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Speed 400 PBF Plans?

Old 02-26-2003, 02:59 PM
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crotts
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Default Speed 400 PBF Plans?

I have the radio, battery, speed control and motor left over from an old Zagi 400 and have been thinking of trying to make a PBF around that equipment.

Are there any existing plans that anyone knows of? Or if not, is there a standard way I can calculate how large to make my PBF?

Any other experience with electric PBFs or advice?

Thanks,
Neal
Old 02-26-2003, 03:05 PM
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ChrisSpad
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Default Speed 400 PBF Plans?

2 things you need to consider: all up weight, and wing loading. Shoot for about 9 or 10 oz wing loading, and the all up weight needs to be less than the torque the engine produces, if you want t o hover.
Old 02-26-2003, 03:25 PM
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crotts
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Default Speed 400 PBF Plans?

I know the flying weight of the complete Zagi was 19 oz., so for the sake of argument (since I'm not at home where I can weight the onboard gear) I'll say my final flying weight is somewhere in that neighborhood, although I certainly expect a small square of coroplast to weight less than a 48" foam wing.

Anyway, to get a loading of 10 oz/ft, I would need a total area of 1.9 sq ft. Right? If so, then I would be looking at a square about 1.4 ft in each dimension.

Is there any danger in going with a lighter loading (knowing of course that weight is a factor)?

What about CG?

Thanks,
Neal
Old 02-26-2003, 03:44 PM
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ChrisSpad
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Default Speed 400 PBF Plans?

there's nothing wrong with going for a lighter wing loading at all. Thats even better.
The problem comes in the thrust department. A pbf will fly with considerably less thrust than what it weighs, but, to get it to hover, and such, it needs the thrust. Not sure how much a speed 400 puts out, but i would think that would be the limiting factor.
4 mil coro weighs 2.33 oz/ft^2, and 2 mil weighs 1.5 oz/ft.^2. So, with 4 mil, you'd be looking at a weight of somewhere between 5 and 6 oz. 2 mil could be made to work, but, it'll require some reinforcement, probably it'd end up about the same weight.
Old 02-26-2003, 03:51 PM
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crotts
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Default Speed 400 PBF Plans?

Good info. The full-battery output of the Zagi motor is a little better than 16 oz. So, with hovering in mind I'd have to beat that weight. I actually hadn't even thought of hovering. I just hate the thought of all that stuff sitting there and not flying in something. The thought of spending $10 and an hour or two to have something in the air was very appealing.

I think I'll just start and see where it goes. If the weight is looking close, I may look for some ways to trim weight and acheive the hovering weight.

Thanks,
Neal

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