On April 30, 2005, about 1635 eastern daylight time, an unregistered amateur built Kolb Mark III, was substantially damaged during a forced landing, following a loss of engine power after takeoff from a private airstrip in Clay Center, Ohio. The certificated private pilot sustained minor injuries, while the passenger was seriously injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local personal flight conducted under 14 CFR Part 91. According to the pilot, he had flown the airplane with the passenger earlier in the day for approximately 1.5 hours, and noted no abnormalities with the engine. After refueling, the pilot and passenger again boarded the airplane, and departed on another flight to conduct takeoffs and landings. During the initial climb after a touch-and-go landing, about 50 feet agl, the engine began to slowly lose power and the airplane structure began to vibrate. The pilot elected to return to the airstrip, and performed a 180-degree turn. As the airplane neared the airstrip, the engine regained power, but then subsequently began to surge. The pilot recalled that in the past, the engine would lose power, but would always regain power a few seconds later. He decided to continue the flight, and after flying over the runway, chose to return back to the runway in case the engine lost total power. During the turn towards the runway, approximately 30-40 feet agl, the engine again began to lose power. The pilot lowered the nose in an attempt to gain airspeed and level the wings; however, the right wing struck the ground and the airplane cartwheeled before coming to rest. The pilot noted that the engine continued to run for about 1 minute after the accident. The pilot maintained the airplane and no maintenance records were kept. The airplane was powered by a 2-cycle, 2-cylinder Rotax 532 engine. The Federal Aviation Administration was not notified of the accident until one of their inspectors noted it on the Internet on May 3, 2005.