On October 2, 1999, about 0845 hours Pacific daylight time, an experimental Ismari Canard C3A, N4526W, owned and operated by the pilot, experienced a partial loss of engine power during initial climb from the Henderson, Nevada, airport. The commercial pilot made a forced landing in rough terrain, and the homebuilt airplane was substantially damaged. The personal flight was conducted under the provisions of 14 CFR Part 91. The pilot was not injured. Visual meteorological conditions prevailed at the time of the local area flight, and no flight plan was filed. The flight, which lasted about 3 minutes, was originating at the time of the accident. The pilot reported that upon climbing 100 feet above ground level the engine began vibrating, sputtering, and losing power. Unable to resolve the problem by adjusting the mixture and throttle controls, and with reduced rpm, the pilot was unable to maintain flight. He made a forced landing in desert terrain, about 1 mile southwest of Henderson. The Federal Aviation Administration (FAA) coordinator performed a visual, external examination of the engine. No evidence of case or cylinder damage was noted. Oil was present on the dipstick, and the carburetor was intact without any apparent damage. The throttle control was found intact.