The 8,633-hour airline transport pilot executed a forced landing to a field after the single-engine experimental airplane he was flying experienced a total loss of engine power. The pilot reported in the NTSB Form 6120.1 (Pilot/Operator Aircraft Accident/Incident Report) that he departed on a local flight approximately 15 minutes prior to the mishap. Prior to the flight, all systems checked-out normal and the weather was reported as visual flight rules for the duration of the flight. The pilot stated that he was flying at 2,400 feet mean sea level over a densely populated urban area when the engine lost power. He added that at the time of loss of engine power the left fuel tank was selected and the tank was two-thirds full, while the right fuel tank was completely full. The pilot stated that he immediately turned on the fuel boost pump and switched fuel tanks when the engine lost power. His actions did not restore engine power so the pilot established an airspeed of 80 knots and began looking for a suitable landing area. The pilot was able to land the airplane in a vacant field with full flaps in a wings level attitude with the tail wheel touching down first. The main landing gear subsequently "gave way and collapsed" allowing the airplane to come to rest in the upright position. The pilot and his passenger were able to exit the airplane unassisted and received no injuries. The airplane sustained structural damage to the right wing and main landing gear. The weather near the accident site was reported as wind from 330 degrees at 5 knots, clear skies, 10 miles visibility, and a barometric pressure setting of 30.02 inches of Mercury. The reason for the loss of engine power could not be determined.