On October 10, 2000, at about 1130 eastern daylight time, a Harwell/Gardner, Wag-Aero Cubby, N909GH, registered to a private owner, operating as a 14 CFR Part 91 personal flight, experienced a reported total loss of engine power in the traffic pattern at Berry Hill Airport, Stockbridge, Georgia. The pilot made a forced landing to an open field and crashed. Visual meteorological conditions prevailed and no flight plan was filed. The airplane sustained substantial damage, and the pilot reported no injuries. The accident occurred about 9 minutes after departing Berry Hill Airport. The pilot stated he departed from runway 11 and turned crosswind at about 500 feet when the airplane experienced a total loss of engine power. He attempted an engine restart with negative results. A forced landing was made to an open field. The left main landing gear collided with a berm and the airplane nosed over inverted. Examination of the engine assembly and components by the FAA did not reveal the source of the reported loss of engine power by the pilot. (See FAA Inspector statement an attachment to this report.)