New Alaska Titans depend on z-drives


When Western Towboat of Seattle started building its first Titan ASD long-haul tug at its base on the Seattle Ship Canal in 1995, owners Ric and Bob Shrewsbury were simply responding to the growth of barge service to southeast Alaska. They could hardly have imagined that this demand for more powerful tugs would continue unabated for the next 20 years, that Western Titan would be followed by five sister ships and that the Titan class would become synonymous with excellence in design and construction.

The newest is Arctic Titan, launched in 2012. It is the 18th boat Western has built and the first to have a rating for light ice conditions. The hull now under construction will be called Bering Titan. These boats, along with Alaska Titan (2008), take advantage of Caterpillar’s latest 2,682-hp C175 engine rated at 1,600 rpm. They provide over 500 hp of additional power, turning Centa carbon fiber shafts connected to Schottel z-drives with four-blade, 104-inch-diameter stainless-steel propellers. The bollard pull is estimated to be around 80 tons.

The bulk of Western Towboat’s fleet has been committed to towing barges for Alaska Marine Lines, now a division of Lynden Transport, since 1976. “We have two routes: Southeast Alaska — the inside route — and Whittier — the outside route — across the Gulf of Alaska with a cargo of railroad cars on the deck and containers stacked on top,” Ric Shrewsbury noted. Both routes have three trips a week in the summer and two in the winter. Whittier is once a week year-round, and southeast is twice a week in winter — three times in the summer.

“It’s 2,000 miles to Whittier in Prince William Sound, nonstop,” he pointed out. “It can be tough out in the Gulf of Alaska in winter storms, we can handle seas up to 15 feet, but too much of that can start to loosen a wagon’s tie-downs. The round-trip is 15 days in the summer but it can stretch out to three weeks in stormy weather. We burn about 55,000 gallons of fuel, round-trip.”

The Inland Passage also has its drawbacks although it’s only 650 miles from Seattle to Ketchikan. If the weather is good the average speed is 10 knots, burning 5,000 gallons per day. But then they have to drop cargo at Petersburg, Juneau, Haines, Sitka and Kake, stopping two or three times a day, then load up with frozen fish containers during the salmon season. “There’s a crew of five and everyone works on deck during the stops to keep things moving,” Shrewsbury said. “The tug has to come alongside every day so the crew can check all those reefers to make sure they are powered up and kept cold.”

The Titans use a soft-loop bow fender and a laminated stern fender from Schuyler.

It’s in Alaskan waters at the far end of the barge route that the twin ASDs, the tug’s defining feature, really pay for themselves, Shrewsbury explained on a wet and blustery day beside the canal. “There is no local tug service in these small ports, so the service depends on the crew docking the barge alone — no matter the weather. In the 1980s my brother and I were running two boats ourselves full time, using old Navy tugs. We always got the job done, but it takes a lot more time and effort with a straight shaft boat.” 

“The z-drives cost more initially, but frankly, it doesn’t make sense to me to build a tug without them,” he stated confidently. “They do a better job on the tow line and into the dock, and remember, you don’t have to purchase and maintain rudders, shafts and steering gear.” (However, most operators are still content to run straight shaft boats that are well past their prime and call for a local tug if they need help.)

The new barges all have Nautican Hydralift skegs and some deadrise forward to keep them running straight on an 800- to 1,000-foot towline. But at every port, the crew depend on the Norwegian-made Rapp Marine winch to recover the towline before docking. One particular feature they wanted was a way to wind the shot of 3-inch surge chain on top of the 3,200 feet of 2.25-inch wire on a single drum. To do that, they needed the level-wind rollers offset to accommodate the large chain links. 

The Seattle branch was able to do that and incorporate a computerized constant tension render/recover system. The winch tension is controlled by Rapp’s PTS Pentagon system with a touch-screen monitor near the helm station. Western assembles its own design of basic headline winch in the shop and fits it with 150 feet of 2.5-inch Spectra line. Both winches are hydraulic, operated by the pilot from the console in the house. “Nobody needs to be manning the winch on deck. We’ve always done it that way since 1987 when we built our first z-drive boats,” Shrewsbury stated.

Westrac and the first three Titans were powered by Cat 3500 series engines, either V-12 or V-16, which were the standard powerplant at Western for over 20 years. Caterpillar had managed to double their rated horsepower during that time, which was welcomed by the Titan crews, because the size of the standard deck barge at Alaska Marine Lines had more than doubled from 150 by 42 feet to 400 by 100 feet, and the load had increased to 400 to 500 20-foot containers stacked five to six high, topped off by buses, trucks and fish boats.

A Rapp Marine multispeed winch with PTS Pentagon autotow, for recovering the towline before docking.

The first Titan began when Bob Shrewsbury made some basic drawings of the new ASD boat they envisioned in 1993 and took them to Jensen Maritime Consultants. They drew the double-chine hull that is still used today, and all the engineering, but consulted with the Ric and Bob on every aspect of the layout. 

Today, before they start a new boat, the brothers, their tug crews and the building team, most with more than 30 years’ experience, continue to devise easier, faster ways to build the next boat, which Jensen incorporates into the plans. “The details on our boats are all worked out by the people who work on them and have to maintain them,” explained Ed McEvoy, the port engineer at Western since 1984. 

“That’s why the main engine filters are grouped on the engine base at the rear end, and the Baldor hydraulic pumps for the Rapp winch are mounted on the aft bulkhead at eye level,” he pointed out. There is a lot of stainless steel on the deck, including the cap rail, hand rails, bullnose and staple; this prevents rust and all the work it takes to stay ahead of it. 

The reliability of all these systems depends on a highly skilled maintenance team of diesel mechanics with a well-equipped machine shop and a vast supply of parts. The tugs typically run over 5,000 hours a year and engines are replaced after about 25,000 hours. There are at least 10 spare Caterpillar engines stacked in the warehouse that are ready to swap out, plus a half dozen gensets. 

All of the tugs are built with removable stacks that reveal an opening big enough to lower an engine vertically through the deck. This helps keep the time to change one engine to two to three days. The Titans have taken this standardization to the next level, with most machinery identical on all boats, simplifying maintenance and allowing them to share spare parts if a breakdown occurs far from home. 

Schottel z-drives turn four-blade, 104-inch-diameter stainless-steel propellers. The bollard pull is estimated to be about 80 tons.

McEvoy also introduced a computerized maintenance log that keeps track of every issue on all 21 tugs, who is fixing it and how to prevent it from reoccurring. During visits to the company base, the 108-foot Pacific Titan (2000), 120-foot Gulf Titan (2001) and the 120-foot Ocean Titan (2004) were all alongside and it was almost impossible to see any signs of aging, as they are all maintained to such a high standard. Gulf Titan had some mechanics working on engine cooling hoses, but when it departed in the afternoon to start the next Alaska run, the engine room was again spotless. 

The pilothouse is aluminum with full visibility, a feature not seen on older tugs. The helm is the same twin console setup seen on most ship-handling tugs with the winch control panel immediately aft on the port side. The Titans all have a conspicuous amount of mahogany framing the windows, as well as attractive wood-grain paneling, providing a traditional touch to an otherwise high-tech environment.

The Titans are all fitted with a large soft-loop bow fender and a laminated stern fender from Schuyler, with airplane tires rigidly attached amidships. On the run down to the barge-loading dock, there was a surprising lack of noise or vibration in the accommodation areas. They too are well trimmed in wood and easy on the eyes. All rooms have air conditioning, and there is satellite phone available as well as the now-standard flat-screens and DVD players. The galley is well equipped with a Lang stove and Cospolich refrigerator and freezer.

Interestingly, there is no pressure to finish Bering Titan. There will definitely be work for it with Alaska Marine Lines when it is launched, but right now AML has a more pressing need for a new loading ramp for use in an Alaska port. It will have a 100-ton capacity to support the giant forklift trucks that stack and unload the containers. So that will be the priority for Western Towboat’s building crew until the summer. 

By Professional Mariner Staff