I have a nice light simple stick, and with an out runner brush-less motor and an 8 cell pack I get about 9 minutes duration with a 9x7 gws prop, now if I change the prop to a faster turning 5x4 the white push on kind that are very efficient and very light, can I still get the power and more speed as if it were a flying wing type plane and yet have at least 7-9 minutes of flying time?

If you are using a 9x7 now, and the power is acceptable, but you are looking for a little more top speed, something around a 7x7, 7x8, 8x7 would be the range I would look at. Going all the way down to something like a 5x4 is going to give you next to nothing in terms of overall power.

THANKS SO MUCH FOR THE INFORMATION ON THER PROP SIZES .AS I GAIN IN TOP SPEED CAN I THROTTLE DOWN AT TIMES AND GET THE SAME DURATION OR MORE WITH THE SMALLER PROPS? I HAVE HAD EXPERIANCED THE BRUSHED TYPE SPEED 400S BUT NOT THIS NEW BRUSHLESS I HAVE NOW WHICH I REALLY LIKE.

Yes, you should still be able to throttle back at times to conserve battery juice. The main difference you will notice is that you will have to have the throttle up a little higher on the stick, but it basically all balances out, since the prop. will be a bit smaller and most likely pull less amps than the 9x7. Your flight times will be relatively close to what you are getting now, they should be a tad longer due to less current draw.

Thanks again .

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.