On August 2, 2009, about 1353 central daylight time, an experimental amateur-built Gallagher Junior Ace airplane, N413G, sustained a loss of directional control during a crosswind takeoff from runway 18 (8,002 feet by 150 feet, dry grooved concrete) at the Wittman Regional Airport, Oshkosh, Wisconsin. The airplane ground looped and subsequently sustained substantial damage. Visual meteorological conditions prevailed at the time of the accident. The airline transport rated pilot and the student pilot were uninjured. The 14 CFR Part 91 instructional flight was not operating on a flight plan. The flight was originating at the time of the accident and was destined for the Poplar Grove Airport, near Poplar Grove, Illinois. The student pilot was seated in the left seat which was equipped with rudder pedals with brakes. The airline transport rated pilot held a certified flight instructor certificate and was in the right seat which was equipped with only rudder pedals. The right seat pilot said that at 50 mph he called "tail coming up." The crosswind procedure at that point required "more right rudder" inputs and his right rudder pedal broke off at its weld. He "yelled" for the student pilot to apply right rudder. The right seat pilot said that the ground loop started and that he closed the throttle. The right seat pilot stated, "I welded finger strap reinforcements to the left set of rudder pedals, although not called for in the plans. ... I would now recommend reinforcements on all rudder pedals."