The flying monkeys got me...

Helis and fixed wing

AMA 957918
IRCHA 4345
AMA Intro Pilot Instructor

Friday, April 4, 2014

Sbach Power Calculations

I did some power calculations using 6S and various prop configurations using eCalc. I estimated the built up weight at 2500gms, and put what I think is my motor in the calculator (went back to do another 8S calculation and that motor choice was gone.... Odd). The simulations seem to make it clear that 6S will be more than powerful enough, giving in excess of a 2:1 thrust to weight ratio. Turns out 8S is likely to over amp the ESC and is waaaaay more power than it needs. It also is clear that I chose a good prop at 17x7 (though a 16x10 would give a nice increase in thrust I think is overkill). Guess I could have gotten a cheaper amp if I had done the calcs first, and not bought a HV ESC...Click the images to enlarge.

Power Setup:

Motor: Turnigy Aerodrive SK 5055-430kv

ESC: HobbyWing FunFly 80A HV

6S, 17x7, 60 amps, 1244 watts, 89.5% eff, 5497 gms thrust

6S, 16x10, 65 amps, 1346 watts, 89% eff, 6377 gms thrust

8S, 17x7, 94 amps, 2545 watts, 86.4% eff, 8819 gms thrust



So it looks like my planned setup is a good one. Using about 130 watts per pound (aggressive aerobatic sport flying) at roughly 5.5 lbs gives a power requirement of 715 watts. I exceed that by a fair margin, say, about 42% more if I did my math right. Sweet! I will watt test the setup once I get it together, then see how she flies. I can move to a 16x10 if I want some more thrust and still stay within the power limits of the setup!


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