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Old Jul 13, 2009, 09:05 AM
Twisted Realm's Avatar
United States, FL
Joined Aug 2008
4,239 Posts
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low kv bigger prop vs higher kv smaller prop

I can under stand the above statement for wattage and power reasons, but I don't understand the difference of flight? Do you want more prop area over the plane for harriering and 3d flight? Just wonder what the difference in flight characteristics you get with haven't a larger prop. I'm wondering if you get more or less torque prop whith a large prop? Any thoughts?
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Old Jul 13, 2009, 09:33 AM
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AllBread's Avatar
United States, CO, Denver
Joined Sep 2007
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A larger prop will put more air over the control surfaces at slower speeds, which is usually a good thing while flying 3D. However, you will experience more of the effects of torque, spiral slipstream, and p-factor with a larger prop. Therefore, you'll usually see larger props for 3D and smaller props for IMAC flying (to make a gross generalization).

As far as motor kv, it's all a balance of the motor kv, voltage, prop size, and altitude.
I would be able to swing the same size prop on a higher kv motor in Colorado as you would in New Jersey. I can also get close to the same size prop on a 4s set-up that guys at sea level get on a 3s set-up. Same voltage, same kV, I have to prop up to get the same power which may or may not be desirable.
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Old Jul 13, 2009, 10:25 AM
Twisted Realm's Avatar
United States, FL
Joined Aug 2008
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Quote:
Originally Posted by AllBread
A larger prop will put more air over the control surfaces at slower speeds, which is usually a good thing while flying 3D. However, you will experience more of the effects of torque, spiral slipstream, and p-factor with a larger prop. Therefore, you'll usually see larger props for 3D and smaller props for IMAC flying (to make a gross generalization).

As far as motor kv, it's all a balance of the motor kv, voltage, prop size, and altitude.
I would be able to swing the same size prop on a higher kv motor in Colorado as you would in New Jersey. I can also get close to the same size prop on a 4s set-up that guys at sea level get on a 3s set-up. Same voltage, same kV, I have to prop up to get the same power which may or may not be desirable.

Thats basicly what I thought about having a larger props. But I had no idea the different elevations make that much of a difference. LOL
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Old Jul 13, 2009, 11:01 AM
Registered User
Palmdale, CA
Joined Oct 2008
329 Posts
There are some prop/motor calculators out there that factor in altitude. It is interesting to see how much altitude affects the thrust/prop size.

It is a interesting learning experience to put a small prop (like say a 6" prop on a 40" wingspan plane) and a high KV motor on a 3D plane and see how it handles. I've done that before and it is surprisingly hard to fly post stall.
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