The pilot reported that he was practicing a soft-field takeoff procedure. He stated that he started the takeoff roll with full engine power, full up elevator, and one notch of wing flaps. The airplane initially accelerated down the center of the runway, but as the airplane began to pitch upward it turned to the left. The pilot attempted to correct with right rudder but the airplane continued toward the left side of the runway. The pilot stated that in a further attempt to regain control of the airplane, he lowered the nose and reduced power. The airplane veered off the left side of the runway, struck the precision approach path indicator (PAPI) lights, and then nosed over. The airplane sustained substantial damage including deformation of the wing struts and crushing of the wing leading edges. Postaccident examination of the airplane revealed no pre-impact anomalies.