Skrunda makes it an even SWATH dozen from A & R
'Skrunda' is the first of five 25m class SWATHS for Latvia.
Abeking & Rasmussen’s latest, the Latvian offshore patrol boat Skrunda, is the twelfth SWATH vessel built by the German yard since 1999, but the first of its type completed there for naval patrol service.
That pioneering achievement is, however, nothing new for A&R because Skrunda’s predecessors have all distinguished themselves in new operational sectors. To a boat, the 22 SWATH ships built or on order at the yard, from 25m to nearly 60m in length, are pioneers in areas previously not served by such vessels. ‘No other shipyard worldwide has a pedigree of more SWATH vessels delivered or on order’, the yard declared.
A&R was the first German facility to enter the sector of SWATH (Small Waterplane Area Twin Hull) technology, developed in the 1930s by Canadian Frederick G. Creed. The concept differs from catamaran design in that the twin hulls remain completely submerged, minimising the hull cross section area and ship volume near the water surface where wave energy is located. This increases stability even when seas and speeds are high.
A&R says it was the first to market a reliable and commercially successful SWATH design, but acknowledges competitors in other countries. Luckily for A&R it lost its most potent German rival, the NSW Shipyard in Emden, when that facility converted to wind turbine manufacture in 2009.
Before then, however, submarine specialist NSW had turned out some impressive SWATH vessels like two 49.35m German Customs ships and the biggest SWATH ship ever built in Germany, the 73m naval research and equipment testing vessel Planet.
A&R’s Skrunda is built to GL class ( GL + 100 A5 HSDE OC3, Patrol Boat, + MC Aut) and is the first of five patrol boats for the Latvian Navy. Named after Latvian towns, the series is modelled on A&R’s successful 25.65m pilot tenders. The first, Döse, Duhnen and Wangeroog, proved themselves in tough and much scrutinised service in the Elbe and Weser estuaries, clocking up 3,000 to 4,000 hours a year in 24/7 operation. A&R said it had patented some of their features, including fendering and arrangement.
One of the 25m A&R pilot boats was originally built for another purpose. Handed over in 2004 the ‘odd man out’ was the German Navy’s Explorer, which first served as a minesweeping test system and was the first SWATH boat to fly the flag of the German Government. A&R said it was later re-equipped as the tender Borkum for German pilots.
Two A&R pilot tenders were bought by the Dutch Pilots’ Association in 2005/2006 although further Dutch options were apparently not taken up. However, citing the ‘good operational experience’ of Dutch and German pilots, Belgium’s DAB Vloot (Loodswezen) placed an order in 2009 for three tenders and a 59.9m pilot station ship for delivery this year and next. A further tender for German pilots is also on order for early delivery.
Skrunda was handed over by Lemwerder based A&R at the end of March and the series looks likely to be completed inside a couple of years. A&R said Latvia chose this type because of its durability and seaworthiness. The second boat is being built at Riga Shipyard under a partnership deal signed in 2008, but A&R has not said when it will be ready or how many others will be built there.
According to the A&R data sheet, the Latvian boats are 6cm longer than their pilot boat predecessors at 25.71m long, but they retain the 13m beam of the earlier boats and also draw 2.7m.
They also have what A&R described as ‘a completely new propulsion and accommodation concept’ built on MAN engines rather than the MTU 12V 2000M70 diesels of 788 kW which provided 18 knots on the earlier boats. The yard said it switched engines ‘because they were suitable for the boats and because MAN has a good reputation’.
The two MAN units on Skrunda are Type 2842 high speed diesels, each of 809kW at 2,100 rpm driving two Servogear controllable pitch propellers over Servogear reduction gearboxes. Trial speed was 21.4 knots using this redundant propulsion system but service speed is put at 20 knots with an operational radius of 1,000 nautical miles at 12 knots.
The engines on Skrunda are also in the lower hulls, leaving more space for a crew of eight in the superstructure while even further personnel can be housed, if required, in a spacious wardroom.
The wheelhouse offers all round visibility, with the navigator/helmsman’s position to starboard. A central engine console supervises and controls all technical systems and the boat is equipped with Raytheon X-band radar and ready for the later installation of an electro-optic sensor on the mast head.
Deck installations include a crane aft and a small RIB for shallow water pursuit. To ease man overboard or diving operations, there is an hydraulic lift to starboard. A&R notes that recovery is an important factor in the cold waters of the eastern Baltic, where the Latvian boats will serve, as are also the boats’ fixed fenders for direct boarding.
This is the first SWATH ship from A&R for naval service and thus the first to be capable of mounting armaments. Skrunda is fitted for, but does not carry, two 12.7mm heavy machine guns and there are more options.
Between the two hulls, a 20ft ISO module container can be fitted for a six ton payload which could be armaments or equipment for hydrographic surveys, environmental protection or diving operations.
A & R says the systems on Skrunda have all been chosen with the same consideration for cost effective and low maintenance operation and off the shelf equipment replacement as with earlier commercial 25m boats.
Noting the overall economic advantages of the smaller vessels, A & R adds that ‘smaller SWATH platforms mean reduced life cycle costs, because of the lower maintenance costs for a smaller ship with smaller machinery, lower fuel costs because of a smaller propulsion system and, most important of all, lower labour costs because of the smaller crew on a smaller vessel’.
The yard particularly stresses the high level of comfort on the latest boats with low vibration and noise levels well below 65dB(A). It also highlights their ‘extraordinary’ sea-holding and says the 25m class ‘boasts motion in high sea states comparable to that on much larger and much more expensive conventional vessels of about 80m length’. This seaworthiness qualifies the boats for a wide range of offshore duties, the yard said.
It added that SWATH vessels ‘are always an alternative when motion comfort for personnel on board is important, for example, where extended operation at a high level of mental fitness is required such as during research duties or patrol and surveillance, or where personnel need to relax and recover from stressing duties as pilots or on maintenance station ships’.
Motion comfort was in fact a main reason why the private yacht sector picked up on the potential of the boats and took delivery of the first non-commercial A&R SWATH, Silver Cloud, in 2008.
An agent told MJ a main reason for choosing it was because the American owner’s wife suffered sea sickness on conventional yachts. He said the couple sailed on one of A&R’s 25m pilot tenders in the North Sea before ordering Silver Cloud. The owner said ‘we like the performance, functionality and expedition look of the boat, as well as her interior design’ and praised it as ‘spacious and comfortable’.
The uniquely dimensioned 40.5m long and 17.8m boat is still A&R’s only private SWATH ‘expedition yacht’ and the first European SWATH to be built for pleasure sailing. It is propelled by two turbocharged Caterpillar C32 DITA diesels of combined 1,640 kW output for a maximum 14 knots and has Caterpillar generators.
Another new customer is the offshore wind farm sector’s BARD Group, which took delivery of A&R’s 26.4m long and 13m wide Natalia Bekker in 2010. It was described as the world’s first SWATH tender designed for offshore wind farm maintenance, supply and personnel transfer.
BARD Service CEO Jörg Fangmann told MJ that engineers could now be transferred and wind turbine foundations boarded in waves up to 2.5m. ‘We will retain deployment capability even in bad weather’, he said. To help, Natalia Becker has specially designed rubber fenders for foundations.
Adding yet another operational sector for the versatile SWATHs is the novel 25m hydrographic survey ship for delivery to the Estonian Maritime Administration in 2012. Once again, stability and positive all weather experience with similar boats clinched the order.
The Estonians echoed A&R claims, saying SWATH technology was ‘more expensive then existing technologies’, but that ‘it gives the necessary stability with a smaller hull length’. They also said ‘the cost of building such a ship is comparable to the cost of building a catamaran and more economical than ordering a single hull ship’, adding that the small size of the new ship would ‘significantly lower annual maintenance costs’.
The Estonian SWATH will be like its predecessors but, following the Latvian lead, will get MAN D 2842 diesels and Servogear equipment. It will also have a multibeam echo-sounder, a sound velocity probe, two hydraulic winches, a sub-bottom profiler and a sidescan sonar.
A&R’s biggest SWATHs remain the 59.9m long pilot station ships Elbe and Weser, with Belgium’s 59.9m pilot station ship still to join them. The yard told MJ however that it ‘will design and build even bigger SWATH vessels in future if customers ask for them’.
By Tom Todd
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