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Old Oct 15, 2013, 11:04 AM
got any foam to bash?
Tom Hunt's Avatar
Lake Grove,LI, NY
Joined Aug 2000
5,387 Posts
Quote:
Originally Posted by Alien_Tech View Post
I use no brake and let it spin. A stopped prop has less drag than a spinning one.
Alien Tech is correct here, for all the reasons he has already stated.... mostly the work and energy parts. Though I have spent most of my entire aerospace career in wind tunnel testing, I still don't have "quantitive" numbers to how MUCH more drag a spinning prop is from a stopped one, but I assure you it was easy to see in the data.

I did "SEE" the result flying one of my smallish sport models one day. The model behaved absolutely homesick for the ground when the prop was in "windmill". This prop was rather "large" for the model for exceptional duration under power, but was a lead sled with the power off. One day I put an additional small servo on board to drive a pin into the arc of the spinning prop to stop it (a brake on the ESC was insufficient). The model glide improved subsantially!

it does NOT matter what altitude, size of model or size of prop. The relationship is constant unitl you get into "feathering".

Tom
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Last edited by Tom Hunt; Oct 15, 2013 at 12:07 PM.
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Old Oct 15, 2013, 11:35 AM
I want just one more plane!
timwj1's Avatar
United States, ID, Idaho Falls
Joined Feb 2013
397 Posts
Thank you guys, I knew I wasn't crazy when I converted to the higher RPM motor with the small prop and the plane seemed at least 10 to 15mph faster than the larger prop on landings. It really dumbfounded me at the time but it all makes total sense to me now.
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