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October 9, 2000.
Mono-hulls Versus Multi-hulls
Real Audio

One of the problems faced by a monohull sailboat is that when the wind blows it tilts or 'heels' the boat, thus spilling wind from the sail and robbing the boat of speed. The heeling of monohulls is countered by a keel with a significant weight, often lead, at its lower end. However, the trouble with keels is that they increase the wetted surface area of the boat, which gives the boat a problem with an inexorable law of boat design: the larger the wetted surface, the greater the drag and the slower the speed.

In the history of sailing boat design, one of the great strokes of genius was the invention by Polynesians of outriggers for their canoes-the principle being that instead of using a keel to keep the sail from tipping the boat over, they could achieve the same thing by rigging poles to hold a second, smaller hull parallel to the main hull. The smaller hull would then resist the tendency of the boat to capsize. Such outrigger hulls had smaller wetted surfaces than keels, and were far lighter. Also, even in strong winds, an outrigger can keep the sail nearly upright and pulling fully. In extreme versions of this design the outrigger hull is made the same size as the main hull, and the mast is placed on a platform connecting the hulls-the design called a catamaran. For speed under sail it was not until modern times that the speed of catamarans was equaled by monohulls.

The potential for superior speed of multi-hulls over monohulls was demonstrated in recent years when Dennis Connor used a catamaran to trounce an extreme monohull built by Australia, and in so-doing successfully defended America's Cup. But instead of going forward with this Polynesian-based design the America's Cup Committee banned multihulls from competition, insisting instead that participants battle it out in the traditional (and necessarily slower) monohulls.

If this famous sports trophy were called the Polynesian Cup, rather than the America's Cup, I bet it would long ago have encouraged multihulls, and that we would now be benefitting from the results-the higher speeds that will unquestionably appear once multi-hulls are more fully explored, developed, and encouraged.

Nor is it fair to cite as a disadvantage of multihulls the often quoted problem that they are more dangerous because when they capsize or suffer a knockdown they are just as stable upside down as they are right side up. Some of the fastest, open-ocean monohull sailing craft yet built are designed for the Vendée Globe race-in which solo skippers circumnavigate the Antarctic Continent through the roughest oceans on the planet. Surprisingly, these monohull boats have been found to have exactly the same problem as multi-hulls-remaining resolutely upside down for days at a time (in one case even when dismasted), the 15-foot-long keel with one or more tons of lead on its end, sticking high above the water like a tower, while the skipper huddles in the upside-down cabin, or takes his or her chances outside, clinging to the bottom of the boat. During the 1996-97 Vendée Globe race, this proved to be such a problem that after the race was over the rules were changed to require that these high-speed monohull thoroughbreds be self-righting after a capsize or knockdown and that the designer, builder and skipper sign a certificate to that effect.

The sea is unforgiving and does not suffer fools gladly-a thing we never forget as we slowly make our way around the world.

© 2000 - Roger Payne

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