A trimaran is a multihull boat consisting of a main hull and two smaller outrigger hulls (amas), attached to the main hull with lateral struts (akas).

History

The first trimarans were built by indigenous Polynesians almost 4,000 years ago, and much of the current terminology is inherited from them.

Multihull sailboats (catamarans and trimarans) gained favor during the 1960s and 1970s. Modern recreational trimarans are rooted in the same homebuilt tradition as other multihulls, though there are a number of production models now on the market, such as the folding, trailerable designs of Ian Farrier .

Construction

Trimarans have a number of advantages over comparable monohulls (conventional, single-hulled sailboats). Given two boats of the same length, the trimaran has a shallower draft, a wider beam, less hull area, and is able to fly more sail area. In addition, because of the wide beam, trimarans do not need the weighted keel required in monohulls. As a result, the trimaran offers much better straight-line performance than a monohull, is able to sail in shallower water, and maintains its stability in stronger winds. However, its wider beam makes it a little more cumbersome to maneuver, so tacking and jibing can be trickier.

As the righting moment (the force that resists the opposite torque of the wind on the sails) is produced by a float on either side called an ama and not a heavy protruding keel, trimarans are lighter and faster than a monohull of equivalent length. A lightweight retractable keel is often employed to resist lateral movement, making many models easilly beachable. Most trimarans are nearly impossible to flip sideways given a reasonable degree of caution, however, trimarans can reach speeds so great in a storm that they can plow into a wave and flip end-over-end. This hazard is especially dangerous for a multihull because of their wide beam. The front of the boat, often covered by trampoline, acts as a giant paddle rather than a narrow monohull would. To avoid this unfortunate scenario owners of trimarans are advised to use trampolines with a large weave and employ parachute drogues and sea anchors whenever appropriate.

Safety

Overall, trimarans are much safer than a monohull as the lack of a heavy keel, combined with the two (usually sealed) amas makes for a nearly unsinkable boat.

Because of their stability and safety, trimarans such as the Challenger class have become popular with sailors who have restricted mobility.

Potential buyers of trimarans should look for one that is designed with amas with multiple sealed partitions, controls that all run to the cockpit, a collision bulkhead, partial or full cockpit coverings or windshields, and drain holes in the cockpit that can adequately drain the cockpit quickly, among other things.

Other Types

• Multihull

World Record

The British sailor Ellen McArthur set a new world record for solo circumnavigation of the world in her trimaran B&Q/Castorama, arriving in February 2005 after just over 71 days at sea