On June 7, 2003, at 1209 central daylight time, a Manweiler Acro Sport II experimental home-built airplane, N94SM, was substantially damaged during a forced landing following a loss of engine power near Bartlesville, Oklahoma. The instrument rated private pilot and his passenger were not injured. The airplane, owned and operated by the pilot, was operating under 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the personal flight for which a visual flight plan had not been filed. The local flight originated from the Bartlesville Airport (BVO), near Bartlesville, Oklahoma, approximately 1200. The 2,048-hour pilot reported that he had requested fuel prior to his departure from the Newton Country Airport (EWK). Fuel servicing was not performed on the aircraft as requested by the pilot, and the pilot departed without checking fuel quantity on-board his airplane. While on a formation flight with two other vintage airplanes, the engine loss power when the flight was about 6 miles from the BVO airport. The pilot stated that he performed all of the required actions necessary for an engine restart, but was unsuccessful. The pilot attempted a forced landing in an open hay field; however, the 3 foot tall grass "tripped the landing gear" and the tail-wheel equipped airplane nosed over, and came to rest in the inverted position. Examination of the wreckage revealed structural damage to the vertical stabilizer and rudder. The engine cowling and wooden propeller were also damaged. The pilot confirmed that the fuel system was empty.