The Ocean-going 4×4
Seasickness sufferers will take heart from a new, concept catamaran that uses hydraulic suspension to remove the bumps in even the roughest conditions, writes Lawrence Schäffler.
Looking a bit like a cross between a boat and a ski-doo, the Nauti-Craft catamaran has independently articulated hulls that are connected to the main body of the vessel with an interlinked hydraulic suspension system.
Designed by Western Australia’s Nauti-Craft, the cat’s independent hulls react rapidly to waves, absorbing the bumps without transmitting high forces to the deck and superstructure. This provides a superior level of ride comfort as well as improved control and stability – whether the cat’s stationary or travelling at speed. The ride can be further enhanced with active (automatic) control of the suspension system.
While the concept is revolutionary in the marine context, similar suspension systems have been used by Mitsubishi in the Dakar rally and by Citroen’s WRC team in the world rally championships.
The suspension-equipped catamarans were originally developed for commercial applications – among them delivering crews to service wind farms in the North Sea’s often treacherous conditions. But more recently the boats have begun attracting keen interest from the high-end recreational market.
Ironically though, Nauti-Craft is a R&D facility, not a boatbuilder. And the company, says managing director Ken Johnsen, has no interest in building boats. Instead, the prime strategy is establishing license agreements with boatbuilders in various segments of the global marine market.
This would see Nauti-Craft earning revenue from design and development services, obtaining licensing fees from builders seeking rights to market segments, and for royalties from vessels incorporating its technology.
The company already has three such commercial agreements in place:
• with Australia- and Asia-based boatbuilder Triyards Strategic Marine, building windfarm service vessels for the European market
• with a Middle East-based group developing a luxury ‘quadmaran’
• with a Japanese boatbuilder building high-performance recreational sports fishing vessels.
To date Nauti-Craft has built and tested a number of prototypes, including a four-hull craft (4Play) and, most recently, an 8.5m catamaran 2Play. It has also secured a green light for the development of a purpose-designed 26m vessel – the NautiStrat-26 WFSV – servicing wind farms in the North Sea.
Development of the new vessel has gathered momentum following an Approval in Principal for the vessel from DNV GL.
DNV GL – a Norwegian-based classification agency – is the largest technical consultancy and supervisory to the global renewable energy (particularly wind, wave, tidal and solar) and oil & gas industry.
Some 65 percent of the world’s offshore pipelines are designed and installed to DNV GL’s technical standards. It was created in 2013 following a merger between two leading organisations in the field – Det Norske Veritas and Germanischer Lloyd.
The Nauti-Craft team provided DNV GL with a comprehensive analysis of loads, forces and accelerations anticipated to be experienced by the vessel operating in often severe conditions in the North Sea.
Says Dr Laurie Walker, Nauti-Craft’s operations manager: “One of the key challenges was to demonstrate how a traditional vessel would be seeing up to 3g of slamming accelerations while the Nauti-Craft superstructure would only experience up to 1g.”
The vessel will be built by Strategic Marine and, says project manager Jay Elatam, DNV GL’s go-ahead is an engineering milestone.
“As the NautiStrat-26 concept is such a radical departure from the typical catamaran and hence class rules, DNV GL’s acceptance on the load calculation method forms a solid foundation in designing future vessels fitted with this ride control system.”
Of particular significance for the NautiStrat-26 is Nauti-Craft’s Deck Attitude Control System (DACS). This automatically adjusts and maintains the horizontal attitude of the deck at low speeds and when manoeuvring, relative to fixed structures or coming along side larger vessels like ships.
DACS is auto adjustable for different load conditions and sea states. It features self-levelling of the body with adjustable height.
Marine suspension reduces slamming and jarring motions and improves comfort and safety. It reduces roll and pitch motions and improves planing speed in rougher conditions. Effectively, says Nauti-Craft, it gives a smaller vessel the seakeeping qualities typically found in larger vessels – and yet offers the lower operating costs of a smaller vessel.
The graph below shows the comparison between Nauti-Craft’s 2Play prototype and a standard catamaran of similar size.
While the initial design was geared to a specific commercial application – delivering maintenance crews to wind farms in the North Sea – the technology is suitable for many others. They include small recreational Craft, luxury pleasure craft, commercial and recreational fishing vessels, crew transfer vessels, oil rig support vessel, cruise ship tenders, pilot vessels, high speed military vessels, Coastguard vessels and high speed passenger ferries.