On June 30, 2001, at 1750 Pacific daylight time, a Smith FW-190 single engine experimental airplane, N376FW, impacted terrain about 0.5-miles west of the Reedley Municipal Airport, Reedley, California, shortly after takeoff. The airplane was registered to and operated by the pilot, who was also the builder of the airplane. The airplane was substantially damaged, and the private pilot, who was the sole occupant, received serious injuries. Visual meteorological conditions prevailed for the personal flight operating under 14 CFR Part 91, and a flight plan was not filed. The local flight departed runway 33 on a local area demonstration flight for a prospective buyer. During a telephone interview with the pilot, he reported the temperature was 106 degrees Fahrenheit, and a prospective buyer of the airplane wanted to observe a demonstration flight. The pilot elected to takeoff and fly around the traffic pattern for the buyer. The pilot stated that during the climb, over the runway departure end, approximately 800 feet, the airplane rolled to the left inverted. The pilot did not intend on rolling the airplane, but decided to continue with the roll to right the airplane. As the wings rolled level, the pilot saw he was dangerously close to the ground. The airplane impacted the ground with the left wing and cart wheeled. A farmer, who witnessed the accident, assisted the pilot from the airplane. Two witnesses reported they observed the airplane takeoff then turn toward the left. They then observed the wings rock from side to side before the airplane rolled left and pitch nose down. According to the pilot, he took off on too hot of a day with a high density altitude, and did not maintain sufficient airspeed to keep from stalling the airplane.