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jobu
09-21-2005, 07:21 PM
I have a Kontronic Fun 400-23 brushless motor and I have been using it until now on a wing 27oz. 11.1/1500 direct drive 6x3.5 prop.

I am making a 3d/sport plane should be about 22oz. fw. and now have 11.1/2100mah
I would like to hover and was wondering if anyone has any sugestions if I should put a gearbox on it or fly direct and if so which prop would you recomend?

Thanks
Joe:confused:

jonnyjetprop
09-21-2005, 08:19 PM
I threw some numbers into Motocalc. It looks like 2.5:1 to 3:1 geared would give you 175-225 watts input. The efficiency is lower at 2.5:1 than 3:1. I put in using a 12x6 apc eprop. At 22 oz.,that's 127 watts/lbs. with the 3:1 gearbox.

I'd look at the cobri g/b at http://www.e-flightline.com/. They are great to deal with.

John

jobu
09-22-2005, 01:56 PM
Thanks John,
I have a few Cobri gear boxes now and think they are awesome.
Thanks for doing the legwork. I think 200+ watts should be more than adequate to hover 22oz. Do you think I should go higher gear ratio (4:1) and smaller prop say 11x4.7?
Joe

jonnyjetprop
09-22-2005, 10:56 PM
I thnk that if you wanted to go to a smaller prop, I'd go to a lower gear ratio like 2.3-2.4:1 to keep the current up around 20 amps. This seems to be a sweet spot for the efficiency of the -23 turn motor. Of course, I'd play around with props to tweek the setup. Remember, this are just estimates from Motocalc.

John

jobu
11-25-2005, 04:25 AM
Well the plane ended up at around 27 oz. but it flew excellantly. Even in about 25mph winds 2 weeks ago in the north east.
I used the 3:1 gb from cobri and apc 12x6sf
I could not believe it flew or that I threw it up in that wind.
thanks
joe