The Marineco Mariah

December 20th, significant wave heights of up to 3 metres, wind force 5. Perfect conditions to try Damen’s High Speed Service Vessel (HSSV) 2610 Marineco Mariah. Offshore WIND, along with (potential) customers, Siemens, DONG Energy, WindCat Workboats, Sima Charters, SeaZip, Vestas, Maritime Craft Services and Chevalier Floatels, just to name a few, and other press, was invited to the port of Scheveningen, the Netherlands, for a sea trial of the twin axe catamaran.

Marineco Mariah is the second of a series of four High Speed Service Vessels that Marineco have ordered with Damen. The Marineco Mariah was delivered to her owner just before Christmas 2011, and is now active at the BARD Offshore 1 wind farm in Germany. The first vessel, Marineco Shamal, was delivered in June 2011. The interest for this sea trial was enormous, which resulted in three short voyages having to be planned for the day. During his words of welcome, Jaap Gelling, Damen’s Product Director High Speed Craft, seemed pleased with the rough weather: “Fortunately, it is windy outside, but with no rain. Worst case scenario would have been nice and calm summer weather, as we then wouldn’t be able to show, to full advantage, the vessel’s capabilities.” And we took advantage of it, for sure! Where conventional vessels operating at offshore wind farms are limited to a significant wave height of around two metres, the HSSV 2610, with a maximum of twelve passengers, is at its best in rough weather conditions with a heavy swell.

Rollercoaster ride without seasickness

While boarding for the first trip onboard the Marineco Mariah, we were told not to go outside during sailing. A little disappointing at first, but after leaving the harbour to open sea, it became very understandable. The vessel was lifted by the high waves as were the passengers who were not seated. The windshield wipers were working overtime with white water hitting the windows from all sides. Next to two pilot chairs the bridge offers comfortable seating for six passengers on the port side. Identical to the pilot chairs, the passenger chairs have an air suspension system, each with a built-in compressor. On the starboard side of the bridge, there is seating around a table for more passengers. In total there is seating for up to 24 people available. Cruising with a speed up to 22 knots, sailing felt like a rollercoaster ride. Seasickness in these conditions is a major problem. However, this vessel goes a long way to reduce this problem, the writer of this article, for one, was not seasick at all! The 360-degree visibility on the bridge can partly be held accountable for that, but most important is the axe bow hull form. This hull form was developed together with the Technical University of Delft and combines a deep forefoot with a long and slender foreship with near-vertical sections above the waterline. This significantly reduces pitching motions and slamming, resulting in a much higher sustained speed possible in waves, due to reduced vertical accelerations experienced.

The axe bow concept has been around for some years now and Damen was curious to see if the same concept could be applied to a twin hull configuration. As Mr Gelling said: “What is better than the axe bow? Two axe bows!” Extensive testing was done at the Technical University of Delft and the results showed vertical acceleration levels which were three times less than on conventional catamarans in significant wave heights of 1.5 to 2 metres. Also the resistance proved to be less compared to conventional catamarans with the same displacement: in calm waters, resistance is reduced up to 15%, and in heavier seas up to 25%. This leads to significant fuel savings as well.

The Edinburgh-based Marineco UK is specialised in workboats, tugboats, barges and multicats charter, and operates a fleet of four Damen vessels. When they were looking for a crew transporter for wind farm maintenance in 2010, Damen decided to make its first new HSSV 2610 available for them.

Foam fenders

Marineco was interested. “The first twin axe, Marineco Shamal, was developed and built within one year”, Meredith Dijkstra, Design & Proposal Engineer High Speed Craft at Damen, tells Offshore WIND. “We wanted to be ready to present the vessel during SeaWork in Southampton in June 2011. Marineco Shamal has been delivered in the summer and is now on duty at the Sheringham Shoal Offshore Wind Farm. We still get a lot of feedback from our customers and we expect these vessels to do better than other offshore wind farm crew and supply vessels in the winter season, as the twin axe is more suitable for working in high waves and rough weather.”

One of the changes that have been made as a result of customer’s feedback is the fender system. Originally, the bow of Marineco Shamal was equipped with a row of vertical D-fenders. These fenders increase the contact surface when the vessel is sailing to and against the wind turbine to allow the crew step over from the vessel to the ladder on transition piece. When enough thrust is applied, the bow ‘sticks’ to the tubular structure around the ladder, with the result that only the aft section of the vessel pitches with the swell. However, in practice, the fenders started to disintegrate and the pipes underneath became permanently deformed. Mrs Dijkstra: “We spoke to our fender supplier Ocean 3 about the problem and Ocean 3 designed a new foam fender, which has the same braking path, but more resistant. As a result, the vessel is more ‘sticky’, as we call it, with less pressure on the fender. Marineco Shamal is now testing this new foam fender and of course, Marineco Mariah has been equipped with it as well. The offshore wind market develops with the speed of light. The industry is relatively new and that makes it exciting and challenging to design for this industry.” The foam fenders are divided in three pieces to be able to fit with different configurations of docking pipes on the transition pieces.

In the meantime, Damen does not sit still. In total, 25 HSSV 2610 are currently under construction, of which nine are on order: another two for Marineco, two for GeoSea, which will be used for work at Thorntonbank Wind Farm, two for SeaZip and one for Maritime Craft Services. All will be operating in the offshore wind industry, although according to Mrs Dijkstra, one of the vessels was sold for survey purposes. This vessel is completely fitted with survey equipment. By not placing the stairs inside, it was possible to place a moon pool. However, the vessel has been resold and will now also be operating in the offshore wind industry on delivery. To date there is a total of 16 vessels under construction for stock, fitting in perfectly with The Damen Standard, as Damen’s standarised shipbuilding concept is called. This makes it possible for the company to offer its clients standard hull vessels with proven designs for competitive prices with a short delivery time, but with the option to modify the vessels to the customers’ wishes.

FSC4612

In addition to the vessels under construction, a smaller version, the FSC2008, will soon be launched. This vessel is tailored for crew transfer and transporting cargo. Another recent development is the design of a bigger version of the twin axe, the FCS4612. At first, it was Damen’s idea to provide a solution for the oil and gas industry.

Peter Robert, Business Development Manager Offshore Wind at Damen explained, “The FCS4612 is specially designed for transfer of personnel for the oil and gas industry, but might very well find its way in the offshore wind industry. It can be used for crew transfer and transportation of goods, but also for survey purposes and emergency assistance. It might be a good solution for a shuttle service to a fixed or floating platform, especially in the North Sea. Every offshore wind farm has its own logistical solution, depending on factors like water depth, nearest harbour and size.” The FCS4612 will be able to transfer up to 150 people and reach a speed of over 35 knots. Instead of fenders, the vessel will be equipped with a DP2 system and be suitable for fitting a transfer system like an Ampelmann and can operate either with Special Purpose Ships Code or the International Code of Safety for High-Speed Craft, HSC CODE 2000, specification. Tests are currently being carried out at the Technical University of Delft with the first prototype expected within 18 months.

Gail van den Hanenberg