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Debonair CG Question

Old 01-20-2004, 07:40 PM
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Default Debonair CG Question

Hi, I have built a nice Deb and have managed to keep the weight down conciderably compared to my first one. My new one comes in at about 5.5 lbs. But My tail is heavy. Using the plans I have, they say to test CG at the forward spar. If I go to the rear spar its nose heavy. So its pretty close. But I am fairly new at this and wanted your thoughts. I hate to add weight to it [having kept it to a min]. I already have my batt and reciever fwd. And I made the mistake of mounting the wing already. [I thought I would be close enough].
Thanks Keester
Old 01-20-2004, 07:50 PM
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Default RE: Debonair CG Question

If it's that close try flying it. Then you'll know if you need to correct the CG. If so, try a spinner - very little weight, but it might be enough.
Old 01-20-2004, 08:31 PM
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Default RE: Debonair CG Question

if the cg isn't on the front spar, don't fly it. Chances are it won't fly well otherwise. The simplest solution is to just remount the wing. Drill a new set of holes, and install another set of dowels.
Old 01-20-2004, 09:49 PM
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Default RE: Debonair CG Question

ORIGINAL: ChrisSpad

if the cg isn't on the front spar, don't fly it.
That was my original thought, Chris. But according to the plans the front and rear spars are 1-inch apart. And he mentions the plane is nose-heavy if he balances at the rear spar, tail-heavy if he balances at the front spar. So the CG is off maybe 1/2 or so - if I haven't missed something?

Now your experience is vast. So please tell us, will a 1/2 inch or so make a huge difference in flight characteristics - so much so that the plane shouldn't even be given a test flight? Hmmm! Probably answered my own question .... LOL

For a half inch CG change wouldn't the tie down dowel holes get mighty close? Would a heavier spinner (aluminum, maybe?) give a 1/2 inch CG change?
Old 01-20-2004, 09:52 PM
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Default RE: Debonair CG Question

Flying a triple facet wing (debonaire) with the cg 1/2", or even 1/4" behind the spar is a risky proposition at best. Most actually like to be balanced slightly ahead of the spar (at least mine do).
At 1/2" behind the spar, i suspect the plane will not be flyable. With a 12" chord, your talking about changing the cg by 4%, and thats a large change.

For whatever reason, the triple facet wings don't like to be balanced any behind the front spar, that was the reason i said not to fly it if its behind that point.
Old 01-20-2004, 10:07 PM
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Default RE: Debonair CG Question

Thanks, Chris. That's very good information to know!
Old 01-20-2004, 10:16 PM
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Default RE: Debonair CG Question

Thanks for the advise, I will add weight to the nose. I didnt want to sound silly its just that with my electrics and such I have learned to build as light as possible, you know.. and take pride in it. It wont take that much. But its good info to know. I will take heed. I have enough things against me [like gravity] to take it lightly. Thanks for your advise
Here she is, I wanted to give her a WWI scout like look, but I now realize I dont know what it looks like. Oh well [they are all pretty]
Keester
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Old 01-20-2004, 10:46 PM
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Default RE: Debonair CG Question

Very Nice, Keester! It is pretty!

Good luck on the maiden flight!
Old 01-20-2004, 11:58 PM
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Default RE: Debonair CG Question

I notice you have a wooden prop fitted. Try a plastic one. They are heavier - maybe heavy enough to move the weight forewards 1/4 inch or so and they are slightly more crash resistant. That plus an ally spinner should have the weight in about the right place.
Let us know how it flies.
Old 01-21-2004, 04:39 PM
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Default RE: Debonair CG Question

Unstead of a spinner try a heavy prop nut like Harry Higley sells. That alone will probably change the CG 1/2 an inch.
Old 01-21-2004, 11:14 PM
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Default RE: Debonair CG Question

With the rounded off rear feathers that plane would have really looked nice as a tail-dragger.

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