8/10 offshore catamarans
Offshore multihulls are divided into two groups, cruising and racing, although there are some compromise designs. The reason for this division has a lot to do with safety.
It has been beyond dispute that unballasted multihulls have a greater speed potential thin ballasted monohulls, but at the same time there is a question mark over the safety of offshore multihulls. Development has tended to proceed along two different design theories, one leading to safe and comfortable cruising yachts and the other, to high-performance racers.
The unnerving feature of offshore multihulls of all types is that although very stable when the right way up, they are equally stable upside down. The ballasted keelboat, which will eventually return up from any angle, but a multihull in strong winds reaches the point of no return and capsizes. A favourable point of multihulls, is that they normally remain buoyant after capsized, affording the crew a better than average chance of rescue.
Being faster than keelboats, cruising catamarans also offer a great deal of space because of their square shape. A cruising catamaran of 10-12 metres (35-40 feet) overall can incorporate four private double cabins in the hulls with the addition of a large saloon on the bridge deck. As there is no noticeable heeling under sail it makes life aboard more pleasant than on a comparable keelboat.
Because of their slender hulls, catamarans are generally poor weight-carriers and the skipper must be mindful to temper the desire to fill space with heavy cruising gear. They are generally more expensive to keep in a marina where because of their area the marina charges are often relative to the rate for monohulls.
Conversely, due to multihulls not having deep fixed keels, they can be found moored in water that is too shallow for keelboats. A pleasant cruising feature is the lack of a deep draught so most cruising multihulls can take the ground without any problems and are perfect for visiting shallow bays and beaches.
Prouts of Canvey Island have been one of the most successful builders of cruising multihulls, with a range of comfortable, catamarans up to 45 feet in length. French builders, Multiplast and Edel manufacture larger cats that are suitable for charter use, and can be seen in the Caribbean where comfortable accommodation and simplicity is appreciated by charter clients with limited sailing experience.
Between the racing and cruising boundaries are compromise designs such as the [ Iroquois cat ] and the modern [ Dragonfly 920 trimaran ] , which has a comfortable cruising interior and a diesel auxiliary.
All the Dragonflies deal with the problem of high marina costs by having folding outriggers, which reduces overall beam to about the same amount as a typical cruising yacht. One drawback is that there is considerably less internal space than the equivalent catamaran and trimarans, tend to be similar to long, thin keelboats inside, even with the hull expanded out above the waterline.
The other end of the spectrum is the sporty, high-performance racing catamarans and trimarans. The smallest and popular are the 'micromultihulls' which compete as a restricted class and are about 25 feet in length.
These boats have sleeping accommodation and are extremely fast little racing boats that go along balanced on one hull even in relatively light winds. They involve competent sailing as would a high-performance dinghies and capsizes are not infrequent.
Offshore or ocean racing trimarans are generally more popular than catamarans because in their ease in rigging and their tendency to be faster to windward with the weather hull kept permanently airborne. At one time, there was an 'open' class that resulted in boats of around 80 feet in length, but the expense was great and there was a general agreement to limit the maximum size to 60 feet.
These are the trimarans that are sailed in the major ocean races such as the single handed transatlantic races, the Route du Rhum and others. They are the fastest seagoing sailing boats in the world and hold many of the trans-ocean records. They are often sailed in single handed racing in a very dangerous competition, where the boats sail fast in bad weather and in the dark.
A number of top sailors have lost their lives in these single handed 'ocean spectaculars', which is comparative to the Formula 1 motor racing. They represent the leading edge of maritime design, being constructed of sophisticated lightweight materials such as carbon fibre and Kevlar. Masts are rotating aerofoils similar to day-racing cats but a great deal larger complete with leading edge fully battened mainsails.