THE CERTIFICATED COMMERCIAL PILOT, THE SOLE OCCUPANT, WAS CONDUCTING FLIGHT TESTS ON A NEWLY MANUFACTURED EXPERIMENTAL, AMATEUR BUILT AIRPLANE. WHILE ORBITING OVER AN AIRPORT, THE PILOT DECLARED AN EMERGENCY AND WAS OBSERVED DESCENDING IN A LEFT SPIRALLING DIVE. THE LEFT FLAPERON AND LEFT WING SEPARATED FROM THE FUSELAGE. THE PILOT, WHO WAS WEARING A PARACHUTE, ATTEMPTED TO BAIL OUT OF THE AIRPLANE AT LOW ALTITUDE. THE PARACHUTE FAILED TO SUFFICIENTLY OPEN DUE TO THE LOW ALTITUDE. AN EXAMINATION OF THE SEPARATED FLAPERON DISCLOSED CYCLIC OVERLOAD AND OVERTRAVEL ATTRIBUTED TO FLUTTER. FLAPERON COUNTER WEIGHTS WERE STRONGLY RECOMMENDED BY THE MANUFACTURER TO PREVENT FLUTTER. THE PILOT ELECTED NOT TO INSTALL THE COUNTER WEIGHTS BECAUSE IT WOULD IMPOSE AN ADDITION OF WEIGHT, AND THE PILOT FELT THAT THEY WERE NOT NEEDED.