On September 25, 1996, at 1330 Pacific daylight time, an experimental Ralph Taylor, Royal T, N2554, registered to and operated by the pilot as a 14 CFR Part 91 personal flight, collided with an unknown object while the airplane was maneuvering at 2,000 feet near Kent, Washington. Visual meteorological conditions prevailed at the time and no flight plan was filed for the local flight. The airplane was substantially damaged and the commercial pilot and his passenger were not injured. The flight had departed from Auburn, Washington, approximately one-half hour prior to the accident. During a telephone interview and subsequent written statement, the pilot reported that while flying at 2,000 feet, he was maneuvering the airplane to remain clear of the traffic pattern near an uncontrolled airport. While in a turn, the pilot stated that he felt something hit the airplane. The airplane began to vibrate and the pilot stated that he was having trouble with the flight controls. The pilot declared an emergency to the Renton, Washington, control tower where a landing was made at Renton without further incident. After landing, the pilot inspected the airplane and found that the top and the leading edge of the vertical stabilizer was damaged and bent to one side. The pilot also found that the push rod for the rudder control was broken. Further inspection of the vertical stabilizer by a Federal Aviation Administration Inspector from the Seattle, Washington, Flight Standards District Office, did not reveal evidence of what kind of object collided with the airplane.