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Old Oct 10, 2012, 09:07 AM
i can't learn fast enough
Aubur, NY-- Finger Lakes
Joined Mar 2009
203 Posts
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CG confusion

Well I have this plane all cut and ready to assemble. I have used 2 different CG calculators, and have gotten 2 different locations. 1st is at 14.25 inches from nose and the 2nd is 12.5 inches.
That to me seems like a lot of difference.

Measurements are: Length 35 inches from the point to the back of the elevator.
Width is 33.5 inches., the back of the plane to the start of the angle to the nose is 6.25 inches. Distance from the nose to the start of the angle is 33 inches.
The sweep is 16.5 inches.

Is there anything I am missing.
Thanks much for your time and help.
Terry
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Old Oct 10, 2012, 11:30 AM
Registered User
Staffs, UK
Joined Nov 2003
10,548 Posts
From those measurements I have no idea what shape of plane you're describing. How about a picture/drawing ?

Steve
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Old Oct 10, 2012, 05:06 PM
1 can never have 2 many planes
chambo88's Avatar
Australia, QLD, Surfers Paradise
Joined Sep 2011
639 Posts
i agree, from those specs there isnt anyway i can see to calc the cg just yet.

i use this file in excel and its usually very accurate. see attatched files.

note the "flat wing CG calc" file is only for flat (non-wing profile) type aircraft.

they are both really simple to use. you simply fill in the yellow boxes with the values you have. then scroll down to the "total wing results" next to the graph and your CG for 25% of the MAC will be listed under "location of 25% point". this point is measured from the leading edge of the wing root. sorry if ive over explained this a bit. but i hope it helps
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Old Oct 10, 2012, 05:09 PM
1 can never have 2 many planes
chambo88's Avatar
Australia, QLD, Surfers Paradise
Joined Sep 2011
639 Posts
ahhh says that the files are invalid. if you want i can email them to you..

just pm me your email if so.

chambo88
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Old Oct 10, 2012, 07:49 PM
i can't learn fast enough
Aubur, NY-- Finger Lakes
Joined Mar 2009
203 Posts
Thanks all for your patience.
I guess I did not explain very well, sorry.

My camera is broke, and I have not leared how to hook up my wife's just yet.
Let me try again to explain.

Picture a triangle. Pointy end facing forward.
The bottom is 33.5 wide.
The sides angle down 33 inches, the the side is straight down and is 6.5 inches.
From pointy end to the bottom is 35 inches.
If one were to draw a horizontal line to the left (or right) out 16.5 inches,and then at a right angle a line to the straight side, I believe that is called the sweep.

Hope this is some what better.

Chambo88, I will send you a pm with my e-mail, thanks for the offer.

Terry
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Old Oct 10, 2012, 08:37 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,992 Posts
Sounds like a flying wing. Try entering your dimensions here and if it draws the right shape the CG will be about right too.

http://fwcg.3dzone.dk/

Jack
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