Multihull - Sailboats and Small Vessels

Sailboats and Small Vessels

Multihulls include: Proas, which have two differently shaped or sized hulls with lateral symmetry; catamarans, which have two hulls with longitudinal symmetry; and trimarans, which have a main hull in the center and symmetric stabilizing hulls on either side.

These types of boats have several advantages compared to single-hull boats. The increased distance between the center of gravity and the center of buoyancy provide higher stability compared to boats with a single hull. This allows multihulls to have narrower hulls and thus substantially less wave-forming resistance, which in turn results in greater speed without applying more effort.

In the case of boats under sail, stability serves to hold the vessel upright against the sideways force of the wind on the sails. This stability is provided in multihulls by the weight of the boat itself, in contrast to monohull sailcraft which typically use an underwater counterweight, a ballasted keel for this purpose, especially on larger sailboats. Multihull sailboats are typically much wider than the equivalent monohull, which allows them to carry no ballast, and the reduced weight also makes them faster than monohulls under equivalent conditions (see Nathanael Herreshoff's "Amaryllis", also 1988 America's Cup). It also means that multihulls need not sink or be abandoned if flooded, as opposed to ballasted monohulls who do indeed sink when flooded. The comfort of more onboard accommodation space and more level boats under sail offer substantially improved conditions for crew and passengers, which also contributes to the greatly increasing popularity of multihull sailboats during the past few decades.

There are also multihull powerboats, usually catamarans (never proas), both for racing and transportation. Speed, maneuverability, and space onboard are the main factors for choosing multihull design in powerboats.

... the weight of a multihull, of this length, is probably not much more than half the weight of a monohull of the same length and it can be sailed with less crew effort.