given continuing creasing interest large-sized Scale mod els isnt surprising SAFE FLYING IS NO ACCIDENT 182 Model Aviation WILHAMS ACCESSORIES 4 PILOT STANDARD TSMAN RACING TARY WHEELS AGE TH CONTOUR BALLOON EN AGt 4 ENGINES PRATT & WHITNEY HT HONE PARTS T & WHITNEY HONE WRIGHT E GUNSj LEWIS VICKERS DAU SELLUM SEND $3 FOR FULLY ILLUSTRATED CATALOG$LUAI~1S DEPT MAPAWNEE ST SAN MARCOS CALIFORNIA 92069 I
Edition: Model Aviation - 1990/08
Page Numbers: 34, 35, 182
QSpIa1 '77 childs understand/ ing natural laws / can give us power less noise U Duane Gall RC FLIERS especially Racing Pattern fliers have problem noise No Im going discuss detail fact problem much noise intolerance sport nonpartici pants Nor will say much about men tally debilitating effects staring dB meter too long will simply say standard including dB use muffled tuned pipe significantly im proves noise situation no power loss Tuned pipes both muffled nonmuf fled have around since 1960s use muffled pipes now commonplace RC Pattern muffled pipe ap propriate header can found fit virtu ally two-stroke engine now mar ket modern Schnuerle-ported engine designs benefit use pipe much benefit can expected Ex perimenting Picco 40-powered Scat Cat racer measured drop over 11 dB simply fitting stock MACS #1240 muf fled pipe over open end header same time gained over 1000 rpm significant either changes however change sound qualitythe pipe changed sound raspy drag racer snarl pleasant Saab turbo-style whoosh contrast muffler came engine reduced b dB about half much no no ticeable effect rpm did nothing smooth out sound quality Im convinced complaints about noise have nothing dB rather quality sound mod els make else nonmodeler neighbors tolerate lawn mowers motorcy cles full-size aircraft vastly exceed sound levels model aircraft else Giant Scale models often granted unofficial exemption dB limits flying fields have such limits digress Suffice say use muf fled tuned pipe gives least much reduc tion noise dB meter would indi cateand probably much morewithout sacrificing power Ill now explain can get benefits little no tinker ing fliers think tuned pipe cy lindrical chamber filled voodoo magic Theyre scared use because think need PhD understand Bal derdash youve ever seen six-year-old take bath already know pipe works Just watch kid sits tub leans forward little back little forward again small wave starts traveling end tub other back forth kid soon discovers wave always goes same speed rocking faster doesnt help along rocking just right speed kid adds little energy time wave passes building up real tsunami slams end tub spraying water everywhere fun doesnt end until tub empty adult comes room whichever happens first tuned pipe bathtub above ex ample engine kid goal find point Maximum Splat varying length tub speed kid both length tub pipe determines its resonant frequency speed kid engine needs go achieve Maximum Splat beauty tuned pipe takes otherwise wasted portion engines energyie noiseand returns some engine stroke piston shock wave little burp exhaust travels down diverging cone pipe see sketch gaining mo mentum pulling spent fuel/air mixturethe exhaustbehind out engine same time its also pulling some fresh fuel/air mixture completely through engine carburetor part shock wave hits con verging cone far end pipe reflected back toward engine re 34 Model Aviation 1 flected wave actually pushes some fresh fuel/air mixture upstream ex haust port just before closes packing fresh charge combus tion chamber would otherwise result like supercharging no moving parts small weight penalty addition secondary expansion chamber see sketch diffuses exhaust stream reducing noise further doesnt interfere supercharging ef fect contrast ordinary untuned expan sion chamber muffler simply absorbs diffuses engines sonic energy its equivalent covering bathtub examplekid allwith large plastic bag its just about healthy engine bag kid find point Maximum Splat Start mounting pipe header sans pipe engine Put normal-size propeller front fire up Dont forget ear plugs Needle peak rpm back off slightly rich Shut en gine down Now add pipe pipe generally taches header using short piece neoprene tubing allowing overall length adjusted over range 1 now keep longdont insert metal parts way neoprene tubing can use pair small automotive hose clamps stops set length sembly see sketch Start up engine low throttle ad vance high throttle As engine rpm ap proaches pipes resonant frequency will start come pipe Youll no tice very definite boost power Splat begins doesnt either propel ler too big pipe too short Switch lighter prop eg 10 x 6 9 x 6 10 x 5 try again Manufacturers generally make pipes headers about right anything little long should able get nice boost too much fiddling next step push ends pipe header together until touch side neoprene coupler shortens pipe little Now see engine still comes pipe sitting ground go back original length Set needle valve rich can noticeably reducing rpm ensures engine wont run ning lean air pipe wont hear sag until its very overlean Fly airplane comes off pipe top loops vertical climbs youre sure its because overlean mixturego smaller propeller hear waffling warbling dives youre sure its because overly rich mixturego bigger prop start shortening header % time using saw tubing cutter After cut sure blow out metal shavings before running engine again pumping ac tion pipe will inject right exhaust port Once sounds happy air youre ba sically done During flight testing may NEOPRENE ORDIVERGING SILICONE eSUPLER HEAOER TO CONTROL LENGT4 COUPLER have shortened pipe point wont always come sitting Continued page 182 CONVERGING TAILPIPE RIrv CONE iIOIINING I SECONDAR EXPANSION CI4AIIEER LJTN INTEPMAL BAFFLES SJ4GCIC WAVE ACCELERATIWG IN DIVERGING CONE 7- COMPACTED IJI CYUOJDESPEJT GASES r CTAILPIPE tuned pipe action top drawing depicts typical tuned pipe installation show ing coupler clamps allow minor adjustments overall length tailpipe mount ing bracket cutaway view muffled pipe interior drawing engine has fired releasing spent gases header shock wave travels down pipes diverg ing cone creating partial vacuum carrying spent gases drawing B process has drawn some fresh fuel/air mixture completely through engine header same time reflected shock wave develops far end pipe begins move upstream drawing C reflected wave has supercharged engine fresh fuel/air mixture just before exhaust port closes Any spent gases remain ing pipe will pushed out cycle starts again refer back drawing August 1990 35 authors Scat Cat demonstrates typical tuned pipe installation Its completely stock MACS #1 240 pipe hooked up Picco 40 engine Picco header swinging 9 x 7 Rev-Up propeller engine/header/pipe combo operates about 17000 rpm ground Note pressure line running widest point pipe pressure greatest constant simple twist tie secures aft end pipe MACS nylon fitting total length pipe exhaust port widest point about 12 Cross-Country clarification February column said Great Race put Chicagos SOAR club granddaddy CrossCountry races said because believed guess oldest X-C race still ing conducted having started 1976 Bicen tennial tribute Jerry Krainock Dave Peltz wrote point out Great Race first X C race Jerry San Fernando Valley Silent Flyers clubmates organized first X-C race fall 1975 SFVSF ran contest until about 1987 Jerry goes back much farther X C having set FM-recognized distance records 1972 1974 Dave said Jerry co authors FAT F3H X-C rules hope sets record straight Max Splat/Gall Continued page 35 ground OK engine generally un loads 10-20% air ground rpm may well below pipes resonant frequency though system works Well air want highest possible power output such FAI racing competition theres factor consider engine has rpm rangethe power band peak rpm produces power Manufactur ers often include information instruc tion sheet comes engine Ha threw away didnt case trick have Maxi mum Splat occur have occur engines power band air Recall Maximum Splat depends two factors pipe length engine rpm know engines peak rpm can make ourselves bench prop will spin about speed simulate con ditions air allows us control other factor pipe length gradually cutting pipe header shorter until rings happily target rpm always balance propeller always wear eye protection As zero target rpm bench prop may spin little too fast due assistance pipe Also inevitable result cutting pipe match specific rpm last cut will actually go little too far Its like helpful lady bus says Oh know stop Just watch get off stop before So its best start bench prop little large say 2000 rpm below target rpm have target rpm itself little low say 1000 rpm below engines actual peak time go over target rpm make slightly larger bench prop Shorten pipe time until rpm no longer increases witl cut done whittle new prop i turns 80-90% engines peak rpm ac count 15% unloading alr Fly tht plane using trial error outlined above t find exactly right ground rpm Muffled tuned pipes may cure ills solve elegant fashion twin problems insufficient muffling power needed insufficient power muffling needed modelers used readily available devices perhaps could quil bickering about noise get real bus iness sport hobby enjoy May Splat Giants/de Vries Continued page 41 Japanese Zero Platt kit en tered Precision William Carper Jackson OH Precision Scale model turned everybodys head Frank Mizers Westland Lysander its fully detailed scale interiorincluding such niceties trim wheels complete crew safety harnesses epitomized art Precision Scale functional metal leading etlge slats scale paint job scale Hercules engine frosting cake Giant Scale birds also evident nonscale judging categories black-and-gold Ray Ban special Weeks biplane entered Sport Biplane Big birds invaded OldTimer category well Boehie Giant looked must have taken weeks pro duction Top Flites transparent Mono Kote cover huge wide-angle camera lens couldnt capture stalwart wasnt content just dis play model Upon returning under ground parking garage next hotel Friday afternoon heard unmistakable sound RC engine parked car walked toward engines hum Sure enough flying RC Heli copter goodan opinion confirmed three municipal employ ees formed audience As 1989 RC helium balloonsI counted nine various timesflittered above crowd arena Pickup bal loon races arranged radio prob lems hanging power cables frustrated would-be Phineas Foggs 1990 Giant year Toledo show Given continuing creasing interest large-sized Scale mod els isnt surprising SAFE FLYING IS NO ACCIDENT 182 Model Aviation WILHAMS ACCESSORIES 4 PILOT STANDARD TSMAN RACING TARY WHEELS AGE TH CONTOUR BALLOON EN AGt 4 ENGINES PRATT & WHITNEY HT HONE PARTS T & WHITNEY HONE WRIGHT E GUNSj LEWIS VICKERS DAU SELLUM SEND $3 FOR FULLY ILLUSTRATED CATALOG$LUAI~1S DEPT MAPAWNEE ST SAN MARCOS CALIFORNIA 92069 I
Edition: Model Aviation - 1990/08
Page Numbers: 34, 35, 182
QSpIa1 '77 childs understand/ ing natural laws / can give us power less noise U Duane Gall RC FLIERS especially Racing Pattern fliers have problem noise No Im going discuss detail fact problem much noise intolerance sport nonpartici pants Nor will say much about men tally debilitating effects staring dB meter too long will simply say standard including dB use muffled tuned pipe significantly im proves noise situation no power loss Tuned pipes both muffled nonmuf fled have around since 1960s use muffled pipes now commonplace RC Pattern muffled pipe ap propriate header can found fit virtu ally two-stroke engine now mar ket modern Schnuerle-ported engine designs benefit use pipe much benefit can expected Ex perimenting Picco 40-powered Scat Cat racer measured drop over 11 dB simply fitting stock MACS #1240 muf fled pipe over open end header same time gained over 1000 rpm significant either changes however change sound qualitythe pipe changed sound raspy drag racer snarl pleasant Saab turbo-style whoosh contrast muffler came engine reduced b dB about half much no no ticeable effect rpm did nothing smooth out sound quality Im convinced complaints about noise have nothing dB rather quality sound mod els make else nonmodeler neighbors tolerate lawn mowers motorcy cles full-size aircraft vastly exceed sound levels model aircraft else Giant Scale models often granted unofficial exemption dB limits flying fields have such limits digress Suffice say use muf fled tuned pipe gives least much reduc tion noise dB meter would indi cateand probably much morewithout sacrificing power Ill now explain can get benefits little no tinker ing fliers think tuned pipe cy lindrical chamber filled voodoo magic Theyre scared use because think need PhD understand Bal derdash youve ever seen six-year-old take bath already know pipe works Just watch kid sits tub leans forward little back little forward again small wave starts traveling end tub other back forth kid soon discovers wave always goes same speed rocking faster doesnt help along rocking just right speed kid adds little energy time wave passes building up real tsunami slams end tub spraying water everywhere fun doesnt end until tub empty adult comes room whichever happens first tuned pipe bathtub above ex ample engine kid goal find point Maximum Splat varying length tub speed kid both length tub pipe determines its resonant frequency speed kid engine needs go achieve Maximum Splat beauty tuned pipe takes otherwise wasted portion engines energyie noiseand returns some engine stroke piston shock wave little burp exhaust travels down diverging cone pipe see sketch gaining mo mentum pulling spent fuel/air mixturethe exhaustbehind out engine same time its also pulling some fresh fuel/air mixture completely through engine carburetor part shock wave hits con verging cone far end pipe reflected back toward engine re 34 Model Aviation 1 flected wave actually pushes some fresh fuel/air mixture upstream ex haust port just before closes packing fresh charge combus tion chamber would otherwise result like supercharging no moving parts small weight penalty addition secondary expansion chamber see sketch diffuses exhaust stream reducing noise further doesnt interfere supercharging ef fect contrast ordinary untuned expan sion chamber muffler simply absorbs diffuses engines sonic energy its equivalent covering bathtub examplekid allwith large plastic bag its just about healthy engine bag kid find point Maximum Splat Start mounting pipe header sans pipe engine Put normal-size propeller front fire up Dont forget ear plugs Needle peak rpm back off slightly rich Shut en gine down Now add pipe pipe generally taches header using short piece neoprene tubing allowing overall length adjusted over range 1 now keep longdont insert metal parts way neoprene tubing can use pair small automotive hose clamps stops set length sembly see sketch Start up engine low throttle ad vance high throttle As engine rpm ap proaches pipes resonant frequency will start come pipe Youll no tice very definite boost power Splat begins doesnt either propel ler too big pipe too short Switch lighter prop eg 10 x 6 9 x 6 10 x 5 try again Manufacturers generally make pipes headers about right anything little long should able get nice boost too much fiddling next step push ends pipe header together until touch side neoprene coupler shortens pipe little Now see engine still comes pipe sitting ground go back original length Set needle valve rich can noticeably reducing rpm ensures engine wont run ning lean air pipe wont hear sag until its very overlean Fly airplane comes off pipe top loops vertical climbs youre sure its because overlean mixturego smaller propeller hear waffling warbling dives youre sure its because overly rich mixturego bigger prop start shortening header % time using saw tubing cutter After cut sure blow out metal shavings before running engine again pumping ac tion pipe will inject right exhaust port Once sounds happy air youre ba sically done During flight testing may NEOPRENE ORDIVERGING SILICONE eSUPLER HEAOER TO CONTROL LENGT4 COUPLER have shortened pipe point wont always come sitting Continued page 182 CONVERGING TAILPIPE RIrv CONE iIOIINING I SECONDAR EXPANSION CI4AIIEER LJTN INTEPMAL BAFFLES SJ4GCIC WAVE ACCELERATIWG IN DIVERGING CONE 7- COMPACTED IJI CYUOJDESPEJT GASES r CTAILPIPE tuned pipe action top drawing depicts typical tuned pipe installation show ing coupler clamps allow minor adjustments overall length tailpipe mount ing bracket cutaway view muffled pipe interior drawing engine has fired releasing spent gases header shock wave travels down pipes diverg ing cone creating partial vacuum carrying spent gases drawing B process has drawn some fresh fuel/air mixture completely through engine header same time reflected shock wave develops far end pipe begins move upstream drawing C reflected wave has supercharged engine fresh fuel/air mixture just before exhaust port closes Any spent gases remain ing pipe will pushed out cycle starts again refer back drawing August 1990 35 authors Scat Cat demonstrates typical tuned pipe installation Its completely stock MACS #1 240 pipe hooked up Picco 40 engine Picco header swinging 9 x 7 Rev-Up propeller engine/header/pipe combo operates about 17000 rpm ground Note pressure line running widest point pipe pressure greatest constant simple twist tie secures aft end pipe MACS nylon fitting total length pipe exhaust port widest point about 12 Cross-Country clarification February column said Great Race put Chicagos SOAR club granddaddy CrossCountry races said because believed guess oldest X-C race still ing conducted having started 1976 Bicen tennial tribute Jerry Krainock Dave Peltz wrote point out Great Race first X C race Jerry San Fernando Valley Silent Flyers clubmates organized first X-C race fall 1975 SFVSF ran contest until about 1987 Jerry goes back much farther X C having set FM-recognized distance records 1972 1974 Dave said Jerry co authors FAT F3H X-C rules hope sets record straight Max Splat/Gall Continued page 35 ground OK engine generally un loads 10-20% air ground rpm may well below pipes resonant frequency though system works Well air want highest possible power output such FAI racing competition theres factor consider engine has rpm rangethe power band peak rpm produces power Manufactur ers often include information instruc tion sheet comes engine Ha threw away didnt case trick have Maxi mum Splat occur have occur engines power band air Recall Maximum Splat depends two factors pipe length engine rpm know engines peak rpm can make ourselves bench prop will spin about speed simulate con ditions air allows us control other factor pipe length gradually cutting pipe header shorter until rings happily target rpm always balance propeller always wear eye protection As zero target rpm bench prop may spin little too fast due assistance pipe Also inevitable result cutting pipe match specific rpm last cut will actually go little too far Its like helpful lady bus says Oh know stop Just watch get off stop before So its best start bench prop little large say 2000 rpm below target rpm have target rpm itself little low say 1000 rpm below engines actual peak time go over target rpm make slightly larger bench prop Shorten pipe time until rpm no longer increases witl cut done whittle new prop i turns 80-90% engines peak rpm ac count 15% unloading alr Fly tht plane using trial error outlined above t find exactly right ground rpm Muffled tuned pipes may cure ills solve elegant fashion twin problems insufficient muffling power needed insufficient power muffling needed modelers used readily available devices perhaps could quil bickering about noise get real bus iness sport hobby enjoy May Splat Giants/de Vries Continued page 41 Japanese Zero Platt kit en tered Precision William Carper Jackson OH Precision Scale model turned everybodys head Frank Mizers Westland Lysander its fully detailed scale interiorincluding such niceties trim wheels complete crew safety harnesses epitomized art Precision Scale functional metal leading etlge slats scale paint job scale Hercules engine frosting cake Giant Scale birds also evident nonscale judging categories black-and-gold Ray Ban special Weeks biplane entered Sport Biplane Big birds invaded OldTimer category well Boehie Giant looked must have taken weeks pro duction Top Flites transparent Mono Kote cover huge wide-angle camera lens couldnt capture stalwart wasnt content just dis play model Upon returning under ground parking garage next hotel Friday afternoon heard unmistakable sound RC engine parked car walked toward engines hum Sure enough flying RC Heli copter goodan opinion confirmed three municipal employ ees formed audience As 1989 RC helium balloonsI counted nine various timesflittered above crowd arena Pickup bal loon races arranged radio prob lems hanging power cables frustrated would-be Phineas Foggs 1990 Giant year Toledo show Given continuing creasing interest large-sized Scale mod els isnt surprising SAFE FLYING IS NO ACCIDENT 182 Model Aviation WILHAMS ACCESSORIES 4 PILOT STANDARD TSMAN RACING TARY WHEELS AGE TH CONTOUR BALLOON EN AGt 4 ENGINES PRATT & WHITNEY HT HONE PARTS T & WHITNEY HONE WRIGHT E GUNSj LEWIS VICKERS DAU SELLUM SEND $3 FOR FULLY ILLUSTRATED CATALOG$LUAI~1S DEPT MAPAWNEE ST SAN MARCOS CALIFORNIA 92069 I