On August 4, 1996, at 1530 eastern standard time (est), a Schleicher ASK-13, N11EK, operated by a commercial pilot, sustained substantial damage when during an aborted takeoff, the glider's wing struck a tree stump. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under 14 CFR Part 91. No flight plan was on file. The pilot reported no injuries. The local flight originated at Thompsonville, Michigan at 1530 edt. In his written statement, the pilot said that "just after the tow plane rotated for takeoff, the pilot (of the tow plane) pulled power. The glider quickly gained on the tow plane. I saw the right main gear of the tow plane hit the ground near the right edge of the runway." The pilot did not believe that he could land behind the tow plane. "I released (the tow cable) and turned to the right over an open field of tall weeds. I leveled off (and) made a course correction which realigned me with the runway. (I) used the altitude we had to gain as much airspeed as possible and flew across the weed field until finally settling into the tall weeds. The horizontal plane surface and the left wing were struck by rotten stumps hidden by the weeds." A Federal Aviation Administration (FAA) inspector examined the wreckage at the site. The leading edge of the left wing and the left wing spar were broken. The wood-construction horizontal stabilizer, vertical stabilizer and elevator were broken off. Flight control continuity was confirmed. No other anomalies were found with the glider. The tow plane pilot said that the airplane was not developing full power and decided to abort the takeoff. The FAA inspector examined the Cessna-Vansant 305A tow plane, N54517, at the Thompsonville Airport. Examination of the airplane revealed no anomalies.