The pilot was attending an "Aviation Weekend" sponsored by the town of Crested Butte, CO. He had flown in this area often and was acquainted with the terrain and weather. After being towed to an area near the northwest corner of Mt Crested Butte, a normal release was made. In a radio transmission to the glider, the tow pilot noted that there was very little lift, but maybe he (the tow pilot) had felt something on the north side of the mountain as he was circling back to land after the release. The message was acknowledged by the glider pilot, who then took a picture of the tow plane. The glider pilot then proceeded around the mountain where he crashed on the north face of Mt Crested Butte. An investigation revealed that the glider was on a heading of 070 degrees when it struck a 60 ft pine tree about 20 ft from the top. It had impacted the tree with its left wing root, severing both the wing and the tree. The fuselage came to rest about 100 ft away after partially uprooting a stump.