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seagull AT-6 74" 91-120 Please help with C of G CAN ANY ONE HELP I have this seagull models AT-6 Texan 74" wingspan ment for 91-120 glow the C of G in the manaul doesent ring right to me if you have this plane and it flys ok for you please can you tell me where your C of G is? in the manaul they say 0cm back from leading edge of the wing tips, so we take a strate edge and go wingtip to wing tip at the TE and thats are C of G 80mm the wing cored is 320mm TE TO LE, spar is 110mm placing the c of g 80mm from the body? this sounds very forward to me so much so that 12oz of nose wight and a 6volt flight pack in the nose was the only way of balancing at 80mm the plane flew but felt very very heavy and like it was underpowerd but saying that on landing i couldent slow her down all point to a very nose heavy plane however and this is the bit that confusis me there was a tip stall? not somthing thats commen with nose heavy planes this my have stoped me slowing on landing now im worryed to move the C of G back incase of provoking the tip stall but this plane has been going on for 2years and its time to do or die do i place it on the trusted spar even though its a tappered wing? please can some one help i dont wont complease theoys it will just confuse the issue if you have the right C of G for this plane please post i hope to fly again

Lnewqban

Check this thread for a similar plane:

http://www.rcuniverse.com/forum/fb.asp?m=9511096

You can do the same graphical calculation and locate CG at 25% of the total MAC formed by both shapes of the wing planform.

I don't know the exact dimensions of your plane as to do an exact calculation following this method.
However, I have used the plane of the link, which I scaled up to have 320 mm of chord at the wing root.
For that setup, the CG should be at 107 mm.

Please do the calculation using the actual dimensions of your model in order to determine the exact CG location in your case.

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i'll try the calculation today if i can get my head around it?



seagull at-6 product code 5500162

many thanks for your reply

Lnewqban

Yes, it is confusing.

This on-line calculator may make it easier for you:

http://scherrer.pagesperso-orange.fr...glish/mce.html

This link will explain the concept better than I can:

http://adamone.rchomepage.com/index5.htm

What I did was to divide the area of the half wing into two regular shapes.
Then, determined the center of each area, where the MAC is.
Then, I found the point located at 25% of the LE for each area, where the CG for each area should be located at.
Lastly, using the formula included in the schematic, I found a mean location for the CG of the total area, respect to the LE at the wing root.

Once you have the total MAC, you could use any on-line calculator, such as:

http://www.geistware.com/rcmodeling/cg_super_calc.htm

In any event, the 80 mm seem to be too forward a location for the CG of your plane, and the way the plane flew shows nose heaviness.

And, yes, heavy on the nose planes load the wing more, and tip stalls show up.

This thread discusses tip stalls' why and when:

http://www.rcuniverse.com/forum/m_89...tm.htm#8954798