Pacific Maritime Magazine - Marine Business for the Operations Sector

New Dunlap Tug for Dutch Harbor

 

The new 101-foot by 42-foot, 6,800 HP M/V Gretchen Dunlap, seen here at the Port of Everett, Washington last month, will provide ship assist and towing duties in Dutch Harbor, Alaska. Photo by Chris Philips.

Dunlap Towing of LaConner, Washington was founded in 1925, and concluded its celebration of 90 years of service in December 2015 with the launch of its second ASD tug, the 6,800 hp 101-foot by 42-foot M/V Gretchen Dunlap, built at Hansen Boat Company, in nearby Marysville. The Gretchen was designed by Hockema & Whalen Associates of Seattle specifically for ship assist in Dutch Harbor, Alaska. The new vessel will join the company's James Dunlap, also a Hockema & Whalen design, which has been stationed in Dutch Harbor since 1995.

Although the two tugs are the same length, the Gretchen Dunlap incorporates many recent developments in ASD tug design, including 6 more feet of beam, an updated wheelhouse, and 2,872 more horsepower. Draft is the same at 19 feet, 9 inches. The full-width engine room houses twin CAT 3516C engines with an intermittent rating of 3,386 HP, each driving Rolls Royce 255 P30 FP Z- drives via carbon shafts. The 110-inch diameter propellers are four-blade stainless steel and produce 90 tons of bollard pull, compared to the older boat's 3,900 HP and 54 tons of pull from twin EMD 16-645's.

The engine room also has space to mount the pair of Cat 250 kW ship service gensets and a 76 kW hotel generator in the center. Tankage is provided for 86,000-gallons of fuel, and 13,000 gallons of fresh water. Engine control and monitoring panels in the engine room and bridge are by Auto-Maskin. The engine room electrical panel was provided by Harris Electric, who were responsible for the general wiring and main switchboard. The Vessel monitoring/alarm system was provided by Marine Controls, Inc. Navigation electronics are by Furuno and autopilot by Simrad.

"Ships keep getting bigger, so we needed bigger equipment. This tractor tug has more power than our current tractor tug in Dutch Harbor and will be capable of assisting larger ships to dock when weather conditions are more adverse," Dunlap Towing Company President Jim Dunlap commented. Gretchen Dunlap was designed to meet ABS Class rules with a notation for escort service, plus the requirements of the upcoming Coast Guard Subchapter M rule.

Naval architect Mike Whalen explained that while the vessel was designed primarily for ship assist work in Dutch Harbor, she also needed the capability to push barges and to perform vessel rescue work in the Bering Sea and traditional line haul towing. In order to meet these requirements, a sea-kindly hull form was required that features a deep single chine and flared sides, a plumb bow for pushing and a cutaway stern for maneuvering in reverse. The bow guard was heavily reinforced for high impact loading of the cylindrical fenders.

"We have had good performance results using a deep single chine hull on very wide hulls," Whalen said. There are two benefits to this design: "Most importantly, it provides considerably more roll damping to reduce roll amplitude, which is good for a beamy vessel where the roll period can be fairly short," he noted. "Secondly, as the boat becomes wider, the flow around the hull is less around the waterlines and more along the buttock lines. So the effect of a rounded bilge is less important."

Whalen said, "We made an effort to design the hull to an optimum section-area curve, which assures that the distribution of volume makes for efficient flow of water around the hull."

The tug is equipped with the latest Markey DEPCF-52 constant-tension electric hawser winch on the bow for escort service. The drum holds 500 feet of 10-inch line, with the control panel on the starboard side of the helm. The towing winch is an electric Markey TES-40 holding 2,600 feet of 2.25-inch wire and is controlled from a separate control station on the aft side of the wheelhouse.

The deck layout is characterized by the large beam, which allows wide side decks, plenty of space around the bow winch and on the aft deck. A visible feature on the aft deck is the UHMW pad running to the Smith Berger tow pins to protect the surface from the drag of the tow wire, chain and shackle. The open-ended compartments on the aft side of the stacks are configured for vent containment and are directly above two fuel overflow containment tanks P/S connected to a common fuel vent header. A cylindrical rubber fender by Shibata covers the bow rail while the stem plating is covered by the laminated Schuyler rubber that extends down to the waterline and well aft for barge work.

The galley is well lit, comfortable and fitted with a Lang commercial-grade range, a Maytag refrigerator and a Whirlpool washer/dryer. There is a captain's stateroom on the main deck and in the hold are three two-person staterooms in addition to the engineer's stateroom. Crew comfort was a high priority, with roomy accommodations and reduced sound transmission from the engine room.

Over the past nine decades, Dunlap Towing Company has grown into a fleet that includes nine ocean towing and ten Inside Puget Sound tugs and ten bargesĀ operating throughout the west coast from Western Alaska to California. Some of the company's more remote destinations have been the Alaskan Arctic, Far East to China, Korea, Russia, the Philippines and the US Gulf.

The towing winch is an electric electric Markey TES-40 towing winch holding 2,600 feet of 2.25-inch wire and controlled from a separate control station on the aft side of the wheelhouse. Photo by Chris Philips.

In 1978, Dunlap, along with two other partners, formed Northland Services, a freight company specializing in containerized and break bulk freight barging to Hawaii and Alaska. For service in Alaska, the new vessel's stability was assessed to include an allowance for hull icing in winter. The company's tugs in Dutch Harbor assist the weekly service from APL, Maersk & Matson, plus calls from barges and freighters that bring supplies and pick up frozen and canned seafood. In addition, eight cruise ships will be visiting in 2016.

Gary Hansen and the crew of 30 at the Hansen Boat Company are well known for a large number of successful Alaskan fishing vessels constructed from 1960-1990. They had previously delivered the 101-foot by 36-foot Z-drive tractor tug James Dunlap 101-foot by 36-foot in 1995 and the 122-foot by 38-foot Ocean Tug Phyllis Dunlap in 2001. The new tug was named for Gretchen Dunlap McCauley who is on the Dunlap Towing Company board. Gretchen is the daughter of James Dunlap Sr. and niece of Gene Dunlap, who founded the company in 1925.

 
 

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