even the roughest of conditions, a demand which means the line connecting tug and ship must remain as taut as possible even as the smaller vessel gets tossed about on the waves. To cope with the predominant sea conditions, Robert Allan Ltd., the vessel's
designer, chose to use the new RAstar hull form. The 500 GRT constraint forced some minor modifications to that concept, and forced a shortening of the forecastle. The basic hull form reflects the double chine form that characterizes all Robert Allan Ltd. designs, with a
sweeping chined stern. A large escort skeg is fitted forward which in conjunction with the sponsoned hull shape enhances the indirect towing capability and provides much enhanced roll stability. On trials the vessel achieved a mean bollard pull of 82.5 tons, and a free-run-
ning speed of 14 knots. The vessel has been outfitted for a crew of six. The main deck features generous cabins for the Master and Chief Engineer, both with ensuite facilities and a spacious crew mess/lounge, served by a fully equipped galley. The lower deck contains two
"The Winch"
As was noted in the article, the vessel was truly built around the winch. According to Blaine W. Dempke, President Markey Machinery, credit needs to be dispensed to the people that helped develop the new and powerful winch, specifically Greg Brooks of Towing Solutions Inc., as well as Moran Towing and Groupo Boluda of Spain. The Markey DESDF48WF is a high speed, 760 horsepower double-drum waterfall-type electric hawser winch. This winch uses render-recover technology to minimize the effects of sea-state induced forces and motion anticipated during offshore escort activity at the Energ�a Costa Azul terminal. The winch features two (2) drums, each with 200 meters of 10 inch circumference soft-line in 7-plus layers. A single automatic level wind is situated to service both drums, and the winch also integrates a chain-windlass for 26mm anchor chain, to be used for tug anchoring service. The winch's automatic render-recover technology, pioneered by Markey Machinery, provides safe line control by operating within an upper and lower tension range selected by the tug Captain. Under dynamic sea conditions the DESDF-48WF winch maintains constant line tension and automatically compensates for the tug's surge, heave, and pitch - adjustments nearly impossible for a man to achieve using lever controls. By controlling tension and keeping slack out of the working line at all times, the winch prevents snap-loads from occurring, thus reducing the risk of line breakage and/or damage to the bitts the line is tied off to on the LNG tanker.
June 2009
www.marinelink.com
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