The private pilot was taking off from an off-airport site on a personal, local flight, under Title 14, CFR Part 91. He said that the site was slightly uphill, and that after becoming airborne, he attempted to increase airspeed by "dropping flaps, and lowering the nose." He said that due to rising terrain, he turned the airplane downwind, and the airplane "sank." The airplane touched down on the tundra, and nosed over. He said there were no mechanical problems with the airplane prior to the accident.