At about 13:11 EST, a Cessna 172 and a Let L-13 glider collided while on final approach to the Okeechobee County Airport. The Cessna was substantially damaged but the student pilot was not injured. The glider sustained minor damage and the sole occupant was not injured. The Cessna pilot said that he announced his position on the Unicom frequency and entered the traffic pattern on a left downwind for runway 13. At that time he observed the glider aircraft flying southeast. The Cessna then turned left base, announced it on Unicom, then heard the glider pilot announce that he was on a left downwind for runway 13. The Cessna pilot turned onto final and announced his position. He then felt an impact on the empennage but landed uneventfully. The vertical stabilizer was determined to be displaced to the right. The glider pilot said he was towed to 1,500 feet, released, then circled three to four times southeast of the field, to enter the traffic pattern altitude. He reported hearing another pilot announce that his aircraft was on the downwind leg for runway 13. He turned downwind, base, and final, announcing his intentions on Unicom 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. He observed that the Cessna was pulling away to his left. The gliders fuselage and left wing were damaged.