The private pilot was departing from a 500 foot-long, rough and uneven off-airport site. In the pilot's written statement to the NTSB he stated, in part: "During takeoff from the remote airstrip, [the] aircraft failed to reach flying speed." The pilot indicated that the airplane initially lifted off at the end of the strip, then it mushed into an area of brush-covered terrain at the end of the airstrip. The airplane sustained substantial damage to the wings and fuselage. The pilot noted that there were no preaccident mechanical anomalies with the airplane.