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Old 09-01-2014, 04:41 PM   #1
egrave1
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Default Balancing

I don't know if I am in the right forum or not but here goes.I bought the Dynam sbach 342 1250mm from nitro. My problem is trying to balance this airplane. They recommend the CG at 50mm which I do. But when I get it to balance at that point as soon as I touch the nose it goes all the way down and never comes back to balance and the same for the tail. I just can't get this plane to balance. When I was doing glow engine airplanes when push the nose down it came back to balance. Does anyone have any suggestion
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Old 09-01-2014, 05:16 PM   #2
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Did you try turning it over? Though with a mid-wing stunt plane it may still be the cg is vertically at the wing, instead of being below the wing like a high wing, or a low wing balanced upside down.
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Old 09-01-2014, 07:02 PM   #3
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The issue is the mid wing design and having the CG be above where you are supporting the airplane. When you are supporting from below center of mass then the plane won't self-level if disturbed.
This is why high wings are always balanced upright and low wings are often balanced inverted.
Mid wing can have the CG centerline the wing and thus have center of mass above where you support it both upright and inverted.

CG is actually a point in 3 dimensions event hough we typically only check in the fore-aft and occasionally side-side there is also a vertical component.

A way to find exact CG is to hang the plane with 3 strings all coming together to a single point and then hang a plumb bob from the same point. The plumb bob will point at the CG. Readjust so the plane is hanging at a different angle and the plumb bob will still be aimed at the CG.
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Old 09-01-2014, 08:51 PM   #4
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As noted in previous replies, try it both upright and inverted and see if it's stable either way. if not it's not really a big deal, just find the point where it balances level for a moment or two and where it's just as likely to tip either way.

I never get too excited about precise CG position. For the maiden if in doubt err toward slight nose heaviness then you make your fine adjustment based on how it flies. After all it's how it flies that's important rather than replicating the CG position advised in the manual to the last millimetre.
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Old 09-01-2014, 09:25 PM   #5
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Thanks for the help I will find where it balance's at the CG and try to fly it
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