The future shape of fast ferries

Austal Ships claims it will revolutionise fast sea transportation with its innovative trimaran vessel – a craft promising greater operating efficiencies, the ability to cope with rough seas while offering passengers and cargo superior sea-keeping and comfort. The design will be publicly tested when Fred Olsen?s Spanish ferry operation takes delivery of a 126.7m ropax fast ferry in the second half of 2004.

Claimed that it will be the world?s largest high-speed multihull ferry, the Auto Express 126 will be built at the Western Australian shipbuilder?s Fremantle shipyard. The $66.5 million state-of -the-art trimaran is the result of more than three year?s research and development in collaboration with the ship owner which involved extensive fluid dynamic work and multiple tank testing sessions at some of the world?s leading facilities. Austal also built and trialed an 11m manned technology demonstrator and has modelled the vessel?s structure in detail using sophisticated finite-element techniques.

The project gave rise to a number of significant new technical features, particularly in the area of the hull form, although details about this, i.e. deadweight or carrying capacity, its speed in rough seas and its propulsion plant or other equipment, have been withheld for commercial reasons.

According to James Bennett, Austal?s technical manager, the option of using a pure SWATH hull form was considered but it was decided that this would be impractical as both the vessel speed and deadweight requirements would result in a commercially suspect vessel. Bennett says that Austal?s semi-SWATH catamaran hull form would have been suitable for the required speed and deadweight but, in view of the sea conditions encountered in the Canary Islands, the new trimaran hull form was chosen to enhance comfort. The ride of both the semi-SWATH and trimaran hull forms are claimed to be superior to a chined hull form.

Both the shipbuilder and the ship owner claim the new hull form is set to revolutionise fast sea transport and that the slender stabilised monohull, more commonly referred to as a trimaran, represents a major breakthrough for multi-hulled vessels. The characteristics of this new vessel, with a beam of 30m, will improve overall efficiency in terms of passenger capacity, deadweight and freight lane metres by more than 35 per cent. At the same time, it is claimed that passenger comfort will increase by 25-40 per cent depending on the route and sea conditions. When the newbuilding enters service in the latter half of 2004, Austal believes it will be the world?s largest all-aluminium ship and expects it to generate considerable interest among ferry operators.

With power provided by four diesel engines driving waterjets, the trimaran will be able to maintain Fred. Olsen?s projected service speed in excess of 40 knots and provide the capacity to carry 1,350 passengers, over 340 cars and a substantial number of trucks. It is probable that the high speed main diesel engines will be supplied by MAN B&W (Ruston RK280s) driving Kamewa waterjets through gearboxes from Reintjes.

Fred. Olsen pioneered the use of large high-speed ferries in the Canary Islands and currently operates three fast ferries and two conventional vessels. The company carries almost three million passengers, half a million cars and 250,000 lorries annually in the five services that it offers in the Canary Islands. One of the conventional vessels will be replaced in September by a new 66m Auto Express catamaran on order at Austal Ships. The ferry owner, however, recognises that the catamarans have some limitations in terms of capacity and especially passenger comfort when operating in rough seas around the Canary Islands. This led them to the conclusion that further research was needed in order to develop a new concept for high-speed vessels combining the good comfort provided by the soft movement of monohulls, with the low resistance and very good stability and carrying capacity of catamarans. In addition, the company wanted to stay with diesel engines rather than getting involved in gas turbine technology which it is convinced would have led to unacceptably higher operating costs.

Is this the beginning of the end for big catamarans?

The consensus among those contacted by The Motor Ship is it is not because catamarans, which offer substantial manoeuvrability, are ideal for many applications and can accommodate requirements such as port fit issues or a drive through vehicle deck.

Austal?s managing director Bob McKinnon says he believes there will always be a significant role for its catamaran designs in the fast ship market as they provide levels of seakeeping and passenger comfort that are ideal for many applications.

Generally speaking, however, the Austal trimaran design will provide a higher level of comfort than other fast ferries operating at the same speed in a wide variety of sea conditions. “Therefore operators may choose to maintain a higher speed without degrading comfort, or provide greater comfort while operating at the same speed,” says McKinnon.

Leading high speed ferry broker, International Broking Services (IBS), says trimarans represent yet another approach on the constant evolution of high speed ferry technology.

IBS sales director James Aitkenhead states there will always be a place for the more conventional catamarans and monohulls in the market. “Over the years there?s been a series of technological developments that promise to revolutionise the high speed ferry industry,” says Aitkenhead. “A trimaran offers better sea-keeping in rough sea conditions, however one has to acknowledge that the purchase of any high speed ship will always involve some sort of compromise on design, the comfort and operational efficiencies offered by the vessel and the cost that the ferry operator is willing to pay.”

Incat chairman, Robert Clifford, says Fred Olsen has made a ?courageous decision? in buying a trimaran, which he believes has only limited redeeming features. He went on to say that while the long vessel may perform better in a head sea, catamarans offer the advantages of being lighter and easier to manoeuvre. “This trimaran is really a monohull with two small stabilisers, they are not really three equal sizes, and the decision to purchase it has been a very courageous decision by the operator.”