The student pilot, with one passenger, reported he was departing from a remote off-airport site, downhill, and with a light and variable tailwind. Just after takeoff, he said that a tailwind gust kept the airplane from climbing, and the main landing gear wheels struck a hill at the departure end of the site. The airplane subsequently nosed over, sustaining substantial damage to the wings, fuselage, and empennage. The student pilot reported no preaccident mechanical problems with the airplane.