On July 4, 1998, about 1135 eastern daylight time, a Piper J3C-65, N42760, nosed over during a forced landing near Zellwood, Florida. The airplane was operated by the registered owner under the provisions of Title 14 CFR Part 91, and visual flight rules. Visual meteorological conditions prevailed. A flight plan was not filed for the local, personal flight. There were no injuries to the private pilot, and the airplane was substantially damaged. Origination of the flight was the Bob White Field Airport, Zellwood, Florida, about 1000 on the same day. According to the pilot, he was conducting touch and go landings at the Bob White Field. Just prior to turning crosswind on the fourth departure, the engine lost power. The pilot applied carburetor heat and full throttle, but the engine continued to lose power until it quit. A forced landing was made in a farm field. The wheels sank into the soft ground, and the airplane nosed over. After the accident, the engine and fuel were tested. The engine started, ran at a low revolutions per minute (RPM), and was able to produce maximum RPM. The magnetos were checked while the engine was operating, with no discrepancies noted. According to the FAA inspector, there was no problem with the operation of the engine during the test run. There was fuel in the airplane, approximately 3/4 of a tank. It was drained and examined, with no water or sediment found. The Carburetor Icing Probability Curve was reviewed, and the conditions were on the outside edge of the visible icing curve.