Many questions, one 'Solution'
It might sound simple: having one capable, well-worked vessel, Netherlands-based DUC Marine went about designing another. However, the ‘Solution’ has had to resolve some conflicting demands.
Over the last few years, DUC Marine’s first vessel RAM has had a utilisation rate of near 100%, covering everything from salvage and wreck removal, inspection and repair, soil investigation campaigns, UXO-clearance, cabling and other windfarm projects. But one special quality is its stability, operations manager Ewoud Visser told MJ.
“Ram sits just like a swan in the water without rolling or pitching too much, so we wanted a second vessel with these attributes,” he explained. “The other point is that RAM has quite a shallow draft for its size, giving us a number of advantages especially in operations around the German Bight.”
So the new 55m hull, built by Dutch yard Shipcon in its Dodewaard facility, has received quite a lot of attention: fellow Netherlander Herman Janssen, a naval architect from Monnickendam, worked closely with DUC to accommodate its ideas. “First of all it has a minimum draft of only 2.8m, and instead of a normal rounded bilge keel, we decided we wanted a vessel with a rectangular keel and a flat bottom like our RAM,” explained Mr Visser. He added the Dutch tank testing institute, Marin, showed a certain amount of initial disbelief: “However, when we’d put the model through the tests they conceded we were right about the seakeeping characteristics.”
The design did evolve with feedback from Marin: for example instead of a larger bulb at the front of the bow the computer simulation tests showed a much smaller one was still efficient at wavebreaking and more effective at keeping up transit speeds. The necessary push comes from robust Omega Verhaar, fully azimuthing 650kW tunnel thrusters powered by six, 475kW Volvo Penta D-13s supplied by Haisma Ship & Industrial Engines. This gives Solution 12 knot cruising pace and a 14.7 knot top speed.
The low water draft has been matched with a low airdraft, “which all makes for a better for DP plot around the windfarms: neither the current or the wind has too much influence compared to bigger, deeper vessels” said Mr Visser.
The vessel’s Praxis Automation DP2 system is essential: a vessel is often unable to lower an anchor near the live cables attached to working windfarms, “so although using the four-point mooring system is better for fuel consumption, operations quite often have to rely on DP2 systems to keep stationary” said Mr Visser.
However, the hull shape had consequences for the 450kW bow thrusters and therefore the DP2 system which weren’t straightforward to resolve: “Firstly we envisaged a pair of standard tunnel thrusters, but as the vessel has a very shallow draft, these thrusters came out of the water at approximately 5 Bft winds.” And this, he said, means stopping operations as a complete dynamic positioning response is necessary in order to protect both divers and equipment.
A standard retractable unit might have been the answer but, “you need to be able to accommodate the big boxes that hold them, not so easy in a vessel like this where there’s a lot of pressure on space” said Mr Visser. After a lot of scratching of heads, the answer was found: changing one of the forward thrusters to an Omega Verhaar swing-up model.
On its main 250m2 working deck the container locks are flush mounted to allow for an easy hook-up of dive containers and LARS, plus there is a special area for containerised accommodation, an office or workshop: “All the lines, water, electricity, sewerage and so on are all in place,” he said, making everything ‘plug-and-play’.
Following hull completion, the Hoekman Shipbuilding yard will fit the vessel amidships with an Iron Fist, 90 tonne knuckleboom crane and another, larger 200 tonne knuckleboom on its aft deck. The main crane has a Dromec Active Heave Compensated winch (effective for loads of 10 tonnes in up to Sea State 4) and to give extra capability, this line can also be led over the 20 tonne A-frame. The stern roller has a position for a 50 tonne towing/tugger unit if required and the anchor winches, also from Dromec, will have spooling devices to help take care of their 600m lengths of wire.
Other elements have also been thought through: two 1.2 m survey moonpools have rails inside which will enable a deployment frame to keep any tools in their correct orientation, “otherwise they might start to spin” explained Mr Visser.
More, DUC has made sure there’s room for a whole Amplemann or similar gangway to be installed. ESU, a Dutch company based in Urk, took on the large, complex task of installing the electrical distribution system that underpins Solution’s multiple power needs.
The Dutch tour-de-force continues inside with fittings for internet and TV connection in the cabins; these can cope with over a dozen people in spacious single occupancy, or up to 42 people on shift rotations. As it’s important that both client and crew can keep a certain privacy the cabins are divided with client personnel on the lower deck level and crew on the upper deck. Cabin and mess areas are supported by Breman Shipping aircon, galley equipment comes from local company Hakvoort and seating is supplied by De Flux, another company based in nearby Urk.
Flexible enough for diving, ROV-operations and light construction work such as foundation grouting, it’s also especially suited for survey work as the diesel-electric running is really very quiet. Ewoud Visser added that the company’s name for its new boat is more than a quip: “No matter what the problem, we have the Solution.”
By Stevie Knight
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