Five Hulls Make Ships Faster

A Five-Hulled Ferry that uses 25% less fuel than current ships yet can travel twice as fast is being developed by its British designers. Known as a pentamaran, the ship uses a long, slender main hull and two pairs of outriggers, called sponsons, to provide stability.
The design has already been sold to an American company, which plans to launch a passenger version of the ship. It claims the ship will be able to travel at up to 80mph. According to Nigel Gee, managing director of the company, his ship's main advantage is its high speed. Gee's pentamaran is made from steel which, although heavier, is far cheaper. "We can produce a steel pentamaran capable of 80mph for less than the cost of an existing 25mph aluminium vessel," says Gee. He has spent two years developing the pentamaran idea and although a full-size ship has not yet been built, computer simulations and model testing have persuaded several shipping companies to back the project.

Current high-speed ship designs fall into two camps: the monohulls and the catamarans. The length of the hull determines how fast a ship can go. The longer and thinner it is, the faster the ship will go but the less stability it will have. Catamarans are faster than monohulls but are still heavy. Gee and his team decided the only way to design a faster ship was to take a very long, slender main hull and try to make it more stable. Sponsons (or outriggers) create drag in the water, so the designers had to find the best place to put them, and decide how deep in the water they were to run. After experimenting with several designs, the team found that using two pairs was the best solution. This allowed a large hull with space for passengers and cargo, but also made the pentamaran stable and safe.
The pentamaran also gives a smoother ride for passengers, and Gee hopes this will eventually lead to cruise ships being designed around the concept. The design cannot be used on a boat less than 50 metres long as the drag from the sponsons becomes too great.
"Because of the sponsons, the ride is incredibly smooth, and despite the fact that these ships go so quickly, they are incredibly safe. If the ship is leaning to one side, the front sponsons enter the water, slowing the ship and levelling it up," says Gee.