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Old May 05, 2001, 03:37 PM
Dandi6065 is offline
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DAve caNDI,& 5#'s of fury
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How do you determine the Center of Gravity??



I need help determining the C G of my first scratch built project.
A park flyer, stick type.
Is the CG determined by just using the total length of the plane and using half ?????
Please help me to figure this out
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Old May 05, 2001, 06:13 PM
CoClimber is offline
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CG is based on the wing, not the fuselage. For a plane to be stable in pitch, the CG must be in front of the center of lift. So, on a typical wing, the CG will be somewhere around 1/3 back from the leading edge of the wing, that is, 1/3 of the wing chord. If it is too far back, the plane will be unstable and you will have a hard time keeping the plane level.
Old May 05, 2001, 06:56 PM
Steve Wrona is offline
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I am M I G H T Y !
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Dandi,
I really appreciate you starting this thread! Ive begun building a few MHLGs out of Depron and CF arrow shafts and have been having some difficulty determining the CG. Thanks CoClimber for the info!
Steve
Old May 05, 2001, 11:56 PM
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as a rule of thumb i use, i always ballance my scrath built planes on my spar, or the peak of the curve of my rib. hope this helps
Old May 06, 2001, 08:28 AM
Larry Marshall is offline
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Quote:
Originally posted by will62085:
as a rule of thumb i use, i always ballance my scrath built planes on my spar, or the peak of the curve of my rib. hope this helps
This is something of a Catch-22 as most designers put the spar near the CG :-)

Cheers --- Larry

Old May 06, 2001, 09:57 AM
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ahh, i never thought about that...but also, the spar is always at the peak of the curve of the rib...ive always balanced my planes this way and never had trouble...there is such a wide ballance area that a plane can "fly" but fine tuning it is up to you.
Old May 06, 2001, 05:13 PM
Dandi6065 is offline
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DAve caNDI,& 5#'s of fury
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Thanks for all the help
I just love Ezone
Old May 06, 2001, 09:05 PM
Arizona Chuck is offline
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Old Desert Rat
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**Repeat from Modeling Science**
I just added a C.G Locator on my web site. It is a strange formula but it has worked for me many times.
I would like someone to go in and check it out to see if I got in right. I really need someone to check my formula, my math is very limited.
Nothing like letting you stupidity hang out for everyone to see. My mother didn't have any smart boy babies.
.
Click on the CG icon http://www.geocities.com/azchuckrc/Howto/howto.html
..AZ Chuck
Old May 07, 2001, 05:44 PM
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What about the angle of attack of the wing? What should that be relative to the tail?


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