The pilot reported that he returned from a local flight and was practicing touch-and-go landings. During the second takeoff, as the airplane gained altitude, the engine began to gradually lose power. Unable to return to the runway, the pilot initiated a precautionary landing to a strip of gravel that is perpendicular to the runway. During the landing, the right wing was substantially damaged.
The pilot reported that he did not believe there was problem with the engine, but that the problem was with the fuel-to-air mixture caused by the fuel pressure regulator not keeping a continuous constant pressure that led to the gradual loss of engine power.