CofG,

I'm with Northwing. Unless you enjoy mathematical manipulations, weigh the damn bird when it's finished. Then you'll know, for true--if you NEED to know. I don't. I set the CG where it's supposed to be and fliy the bird, trim it out, test the stalls and go from there.

It's not that I don't love math less, but I love flying more.

Jack