I´m building a plane and wanted to make sure the formulas are right on it. The problem I have is that the fuse is already built and I found the formulas later. In this forum there are some links to formulas and if I want the CG to be at 30% MAC the my static margin comes out at 48.7%!!! The specs on the plane are as follows:
Cord = 23.5"
Sweep is 0
Wingspan= 140" the fuse cuts the wing in half and is installed with aluminum tubes so
Half span= 70"
Fuse width at wing= 10"
Distance between Leading Edges= 75.5"
Wing area (without fuse included)= 3290 Sq. In
Tail cord= 14"
No sweep
Tail half span 24.5"
Tali span 49"
tail Area= 686 Sq. In.

In the formulas the CG comes at 7.05" back from leading edge, the wing aerodinamic center at 5.88" back from LE at root, my neutral point at 18.49" back from LE and the distance between CG and Neutral point at 11.44 or 48.7% static margin.

It is a big plane as you can see, the wing is semi-symetrical andwill be pulled by a Mac Minarelli 125 twin gaser. It´s sort of a giant second step aircraft meant to have very stable flight... but now that I found the formulas I´m thinking that I should not fly it until i have some assurance that it will not crash because of bad proportions.
BTW the estimated weight will be around 38 to 42 pounds.
Any help in getting that static margin right and hints on how to do it are VERY welcome
John

I found the formulas here http://www.rcuniverse.com/forum/m_2867994/tm.htm


OHH and the aspect ratio of this wing is 6