On July 8, 1999, about 1530 Eastern Daylight Time, a Pilatus B-4 glider, N20RK, was substantially damaged while landing at Vansant Airport (9N1), Erwinna, Pennsylvania. The certificated commercial pilot was not injured. Visual meteorological conditions prevailed for the local flight. No flight plan was filed for the personal flight conducted under 14 CFR Part 91. The pilot stated that he flew a left traffic pattern to Runway 23 at 9N1. On short final approach, approximately 100 feet from the runway threshold, a gust of wind forced the glider to the left, into trees. When asked about other available runways, the pilot stated that the other runways are reserved for "motorized" traffic. He further stated that although he did not obtain a full weather briefing, he did telephone a recorded weather forecast system, provided by the National Weather Service. At an airport approximately 17 miles away, at 1551, the reported winds were from 280 degrees at 10 knots, gusting to 19 knots, and varying from 250 to 320 degrees. According to a Federal Aviation Administration Inspector, and a representative from Pilatus, there was no maximum demonstrated crosswind component for the accident glider. Examination of the wreckage by the inspector revealed no pre-impact mechanical malfunctions, nor did the pilot report any.