The pilot stated that he was repositioning the tail-wheeled airplane from a 720-foot grass strip to an airport for maintenance. He computed a takeoff distance of 450 feet and completed two practice takeoff runs to verify that the airplane was able to take off from the short runway. During the practice runs, with the airplane about 400 feet down the runway at an airspeed of 50 knots, the tail would rise normally and the pilot would abort the takeoff. During the accident takeoff roll, about 400 feet down the strip, the airplane encountered a dip in the terrain and briefly became airborne. The airplane settled back onto the runway and the pilot continued the takeoff, rotating airborne about 100 feet prior to a cornfield off the departure end of the runway. The pilot attempted to gain altitude, but the airplane struck corn stalks and descended into terrain. During the accident sequence that airplane incurred substantial damage to the fuselage, wings, and engine firewall. The pilot reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation.