The investigation was unable to determine who was actually flying the airplane at the time of the accident. A 3,100 hour commercial pilot, who was the owner and builder of the experimental airplane, was in the right seat. The left seat was occupied by his private pilot son who had about 128 hours. They were attempting to land at an uncontrolled airport on runway 25. The airport manager and fixed base operator at the airport stated that the winds were out of the south at about 25 mph with gusts to about 30 mph. The operator further stated that the airplane had made two or three close in left hand approaches, each time overflying the runway centerline on the turn to final and correcting with steep banked turns back to the runway. Witnesses reported that the airplane rolled inverted while on final approach from what appeared to be an 'accelerated stall.' The aircraft was examined at the accident site by an FAA airworthiness inspector who reported finding no preimpact mechanical malfunctions or failures.