On July 3, 1994, at 0758 Pacific daylight time, an experimental homebuilt Adams Thorpe T-18 airplane, N51079, nosed over while attempting a forced landing in a field adjacent to runway 29R at Stockton, California. The aircraft was owned and operated by the pilot and was on a local area test flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft incurred substantial damage. The certificated private pilot, the sole occupant, sustained minor injuries. The flight was originating at the time of the accident. According to information provided by an Federal Aviation Administration (FAA) inspector from the Oakland, California Flight Standards District Office, the accident flight was the second flight of the aircraft since certification on April 6, 1994. The aircraft has a Mazda NSU wankle rotary automobile engine installed and is operated on automotive gasoline. The pilot was on initial climbout after takeoff when the engine suddenly quit. The pilot was unable to make the runway and executed a forced landing in a field near the airport. The aircraft nosed over after encountering soft, rough terrain. The pilot reported that the fuel lines and fuel pump do not have any thermal shielding and he believes the engine failure was due to vapor lock.