The advent of a new marine diesel engine design is rare enough, but when a new engine is mated to a new Z-drive model from a new manufacturer and put into a new tug design, the result is worth noticing.

That’s why the 104’×36’ tug HMS Frontier, with its “greenhouse” wheelhouse and athletic abilities, is bound to get noticed around the Long Beach, Calif., docks where she’ll be working.

The Frontier, built by Thoma-Sea Boatbuilders, Houma, La., for Seattle’s Harley Marine Services Inc., is only the second tug to get the new Cummins QSK60 engine, said Capt. Gary Smith of Harley Marine. “And it’s the first vessel of any kind to get the new Rolls-Royce A3 SD (Stern Drive) Z-drives.

“In terms of lines and construction, the Frontier’s no radical departure, but the way she’s designed to take maximum advantage of her propulsion is part of an ongoing revolution in tugboat construction,” added Smith, one of the vessel’s project managers.

SOMETHING DIFFERENT

Delivered to Harley Marine in early January, the HMS Frontier is the second vessel built by Thoma-Sea to this design, according to Frank Basile of Houma-based Entech & Associates Inc., the vessel’s designer. The first, the Point Clear, was delivered last year to Cenac Towing to handle ships on the Mississippi River.

“We’ve been following the Point Clear to see how [the design] works,” Basile said, “and we understand that she’s the most requested vessel in the Cenac fleet. The ship pilots really appreciate her maneuverability and power.”

According to Basile, yard owner Bobby Thomassie was so impressed with the Entech design that he started the Point Clear on speculation, with no buyer in sight. It was only after the vessel was well on her way toward completion that Cenec Towing approached Thomassie about buying her.

“I was talking to Harley (Franco, owner of Harley Marine Services) at the 2002 International WorkBoat Show where we were looking at Cummins’ exhibit of their new QSK60 engines, and I suggested that we consider putting these engines, the largest Cummins has ever made, into a new boat of the Point Clear design,” Basile said. “Harley was enthusiastic, and the Frontier is the result.”

“A good harbor tug has to be good at different things—sometimes at the same time,” said Harley Franco, the boat’s owner and operator. “We were looking for a versatile, all-around design as well as the latest in propulsion technology, and the Frontier represents both of those things.”

Although the new engines are similar in design to Cummins’ well-proven KTA50 series of diesels, they represent a quantum leap in horsepower. The KTA50 produces 1,800 hp at 1,800 rpm, while the QSK60 produces 2,300 hp at 1,800 rpm, a 27 percent increase.

“The real difference in this engine is that it meets the 2007 EPA Tier III emission requirements three years early,” said Calvin Klotz, director of marketing for Cummins Mid-South, Kenner, La. Klotz added that changes to the engine’s design include high-pressure, low-temperature injection, and an electrical governor.

With 4,600 hp pushing water in any direction the operator wants, the HMS Frontier is both agile and powerful. “She doesn’t have the ‘dough-dish’ look of most Z-drive tugs,” Basile stated. “Although she doesn’t have a box keel, her moderate beam and aft skeg give her a grip on the water without excessive tripping when working at an angle to the ship’s movement.”

Basile said he meant for the design to be a balancing of factors—of weight vs. power, of maneuverability vs. course-keeping—and the Point Clear proved that the balance is on target. “After a year of studying the Point Clear’s characteristics, we couldn’t find anything about her hull lines that we wanted to change for the Frontier.”

Another positive is the tank design, which enhances the vessel’s ability to resist side-loads. “We put large ballast tanks low in the boat,” Basile said. “This helps with seakeeping as well as shiphandling. I designed the boat for long-distance towing as well as harbor work.”

In fact, according to Smith, the Frontier will start earning her keep on the voyage to Long Beach, via the Panama Canal, by towing a barge under contract. A temporary towing winch has been fitted to the afterdeck for that purpose.

PLENTY OF DRIVE

Another way in which the Frontier differs from many other Z-drive tugs is her single afterdeck.

“Most Z-drives have a raised platform at the stern,” Basile said. “This does give more room for the drive and allow it to be taken out while the boat’s in the water, but it’s a more complex construction. It interferes with the tow cable when the boat’s doing towing work, and it reduces the size of the afterdeck. It’s rare for a Z-drive itself to break down, and the disadvantage of having to go into drydock for repair are outweighed by the advantages of a clear afterdeck and simpler construction.”

This Z-drive model is the first to be produced by Rolls-Royce after the company’s acquisition of Ulstein and Aquamaster. According to Smith, the units are basically Aquamaster 1650s designed to use wet clutches, an Ulstein feature. The thrusters are controlled by Helicon remote-control levers mounted to the sides of the pilot’s chair in the wheelhouse.

“We’re still learning these units,” said Dan Seiley, the HMS Frontier’s engineer. “Rolls-Royce hasn’t even issued manuals on them yet.”

A Markey DYSF winch with a maximum line pull of 265,000 lbs., carrying 600’ of 8.5”-dia. Kevlar-based Amsteel Blue towline, is mounted on the foredeck. A Markey strain gauge in the wheelhouse monitors the winch’s performance.

The boat’s scantlings reflect the certainty of long years in the rough-and-tumble world of shiphandling, pushing around ships of up to 70,000 tons of displacement. She carries a wraparound reinforcing plate of 1-1/2” steel extending from the deck two feet down the topsides. The bottom is made of 1/2” and 3/8” plate, the topsides of 3/8” plate, and the house of 1/4” plate.

The possibility of long-distance towing work was considered in the design of the accommodations.

The five-person crew is berthed in a master’s cabin and two double-bunk cabins, and the boat is outfitted with full equipment for extended voyaging, including freezer and laundry facilities.

For harbor work, good visibility from the wheelhouse is essential, and this represents one of the most obvious differences between the HMS Frontier and traditional harbor tugs. The Frontier’s “walls of windows” give her unrestricted operator visibility in 360°, and the monolithic (non-laminated) glass used in the Sea Glaze windows provide exceptional strength and clarity.

Two Onan generators provide 95kw each of service power for the vessel.

The vessel’s electronics package was chosen with her dual role in mind.

A Furuno GPS, Simrad HS 50 gyroscope, and a Robertson AP-9 autopilot keep her on course. Other open-water gear includes a SEA C-235 SSB high-frequency radio, Furuno 207 weatherfax, and two Simrad RA 73 72-mile radars.

As the U.S’s busiest seaport, with its crowded docks and narrow waterways, Los Angeles/Long Beach represents a challenge for any harbor tug, but Franco is confident that the Frontier will stand out.

“Service is the dominant factor for success in the shiphandling business,” he asserted. “You’ve got to provide the best boats as well as the best crews and dispatchers. And the Frontier is among the best. I’m sure she’ll get the same reception in Long Beach that the Point Clear has gotten on the Mississippi River.”