On September 29, 2001, at 1425 eastern daylight time, an AviaStrottel AC 4C glider, N68PR, collided with the terrain during takeoff on runway 10 (2,800 feet by 75 feet, grass) at the Brooks Field, Marshall, Michigan. The private pilot was seriously injured and the glider received minor damage. The 14 CFR Part 91 flight was operating in visual meteorological conditions without a flight plan. The flight was originating at the time of the accident. The pilot reported that approximately 200 feet into the ground run, the glider became airborne. After reaching an altitude of about 5 feet, the glider settled to the runway and bounced. The pilot reported that he was wearing headphones, which slipped forward when the glider contacted the runway. As the headphones slipped forward, the pilot's hat was pulled down over his eyes. The glider became airborne again and because he was unable to see the tow plane, the pilot released the glider from the tow. The glider impacted hard on the runway and the pilot suffered a compression fracture in his back.