Abstract: A low drag ship hull generally includes a side air cavity initiated by wetted bow section, bottom air cavity initiated by wetted bottom nosepiece, wetted stem section that closes a lower portion of the side cavity, wetted bottom tailpiece that closes the bottom cavity, stabilizing fin, and propulsor. The bottom of a catamaran hull cross structure includes bow impact alleviator. Optional flaps in the stabilizing fins, together with optional all-movable canard fins are used for control. Different wetted bow sections and retractable plates are used for starting side cavities. A low drag hull may utilize multiple air cavities. A new low drag hull includes a new upper bottom air cavity that is initiated by an upper bottom wetted nosepiece, and closed by an upper bottom tailpiece. Alternative designs include a shortened forward hull spaced ahead of a shortened aft hull, and a hydrofoil-supported trimaran with low drag hulls.

Abstract: The invention relates to the use of gas cavities to reduce frictional drag on underwater surfaces such as hydrofoils, struts, fins, rudders, keels, propeller blades, ship hulls, underwater bodies, and wetted surfaces in general. Each gas-filled cavity is formed behind a discontinuity in the surface that causes the water boundary layer to separate from the surface. Gas is ejected into a region behind the discontinuity to fill the cavity; the gas can be air. If a cavity is open to the atmosphere, then air can typically fill the cavity naturally without air ejection. Cavities can either be closed or open. A low drag hydrofoil may have a closed cavity on one side, and an open cavity on the other side. For closed cavities, the underlying surface can be shaped to minimize cavity closure drag. Various ways to generate cavities, change hydrodynamic forces, and duct gas internally on hydrofoils and struts with cavities are covered.

Abstract: In a catamaran boat, including a propulsion system, and main hull positioned to travel above the water surface, the hull extending longitudinally forwardly, the combination comprising: two pontoons, each spaced below the main hull, the pontoons extending forwardly; support means carried by the main hull and carrying the pontoons, whereby the pontoons are at least mostly submerged below the water surface when the boat is loaded and at rest; the pontoons having associated chines positioned to permit the pontoons to plane on the water surface at typical planing speeds of the boat; the support means having streamlined leading edge structure and upper sponson structure; and the support means having lateral thickness at a longitudinal location spaced at a level above the pontoons and which is less than the maximum width of each of the pontoons at the longitudinal location.