Fat buoy slim

A slimline design looks set to cut the time it takes cargo ships to cross the Atlantic from three weeks to three days – with the potential to revolutionise the whole freight industry.

Transporting goods by air is an uncertain business, graphically and tragically underlined by the terrorist attacks of September 11.

But the knock-on effects of the bombings, not least the crisis in the aerospace industry, are unlikely to create more than a minor interruption to the steady rise in the number of goods sent by air.

As airfreight grows, so does the cost to the environment, through the huge amount of fuel burnt, and to industry, in terms of the high transport prices. But until now there has been no viable alternative to sending cargo by air. Dispatching goods by sea may be much cheaper, but freighters can take up to three weeks to cross the Atlantic – far too long for most perishable products.

Ship designers have long sought to fill this gap in the freight market, and with two recent developments – water jet propulsion and the use of gas turbines – they now appear close to creating a new generation of fast seagoing vessel. The race is on to launch this type of craft.

But how is this breed of ship able to travel so much faster than traditional cargo ships?

The problem with conventional vessels is that as they travel through the sea they push the water out in front of them, eventually creating a single large wave, called a captive wave. This increases the drag on the ship, making it difficult to travel at high speeds, and the effects are worsened by bad weather.

One answer is to make the ships longer and slimmer, says UK naval architect Nigel Gee, who has designed a new jet-powered ship that he claims is capable of crossing the Atlantic in just three days.

The freighter, which is being backed by a Swiss consortium, ADX Express, has a pentamaran design and its long, thin shape enables it to pierce the waves, allowing it to maintain high speeds throughout the journey. The $90m (£62m) vessel is 280m long, with a cargo capacity of 8,000 tonnes. It will have a top speed of 41 knots (around 73kph), compared to most large container ships which average around 25 knots.

Gee, managing director of Nigel Gee and Associates, which specialises in high-speed ships, says the ADX Express is designed to be the most fuel-efficient vessel operating in open seas. ‘The principle is very simple: when you have a big, heavy ship in the water you are going to need less power if you can make it long and slender,’ he says.

This is not a new idea. Ship designers have known for centuries that slimmer ships are capable of higher speeds. But unfortunately these narrow ships had a tendency to tip over, so they were abandoned. Gee and his team got around this by designing what they considered the most perfectly shaped hull, and then stabilising it using outriggers. ‘We wanted to have a design that enabled us to go very fast and have the absolute minimum resistance, so we elected to have two outriggers on each side, two of which are in the water and two just out of the water. The Polynesians have been doing this for about 2,000 years with outrigger canoes,’ he says.

It is not just the shape of conventional ships that prevents them travelling at high speeds. As well as the drag caused by the large captive waves, vessels travelling quickly across high seas also come up against damaging vibrations. When large ships travel at over 30 knots, their propellers begin to cavitate, meaning the pressure on their forward surfaces becomes low enough to boil the water, creating vibrations powerful enough, over time, to weaken the hull.

So the fast freighter is powered by water jets, which take water in through the bottom of the ship, then pumps it out through the back. The advantage of this is that it is very efficient at high speed. Water jets are not affected by cavitation, as the pressure beneath the boat pushing water up into the jets is high enough to prevent bubbles forming on the blades of the water jet’s impeller.

Wider applications

Gee says the market for fast freight ships is there, providing the consortium can deliver goods in as close to the time it takes aircraft as possible, without coming near the cost of air freight. ‘We are looking at getting goods from almost anywhere in the US to anywhere in Europe in seven or at most eight days,’ he says. That competes with airfreight, which takes five or six days, and container traffic, which takes 17 to 25 days.

The consortium has been working on the ship concept for six years, and believes it is ready to go to market. The group recently signed a deal with Spanish shipbuilder Izar to build the vessels, and is waiting for investors.

In the meantime, the consortium is also working with Izar to use the concept to develop two other pentamarans, a roll-on roll-off vessel for transporting trucks and a passenger ferry. Work on these has now overtaken the fast freighter, and Gee expects to receive an order for a large pentamaran this year.

As well as the large amount of cargo unsuitable for long sea journeys that could be transported by fast ships, the freighters could also open up the opportunity for multinational companies to find a global source of components, says Sandy Morris, shipbuilding analyst at ABN Amro. ‘Keeping inventories at a minimum is a huge cost saving, so fast ships should be beneficial if companies can source components globally quickly, and gain economies of scale,’ he says.

The ships could also be used by the military, which traditionally relies on aircraft to carry troops and equipment to war zones, as current large seagoing vessels are not fast enough. Gee has already talked to the Royal Navy and US Navy, and the latter has expressed a strong interest in the development of a military sea lift vessel capable of around 40 knots.

But ADX Express is not alone in this new market. Its direct competitor is the Philadelphia-based FastShip Atlantic consortium, which includes Rolls-Royce, General Electric and ship designer Osprey UK.

The FastShip Atlantic also uses a water-jet propulsion system, and its designers hope that it too will be able to cross the Atlantic in just three days. The ships will be designed to provide a seven-day door-to-door service for companies transporting freight across the Atlantic.

The vessel will have a semi-planing monohull, which acts like a speedboat, surfing the wave rather than pushing through it, reducing the drag. Each ship will be powered by five 50MW Rolls-Royce marine Trent gas turbines, capable of propelling the FastShip at speeds of up to 40 knots.

Using gas turbines means the FastShip is likely to be more expensive than the Fast Freight — estimates have put the projected cost per ship at up to $230m (£160m) – but they produce far greater power than traditional marine diesel engines, for no more fuel. They also emit only four per cent of the sulphur dioxide and five per cent of the nitrogen oxides that diesel engines produce per horsepower.

The FastShip project has received $875m (£608m) from the US Maritime Administration and, like ADX Express, is now attempting to raise the capital to start building the vessels. Roland Bullard, president of FastShip Atlantic, says the company is optimistic that it will be able to finalise its funding arrangements. The fact that the firm is still ‘alive and kicking’ despite the recession in the US is significant, he says.The ships are due to be built at a San Diego yard, and it is thought sea trials will be held later this year, with the vessels predicted to enter service in 2003.

Whichever of the two teams eventually wins the race to secure investment and launch its vessel on to the market first, the new developments in ship design look set to make transporting goods across the Atlantic smooth sailing.