On May 13, 2004, at 1100 eastern daylight time, a homebuilt Mustang II, N78K, was substantially damaged during a forced landing, after experiencing a loss of propeller control while landing at the Fulton County Airport (USE), Wauseon, Ohio. The certificated private pilot sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under 14 CFR Part 91. According to the pilot, while in the traffic pattern at USE, he heard a loud grinding noise, and noted a subsequent loss of airspeed. As the airplane descended, the pilot realized that he would not be able to land on the runway, and performed a forced landing to a field. The airplane was equipped with an automotive V8 engine, which was connected to a propeller speed reducer by a coupling. Examination of the wreckage by a Federal Aviation Administration (FAA) inspector revealed that the drive coupling was disconnected. Further examination of the coupling revealed that the rivets holding the coupling together failed. The pilot added, "a better inspection of the drive coupling may have caught this problem."