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Author Topic: C of G - does your bird have one and where might it be?  (Read 1379 times)

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Online Deerslayer

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C of G - does your bird have one and where might it be?
« on: February 02, 2011, 10:23:57 AM »
I have a write-up on the subject of C of G which I will now post. As well, I will post a spreadsheet, in case someone else finds it useful. Feedback is most welcome, as I am always looking to improve.




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Online Deerslayer

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Re: C of G - does your bird have one and where might it be?
« Reply #1 on: February 02, 2011, 10:25:38 AM »
My previous write-up concerned how you find the C of G in practice, by doing some weighing, and/or estimating how a change in weight or position of some component may affect the C of G location. This is the easy stuff.

This link (which Rolly pointed out to me) delves into the area of determining the more complicated part - where you try to figure out where the C of G SHOULD be, given the geometry of the aircraft. I hope that someone out there takes the time to fiddle around with this, and will post back some of their results. (I am probably too lazy, although I really should "get around to it" sometime).
Anyway, enjoy this:

http://adamone.rchomepage.com/cg_calc.htm
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Flypaper 2

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Re: C of G - does your bird have one and where might it be?
« Reply #2 on: February 02, 2011, 02:39:31 PM »
This is the one I use for flying wings etc. Once you find the Mean Aerodynamic Chord, MAC, on flying wings, CG is usually 20 to 25%MAC  Normal plane configuration would be 25 to 30%

  Gord.
« Last Edit: February 02, 2011, 02:44:55 PM by Flypaper 2 »

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Re: C of G - does your bird have one and where might it be?
« Reply #3 on: February 02, 2011, 04:54:17 PM »
One thing about flying wings (or perhaps more properly termed tailless aircraft, at least if they have any vertical surfaces for control or stability) is that the C of G is typically more critical than with "conventional" aircraft. Depending upon the airfoil, the C of G may have to be well forward of the usual 25%  or 30% that we generally think of. For instance, the Desperado 60, like other Bill Evans Simitar series of models, calls for the C of G to be up at about 12% of mean chord!
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