wolf. Posted October 22, 2008 Share Posted October 22, 2008 In restoring my VE I will install a BMW Motorcycle 2 cylinder engine (which is being sucessfully used since 20 years, up to 125hp out of 178lbs installed). The engine is about 8 inches shorter than a O-200. If I have my prop station 8 inch advanced I can install a longer prop (the engine being geared a longer prop would make sense) Now my question, does a longer prop make sense on the VE, if yes how much longer can it be?? wolf. Quote Cosy Classic flying (ex LX-ACE) Varieze N39JC rebuilding Link to comment Share on other sites More sharing options...
TMann Posted October 22, 2008 Share Posted October 22, 2008 A shorter engine? I wonder how that will effect your CG. Quote T Mann - Loooong-EZ/20B Infinity R/G Chpts 18 Velocity/RG N951TM Mann's Airplane Factory We add rocket's to everything! 4, 5, 6, 7, 8. 9, 10, 14, 19, 20 Done Link to comment Share on other sites More sharing options...
Lynn Erickson Posted October 23, 2008 Share Posted October 23, 2008 In restoring my VE I will install a BMW Motorcycle 2 cylinder engine (which is being sucessfully used since 20 years, up to 125hp out of 178lbs installed). The engine is about 8 inches shorter than a O-200. If I have my prop station 8 inch advanced I can install a longer prop (the engine being geared a longer prop would make sense) Now my question, does a longer prop make sense on the VE, if yes how much longer can it be?? wolf. What would you gain by a longer prop? the prop still has to drive the same aircraft at the same speed with the same HP. if the prop is longer then it may need to be thinner or different blade shape. what does being geared have to do with it. the faster vari ezes are running 3000 + RPM and they use shorter props Quote Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years Link to comment Share on other sites More sharing options...
wolf. Posted October 23, 2008 Author Share Posted October 23, 2008 What would you gain by a longer prop? the prop still has to drive the same aircraft at the same speed with the same HP. if the prop is longer then it may need to be thinner or different blade shape. what does being geared have to do with it. the faster vari ezes are running 3000 + RPM and they use shorter propsthe faster VE are using direct drive engines and you have to run them high for max power, 3000+ needs a short prop to remain efficient. (Actually I was still not able to find out if the short prop recomanded by Burt is due to the high engine RPM of the O-200 or the chance of Propstrike) But a geared engine can turn the prop slower and a bigger prop with higher torque is more efficient (especially if it is a CS) (propulsion is impulse (v x m) so more air at lower speed is more impuls, that's why jet engines are inefficient at lower airspeeds) SInce the VE suffers from high weight and back CG any engine which is lighter and shorter will be of benefit, my question remains -8 inch in prop station how much bigger can the prop be??? wolf. Quote Cosy Classic flying (ex LX-ACE) Varieze N39JC rebuilding Link to comment Share on other sites More sharing options...
ZUCZZ Posted October 23, 2008 Share Posted October 23, 2008 Suppose one must look at the efficency of a longer prop ... at what point would the tip reach max effective velocity? There are some prop programs that can answer this, sorry I have no links to these. Quote I live in my own little world! but its OK, they know me here! Chris Van Hoof, Johannesburg, South Africa operate from FASY (Baragwanath) Cozy Mk IV, ZU-CZZ, IO-360 (200hp) 70x80 prop Link to comment Share on other sites More sharing options...
jdubner Posted October 23, 2008 Share Posted October 23, 2008 There are some prop programs that can answer this, sorry I have no links to these.You could play with Ed Dokus' "PropDesign" program which I ported to MS-Windows many years ago. http://mail2600.com/PropDesign/index.html It's somewhat simplistic but at least the price is right (free!). -- Joe Quote Joe Dubner Long-EZ, RV-8A Link to comment Share on other sites More sharing options...
wolf. Posted October 23, 2008 Author Share Posted October 23, 2008 Guys I need the prop size which the VE airframe geometry would allow if I would retract the prop station by 8" (Don't want to take the VE of my friend and and tilt and measure (rather cumbersome) once I know the max I will talk with the engine designer (since I am opting for a light geared engine I will install one of the new light CS props anyway) wolf. Quote Cosy Classic flying (ex LX-ACE) Varieze N39JC rebuilding Link to comment Share on other sites More sharing options...
Lynn Erickson Posted October 23, 2008 Share Posted October 23, 2008 Guys I need the prop size which the VE airframe geometry would allow if I would retract the prop station by 8" (Don't want to take the VE of my friend and and tilt and measure (rather cumbersome) once I know the max I will talk with the engine designer (since I am opting for a light geared engine I will install one of the new light CS props anyway) wolf. why would anyone know this? there aren't any vari ezes built this way. if your engine is lighter why would you not put the engine back farther and the prop where it is designed to go? with the prop forward it may have more interference drag caused by turbulence of the wings and fuselage. Quote Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years Link to comment Share on other sites More sharing options...
Edge 513 Posted October 23, 2008 Share Posted October 23, 2008 SInce the VE suffers from high weight and back CG any engine which is lighter and shorter will be of benefit, my question remains -8 inch in prop station how much bigger can the prop be??? wolf. I wasnt aware of this 'suffering'' but here is the reason. Quote Self confessed Wingnut. Now think about it...wouldn't you rather LIVE your life, rather than watch someone else's, on Reality T.V.? Get up off that couch!!! =) Progress; Fuselage on all three, with outside and inside nearly complete. 8 inch extended nose. FHC done. Canard finished. ERacer wings done with blended winglets. IO540 starting rebuild. Mounting Spar. Starting strake ribs. Link to comment Share on other sites More sharing options...
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