On August 6, 2017, at 1551 central daylight time, an amateur-built RA2 airplane, N952RA, impacted terrain near Hector, Minnesota. The commercial pilot and passenger were seriously injured, and the airplane was substantially damaged. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan. The local flight was originating from the Hector Municipal Airport (1D6), at the time of the accident.In an interview with the responding Federal Aviation Administration inspector, the pilot reported that on the takeoff roll, he pulled back on the control stick and the airplane did not take off. It bounced a couple of times and then pitched straight up. The airplane did not respond to the pilot's control inputs; he pushed the control stick forward and did not feel as though he had any elevator control. The pilot added that he reduced the engine power and felt the airplane stall. The nose of the airplane dropped, and the airplane impacted the terrain. Substantial damage was sustained to the fuselage. Examination of the airplane found that the control stick was not connected to the elevator bracket. A search of the wreckage did not locate any nut that would have secured the bolt. The airplane was recently acquired by the pilot. It was transported in three parts, so the pilot assembled the airplane. When the pilot was queried about how he would have secured the bolt for the control stick, he reported that he would use a castellated nut with a cotter pin. However, he could not remember installing the nut. The airplane had flown 6 or 7 times prior to the accident. An NTSB Form 6120 was not submitted by the pilot.