On June 5, 1994, approximately 1330 mountain daylight time, a Glasflugel Standard Libelle, N3992, was substantially damaged during landing at Wellington, Colorado. The private pilot was not injured. Visual meteorological conditions prevailed. The following is based on the pilot/operator report. The glider was towed aloft and released 2,000 feet above the ground. The pilot said that although it was his intention to capture a thermal and climb to a higher altitude, he encountered "strong sink" instead and he decided to return to the gliderport. He entered the traffic pattern at low altitude and when he turned onto the base leg, he realized he would be unable to clear obstacles between him and the runway. The pilot said he attempted to turn into the wind but did not have sufficient altitude, and the glider landed in a field "with a strong right side drift." When the tail wheel contacted the ground, the "side motion" caused the tail boom to separate.