On June 15, 2006, about 1330 central daylight time, a Piper PA-18A-150, N9779D, operated by Wabash Valley Soaring Association Inc., received substantial damage on impact with a runway sign during landing rollout at Lawrenceville-Vincennes International Airport, Lawrenceville (LWV), Illinois. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 personal flight was not operating on a flight plan. The commercial pilot received no injuries. The flight originated from LWV at an unknown time. The pilot stated that he was participating in glider tow operations at the airport that day. During the accident flight, he released the glider he was towing over the airport, flew south of the airport to lose altitude, and entered the traffic pattern for landing on runway 27 (5,198 feet by 150 feet, asphalt). He observed another aircraft taking off from runway 27 and decided to land on the grass next to the runway. During his rollout, he observed a glider approaching the airport from the north which appeared to be landing in the opposite direction. The glider appeared to overshoot the runway centerline and was headed for the accident airplane. The pilot turned right towards the runway to avoid the glider, but the glider "turned or corrected" towards him. The pilot reported turning back to the left to get out of the glider's way when he impacted the runway sign. The tow pilot stated that he did not hear any radio transmissions from the glider on the LWV common traffic advisory frequency. According to the Airport Facility Directory, runway 27 had the same traffic pattern for engine-driven aircraft and gliders.