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Mar 09, 2012, 10:57 PM
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Need advice building a plane.

Figured I should cross post this here to get some more exposure.

I've wanted a Sbach ever since I fist saw one and am trying to decide between these two:
The 39" "BX"

The 40" "SC"

I originally wanted the "bx" because it looked a little more durable but I don't think that is the case any more and would rather have the more scale looking "SC".

I already have my servos ( ordered. Those servos look comparable to the HS-65MG's but a lot cheaper and are digital so I should be able to get more than 90 degrees of travel out of them.

I am probably going with a 4A esc ( The 40A is probably way more than needed but it seems to be the smallest size with a built in 6V BEC. Or are there any other smaller switching ESC's with a built in 6 volt BEC. The HobbyWing I linked is switchable between 5.25 and 6V but I think 4.8 and 6V would be better. Then I could run on 4.8V to conserve battery when faster throws and higher torque isn't needed. Or would a smaller more appropriate sized ESC and a seperate BEC be better?

Batteries will be Gens Ace 25C in either 1000 or 1300mah.

Choosing a motor has been the most difficult for me so far. Matching kv's to props, etc... The recommended motor is the Dualsky XM2834CA-9 980Kv which weighs 70g. So I'm looking for other motors in the 70g range which are the:
Hengli Brushless Outrunner Motor W3542-850
Twisted Hobbys 1250kv Telink motor
I believe the same 1250kv motor but a lot cheaper.

After doing some research and playing with WebOcalc I think I've determined a APC 11x5.5 E would be the most efficient prop for this plane.

This is with the recommended Dualsky 980kv motor:

Is 1.4 to 1 about the best I can do with a 70g motor? I'd like around 2-2.5 to 1 I can't seem to get any slow fly props on WebOcalc but it's my understanding that you should only use them when you can't fit a larger prop. And that they'll make more thrust but at a higher amp draw.

This on is with the 1100 kv motor from Twisted Hobbys:
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Mar 10, 2012, 09:42 AM
Registered User
Have you considered the 48" version, generally the larger ones fly much better than the smaller ones. Of course they are a little more expensive, but from my experience it's well worth it.

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