by Bryan Cotton » Sun May 11, 2014 10:45 am
Lsaircraft,
Prop diameter is chosen by RPM. The goal is to keep the tips subsonic. If you go bigger diameter, the excess power gets converted to noise rather than thrust. With a high RPM high power engine, you absorb the power by increasing pitch or chord.
Also, big props are good for static thrust at low speeds. Small props are good for thrust and efficiency at high speeds. There was a axiom in the helicopter industry that holds true here: what is good for low speed is bad for high speed, and visa versa. If you have sufficient climb performance with a small prop you will help your high end - a good tradeoff.
Bryan Cotton
Poplar Grove, IL C77
Waiex 191 N191YX
Taildragger, Aerovee, acro ailerons
dual sticks with sport trainer controls
Prebuilt spars and machined angle kit
Year 2 flying and approaching 200 hours December 23