I am looking for another scratch project, and this time I want to build a good 3D plane. And I was wondering what makes a 3D plane able to do 3D (Large control surfaces are a given I know). But should it have a long tail? Short? These are the types of theings I want to know.

I would prefer an IMAA legal biplane. And it would be nice if it was glow powerd. I dont want plans, I want to design it so any proportians of wing area to side area etc. would be appreciated.

Thx Collin

tail moment i think is 2xwing chord. Wing area shouldn't be an issue on a bipe, but go with ultimate type dimensions as a base

If its a big 3D bipe your wanting try looking around at other successful designs of the same sort.

Just had a bright idea (possibly?)

Was just looking at the consistancy of some foam I have a wing pinned on (differnt story wont get on that now).

The foam is a panel of "R" insulation...its a light foam but coated in a sort of saran wrapish stuff wich makes it really tough and springy. Each sheet of this stuff is about 3/4 of an inch thick and you can grab a 12' by 6' sheet for 8 bucks.

So I was wondering, how about glueing 6 or 7 of these sheets together and carving the fusalage and wing from it? Then reinforcing them with carbon fiber rods and fiberglass (I would still have a plywood firewall and similar bits). After all that sand it down smooth and cover it.

Then you might have this

www.3dbiplanes.com

I was thinking more along the lines of 80+" ...is foam strong enogh to take this?

One other thing, what style wing is best for 3D? The thing I see most often is a swept back LE and a strait TE...but is this really best for performance at slow speeds? Or is it different for biplanes?

That foam is fairly dense, and the clear film covering must be removed before use. It won't laminate with it on there, and it will make a mess anywhere it reaches the OML. I know a guy that makes all his planes out of foam, and they are all way too heavy for 3D. 3D models are basically monokote stretched over the minimum amount of structure required to make the appropriate shape, while providing the minimum amount of strength required for the extreme flight loads achieved in 3D flight. In other words, won't really work that well, especially the larger you go.