Old 10-01-2011, 01:16 AM
  #76  
kyleservicetech
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Originally Posted by GFH View Post
I'm no dummy but it seems to me everyone has two different names for everything and one uses apples for measurement and the other oranges.

I've been a gas guy and decided electric for the next

SO I'm confused .............what do I need.

The model is 10 pounds a Jerry Bates Interstate Cadet (similar to a J3). Recommended power is a 60-90 2 stroke or 90-120 4 stroke or 23cc Gas.

What do I put on it for power? I might also use it to tow gliders up bt what is suggested with and without the towing option?

Cheers and thanks

G
Lets see, you need a minimum of 100 watts per pound of airplane, so that is 100X10 or 1000 watts. Since your model calls for up to a 120 4 stroke engine, that would be on the order of perhaps 150 watts per pound or a little more.

That is getting into serious electric motor horsepower. A wide variety of electric motors from a lot of different suppliers are available for this purpose. The question is which one to use?

One program that will help a lot is www.motocalc.com, free for 30 Days, then $39. You can enter in your models wingspan, area, weight without motor and battery, and it will give you an idea on how well the model will fly.

I'm an admitted Hacker nut, and would look at a Hacker A60-6SX. This motor would be an expensive, but very good power unit that will definitely pull your model around. Running this motor on an 8S1P (8 series, 1 parallel) LiPo pack with about 5000 Mah will allow this motor to turn a 16X8 APC-E (Electric) prop at around 9000 RPM. Motocalc indicates this motor will be running around 91% efficiency, a pretty good value. Again, per Motocalc, this motor will be pulling around 1900 Watts at full power, which turns out to be around 2.5 Horsepower. That comes out to about 190 Watts per pound, which will give plenty of power to haul up a sailplane in tow. I'm guessing on the wingspan, wing area and bare weight of your model as 66 inch span, 950 square inches, and 120 ounces bare weight with everything but the motor and battery.

Nice thing about the Hacker motors, they will do what their specifications say they will, and will do it year after year.

9000 RPM on a 16 inch diameter Electric prop might be pushing the maximum RPM limits on an APC-E prop, you might have to go to a glow engine type of prop on this setup.

As for speed controls check out the Castle Creations 75 Amp Phoenix ICE ESCs. The CC units work, and work well. (Looks like CC is out of stock on most everything, but perhaps other on line hobby stores will have one.)

Last edited by kyleservicetech; 10-01-2011 at 01:39 AM.
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