On October 3, 1997, at 1500 central daylight time, a Grob 103 glider, N921G, was substantially damaged while landing near Caddo Mills, Texas. The commercial pilot, sole occupant of the glider, was not injured. The glider, owned by a private individual, was being operated by Southwest Soaring Inc., of Caddo Mills, Texas, under Title 14 CFR Part 91, at the time of the accident. Visual meteorological conditions prevailed for the personal flight for which a flight plan was not filed. The local flight originated from the Caddo Mills Municipal Airport at approximately 1330. Witnesses at the Caddo Mills Municipal Airport observed the glider land hard and porpoise 3 times while landing on runway 31. After the landing, the pilot was reported to have examined the glider for damage before signaling for the tow plane pilot to come over and proceed to be hooked and towed for a second flight. In the enclosed NTSB Form 6120.1/2, the commercial pilot stated that both of his flights appeared normal in all respects with the exception that he used a higher than normal final approach speed to compensate for the prevailing gusty winds. The private pilot reported that at the time of the mishap, the winds were from the north at 10 knots with occasional gusts to 15 knots. While performing a preflight inspection, a student pilot and his flight instructor, who were scheduled to fly the glider after the commercial pilot's second flight, discovered that the glider was damaged. Examination of the glider by the operator, the FAA inspector and 2 additional maintenance technicians revealed that the damage to the glider included structural damage to the tail wheel, the rudder assembly, the lower portion of the empennage, and the main landing gear well. The tow plane pilot, who also witnessed the gliders' first landing, submitted a statement of his observations. According to the tow pilot, "the first touchdown was hard enough to bounce the Grob back airborne sharply and a second touchdown followed that again bounced the [Grob] 103 back airborne. At the third touchdown the [Grob] 103 stayed on the runway." The commercial pilot stated in the enclosed Pilot/Operator Report, that he considered the damage to the glider to be minor. The commercial pilot had accumulated a total of 93 hours in gliders, of which 16 were in the Grob 103 glider. The documentation submitted by the operator to substantiate the damage incurred by the glider is attached to this report.