On August 20, 2016, about 1000 eastern daylight time, an experimental amateur-built Kitfox 4-1200, N51TM, was substantially damaged while landing at Canandaigua Airport (D38), Canandaigua, New York. The private pilot was not injured. The airplane was registered to and operated by the private pilot as a personal flight conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the flight that originated from Whitfords Airport (B16), Weedsport, New York, about 0920.The pilot reported that while landing on a turf airstrip adjacent to runway 31, a rudder pedal torque tube separated and the airplane departed the right side of the runway. The airplane subsequently impacted an uneven field and came to rest upright. Examination of the wreckage by a Federal Aviation Administration inspector revealed substantial damage to the wings and fuselage. The separated section of rudder pedal torque tube was retained and forwarded to the National Transportation Safety Board Materials Laboratory for further examination. Metallurgical examination revealed that the vertical torque tube for the right rudder pedal fractured at a fillet welded intersection where it attached to a horizontal torque tube. The fracture surface exhibited a small thumbnail like fatigue region followed by an overstress region. The single-seat, high-wing, tailwheel-equipped airplane, serial number C9406-0031, was assembled from a kit by the pilot in 2000 and issued an FAA experimental airworthiness certificate. Its most recent condition inspection was completed on August 8, 2016. At that time, the airframe had accumulated 547.4 total hours of operation. It had flown an additional 3.3 hours from the time of the last inspection, until the accident. The FAA inspector that examined the wreckage further stated that although assembly of the accident airplane was completed in 2000, the kit was actually a 1994 model. On August 22, 1995, the kit manufacturer released Service Letter No. 47 (SL-47), applicable to the accident airplane model, which advised owners that the company had recently noticed signs of fatigue in rudder pedal torque tubes. The SL instructed owners to inspect the areas for fatigue and offered a reinforcement kit (P/N 35015.000) for $59.95. Further, in 2000, the kit manufacturer redesigned the rudder pedal torque tubes for subsequent models, to include a reinforcement similar to what had previously been offered in the reinforcement kit. The inspector added that the accident airplane was not equipped with the newer rudder torque tube design, nor was it equipped with the reinforcement kit offered in SL-47.