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How do I determine the best e propeller?

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Old 09-19-2016, 11:52 AM
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johntursi
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Default How do I determine the best e propeller?

I used to fly wet fuel but have not flown in several years, I wanted to get back into flying and into electrics. So i took a partially built 40 size trainer, a bunch of inexpensive parts and converted it to an electric tail dragger. Electronics are; motor Turnigy 530Kv 795W, 5S 4000ma, 60A ESC. My one and only prop (I have not flown it yet) is an 11x7e. The airplane RTF weighs 6.5 lbs. I static ran the motor with the following results; with the battery at 95% capacity and full throttle I recorded the following - 20.13A, 20.02V, 403W. I did not record RPM. How do I determine the most efficient prop size and pitch??
Thank you in advance for your thoughts.
John
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Old 12-07-2017, 10:17 AM
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jollyroger
 
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You're going to have to experiment a bit. An 11X7 is a bit of a speed prop which you don't need for a trainer. I would try a 12X6, 13X6.5 and even a 14X7.
keep in mind how much prop clearance there is.. For a plane that size I think the KV is a bit low but with the right prop it should work ok.
You do not want to push the motor to to its max current rating , stay within 80-85% The only Turnigy motor with 530KV that I could find is the 4206.Is that what you are using?
For any particular plane I consider how much prop clearance there is and work from there. I match the motor with the type of air frame, so for a trainer, you do not need a hot motor, you're going to need to get at least 600+ watts in and maybe a bit more due to losses in the motor. A 5S pack looks fine all you need are some larger props.
My favorite brands are Scorpion and Cobra motors as the stateside distributor, Inov8tive Designs, tests all the motors for performance using various battery pack and prop sizes.
Good luck.
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