Technique George M Myers OK GEORGE propeller equations fine dont have PGF Chinn report engine So deter horsepower engine putting out theme has run through several communications have received since preparing February 1977 column Strictly speaking would need test stand measure torque rpm under carefully calibrated controlled condi tions However will now describe field test requires tachometer calculator advantage field test measures everything engine wear fuel muffler effects needle-valve tech nique density altitude etc re quiring quantify anything dis advantage results ap proximate first step run engine airplane measure rpm second step calculate horsepower using equation 263 easy have calculator does operation Y X Ifnot see Fig 1 equation HHorsepower R rpm K constant function propeller profile diameter pitch have worked out table K values two-bladed propeller using Top Flite Super M wood props Other profiles de serve different K values havent time resources develop right now check box propellers marked same will find really quite different difference significant change K want accurate use Top Flite Super M props calibrate en gine switch other brand Fig 1 shows K factors Lets assume have Supersnarl engine cowbell muffler running panther-sweat turns TF Super M 11/7 11000 rpm calculate horsepower follows H _ 092 11300/V /horsepower Now lets assume bolt Fox tuned-pipe muffler like Cutlass picture rpm increases 12000 12000\ 264/263 H11300 1106 117 /horsepower gain 2 1% Honestly first saw Fox pipe thought looked pretty silly bought about $16 got 1000 rpm increase Now think looks like designed plane Thanks Duke Additional plus features Its qui eter muffler came engine plane easier clean up because half plane front 8 FIG 1 K-factors two-bladed wood propeller Diameter91011121314 Pitch 61530014000121001080099009100 71480013000113001030095008800 8140001210010600910090008600 Note Linear interpolation fractional sizes adequate example K far 11506 propeller 11450 FIG 2exhaust stays clean No idle problems H versusfor typical range valutoeither KWhen come fit pope 16non-Fox engine need adapter mounting strap Take look SEMCO parts dealers pin-board think youll find what need Some folks have asked dont measure static thrust determine H correct propeller answer Because doesnt solve problem basic idea February 1977 column 06 Iyou want match airspeed Ipropeller wants go given horse 04power level speed air plane can reach horizontal unacceler 7 8 9 10 11 12ated flight same horsepower RStatic thrust increases propeller diKameter increases pitch reduces Unfortunately maximum thrust will PROCEDUREusually obtained propeller thats 1 Measure rpmtoo slow fly airplane 2 Find K prop Fig 1 Getting back uses equa 3 Compete R/Ktion might want pick best prop 4 Enter Fig 2 Read op over horsepower Hwithout trying store FIG 3 FOX PIPE TEST DATA 13 12 wII 0 10w 0 9 7 -K 10K Ilk K MUFFL 9 12K 13K 14 K 15 K RPM Prop TF Super M AHM-ST Rev-Up 2 TF TF Pitch/Dia 11/75 11/7 115/B 10/5 9/8 9/7 K 11700 11300 11450 15000 14000 14800 Pipe rpm 11000 11200 12500 15000 14200 14800 HMuffler rpm 85 10500 98 10800 126 11800 100 14200 103 13600 100 14200 H 75 89 108 87 93 89 10 Model Aviation make decision First collect what have way propellers might acceptable run engine Record rpm calculate horsepower devel oped Plot own horsepower rpm curve Fig 3 comes data collected testing Fox pipe Dont bother telling engine needs new ring its order Fox tuned pipe fitted authors Cut lass found gave him 1000 mbre rpm Rev-Up 115 x 6 prop No idle problems Try make sure testing behind propeller because always possibility youll throw blade particularly using small propellers big engines Looking data 11 X 6 RevUp Special Pro Series 2 looks like ideal prop particular combination day engine fuel muffler propeller Off flying field find out few test flights later have information. 115 X 6 best particularly gratiling because plane took lot work develop point liked its handling characteristics order get balance point far enough back mount fuel tank over rear half wing fuel draw became problem Muffler pressure inadequate prevent leaning out vertical ma neuvers tapped crankcase timed pressure like Cox engines pressure too much carburetor Finally bought Robart Super Pumper vented tank atmosphere problems solved engine will run vertical position long fuel tank Fox tuned pipe RevUp 115 X 6 prop engine has sufficient power climb vertically long want center gravity back belongs airplane performs ma neuvers ease including very rapid snap roll always gets people ask ing What heck thats left reduce dihedral wing improve four-point roll Im beginning like Cutlass Thats month Send suggestions George M Myers 70 Froehlich Farm Rd. Hicksville NY 11801 March1977 11 Denis Donohues El Tigre shown end product idea started forming mind back 1970 design featured July 1974 American Modeler attention toward aerodynamic cleanliness speed power combination Ross 60 engine Rev-Up 11-7 1/2 Author gives clues determining best propeller
Edition: Model Aviation - 1977/03
Page Numbers: 10, 11
Technique George M Myers OK GEORGE propeller equations fine dont have PGF Chinn report engine So deter horsepower engine putting out theme has run through several communications have received since preparing February 1977 column Strictly speaking would need test stand measure torque rpm under carefully calibrated controlled condi tions However will now describe field test requires tachometer calculator advantage field test measures everything engine wear fuel muffler effects needle-valve tech nique density altitude etc re quiring quantify anything dis advantage results ap proximate first step run engine airplane measure rpm second step calculate horsepower using equation 263 easy have calculator does operation Y X Ifnot see Fig 1 equation HHorsepower R rpm K constant function propeller profile diameter pitch have worked out table K values two-bladed propeller using Top Flite Super M wood props Other profiles de serve different K values havent time resources develop right now check box propellers marked same will find really quite different difference significant change K want accurate use Top Flite Super M props calibrate en gine switch other brand Fig 1 shows K factors Lets assume have Supersnarl engine cowbell muffler running panther-sweat turns TF Super M 11/7 11000 rpm calculate horsepower follows H _ 092 11300/V /horsepower Now lets assume bolt Fox tuned-pipe muffler like Cutlass picture rpm increases 12000 12000\ 264/263 H11300 1106 117 /horsepower gain 2 1% Honestly first saw Fox pipe thought looked pretty silly bought about $16 got 1000 rpm increase Now think looks like designed plane Thanks Duke Additional plus features Its qui eter muffler came engine plane easier clean up because half plane front 8 FIG 1 K-factors two-bladed wood propeller Diameter91011121314 Pitch 61530014000121001080099009100 71480013000113001030095008800 8140001210010600910090008600 Note Linear interpolation fractional sizes adequate example K far 11506 propeller 11450 FIG 2exhaust stays clean No idle problems H versusfor typical range valutoeither KWhen come fit pope 16non-Fox engine need adapter mounting strap Take look SEMCO parts dealers pin-board think youll find what need Some folks have asked dont measure static thrust determine H correct propeller answer Because doesnt solve problem basic idea February 1977 column 06 Iyou want match airspeed Ipropeller wants go given horse 04power level speed air plane can reach horizontal unacceler 7 8 9 10 11 12ated flight same horsepower RStatic thrust increases propeller diKameter increases pitch reduces Unfortunately maximum thrust will PROCEDUREusually obtained propeller thats 1 Measure rpmtoo slow fly airplane 2 Find K prop Fig 1 Getting back uses equa 3 Compete R/Ktion might want pick best prop 4 Enter Fig 2 Read op over horsepower Hwithout trying store FIG 3 FOX PIPE TEST DATA 13 12 wII 0 10w 0 9 7 -K 10K Ilk K MUFFL 9 12K 13K 14 K 15 K RPM Prop TF Super M AHM-ST Rev-Up 2 TF TF Pitch/Dia 11/75 11/7 115/B 10/5 9/8 9/7 K 11700 11300 11450 15000 14000 14800 Pipe rpm 11000 11200 12500 15000 14200 14800 HMuffler rpm 85 10500 98 10800 126 11800 100 14200 103 13600 100 14200 H 75 89 108 87 93 89 10 Model Aviation make decision First collect what have way propellers might acceptable run engine Record rpm calculate horsepower devel oped Plot own horsepower rpm curve Fig 3 comes data collected testing Fox pipe Dont bother telling engine needs new ring its order Fox tuned pipe fitted authors Cut lass found gave him 1000 mbre rpm Rev-Up 115 x 6 prop No idle problems Try make sure testing behind propeller because always possibility youll throw blade particularly using small propellers big engines Looking data 11 X 6 RevUp Special Pro Series 2 looks like ideal prop particular combination day engine fuel muffler propeller Off flying field find out few test flights later have information. 115 X 6 best particularly gratiling because plane took lot work develop point liked its handling characteristics order get balance point far enough back mount fuel tank over rear half wing fuel draw became problem Muffler pressure inadequate prevent leaning out vertical ma neuvers tapped crankcase timed pressure like Cox engines pressure too much carburetor Finally bought Robart Super Pumper vented tank atmosphere problems solved engine will run vertical position long fuel tank Fox tuned pipe RevUp 115 X 6 prop engine has sufficient power climb vertically long want center gravity back belongs airplane performs ma neuvers ease including very rapid snap roll always gets people ask ing What heck thats left reduce dihedral wing improve four-point roll Im beginning like Cutlass Thats month Send suggestions George M Myers 70 Froehlich Farm Rd. Hicksville NY 11801 March1977 11 Denis Donohues El Tigre shown end product idea started forming mind back 1970 design featured July 1974 American Modeler attention toward aerodynamic cleanliness speed power combination Ross 60 engine Rev-Up 11-7 1/2 Author gives clues determining best propeller