The January 2004 issue of Soaring has an article on building an enclosed trailer. There's also a short pictorial about building a Schreder type trailer he

http://soaridaho.com/Schreder/Constr...1/Trailer.html

If you build a non-clamshell type, build it big. Most of the disadvantages of tube trailers disappear if they're built with a little extra room instead of using the common approach of making them just big enough to contain the glider. The Soaring article shows a nice sized trailer. One of the first things that comes up on a search is the Adelaide University Gliding Club bit on how to build trailers. Ignore that one. They tell you to put the wing roots and fuselage nose at opposite ends of the trailer. Don't do that unless you hate yourself, your back, your glider and all of the friends who help you with rigging your ship.