A TRIMARAN warship, with three narrow hulls, would need only half the power of conventional vessels to achieve the same top speed, according to its British designers. Vosper Thornycroft, a shipbuilding company based in Portsmouth, will unveil a model of a 1500-tonne trimaran frigate next month at the Idex defence exhibition in the United Arab Emirates.
The triple-hull design is widely used for sailing vessels, and a trimaran holds the world record for the distance sailed in 24 hours. But there has been little previous interest in developing powered versions.
Trimarans have a slender central hull that creates much less drag in the water than a single, wide hull. This reduces the power needed to drive it. Two narrow hulls, called outriggers, are connected to the central hull by a crossdeck. The outriggers make the vessel very stable. According to Robert Mulligan, technical director of Vosper Thornycroft, the difference in drag means that a trimaran warship could travel at over 55 kilometres per hour using only half the power required by a monohull to achieve the same speed.
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The crossdeck of a trimaran also increases the available deck area, providing more room for weapons and other equipment. Vosper plans to make its trimaran 18 metres wide, while the beam of a comparable monohull would be 11.5 metres. The wider deck will allow the trimaran warship鈥檚 heliport to be sited farther from the edge of the vessel. This would enable helicopters to operate in heavier seas.
Mulligan admits that the design does have one disadvantage: 鈥淵ou need a bigger dock than for a conventional frigate 鈥� we would have to look at mooring facilities.鈥�
The Naval Architecture Research Group at University College London recently investigated the feasibility of powered trimaran vessels. The researchers found no technical reason why there should not be naval trimaran frigates and suggested that the outriggers might even provide significant protection from sea-skimming missiles.
The design of a trimaran鈥檚 outriggers is a major factor in the stability of the ship and this gives trimarans a further advantage. Changes in the weight and distribution of a ship鈥檚 payload often require modifications to the ship in order to maintain its stability. Because a trimaran鈥檚 outriggers are relatively easy to modify, the triple-hulled ships are simple to alter when the payload changes. Mike Porter of the Royal Institution of Naval Architects says: 鈥淚t鈥檚 an interesting design. We鈥檙e certainly keen on the concept and think it鈥檚 something the Navy should be looking at.鈥�
Before a full-scale ship can be built, the Vosper Thornycroft team will carry out further checks on the hydrodynamics of the design, and measure the stresses on the outriggers. 鈥淲e could be in a position to sign a contract with a customer in 12 months,鈥� says Mulligan. 鈥淏y the year 2000, there鈥檚 no reason why there could not be a trimaran warship in the water.鈥�
