The private pilot reported that on final approach to the unimproved landing site, at about 50 feet above ground level, he detected a "sinking feeling," followed by a "drastic" loss of airspeed. The pilot stated that he applied full throttle in an attempt to go around, but the sinking continued and the airplane "pancaked" onto the ground. The pilot reported that he had not encountered any turbulence during the flight, but there were [rain] showers within approximately 10 miles of the landing site. The pilot reported no mechanical failures or malfunctions with the airplane at the time of the accident. The airplane received substantial damage to both main landing gear and the fuselage.