On May 2, 1999, at 1045 hours mountain standard time, an experimental R.M. Bishop Aero Spec 2150, N2103Z, veered off runway 24 and ground looped during the takeoff ground roll at the Payson, Arizona, airport. During the accident sequence, the airplane encountered tall brush vegetation. The airplane, operated by the pilot under 14 CFR Part 91, sustained substantial damage. The private pilot and one passenger, the sole occupants, were not injured. Visual meteorological conditions existed for the personal flight and no flight plan was filed. The flight was originating at the time of the accident and was scheduled to terminate at Falcon Field, Mesa, Arizona, on the day of the accident. In a written statement, the pilot reported that as he taxied the conventional gear airplane onto runway 24, he checked the windsock to the south and it displayed a calm indication. The pilot stated that as he brought the tail up on the takeoff roll, the airplane began to yaw to the left. He attempted to apply right rudder input to return the airplane to centerline. The pilot stated that as he approached the side of the runway, he noticed the airspeed indicator at 60 knots, and he attempted to takeoff in ground effect. He reported that he was unable to get the airplane airborne and went into the grass at a high rate of speed. The pilot stated that he attempted to regain control of the airplane with rudder input and light braking; however, the airplane spun around in the brush left of the taxiway before it came to a stop. The closest weather reporting station 57 miles northwest of the accident site at Prescott, Arizona, was reporting winds as variable at 3 knots. The pilot had a total of 9 hours in the experimental airplane.