On May 23, 1994, about 0900 central daylight time, a Cessna 152, N80812, was substantially damaged when it struck a fence post during an aborted soft field takeoff at Rushenberg Field, Harlan, Iowa. Neither the certificated flight instructor nor the commercial pilot, who was receiving dual instruction, were injured. The 14 CFR Part 91 instructional flight originated from Omaha, Nebraska, without flight plan and operated in visual meteorological conditions. According to the flight instructor, once the airplane did not become airborne at a predetermined point on the runway, he aborted the takeoff roll by reducing the power to idle and applying the brakes heavily. The airplane slid slightly on the wet, grass runway, but did not stop. In an attempt to prevent the propeller from striking a fence located at the end of the runway, the instructor steered the airplane to the left. The airplane impacted a fence post, bending the tail to the left. No preimpact mechanical abnormalities were reported by either pilot.