The pilot/owner of the recently purchased experimental amateur-built airplane submitted a report to the NTSB immediately after the accident. He explained that as he maneuvered the airplane in a left crosswind turn, the gullwing-styled cabin door opened, “creating significant noise and buffeting that affected aircraft stability and directional control.” The pilot said he attempted to secure the door and stabilize the airplane, but that it continued in a left descending turn that he could not arrest, and that he ultimately reduced power and completed a “mushing stall to ground contact” that resulted in no injury to himself but substantial damage to the airframe. A conversation with the airplane kit manufacturer revealed that the airplane was controllable with a door open in flight. He said the airplane required vigilance and proper use of the rudder to maintain coordinated flight and added that those transitioning from production airplanes benefitted from “differences training” because of the design and function of the pedals. An FAA inspector inspected the doors on the airplane and found that they closed and locked securely, and he confirmed flight control continuity. In conversation with the pilot after the inspection, the pilot volunteered that there was nothing wrong with the flight controls of the airplane and that he “may have overcontrolled the aircraft while trying to close the door” which resulted in the hard landing.