HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old May 05, 2001, 02:37 PM
DAve caNDI,& 5#'s of fury
Dandi6065's Avatar
Oscoda, MI :)
Joined Jan 2001
529 Posts
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
Dandi6065 is offline Find More Posts by Dandi6065
Reply With Quote
Sign up now
to remove ads between posts
Old May 05, 2001, 05:13 PM
Mountain Models Wannabe
CoClimber's Avatar
Ithaca, NY USA
Joined Mar 2001
4,370 Posts
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.
CoClimber is offline Find More Posts by CoClimber
Reply With Quote
Old May 05, 2001, 05:56 PM
I am M I G H T Y !
Steve Wrona's Avatar
Ipswich, England
Joined Feb 2001
486 Posts
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
Steve Wrona is offline Find More Posts by Steve Wrona
Reply With Quote
Old May 05, 2001, 10:56 PM
Registered User
Marietta, GA, USA
Joined Mar 2001
168 Posts
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
will62085 is offline Find More Posts by will62085
Reply With Quote
Old May 06, 2001, 07:28 AM
Registered User
Quebec, QC, Canada
Joined Mar 2001
104 Posts
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

Larry Marshall is offline Find More Posts by Larry Marshall
Reply With Quote
Old May 06, 2001, 08:57 AM
Registered User
Marietta, GA, USA
Joined Mar 2001
168 Posts
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.
will62085 is offline Find More Posts by will62085
Reply With Quote
Old May 06, 2001, 04:13 PM
DAve caNDI,& 5#'s of fury
Dandi6065's Avatar
Oscoda, MI :)
Joined Jan 2001
529 Posts
Thanks for all the help
I just love Ezone
Dandi6065 is offline Find More Posts by Dandi6065
Reply With Quote
Old May 06, 2001, 08:05 PM
Old Desert Rat
Arizona Chuck's Avatar
Rimrock AZ. USA
Joined Mar 2000
1,113 Posts
**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
Arizona Chuck is offline Find More Posts by Arizona Chuck
Reply With Quote
Old May 07, 2001, 04:44 PM
Registered User
maciek's Avatar
Worcester, Ma, USA
Joined Feb 2001
277 Posts
What about the angle of attack of the wing? What should that be relative to the tail?
maciek is offline Find More Posts by maciek
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
How do you determine which motor to use? psycho_klown66 Power Systems 7 Dec 29, 2004 09:23 PM
Question How do you determine downthrust angle? PfalzPflyer Power Systems 11 Dec 11, 2004 09:37 AM
How do you determine prop size. Solcat Power Systems 3 May 03, 2004 07:34 PM
How do you determine Wing loading McGrrr Beginner Training Area (Aircraft-Electric) 9 Oct 15, 2002 09:08 PM
How do you determine the Center of Gravity?? Dandi6065 Power Systems 8 May 08, 2001 12:11 AM