On August 4, 1996, at 1030 central daylight time, a Beech E-55, N142P, owned and operated by a private owner, was substantially damaged during a wheels up landing near Brownwood, Texas. The private pilot, sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed for the Title 14 CFR Part 91 personal flight. A flight plan was not filed for the cross country flight that originated near Del Rio, Texas, at 0900. The pilot reported that he was flying in the traffic pattern at Brownwood Airport concentrating on practicing a "close/precise pattern." The pilot did not look at the landing gear and flap levers, and he inadvertently added an extra notch of flaps instead of extending the landing gear during the base leg of the traffic pattern. The pilot also reported that the landing gear warning horn did not sound. Both propellers, the belly of the airplane, and structural formers were bent.