Seagull Ultimate Bipe C of G

- S
- senator59
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posted 13 years ago

Sun, Nov 9, 2008 2:56 AM

I am putting the finishing touches on my Ultimate Bipe and was
wondering about the CG. The manual says its between 10 and 13 CM back
from the leading edge of the top wing, This places it pretty far back
from the leading edge. Has anyone built one of these and can verify
that the CG distance is correct?

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- M
- Morgans
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posted 13 years ago

Sun, Nov 9, 2008 12:01 PM

Where is the 25% point on the lower wing, and what percentage of wing area is the lower wing vs. the upper wing? Then you have to take the incidence of the upper wing compared to the lower wing into account, also.
Biplanes are complex. Go with the manual, and adjust it after that if you don't like how it flies.
All that said, if someone weighs in with actual experience, that would be interesting.

- M
- Martin X. Moleski, SJ
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posted 13 years ago

Sun, Nov 9, 2008 2:13 PM

On Sun, 9 Nov 2008 07:01:51 -0500, "Morgans" wrote in :

Nice pun ("weighs"). :-O
The best article I've read is by Jerry Neuberger.
I don't know the original source, but there is a legible copy of it in this newsletter.

formatting link

It used to be on the AMA website.
Draw the pictures and do the calculations. They may help prevent you from having to learn from mistakes. ;o)
Marty

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- <rmaheuxr
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posted 13 years ago

Mon, Nov 10, 2008 12:21 PM

FWIW, I tried Jerry Neuberger's method on a park flyer I'm building (30" constant chord wing) and came up with a CG location within 1/16" of that which the manual called for.

- E
- Ed Cregger
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posted 13 years ago

Mon, Nov 10, 2008 8:41 PM

------------
This must be a generational thing. This "actual experience" thing is what I'm referring to.
What if the person with the "actual experience" did it wrong and totalled his/her model? Is that as good as someone that has been designing, building and flying different kinds of biplanes all of his/her long life, but may not have actually used the particular model that you have?
Do yourself a favor, OP. Lose this insult now. You are alienating many who could accurately help you.
I'm offended. Figure it out yourself like I had to do.
Ed Cregger

- M
- MJKolodziej
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posted 13 years ago

Mon, Nov 10, 2008 9:06 PM

That was not the OPs comment. It was Jim's comment about his own advice. The insult was not there. As in everyting the insust is in how YOU take it not how they meant it. Having one of your bad days? I feel your pain. Take a deep breath, chill. You are not up to your usual good spirits. :) mk

- E
- Ed Cregger
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posted 13 years ago

Mon, Nov 10, 2008 9:34 PM

----------
Doh!
You are correct. Not feeling great. Thanks for pointing out the error of my ways.
Ed Cregger

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