Jet Stream
New waterjet applications extend the range of

10/1/2010

There have been a number of interesting ways in which waterjets have replaced traditional prop-and-rudder arrangements for propelling and guiding a workboat from one point to another.

One of the most recent examples is a pair of ferries built for the Canadian company La Traverse D'Oka that are powered by waterjets from North American Marine Jet .

The original ferries operated by the Hudson, Quebec, ferry service west of Montreal, consisted of an 80-foot barge that carried up to 10 cars, and a small "Chris-Craft-looking" towboat.

"When they got to the other side, they would slingshot the barge to turn it and get it into the slip. It took a lot of time and was pretty unique," said North American Marine Jet's Jason Hill.

In an effort to reduce landing times and to carry more vehicles on the 2-km run, La Traverse D'Oka went to Navtech in Quebec City, Quebec, to come up with two replacement ferries.

"We took the existing barges, added a hull on each side of the barge and extended the deck between the two hulls," said Navtech's Thomas Barbeau. By extending the deck on the now-catamaran ferries to 120' × 36', the ferries are able to carry 18 cars.

In place of the towboat, Navtech put a 360 SDgr Traktor Jet 457HT in the bow of one hull and the stern of the opposite hull. Each jet is powered by a 285-hp Cummins diesel. With that power arrangement, the ferries "could achieve the desired speed of 7.8 knots at 1,400 rpm, and at this rpm, the thrusters were only using 118 horsepower each," Hill said. "That's the first time we've put 360-degree jets in a ferry."

Barbeau said that while it's not unusual to find shallow-water ferries with jet thrusters at opposite ends of the boat in Europe, "in North America, I don't know if this is the first, but it's not that common."

 

WIND SPEED

Another application where waterjets are especially effective is for boats that service the nascent offshore wind farm market.

"We are getting inquiries from naval architects and builders," said Graham Scott with Ultra Dynamics , the builder of the UltraJet waterjet.

Ultra Dynamics has likely been receiving inquiries because the UK-based company has already supplied waterjets on boats up to 72' that service wind farms in Europe.

Certainly the ability to control a boat at low speed and zero speed is critical for the operator of a wind-farm boat. "You need to be able to operate for many hours, sometimes at zero speed," said Scott.

No matter where the sea and wind is coming from, a wind tower can only be approached from one direction because the boat's bow has to line up and fit into a single vertical tube. "You have to approach cautiously, so control is very important. Once contact is made you have to have a steady, solid non-cavitating thrust at zero boat speed while the boat is being bounced up and down," Scott noted.

So far, the company's 377 through 575 waterjet models have been used in wind-farm boats. In 2011, UltraDynamics will bring out its new waterjet, the 650, with an improved nozzle for better low-speed steering.

The newest waterjet from HamiltonJet is its HT900. This completes the HT series, which also includes the HT1000 and the HT810. With a 900-mm (35.4") impeller, the HT900 is for large, high-powered boats, like the 190-foot fast supply boat being built by Gulf Craft in Louisiana. The supply boat will have four HT900 jets onboard, each driven by a 3,434-hp MTU engine. That should push the fast-supplier to over 30 knots at the top end and around 25 knots service speed.

Twin Disc Inc. is now the distributor for MJP waterjets in North and South America, the Pacific Region, Italy and Israel. MJP (Marine Jet Power), which is headquartered in Sweden, had been without a U.S. distributor for a while until hooking up with Twin Disc.

"Twin Disc has been working to establish and re-establish contacts and working relationships with boatbuilders, naval architects and fleet operators," said Chuck Balboa with Twin Disc. MJP jets have an input-power range of about 1,300 to 20,000 hp.

 

 


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