On June 24, 1995, at 0845 central daylight time, a homebuilt Bushby Mustang I, N30878, piloted by a private pilot, impacted the terrain one-quarter mile east of runway 27 (2,670' x 190' dry/turf) at Shelbyville, Indiana following the initial flight of the airplane. The airplane sustained substantial damage and the pilot received minor injuries. The 14 CFR Part 91 flight was operating in visual meteorological conditions. No flight plan was on file. The local flight departed at 0840. The pilot stated that he did not intend to fly the airplane, but rather conduct high speed taxi tests on runway 36. He reported that the airplane became airborne and seemed controllable so he elected to continue the flight. During the climb he realized that the airplane required full right aileron and full right rudder to maintain level flight. He said he found that increasing the airspeed made the condition worse so he reduced power. He initially elected to land on runway 36; however, traffic on that runway prevented his doing so. He then continued, planning a landing on runway 27; however at the reduced power necessary to keep the airplane controllable, he realized that he would not make it to runway 27. He then elected to conduct a forced landing in a crop field one-quarter mile east of runway 27. On touchdown the airplane went through a fence. A post accident examination failed to reveal the nature of the control difficulties. Continuity was established; however, travel could not be verified due to the damage to the airframe. No other anomalies were noted in the control system of the airplane.