The pilot reported that he entered a right traffic pattern and established 80 knots on final approach. During the final approach he reduced engine power to idle and began to flare the airplane. The pilot stated that he believed that he flared higher than normal and he held a steady pitch attitude. As the airspeed decreased the airplane unexpectedly dropped and impacted the runway hard. The pilot lost directional control and the airplane skidded off the runway into a grassy area. The subsequent impact resulted in substantial damage to the lower fuselage and rudder. The pilot report no preimpact malfunctions or failures with the airplane that would have precluded normal operation.