twohull

Twohull refers to a watercraft configuration that uses two parallel hulls. The most common form is the catamaran, in which two slender hulls are connected by a frame, deck, or trampoline. The name catamaran derives from Tamil, from phrases meaning tied wood or linked hulls, reflecting historical boats built in the Indian Ocean region. In naval architecture, twohull vessels are part of the broader category of multihull boats, alongside monohulls (one hull) and trimarans (three hulls).

Design and performance characteristics vary with size and purpose. The two hulls provide a wide beam, which yields high initial stability and a spacious deck area relative to the length of the boat. A shallow overall draft is common, enabling access to shallower harbors and beaches. However, interior volume can be more limited per hull compared with a similarly sized monohull, complicating layout and accommodations. The ride in waves can differ from that of a monohull, as each hull responds to waves individually, sometimes producing distinct motion characteristics that influence comfort and seaworthiness.

Types within the twohull category include sailing catamarans, which pursue speed and handling advantages from reduced hull resistance, and motor catamarans, which emphasize passenger capacity, stability, and efficiency for commercial use. Twohull designs are widely used for recreational sailing, racing, passenger ferries, and certain military and research applications. The development of modern materials and manufacturing has expanded the viability of twohull vessels, leading to a broad range of sizes and configurations.