According to the pilot, after rotating and obtaining the best angle of climb airspeed, the airplane began descending "as if it had lost lift or something was pushing it down." The pilot said that the airspeed was still at best angle of climb airspeed but the airplane was descending. As impact with terrain was assured, the pilot set up for a forced landing. The airplane subsequently impacted rising terrain about 150 to 200 feet from the departure end of the runway, which resulted in substantial damage to its right wing. The pilot reported that winds were variable at 6 knots, with gusts to 15 knots, and added that he felt the accident was the direct result of wind shear and could not have been prevented or detected. The pilot reported no anomalies with the airplane or engine that would have precluded normal operation.