The homebuilt aircraft was on downwind leg of the traffic pattern, after initial takeoff, when it went into a dive and collided with the ground. A witness said he heard a power reduction before the dive and power added again as it started down. The pilot's son said his father had control flutter problems at speeds above 100 mph. This was verified by a logbook entry. By reducing speed, the flutter went away. Thus, the flaperon (aileron) push rods were modified by the pilot. The modification consisted of a doubler, 2 bearings and a 1 inch hole to retain the bearings. During a post accident inspection, it was found that the bellcrank arm had separated from the bearing. It was found that the drilled hole was irregular and large enough to allow the bearing to slip through the hole. The bearing was the only means of retaining the bellcrank to the fulcrum point. The right aileron at the accident scene was separated from the main wreckage and the control push rods to the elevator were broken at the bracket attached to the elevator.