The purpose of the flight was for the flight instructor to provide tailwheel training to the pilot receiving instruction, who did not hold an endorsement to flying tailwheel-equipped airplanes, and who had recently purchased the experimental amateur-built airplane. It was the first flight for either pilot in this make and model of airplane and the takeoff was performed by the pilot. The flight instructor stated that airplane’s acceleration was slower than he expected, but given his lack of experience in this airplane, he did not feel it was abnormal. When the airplane was about 50 ft above ground level, the pilot and flight instructor stated that the airplane stopped climbing. The pilots then elected to land on the remaining runway and the flight instructor took over controls, lowered the airplane’s nose, and reduced engine power. He noted that the airplane “dropped quick,” so he then increased the engine power. Upon touchdown, both landing gear collapsed, and the fuselage sustained substantial damage. The flight instructor further described that the airplane had touched down “hard,” but he was surprised that the landing gear had collapsed and that he landed other airplanes in the past with similar force and not experienced any problems. Prior to the flight, the pilot performed a weight and balance calculation and determined that the ramp weight would be 1,156 lbs, about 6 lbs above the airplane’s maximum demonstrated weight. The pilot stated that he expected that 6 lbs of fuel would be consumed during taxi and runup. Postaccident review of the weight and balance completed by the pilot revealed was based on the airplane’s original empty weight, which did not account for multiple propeller model changes, the addition of avionics, structural repairs, and a modification of the landing gear design. Additionally, the weather conditions at the time of the accident included a density altitude that exceeded 3,000 ft. Based on the Federal Aviation Administration Koch chart, this density altitude correlated to a loss in rate of climb performance of 35%. The flight instructor stated that there were no preimpact mechanical malfunctions or failures of the airplane that would have precluded normal operation. The pilot also stated that there were no engine problems, but he reported that the experimental amateur-built airplane’s landing gear had been custom built and had not been designed by the airplane’s kit manufacturer. He also stated that the landing gear had previously collapsed and had been repaired by the previous owner/operator. A review of the airplane’s maintenance logs confirmed that the airplane had been damaged and repaired on at least three documented occasions. Given the uncertain nature of the airplane’s weight and balance, it is likely that the airplane was being operated near or in excess of its maximum gross weight during the accident takeoff. Combined with the detrimental performance impact of the density altitude at the time, it is likely that the airplane was unable to climb out of ground effect during the takeoff due to these combined factors. After aborting the takeoff, the flight instructor’s power management, in combination with the airplane’s excessive weight, resulted in a hard landing and the subsequent landing gear collapse. Whether the landing gear collapse was solely the result of that hard landing, or had been exacerbated by the landing gear’s design, or its previous damage and repair, was not determined.