Best OSV – Large Crewboat – Umo Green (Photo: Marsun)
Best OSV – Large Crewboat – Umo Green (Photo: Marsun)

AWARDS 2022 | Best OSV – Large Crewboat – Umo Green – WIND Naval Architects & Marsun

A most interesting craft, whose concept shows considerable enterprise on the part of both designer and builder.

Trimarans remain rare in the world of workboats, but they do have obvious advantages. This triple-engined and waterjet-propelled example could well be a sign of things to come.

"It is the latest design in an evolution of a series of trimaran crewboats wherein the focus is on offering improved comfort and operability under high-speed transit conditions and during extended offshore operations," WIND Naval Architects told Baird Maritime. "The trimaran hull consists of three slender hulls with motion characteristics and freeboard being optimised to minimise both acceleration and seasickness during high transit speed and low speed manoeuvring. The centre hull is essentially a very slim monohull that cuts through the waves with minimal effort, whilst the slender sidehulls provide soft roll stability without generating the bumpy roll- and pitch-induced accelerations often experienced on catamarans."

The designer added that, combined with large active foils that provide significant roll and pitch damping, the result is comparable to being onboard a much larger vessel. To further reduce the motions at low speed and during crew transfer operations, the crewboat is equipped with a ballast system that, when combined with the small waterplane area centre hull, brings the vessel into SWATH mode. This allows the vessel to operate offshore even under conditions that would require other vessels of similar size to return to safe harbour.

"We have performed significant in-house CFD studies as part of the development to optimise the foil configuration. It is a truly foil-assisted vessel whereby 50 per cent of the displacement is carried by foil lift at service speed. The foils give a reduction in fuel consumption of almost 30 per cent compared to earlier versions without the new foil system. With a top speed in excess of 35 knots at 15 tonnes deadweight, being six knots above contract speed, UMO Green provides a fast transit to an offshore site with an energy consumption less than that of any known crewboat of comparable size and capacity in the market. The sea trials showed that a speed of 30 knots is achievable in 1.5- to two-metre head seas while still maintaining a comfortable ride."

"The new trimaran crewboats are the first that were built successfully in Asia under the HSC High Speed Craft Passenger Notation, as well as also the first crewboats to be built in Asia for offshore windfarm support duties," added shipbuilder Marsun."

The vessel is also notable for having four fully MLC-compliant crew cabins and sleeping for six to eight personnel within the comfort and space criteria set by the Danish Maritime Authority. The noise level ranges from 45 to 65 dBA, which, combined with the low accelerations from the hull design, enable the crew to remain offshore for extended periods without having to transit back to port overnight.

Meanwhile, a 50-cubic-metre climate-controlled storage room below the cargo deck provides a safe environment to deliver critical service parts from tropical areas in Asia to the areas in the northern hemisphere that experience harsh winters. Combined with the expansive 120-square-metre cargo deck and a well protected sidewalk on the starboard side, the flush deck provides a safe and stable work environment for crew and technicians alike.

WIND said that having three identical and independent drivelines in three separate engines rooms ensures high flexibility and redundancy in operation, whilst spare parts can be kept at a minimum, thus the aim is to make the sidehulls as slender as possible to optimise comfort. The challenge therefore lay in fitting the engines in the sidehulls, which required several design iterations done together with Marsun to place all the equipment in the most accessible locations. Engine room ventilation and removal hatches also presented space constraints that impact design flexibility, but it was possible for the designer to deliver a functional arrangement that also allows an efficient engine removal path in all three hulls should the engines need to be swapped quickly.

"Learning from previous designs," said WIND, "where we had a resiliently mounted superstructure and several piping systems penetrating into the hull through flexible arrangements, we moved all tanks, piping, and system components related to sanitary systems into the superstructure bottom structure. This allowed us to completely separate the piping in the hull and the accommodation and thereby save significant weight as well as outfitting time. The entire superstructure can now be outfitted whilst sitting on the workshop floor, without impacting the hull outfitting."

"We learned from this project that it is possible to construct high-quality multi-hulls within maximum weight limits," added Marsun.

For WIND, the rapid development of crewboats over the last 10 years has resulted in new rules being crafted to meet the requirements for number of passengers, crew accommodation, and hybrid notation, to mention some. Thus, whereas the typical crewboat has measured 20 to 26 metres long and was designed for daytime operation with limited crew facilities, the company focused on designing larger 30-metre crewboats with better crew facilities aimed at 24-hour operations over a service life lasting many years, and this also applied to hybrid-powered newbuildings.

"Owners are finally seeing the benefit of adding these larger and more capable vessels to their fleets," WIND told Baird Maritime. "Also, a hybrid system currently makes a lot of sense for an operating profile that dictates more low speed and idle operation offshore, instead of the high-energy demanding transit to and from shore every day. With increased efficiency from hydrofoils, lighter batteries, offshore charging stations and a better overall understanding of how to best employ hybrid systems, we will see that these alternative drives will become useful for both the transit phase and low-speed sailing offshore."

Marsun meanwhile said it is focusing on electrification and green technologies. Thus it is working closely with WIND and other suppliers to be ready to integrate tailored solutions to satisfy clients' requirements.

The year 2022 provided continued business growth for both WIND and Marsun. In addition to collaborating on Umo Green and its sister crewboat, WIND secured a contract for two 30-metre crewboats in the United States while Marsun began promoting its windfarm crewboat offerings to prospective customers in Asia, as the vessels are designed for the challenging offshore sea conditions in the region.

"We also made inroads into the smaller craft market," added WIND. "We are presently working on a 10-metre monohull workboat and a solar-powered electric craft designed in partnership with Norwegian firms. We have also worked closely with a Norwegian company over the last two years to develop a range of electric fully foiling crew and passenger boats, one of which is currently under construction in Asia."

WIND is also developing a new generation of trimarans capable of even faster speeds to reduce transit times for customers in both the offshore oil and gas industry and wind turbine servicing market. The company said it has had a full order reserve since it began operating in 2015, and 2022 is its busiest year to date.

Marsun remarked that, with regards to hull design, there are many further developments in the market that enable multihull vessels to offer more benefits to meet customer requirements.

"We are open to designs from global firms," the builder told Baird Maritime. "For multi-hulls, based on our experience building these two trimarans for U-Ming Marine, we have found this to be a viable solution for addressing many issues such as ensuring seakeeping in rough waters, transfers and transits in more than two metres significant wave height, and achieving high speed with very efficient fuel consumption."

Marsun is also working with suppliers on the hybrid drive arrangements for its crewboat offerings after having realised that decarbonisation and the use of green technology are increasingly important trends. The development of high-performance crewboats is also another area being considered by the company as a means of satisfying customer requirements.

"We are working with designers to offer more valuable benefits in the areas of safety, seakeeping, crew comfort, high-speed transits, and operability in two-metre significant wave heights," Marsun replied when asked about the future of the South-East Asian workboat industry. "Such benefits can be highlighted when delving into the offshore support and even the high-speed passenger ferry markets in the region, and even as far away as Europe."

"In Scandinavia," added WIND, "fast ferries, Ro-Pax ferries, and pleasure craft are gravitating towards hybrid and even full-electric operation. We are also seeing continued development in the areas of power infrastructure including stations for swappable batteries. Power infrastructure in general is evolving fast and we see that, in particular, fully electric hydrofoil and foil-assisted vessels are developing rapidly to meet various range and emission requirements, hence our participation in several innovative projects that will be introduced publicly in the coming years."

Baird Maritime / Work Boat World