On December 19, 1998, about 1311 eastern standard time, a Cessna 172M, N9295H, registered to a private individual, and a Let L-13 glider, N98KK, registered to Mid Florida Soaring Association, collided while on final approach to the Okeechobee County Airport, Okeechobee, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for either flight. The Cessna flight was operating under the provisions of 14 CFR Part 91, as an instructional flight and the glider was operating under the provisions of 14 CFR Part 91, as a personal flight. The Cessna airplane was substantially damaged and the student pilot, the sole occupant, was not injured. The glider was substantially damaged and the private-rated pilot, the sole occupant, also was not injured. The Cessna flight originated about 41 minutes earlier from the Charlotte County Airport, Punta Gorda, Florida. The glider flight originated about 15 minutes earlier from the Okeechobee County Airport. The pilot of the Cessna airplane stated that when the flight was about 20 miles from the destination airport, he monitored the UNICOM frequency and noted that runway 13 was the active runway. The flight continued then when about 5 miles from his destination, he announced his position on the UNICOM frequency. He entered the traffic pattern at 1,000 feet msl, at a 45-degree angle midfield position for a left downwind for runway 13, which he announced. At that time he observed the glider on the upwind leg. The Cessna flight continued then turned left base, which was announced, and at that point in the flight, he heard the pilot of the glider announce that his flight was on a left downwind for runway 13. The Cessna flight turned left base then final, which he announced on the frequency; and he observed the glider abeam his position at a higher altitude. While on final approach about 500, he felt an impact on the empennage and realized he had no rudder control. He continued the approach, landed uneventfully on the paved runway, then taxied the airplane to the ramp. The vertical stabilizer was displaced about 45 degrees to the right, and the left elevator exhibited red paint transfer and an indentation on the upper surface at about a 45-degree angle from the longitudinal axis about midspan of the control surface. Also an indentation oriented in the same direction was found on the upper surface near the outboard portion of the elevator. The pilot of the glider stated that the flight was towed to 1,500 feet, released, then circled three to four times southeast of the field, to enter the traffic pattern at the proper altitude. He reported hearing the Cessna pilot announce that his aircraft was on the downwind leg for runway 13, but reported that he did not hear any other radio calls from the pilot of the Cessna airplane. He turned left downwind, base when at a 45-degree angle to the runway, then onto final approach to the grass runway. He announced all legs while in the pattern on the UNICOM frequency using a portable VHF transceiver. While on final approach to the grass runway which is located west of runway 13, he heard and felt an impact at about 200 feet. He observed that the Cessna was pulling away to his left and had landed on the paved runway. He continued the approach and landed on the grass runway. Damage to the right side of the fuselage along a stringer was noted and the lower section of the wing tip was displaced upwards.