Many of the gliders were made of a foam that could absorb the shock of bad landings or even crashing into each other in the air, which is great fun. Other planes were of composite construction and designed more for high performance. Some of the guys were really creative in the gliders they designed such as the giant C5 glider pictured or a radio controlled bald eagle.
Video of 50+ m.p.h. Wind
My Article on Slopeflyer.com from 2002