On March 21, 2018, about 1745 central daylight time, a Cub Crafters PA18-150 airplane, N226JK, experienced a loss of engine power after takeoff from runway 36 (1,800 ft by 50 ft, turf) at the Eagle Creek Airport (51OK), Beggs, Oklahoma. The pilot sustained a minor injury; the passenger was not injured. The airplane was substantially damaged. The airplane was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 flight. Day visual meteorological conditions prevailed. The flight was not operated on a flight plan. The local flight was originating at the time of the accident.The pilot stated that the pre-takeoff engine run up was normal. The accident takeoff was uneventful until the airplane reached about 50 ft above ground level when the engine lost power. The engine regained power momentarily, but then lost power again. The pilot executed a forced landing to an open grass area near the approach end of runway 8. The airplane impacted a ditch during the landing which caused the landing gear to collapse. The airplane came to rest upright. The left wing struts were buckled, and both wings were deformed near midspan. The lower portion of the engine cowling exhibited upward crushing damage. The engine was displaced upward and to the left. The firewall and lower fuselage were deformed. The left side of the fuselage exhibited damage to the structural tubing along the cabin and baggage compartment. A postrecovery examination of the airframe and engine did not reveal any anomalies consistent with a loss of engine power. A detailed summary of the examination is included in the docket associated with this accident investigation. The pilot reported that about 30 gallons of fuel were on-board before takeoff. He stated that the fuel selector may not have been fully in the both position detent at the time of the accident takeoff, and as a result, the engine might have lost power due to fuel starvation.