On November 25, 1997, at 1500 central standard time (cst), a Hall RV-6, N36AH, operated by a commercial pilot, sustained substantial damage when on takeoff the airplane made an uncontrolled left turn. Subsequently, the pilot reduced power and the airplane impacted on the runway. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under 14 CFR Part 91. No flight plan was on file. The pilot reported no injuries. The flight was originating at Blair, Nebraska, when the accident occurred. In his written statement, the pilot said that during the initial takeoff as the tail wheel came off the ground, the airplane began to "fishtail." When the pilot made rudder corrections, the airplane's directional control got worse. The airplane became airborne entering an uncontrolled left turn. The pilot said that he did not have "positive response" when he turned back parallel to the runway. The pilot reduced power to land. The nose of the airplane tracked right, away from the runway heading. The pilot tried to turn back to the left, but the airplane's controls would not respond. The pilot reduced the power to idle and impacted the ground in a left nose down slip approximately 20 feet left of the runway. The airplane skidded across the ground and came to rest in the center of the runway. A Federal Aviation Administration (FAA) inspector examined the airplane at the accident site. The spinner and lower cowling were crushed inward. The firewall showed buckling at the bottom. The left side of the fuselage from the cowling, through the cockpit and aft to the empennage showed heavy skin wrinkling. The left main landing gear was bent aft and embedded in the bottom fuselage skin. The left wing tip was crushed inward and broken aft. The left forward wing spar was broken aft. The wood propeller was broken aft and split. Examination of the engine and engine controls revealed no anomalies. Examination of the airplane's rudder controls revealed that a fracture had occurred outside of the weld attaching the base of a T-shaped bar, forming the foot rest of the pilot's left rudder pedal, to the torque tube connecting the left and right seat left rudder pedals. Further examination of the broken parts revealed a fatigue crack on the torque tube, originating on the rear outside portion of the fracture.