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May 05, 2001, 02:37 PM
DAve caNDI,& 5#'s of fury
Dandi6065's Avatar

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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May 05, 2001, 05:13 PM
Mountain Models Wannabe
CoClimber's Avatar
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.
May 05, 2001, 05:56 PM
I am M I G H T Y !
Steve Wrona's Avatar
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
May 05, 2001, 10:56 PM
Registered User
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
May 06, 2001, 07:28 AM
Registered User
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

May 06, 2001, 08:57 AM
Registered User
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.
May 06, 2001, 04:13 PM
DAve caNDI,& 5#'s of fury
Dandi6065's Avatar
Thanks for all the help
I just love Ezone
May 06, 2001, 08:05 PM
Old Desert Rat
Arizona Chuck's Avatar
**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
May 07, 2001, 04:44 PM
Registered User
maciek's Avatar
What about the angle of attack of the wing? What should that be relative to the tail?