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Old Mar 06, 2012, 11:37 AM
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hog2soar's Avatar
Central California
Joined Jan 2010
962 Posts
Question
Is there a prop conversion chart to go from apc to folding

Is there any kind of a chart or formula to determine what size folding prop would be equivilant to say an apc prop?

A lot of the motors give you the recommended prop size,but very few give you folding prop sizes. How do you determine what size folding prop would be required for any given motor?

Thanks in advance for any advice.

Eddie
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Old Mar 06, 2012, 03:08 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,263 Posts
I don't think there is a major difference between a fixed blade prop and a folding prop, other than possible blade shape. That can also go for different prop manufacturers of the same sized prop.

If for instance you used a 10 x 6 fixed blade prop, I would expect a 10 x 6 folder to give similar results, (from the same manufacturer). I wouldn't expect to increase or decrease a diameter to compensate.

But as always the 'proof of the pudding' is in the flying, (and watts drawn).

Here's the APC web site - http://www.apcprop.com/pindex.asp

If you scroll down a bit you should see a small menu on the left that also links to their folding props.

Also try their 'Home' page, (link at top), for more information.
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Old Mar 06, 2012, 07:07 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,957 Posts
You have to have a watt meter and run them up and see how they do, there is simply no better way. But I would consider the test data for a fixed prop of the same diameter and pitch to be rough approximation of what to expect.

The attached image is from Aeronaut, it is handy to get in the ball park with as far as choosing props. The left/vertical column is the power in watts and the bottom/horizontal scale is the RPM in 1000's. So if you have a 200 Watt motor (i.e., the watt meter says that it is pulling 200 Watts) you can look for the straight line that represents a given prop and see what the RPM would be for that.

Or, if you have a prop you can look at the RPM you want to turn it and see how much power is required.

But all thing considered, there is no substitute for testing with a watt meter. And checking for excess heat with your finger tips too.

As for the various cheap Chinese props, there is no published info so you unless you can find some test data from a user you just try it and see how it goes.

A while back I ran a motor up with a Graupner CAM folding prop and then with two pairs of the cheap "hy" or Haoye folding blades from R2 Hobbies and got the following results:

Graupner 10 x 6 12A 115W
Haoye 11 x 8 15A 152W
Haoye 12 x 8 18A 184W

I wasn't making detailed or accurate measurements but the results on all of those compare pretty well with the numbers on that Aeronaut graph.

The Aeronaut and Graupner props are definitely slimmer and thinner and look and feel like they are made better than the Chinese Haoye blades. And they folded closer to the spinner and fuselage too.

Jack
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Old Mar 07, 2012, 11:15 AM
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hog2soar's Avatar
Central California
Joined Jan 2010
962 Posts
Thanks guys. I just needed a place to start.

Eddie
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Old Mar 08, 2012, 11:49 AM
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snoopy_schulz's Avatar
Germany, lake of constance
Joined Oct 2010
407 Posts
Hi hog2soar

In the attachment i have APC and Aeronout prop data.

Best regards
Micha
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Old Mar 08, 2012, 05:33 PM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,200 Posts
I have just two comparative data points for you... I tested a MicroDAN 2505 3D motor (~1275Kv) with a whole suite of props, but amongst them were a stock 8x4 APC E and an 8x4 APC folder... apples to apples!

8x4 APC folder:
10.9v, 7.10A, 77W, 11040rpm, 41.8mph, 431g, 15.18oz, 5.60g/W

8x4 APC E:
10.9v, 10.65A, 116W, 9510rpm, 36.0mph, 602g, 21.20oz, 5.19g/W

... the 8x4 APC E produces 40% more thrust, but at 14% lower pitch speed, and requires 50% more power to do so.
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Last edited by Dr Kiwi; Mar 08, 2012 at 09:36 PM.
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Old Mar 08, 2012, 05:38 PM
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Dennis Everett's Avatar
United States, CA, Ontario
Joined Mar 2002
7,669 Posts
when changing props from one mfg to another , you need to watt check your setup , ive gone from a apc-e to another prop , same size , was about 30% different amp draw ....
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