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Old Feb 25, 2002, 12:10 PM
Registered User
South Africa
Joined Feb 2002
1 Posts
Unstable SoarStar.

Hi.

My SoarStar likes to porpoise. I suspect my C of G is out. When I lift my SoarStar by the wing struts, the nose drops slightly. Is this the correct way of determening the C of G or am I doing something wrong?

Thanks - Mike
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Old Feb 26, 2002, 08:22 AM
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Matt M's Avatar
Seattle
Joined Nov 2001
74 Posts
An easy way to find the CG is to balance the model on the ends of your index fingers (same place on each side of the wing) and see how far back on the wing it ends up balancing.

Typically, a good starting point is around the quarter chord (1/4 the wing chord from the front of the wing) and moving from there.

A forward CG will not fly well. An aft CG may not fly twice.

Once you see it explained and measured, you will have it. Sometimes descriptions are hard to follow.

Hopefully this is not the case here

HTH
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Old Feb 26, 2002, 08:46 AM
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Boise, ID 83703
Joined May 2001
266 Posts
CG + Trim

Check the CG according to your instructions. Yes a little down is better than tail heavy. Much better. Also, if you trim it with to much up elevator, it will tend to do the same porpoising, but should be fairly mild. Don't know what your throttle position is during all of this, but you may want to back off to the 1/3 to 1/2 position after you have some altitude for safety.
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Old Feb 26, 2002, 09:05 AM
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Radek Z's Avatar
Pampigny, Switzerland
Joined Oct 2001
412 Posts
I had the same thing on Wingo when I started. I moved the battery all the way forward (1" forward) and began to fly that way (obviously after help from e-zoners).

Interestingly enough over some twenty flights which followed I kept pushing the battery back and eventually I kept flying with the original position. I guess as you develop the feel for the plane you can control it better even if it's quite twitchy. It obviously glides better with the CG aft.
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Old Feb 26, 2002, 09:20 AM
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Clifton, Va., USA
Joined Sep 2000
632 Posts
Bingo, Radek. I like my Wingo CG back, too, for the same reason--better glide. Ultimately, it's a matter of preference and what one is comfortable with.
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Old Feb 26, 2002, 09:26 AM
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Pampigny, Switzerland
Joined Oct 2001
412 Posts
Yup, but it took some time to get used to. If someone on the e-zone would not tell me to move the battery forward in the begining I would be probably very frustrated. So for Mike: battery forward and forget about the durtion records for the time being.
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Old Feb 26, 2002, 09:29 AM
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Clifton, Va., USA
Joined Sep 2000
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Three or four flights and he'll start sliding that battery further and further aft.
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Old Feb 26, 2002, 09:48 AM
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South Africa
Joined Jan 2000
19 Posts
Thanks for the advice

To everyone who has replied to my mail. I was starting to think that nobody wants to talk to me. I really appreciate the replies. I will move the battery forward and try flying my SoarStar like that.

TTFN - Mike
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