On September 10, 1994, about 0910 central daylight time, an experimental Snider CP328 Super Emeraude, N90484, sustained substantial damage during a forced landing in Painton, Missouri. The private pilot sustained minor injuries. One pilot rated passenger sustained serious injuries. Visual meteorological conditions prevailed for the personal flight conducted under CFR 14 Part 91. No flight plan was filed. The flight origniated from Painton, Missouri, at 0904. In his written statement, the pilot thoroughly described his preflight procedures and said he pulled the engine through two revolutions. He said he was climbing on course when the airplane began shaking violently. He reduced the throttle, lowered the nose of the airplane, and turned the magneto switch to the off position. He said the shaking did not subside and was so violent he could not read the airspeed indicator. He sought an appropriate pitch attitude and conducted a forced landing in a soybean field. During the landing, the airplane nosed over. The pilot reported the smell of fuel and said he was initially trapped in the airplane. He said he managed to eventually free himself and the passenger. The pilot reported that the hand carved wood propeller had failed. He said that one blade had delaminated and had split from the tip to the hub. A "good sized piece" had separated in flight.