The short answer is that you have to make them to suit the purpose, but...
A typical layup for a .60 to 1.20-size pattern fuselage could be made with two layers of fiberglass cloth, say 2 oz. or 4 oz. cloth for the surface, and perhaps 5 oz. or 6 oz. cloth on the inside. Many variations are possible, with combinations of different types and weights of cloth, the use of Kevlar, carbon fiber, Nomex, etc..
We've just had an extensive discussion on this over on the "Design, 3D/CAD" page, which included comments and photos by the designer of the "PTX Vector" pattern plane. It's at
http://rcuniverse.com/showthread.php...893&forumid=58
There's also info on my web site, (Click the "www" button, below) including tutorials on how to make plugs and molds, a description of the "J-45" pattern plane I've designed, accurately predicting structural weights, and more. (free, non-commercial site)
The best bet, as with most aspects of fiberglass construction, is to talk to everyone you can, to see what they do, read all the articles and web sites you can, make some small test samples, then go for it!
Good luck.