ORIGINAL: ozrcboy
I might be wrong but it was my understanding that in general a bigger prop was *more* effecient. You go to smaller props because:
- You can spin the prop because of ground clearance
- You are after pitch speed more than thrust
If you want longer flight duration reduce the throttle - I think going to a smaller prop will probably make it worse.
Reducing or increasing prop size is typically about either increasing top speed and pitch speed, or increasing thrust - flight duration is a different topic.
I am not sure if I would say, in general, that larger dia. props. are more efficient. It depends on what you are trying to do, and the model you are trying to do it with. The larger dia. prop. with a comparable pitch is definitely going to produce more thrust. The smaller dia. prop., with a comparable pitch is going to produce more top speed, just based on the increased RPM's. In terms of flight duration and amp draw, if the pitch is comparable, the larger dia. prop. is going to pull more amps than the smaller prop., which will drain the pack quicker. The smaller dia. prop. is going to work a lot harder in terms of RPM's to get close to the amp draw of the larger dia. prop., but won't quite draw as much juice. If I am making any sense
This is at least, my experience based on testing with several different planes and power systems.
I took his inquiry as he was looking for a little more speed out of the plane, but with a comparable flight time. Bumping down in prop. dia, and up in pitch should accomplish that.