On May 24, 2003, at 1610 central daylight time, a Glasflugel Libelle 201B glider, N3650, piloted by a private pilot, sustained substantial damage when it struck a rock while landing in a field near Hampshire, Illinois. The pilot reported no injuries. The 14 CFR Part 91 personal flight departed Sky Soaring Airport (55LL), Union, Illinois, at 1330 on the local flight. Visual meteorological conditions prevailed at the time of the accident. According to the pilot, at 3,000 feet above ground level (agl) the glider released from the tow aircraft. The pilot reported that during the 2 hour and 40 minute flight he had reached a maximum altitude of 8,200 feet agl. The pilot reported that the glider lost altitude during the remainder of the flight. The pilot stated he realized he would be unable to reach 55LL and decided to perform an off-airport landing to an nearby agricultural field. The pilot reported that upon landing he felt the tail wheel strike something hard. When he exited the aircraft, he found he had struck a large rock which was not visible when he made his approach.