The pilot was landing on runway 31, and reported that the airplane's flight path was "straight down the center line" of the runway. The airplane "porpoised" on touchdown twice, veered off the left side of the runway, and subsequently came to rest in a field. The airplane sustained structural damage to the landing gear and left wing spar. The winds reported at the airport about the time of the accident were from 340 degrees at 10 knots. The pilot reported about 580 hours of total flight experience, which included approximately 87 hours in the same make and model as the accident airplane. He did not report any mechanical anomalies with the airplane.