On May 9, 1999, at 1940 central standard time (cst), a Piper PA- 18-L21B, N3VU, operated by a private pilot, sustained substantial damage when on landing, the airplane veered right, off of the runway, and nosed over. 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 and passenger on board reported no injuries. The local flight originated at the O'Neal Airport, Vincennes, Indiana, at 1840 cst. In his written statement, the pilot said he made a smooth touchdown about halfway down runway 21 (2,350 X 100) at the O'Neal Airport. The pilot said that shortly after touchdown, the airplane hit a rough spot on the runway. The airplane bounced into the air, and the tail began to shift around. The pilot said that he couldn't get on the brakes because he was busy trying to keep the airplane straight. The airplane veered to the right and departed the runway into a wheat field. The plane slowed, but suddenly stopped and nosed over slowly on to its back. The pilot described the weather, at the time of the accident, as clear and no wind. The airplane was examined at the airport by an airplane and powerplant (A&P) mechanic tasked by the Federal Aviation Administration (FAA). The airplane showed damage to the engine cowling, forward fuselage and windscreen. The left wing strut was bent inward, three feet inboard of the wing attach point. The leading edges of both wings were dented inward at the inboard 3 ribs. The vertical stabilizer and rudder were bent. Flight control continuity was confirmed. Examination of the engine, engine controls and other airplane systems revealed no anomalies.