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Old 01-17-2011, 08:04 AM
  #11  
Larry3215
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Join Date: Mar 2006
Location: Gig Harbor, Wa USA
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Im a big fan of building as 'lite' as possible. If you add in that you only want to do mild aerobatics, then I see no reason to add the weight.

You could probably even get by with smaller cells than the 5000's and still get reasonable flight times.

However, I would wait to order any packs until you have the model mostly built and the motor mounted. Then you will see what you need in terms of weight in the packs to get a good CG.

No point in adding lead when you could use battery instead.

On the other hand - on all my large models I go with the highest voltage I can and choose motors, gear boxes etc to maximize power and minimize weight.
Higher voltage allows you to get higher power levels at lower amp levels.

For example, to get 2000 watts on 10S means you have to draw in the 57 amp range. To get the same 2000 watts on 12S means your max amp draw goes down to 47 amps.

That means you can either pull more amps on a 12S setup for the same flight time - or have the same power and fly longer and have all your components run cooler.

Heating is a function of I^2*R so heating losses go up (or down) as the square of the current. So yopu can generally get a slightly more efficient system by going with higher voltage.

On my 86" Yak I used a Neu 1515 motor and ran it on 12S with a 22" prop at about 3200 watts peak. My model weighed right at 18 pounds all up.

I used the same power system on a GP Ultimate that also ended up about 16 pounds.

By the way, dont be surprised if your model ends up a few pounds heavier than advertised.
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