Composite speed sailboat readied to break 50-knot barrier

Sailrocket (Bitterne Manor, Southampton, U.K.) is using new design concepts and composites to make its Sailrocket speed sailboat, in hopes of breaking the existing speed record of 46.25 knots (the goal is 50 knots). Its unique counterfoil design bypasses the stability problems encountered by monohulls and multihulls. The sail and keel elements are positioned so that the boat experiences almost no vertical lift, allowing wind gusts to increase speed, without causing the craft to tip or overturn. At speed, the Sailrocket rides on two small planing surfaces under the thin 9m/29.5 ft-long main fuselage. The leeward float at the end of its 8m/26-ft-long beam flies just above the surface, supported by aerodynamic lift, and the sail loading is reacted by a single, inclined hydrofoil, rising from the forward planing surface. It is steered using an inclined, surface-piercing rudder that is operated by a pilot positioned at the aft end of the fuselage.

The Sailrocket took about six months to design and 18 months to build at NEG Micon's Southampton, U.K. factory (a noted manufacturer of large wind blades). Several types of software aided structural design, including Autocad LT (Autodesk, San Rafael, Calif., U.S.A., used for general line drawings of parts), MultiSurf (Aerohydro Inc., Southwest Harbor, Maine, U.S.A., to create hull shapes), Rhino (Robert McNeel & Assoc., Seattle, Wash., U.S.A., for 3-D modeling) and PATRAN for the finite element (FE) structural modeling. The main hull and crossbeams are a sandwich of carbon fiber/epoxy facesheets with an aramid honeycomb core, vacuum bagged into female molds made using wet layup glass/epoxy with a 300g 0°/90° fabric backing the gel coat, followed by 10 layers of 450g biaxial glass/epoxy. Wood stiffening frames were bonded in place with glass/epoxy before demolding from the plugs. The facesheets for all parts were hand layed up, using low-temperature-cure (85°C/185°F) carbon/epoxy prepreg from SP Systems (Southampton, U.K). The core is 8 mm Nomex honeycomb from Aerocell (Marysville, Wash., U.S.A.). Total weight without a pilot is 174 kg/384 lb., just over the target weight of 170 kg/375 lb. In test runs so far, the boat has reportedly demonstrated great stability and has topped out, to date, at 27.9 knots.