The pilot reported completing a preflight inspection, taxi, and engine runup with no anomalies observed. The pilot reported that he then taxied to the end of the grass runway, held the yoke in the full aft position, and applied full throttle to perform a soft-field takeoff. The pilot stated that while rolling down the runway, he experienced pitching and bouncing of the airplane. At an airspeed of 60 mph, he began to relieve the yoke back pressure, expecting the airplane to begin to liftoff; however, the airplane remained on the runway at 70 mph. At this point, the pilot elected to abort the takeoff and he brought the engine throttle to idle, then applied brake pressure to both brakes, but the airplane began to skid. The airplane continued past the end of the runway, and impacted vegetation and a wire fence. The pilot reported there were no mechanical malfunctions or failures that would have precluded normal operation. A postaccident examination of the airplane revealed it had sustained substantial damage to the left wing and the fuselage. A photograph taken of the airplane shortly after the accident revealed that the flaps were in the retracted position. According to the airplane’s Pilot’s Operating Handbook, “Soft field takeoffs are performed with 20° of flaps.” Additionally, according to the FAA Airplane Flying Handbook, for a soft field takeoff, the pilot should lower the wing flaps prior to starting the takeoff to provide additional lift and to transfer the airplane’s weight from the wheels to the wings as early as possible. It is likely, that due to the flaps being retracted, the rough grass conditions resulted in additional drag on the wheels, preventing the airplane from accelerating sufficiently for flight.