CG for a Biplane??

[skylane42]

Anyone have the formula for the calculation of the CG on a Biplane or the CG on The EZ pitts?

[adam_one]

I don't have the formula for the biplane CG, but you may find the wings' AC location according to the drawing below.
Usually the CG is rather close to the wings' AC location provided you don't have a too big tail arm moment.

[skylane42]

Thanks Adam, I found the formula and your drawing helps.. but balance at 23%? Not to argue but normally I find a plane balances around 28%-30%. On a monoplane that usually works out to be on or about on the spar.

[adam_one]

Thanks Adam, I found the formula and your drawing helps.. but balance at 23%? Not to argue but normally I find a plane balances around 28%-30%. On a monoplane that usually works out to be on or about on the spar. Yes, your figures are right about the CG location for conventional monoplanes, but the AC point shown above is the Aerodynamic Center of the both wings together.
For a conventional monoplane the AC is located at 25% of MAC, while the CG location depends on several factors such as wing area, stab area and the distance between the wing and stab AC's.
The formula for conventional monoplanes doesn't apply to biplanes because the biplane's stab is subject to much more interference from the two wings' downwash than the monoplane's stab is.