Triton trials trimaran form

When it comes to high-speed commercial vessels, shipowners are spoilt for choice with a range of catamarans, air cushion craft, pentamarans and semi-displacement hulls either already in service or under consideration. Another hull form, in the shape of the trimaran, is now being put forward as a viable alternative to add to this choice.

Trials of the trimaran hull have been carried out over the past two years with the research vessel Triton. Triton was built and delivered by the UK shipbuilder Vosper Thornycroft in August 2000. Funded by QinetiQ, the former UK defence evaluation and research agency (DERA), the 1,100t displacement vessel is the largest motor-powered trimaran ever built. It is being used as an ocean going technology demonstrator to assess the option of the trimaran concept for future surface combatant frigate requirements.

The

concept?s hull form is also seen to have potential in the commercial market.

Demonstrator vessel construction

The

initial structural design was carried out in accordance with the ?high speed and light craft rules? of DNV.

The

Norway-based classification society used its SWAN package to simulate structural loads resulting from motions in a seaway at various speeds and headings. QinetiQ also gathered extensive feedback during model tank testing at its Haslar facilities.

The

result is a main hull having a round bilge shape with underwater sections approaching semi-circular shape amidships. A gentle rise of the bottom lines aft leads to a counter-stern transom with minimal immersion.

The

side hulls are of multi-chine design on the outboard face with a flat plain inboard face for ease of manufacture.

The

demonstrator was built at two thirds the size of a full-scale warship. Although not armed, it is capable of carrying containerised Naval military systems at sea. With an overall length of 98m and a beam of 22.5m, the Trimaran demonstrator meets the structural constraints of the ship?s plating and longitudinal stiffening.

The

main hulls and bridge deck are of steel construction.

The

diesel electric propulsion system consists of two Paxman 12VP185 diesel generators with a total output of 4MW.

The

re is a single conventional shaftline in the main hull plus a right angle drive thruster in each side hull.

The

main shaft drives a single 3.5MW AC propulsion motor which turns a FP propeller through a reduction gearbox.

The

vessel has a service speed of 20 knots. A 350kW thruster is fitted to each side hull to give a backup propulsion capability of 8 knots. More powerful engines would drive the vessel to a theoretical maximum speed of 25 knots.

The

outer hulls can be fitted with waterjets, propellers or Z-drive systems if required. Speeds of 40 knots are envisaged for a full-scale version.

Advantages of

trimaran design

Although the trimaran development has been driven by frigate type applications, concept studies have been carried out for other quasi military roles including offshore patrol, coastguard duties, and also for future vessel development such as the Mini Landing Platform Helicopter ship (Mini LPH), fast roro rapid deployment support ships, and air-capable stealth vessels.

The

trimaran design

is faster and more manoeuvrable than an equivalent sized mono-hulled craft, says QinetiQ. It adds that Triton has proved that the triple-hull design offers a reduction in drag of 20% compared to a conventional mono-hull vessel.

The

se benefits could translate into major production and through-life cost savings, mostly attributable to a reduction in the engine power required to achieve speeds currently attainable in an equivalent mono-hulled ship.

Triton?s triple-hull also offers stability and a vast increase in the available deck area. Increases in size and, to some degree, location of the superstructure can be easily accommodated without affecting the ship?s stability, says QinetiQ.

The

required stability can be obtained by adjusting the size and distance from the main hull to the side hulls with little impact on drag and weight.

Trials program

Using a

trimaran design

for a warship is a radical departure from standard naval architecture so other navies are closely watching the trials programme.

The

purpose of the trials is to assess and confirm the ships general handling performance, architectural and structural performance and its sea-keeping behaviour compared to a conventional monohull design.

The

extensive sea trials have been undertaken in a wide range of weather conditions up to a sea state of 7 to 8 with the ship sailing at short notice to stormy sea areas around Ireland, south Iceland and off the Norwegian coast.

Using a

star trajectory pattern the trimaran was subjected to every conceivable wave pattern. QinetiQ says there were very few instances where it shipped green seas over the bow. Special attention was paid to the slamming effects under the decks linking the hulls. QinetiQ says the vessel?s handling capabilities have validated the designers? claims by confirming the naval architectural performance.

The

US Navy, together with the UK Ministry of Defence, is testing trimaran concepts using Triton. US-based NAVSEA has provided state-of-the-art onboard monitoring technology, called the Trials Instrumentation System (TIS).

The

function of TIS is to acquire, archive, display, and present the data generated from Triton?s structural and sea keeping trials.

The

TIS will remain onboard to support future trials, including the planned installation and testing of a US Navy Integrated Power System (IPS).

Commercial

opportunities

QinetiQ and Vosper Thornycroft have signed an agreement to jointly market trimaran technologies/ designs worldwide, with the exception of the UK defence market. QinetiQ?s design capabilities are the creative force behind Triton with Vosper Thornycroft providing the shipbuilding skill and detailed design to make QinetiQ?s Triton research a reality.

The

official price of Triton was £13 million ($20 million), but there are suggestions that it cost the shipbuilder a lot more.

The

partnership intends to exploit what the partners see as the vast commercial potential for powered trimaran ship designs. This potential includes fast roro and ropax ferries, fast passenger ferries and even leisure craft.

The

main market sector targeted is the fast feeder boxship one.

The

optimum length for a Panamax trimaran is around 150m while a theoretical maximum length of just over 200m is envisaged. This gives a potential service speed of more than 40 knots say the partners.

The

limiting factor is the shore based infrastructure facilities, particularly cargo handling equipment where the outreach of current gantry cranes rarely exceeds 17 boxes across.

Another important market is the super-yacht and the mini cruise ship sectors where comfort of passengers is the overriding concern.

The

triple-hulled design is also suited to shallow water requirements such as inland waterway freight vessels.

Bob Short, QinetiQ?s RV Triton programme manager, says that Triton has already gone a long way to validating earlier research and has demonstrated the considerable benefits associated with triple-hulled vessels. He is also quietly confident that trimarans have a huge potential commercial application worldwide and the agreement with Vosper Thornycroft strengthens the UK?s position as a world leader in trimaran technology.

Ultimately, however, one has to recognise that a fundamentally conservative industry such as shipping will take some convincing before it will commit hard cash to a new hull type.

The

same goes for the UK?s MoD when it will have to make a decision between the traditional monohull and the trimaran. Traditions die hard in naval circles and a lengthy gestation period is often needed before new ideas become accepted.

As to the future fate of Triton, it will be available as a trials vessel over a period of 15 years in addition to its original function as a research tool for the trimaran concept.