Feature 1 | TUGS Evolution of the species


A powerful new tug has been brought into service towing freight barges from Seattle to the Hawaiian archipelago, writes David Tinsley


The robust Sigrid Dunlap represents a more powerful, greener evolution of a proven design


incorporates a full double bottom, whereas her predecessor has a partial double bottom. The main wherewithal of the tug


is a Markey TDSDS-36 double-drum tow winch holding 945m and 732m, respectively, of 2.25” (0.06m) tow wire, and a Markey DESW 32-20 winch at the bow with 152m of 5” (0.13m) wire.


operations, the 37m Sigrid Dunlap is an evolution of a powerful tug that has given sterling performance for the past 17 years. Incorporating advances in powering and


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propulsion systems, efficiency and emission control and equipment and crew comfort, the latest addition to the Dunlap Towing fleet has been commissioned into a scheduled barge service linking Seattle with Honolulu. Sigrid Dunlap follows the lines and


layout of the 2001-built Phyllis Dunlap. While maintaining a twin-engine, twin-screw drive configuration,


the


engine room in the latest vessel has been designed for two Enviromental Protection Agency (EPA) Tier 3- and IMO Tier


TECHNICAL PARTICULARS Sigrid Dunlap


Length .................................................37.03m (oa) 35.15m (bp)


Breadth, moulded ....................................11.58m Depth, moulded .........................................5.56m Draught ........................................................5.18m Gross tonnage .....................................559tonnes Main engine power .........................2 × 1,995kW Bollard pull capacity ...........81tonnes (approx.) Generators ............................................2 × 118kW Classification society ......................................ABS Registry ............... La Conner, Washington State


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uilt and designed in America’s Pacific Northwest, and deployed on scheduled ocean barge towage


II-compliant Caterpillar C175-16 diesels, rather than the 6-cylinder 3606 units found on Phyllis Dunlap. Each of the 16-cylinder C175s has a rated output of 1,995kW at 1,600rpm, making for a power concentration of 3,990kW and a bollard pull of about 81tonnes. Drive is through Reintjes WAF 1173


reduction gears, of 8.8:1 ratio, to a pair of fixed-pitch propellers manufactured by Sound Propeller Services of Seattle, which also supplied the tug’s forged steel tailshaſts. Te three-bladed propellers are mounted in Nautican nozzles and the tug employs a Nautican triple rudder system. Te installation confers a free running


speed of 14knots and enables tows at some 9-10knots.


Long-distance capability As with Phyllis Dunlap, Sigrid Dunlap was constructed in Washington State by Hansen Boat Company of Everett, employing a design originally developed and subsequently refined by the Seattle naval architectural firm Hockema Whalen Myers Associates. Hansen has a reputation for commercial


fishing vessels, workboats and towboats crafted to meet the challenges of Pacific Northwest and Alaskan waters. Power, redundancy, robustness and endurance are reflected in the latest tug, whose 690,100litre fuel capacity provides ample range for eastern Pacific Ocean transits, and potentially for other long-distance assignments. She


“Power,


redundancy, robustness and endurance are reflected in the latest tug”


Range of tasks Dunlap Towing undertakes a wide range of operations in and beyond the western seaboard, including log raſt-handling in Puget Sound, vessel and barge assist work in Dutch Harbor, Alaska, and barging to Alaska and Hawaii. Sigrid Dunlap has been taken on by


Alaska Marine Lines to support the sailings maintained by the latter’s Hawaii division, Aloha Marine Lines. The schedule entails departures by towed barge from Seattle every other Friday, docking at the company’s terminal complex in Honolulu (Oahu) 12 to 14 days later. Freight transfers to and from the


neighbouring islands of Kauai, Maui, Hawaii, Molokai and Lanai are made via a connecting inter-island barge service. Payloads on the Aloha Marine route include containers, heavy equipment and vehicles, construction materials, commercial boats and pleasure craſt, bulk liquid fertilisers, caustic soda and a variety of other goods. SBI


Ship & Boat International November/December 2018


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