The pilot/owner was practicing takeoffs and landings in the recently certificated experimental amateur-built gyrocopter at the time of the accident. During run-up, high-speed taxi, and pre-spin of the rotor, the pilot noted no anomalies. While the pilot/owner was not rated in rotorcraft, he did have a student endorsement that limited his flights to in-ground-effect only, and no more than 10 knots of wind. The pilot chose to perform a normal takeoff with a 14-knot tailwind that gusted to 24 knots. At 200 feet above the runway, the pilot determined that the rotor rpm was decaying and the gyrocopter would not climb due to the tailwind. He performed a forced landing off the departure end of the runway, and the gyrocopter came to rest on its side which resulted in substantial damage to the airframe. The pilot/owner reported to the FAA that there were no mechanical deficiencies with his gyrocopter.