The pilot reported that he had conducted six previous uneventful flights on the day of the accident utilizing both runways 18 and 36 for takeoff due to variable winds. He elected to depart from runway 18 on the accident flight, because the windsock indicated a primarily southwesterly wind. The pilot stated that the takeoff roll was normal; however, shortly after liftoff, the airplane encountered a tailwind, which resulted in a degradation of performance. The airplane began to sink and lose airspeed, and the pilot aborted the takeoff. The airplane touched back down onto the runway, and the pilot applied the brakes in an effort to stop the airplane on the remaining runway. The airplane nosed over, which resulted in substantial damage to the vertical stabilizer. The pilot, pilot-rated passenger, and several witnesses reported a wind shift around the time of the accident. Weather reports from a nearby airport revealed that, during the period from about 1 hour 40 minutes before to about 20 minutes after the accident, there was a 40 degree shift in wind direction and an increase in wind speed from 9 knots to 18 knots, gusting to 24 knots. Postaccident examination of the airplane revealed no mechanical anomalies that would have precluded normal operation.