The pilot reported to the National Transportation Safety Board investigator that he had been doing full stop landings at Witham Field, Stuart, Florida. On his sixth takeoff the plane veered slightly left due to P-factor. He corrected with right rudder. His rudder application had minimal effect so he added more right rudder, which caused the plane to ground loop to the right. The ground loop substantially damaged the right wing. The pilot stated that the airplane and engine had no mechanical failures or malfunctions during the flight.