The pilot took off in conditions of turbulence and gusty winds. Witnesses reported the ultralight vehicle pitched and rolled erratically after lift-off. The pilot then made a right climbing turn to a downwind heading and proceeded over a tall tree line toward a field where he ultimately crashed. One witness heard a 'pop', then looked and saw the aircraft descending with the wings folded. Others said the wings flexed upward first, then the aircraft flipped over and the wings reversed and folded around the airframe. An exam revealed upward deformation of the carard, but it had no significant evidence of ground impact. The wings had evidence of both upward and downward bending. The kingpost was bent rearward and its top cap was found 175 feet from the main wreckage. No airspeed indicator was installed. The manufacturer reported that an airspeed indicator was required to judge the speed with the engine running, that the max speed (VNE) was easily exceeded, and that the flight controls became extremely sensitive at higher airspeeds.