Design and assessment of a super high speed, hybrid hydrofoil/SWATH crew boat

Abstract

This thesis presents the preliminary design and assessment of Wavecutter, an innovative super high speed, hybrid hydrofoil/SWATH crew boat. The intended mission of the vessel is the very-fast transportation of crew and cargo, to and from offshore installations. The design builds on Brizzolara's unmanned high speed hybrid SWATH/hydrofoil vessel concept (Brizzolara, 2010), maintaining the dual operating mode: foilborne to reach top speed of 85 knots in moderate sea states and a displacement SWATH to sail in the higher sea states. This vessel is expanding the family of unmanned hybrid SWATH vessels of Brizzolara and Chryssostomidis to include manned vessels (Brizzolara & Chryssostomidis, 2013). The special hydrofoil profile recently optimized and verified by model tests in free-surface cavitation tunnel, has been adopted, to ensure high lift to drag ratios and avoid typical instability phenomena of conventional super-cavitating hydrofoils (Brizzolara, 2013). The surface piercing configuration of the hydrofoils was adopted in order to make the vessel inherently stable, without the use of control mechanisms. The general design phase was focused on the integration of the manned module, internal arrangements, weight estimation, speed profile determination and engine selection. The hydrofoil design phase limits on resizing the four surface-piercing super-cavitating hydrofoils to keep the vessel even keel at maximum speed. To achieve this, the front foils need to have a larger size than the aft ones, due to the trim moment produced by the turbo-jet thrust force. The feasibility assessment phase in foil borne mode confirmed the static stability of the vessel and good seaworthiness in waves. It is recommended that future work be conducted with CFD simulations in unsteady conditions, to obtain a more accurate understanding of the vessel's dynamic behavior.