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Innovative catamaran tug brings power and versatility to shallow waters

Jun 30, 2016 11:52 AM
Catatug 1’s catamaran design gives the boat a draft of just 5.5 feet, allowing it to work effectively in shallow areas that are out of reach of monohull tugs of similar size.

Catatug 1’s catamaran design gives the boat a draft of just 5.5 feet, allowing it to work effectively in shallow areas that are out of reach of monohull tugs of similar size.

In December 2013, Quebec-based marine services company Ocean Group introduced what it called the most powerful harbor tug ever built in Canada. 

At 118 feet long and 8,160 hp, Ocean Tundra was designed for escort, docking and icebreaking duties on the St. Lawrence River and in the Canadian far north. Gordon Bain, the founder and president of Ocean, dubbed that creation “The Beast.”

This year, Ocean has introduced another innovative boat at the other end of the power and size spectrum: a 53-foot, 1,430-hp pushboat with aluminum catamaran hulls. This boat earned the nickname “The Little Beast.”

The boat, Ocean Catatug 1, may be small, but it is extremely capable in the niche for which it was designed — moving barges in shallow waters to support marine construction projects.

The key element in that design is its twin aluminum hulls. By spreading the boat’s weight over the two hulls, the draft is kept to 5.5 feet. Each hull accommodates a 715-hp Caterpillar engine, giving the boat exceptional power for such a shallow draft. As a result, the boat can bring substantial power to places where tugs of similar horsepower cannot go because of their deeper draft. 

Capt. Simon Pierre Landry in the pilothouse of Catatug 1. The boat has an excellent range of electronics for a vessel of its size, including two independent sets of radar, GPS, AIS and digital charts.

“It’s not a big tug, but it’s very useful,” said Philippe Filion, Ocean’s director of corporate and public affairs. “The horsepower is a lot less than other (bigger) tugs, but it’s for a different mission.”

That mission now involves supporting construction of a replacement for the Champlain Bridge, which since 1962 has served as the primary highway gateway to Montreal over the St. Lawrence River. The new bridge and its associated works are expected to cost about $3.25 billion (CAD 4.2 billion). The bridge is scheduled to open in late 2018.

Meanwhile, “The Little Beast” gets to show its prowess in a very big project. Ocean’s base of operations for the bridge work is on the south shore of the river between the existing Champlain Bridge and a parallel ice-control structure located just upstream. 

Sitting at its dock, the little tug is dwarfed by the high span of the steel cantilever bridge passing almost overhead. Yet one aspect of its design makes it stand out visually from the surrounding construction barges and small tugboats — Catatug’s wheelhouse perched atop a slender white tower rising from the port side of the open cargo deck. Together the tower and wheelhouse are about 25 feet tall, with the floor of the wheelhouse situated about 16 feet above the cargo deck, giving the operator a height of eye of about 21 feet. That elevation, combined with the windows all the way around the hexagonal wheelhouse, gives the operator great visibility to manage the movement of the boat as well as operations on the cargo deck and barge. The boat, which is equipped with push knees, will move barges carrying construction materials and equipment. 

“The visibility is perfect, really perfect,” said the boat’s captain, Simon Pierre Landry. “You can see a long way if you have a barge to push. You can see the deck perfectly.”

The tug’s distinctive raised pilothouse gives the operator a height of eye of about 21 feet. That elevation, plus the wrap-around windows, provides excellent visibility in all directions.

The height of the wheelhouse also illustrates the degree to which Ocean consults with its crews when developing a new design. Ocean employs its own team of designers and owns its own shipyard on Isle-aux-Coudres, an island in the St. Lawrence River roughly 75 miles northeast of Quebec City. Landry suggested a high wheelhouse and naval architect Réjean Desgagnés ran with the idea. 

“I had no idea it would be this high,” Landry said with a smile. 

The captain expressed another concern prompted by the ice encountered on the St. Lawrence in winter: While a bulbous bow shape for the hulls might reduce water resistance, it could also pose the risk of hanging up on the ice.

“For now there is no bulb,” Landry said. 

Ice poses other risks, especially for a boat with aluminum hulls. Consequently, the hulls have been reinforced to work in light ice. The boat is very rigid, Landry said, with the reinforcing members of the hull spaced just 6 inches apart.

The boat cannot operate in heavy ice, but it is designed to operate in the presence of ice. 

The Palfinger PK6500m crane has a lifting capacity of 1.5 tons.

Each hull has five separate watertight compartments each with its own pumping capacity. The boat is designed so that even if a power failure occurred in one hull, the power and hydraulic systems from the other side could be used to run the pumps to dewater any flooding compartments. The same is true for the fixed CO2 fire suppression system. If power is lost on one side, the CO2 system will still operate on that side.

The boat has a full line of electronic gear. With two independent sets of radar, GPS, AIS and charts, if any one fails, there is a backup. AIS is not required on a boat of this size, but Catatug has it. “It’s a plus for navigation. You can see the other boats,” Landry said.

He noted that the boat is equipped with an intercom system that allows him to communicate with crew on deck or in the engine rooms. “You can’t stop driving the boat to talk to the deck hands,” Landry observed. With the intercoms, he can continue to keep the boat operating safely while communicating with the crew. 

The St. Lawrence poses a challenging operating environment. There is ice in the winter and strong currents year-round near Montreal. You need plenty of power to move a 300-by-150-foot construction barge carrying a heavy crane in those conditions.

Catatug has what it takes, said Martin Dussault, Ocean’s project manager for the bridge operation. “When pushing the barge, it can do 10 knots. That’s a lot,” he said.

Capt. Landry with one of the two 715-hp Caterpillar C18 diesels. With an engine in each of the two hulls, the boat can continue to operate safely if power is lost to one side.

For construction support, the tug needs to be nimble enough to maneuver barges in and out of crowded work areas. In another setting, building a monohull tug propelled by powerful stern thrusters might have been the solution to provide the required power and maneuverability. But thrusters require at least 15 feet of draft. 

With its 5.5-foot draft, Catatug can work in depths of only 7 feet, a crucial advantage in the shallow waters around Montreal. It would take three or four small normal-draft tugs working together to handle jobs that Catatug can do by itself, Landry said. 

Even without thrusters, Catatug is highly maneuverable because of the distance between its props. With a beam of 31 feet, its two propellers are much further apart than would be the case in a typical monohull with two fixed props. Consequently, Catatug can exert powerful turning forces by exploiting differences in the speed and direction of rotation of the widely spaced props.

Catatug and its crew are operating under contract with the consortium building the bridge, Signature on the St. Lawrence, through November 2018. Ocean may then have to find another major project to keep this innovative tug busy.  

Even here, Catatug may have an advantage over other small tugs. It can be disassembled into five components, each small enough to be transported by highway or by rail (and of course by ship).  So given its versatility and its mobility, Catatug appears to have a long and bright future ahead.

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