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May 05, 2021, 09:49 PM
If it flies, I can crash it.
rocketsled666's Avatar
I have a Goldberg Electra that I built about 35 years ago. On it's maiden flight, I smashed it in to a tetherball post that was literally the only obstacle on the highschool athletic field where I was flying. I cut one wing panel in half, and ripped off the tail. I rebuilt it with an additional 10" in each wing panel, which gets it in the range of the Butterfly, span-wise. With a Mabuchi 540 ferrite brushed motor spinning a 12x8 folder through a 3:1 orbital gearbox (I salvaged from something I bought at a swap meet). With a 1400mAh 7 cell NiCd, all up weight was something close to 3.5 Pounds, the thing flew great (it's been hanging in my basement for better than 25 years I think, haven't flown it any time recently).

By comparison, it has about as much wing as my Carbon-Z Cub, which weighs about 3x more, and that Cub is a floater.

The only real limit on weight for something like the Electra or Butterfly is how aggressive you want to fly it, since the wing is a hardwood spar, not carbon fiber. My Electra loops just fine, but I always worried about breaking the wing. I kept the loops big and graceful. Need more nose weight, mount a bigger motor and/or battery. It won't hurt, and the extra power might get you out of trouble some day, you never know.
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May 06, 2021, 02:38 AM
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scirocco's Avatar
With the rather limited prop clearance the OP has advised - 10" is the max he is happy with - the bigger motor route to balance would need careful consideration, ensuring Kv is at least as high as the present motor.

I'm with Sam - with a 9x7x3 or a 10x7 it will have enough power, and if bigger battery than strictly needed and some lead in the nose is needed - so be it.

I'd really only suggest bigger motor for balance if starting from a clean sheet, in which case balance should be a criterion as much as power and duration. The benefits of a slightly lower all up weight (vs small motor and lead) and better efficiency are available and the cost differential against using a small motor is low. But if one already has a workable motor I just can't see the cost- benefit of changing at this stage.

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