The pilot reported that he was involved in a bi-wing fly-in that was going on at the time of the accident. According to a Federal Aviation Administration inspector, witnesses observed the pilot enter into a side-slip to the left during landing and the airplane touched down in the side-slip on the left wheel. The pilot stated that the airplane was turning left after touchdown and he applied full right rudder to compensate, then right brake to straighten the airplane out. The airplane subsequently changed direction, the left landing gear strut collapsed, and the airplane entered into a slow speed ground loop. There was substantial damage to the lower wing, damage to the propeller, and the landing gear. The pilot reported no pre-impact mechanical malfunctions or failures that would have precluded normal flight.