I am currently getting an X4 cylinder, 150cc, 4 stroke engine 3D CAD Modelled, this engine is initially being designed for Powered Paragliding (PPG), classified as experimental Aircraft, so no certification is required!
I have read several discussions here, that largely relate to large ridged winged Aeroplanes travelling at high ground speed.
PPG is a Low & Slow (22~75kph) Aviation sport, there are obvious differences with this project being;
Most PPG engines max. rev are from 7'000~12'000rpm. Then a Re-drive is used to slow Prop down to approx. .88~.90 mach.
With a PPG, it is the Wing that sets the Speed in flight, not the engine! A larger more powerful engine only provides a higher climb rate or maintain lever flight easier.
Most engines of similar capacity swing a 125cm (49/28") Prop at around 2'700rpm to under 3'000rpm.
The engine we are designing uses a unique engine that has replaced the 100yr old conventional crankshaft with a patented Contra-rotating Trilobe centre drive shaft (CDS) technology, that uses two trilobe cams, that strokes each Piston 6 times on One revolution, thus providing 3 combustions in two revolutions of CDS, this engine will not be revving over 3'500rpm maximum.
Engine is currently 12.5kg and 41cm width x 37cm high x 20cm deep.
I am planing on using Two 100cm (40") Contra-Rotating propellers!
I would appreciate it if anyone could assist/help me if this is an appropriate Sized Prop & what Pitch would be best ?