Jet Power: The latest advances in waterjets

Enforcement officers in a waterjet-powered patrol boat have been waiting for the signal that a drug deal has gone down so they can swoop in and bust the alleged criminals.

The officers can’t anchor because they might have to chase down the drug dealers at a moment’s notice. So for two hours the crew has been trying to hold the boat in one spot, against the tide and a light breeze. It’s tiring. Wouldn’t it be nice if there were an easier way?

Well, there just might be. Government agencies, municipalities and others that plan to build a patrol boat (fireboat or police boat) in the 350- to 1,200-hp range can outfit the boat with HamiltonJet’s HJ series of waterjets. The HJ series features the New Zealand-based company’s new positioning system that automatically maintains a boat’s position and heading.

It’s called JETanchor. It works with new installations and retrofits. It’s not like the dynamic positioning systems that are used with offshore Gulf of Mexico oil and gas installations. “It’s not that precise,” said Jeff Bockmeyer, HamiltonJet’s sales manager for the Gulf of Mexico. “But it does hold you in position within a few meters.”

Captains tend to “overcompensate” to hold position when there’s current and wind, Bockmeyer said. So JETanchor results in a significant reduction in operator workload. It reduces wear and tear on the gear and engine. It also reduces crew fatigue by making it a lot easier to hold position for hours at a time with the throttle and shift levers.

On a much larger scale, HamiltonJet put five of its HT810 waterjets on Seacor Marine’s new fast support vessel, the 206’×43′ Alya McCall.

Seacor Marine's fast support vessel Alya McCall. Incat Crowther photo.

Seacor Marine’s fast support vessel Alya McCall. Incat Crowther photo.

The HT810 jets stretch across the back of the Alya McCall — two on the transom’s starboard side, two on the port side and one in the middle. Each is matched with a 2,680-hp Cummins QSK60 and a Twin Disc MG-61500 SC gearbox.

“The jets on the outboard sides are steerable and reversible,” said Bockmeyer. “The center jet is strictly a boost jet and can’t go in reverse and can’t steer.”

When the Alya McCall is moving from one location to another the inside jet will be running. During docking or at slow speeds, it will be turned off.

THRUSTMASTER DOEN

Armstrong Marine in Port Angeles, Wash., is building a 42′ 36-passenger whale watching boat with a pair of DJ172 Thrustmaster Doen waterjets matched up with 600-hp Cummins M11s for a company in Alaska. When the boat hits the water, it will be the first whale watching boat in the U.S. outfitted with Thrustmaster Doen jets.

It’s also the first since Houston-based Thrustmaster of Texas acquired the manufacturing and licensing rights for Doen in Hawaii and North, Central and South America from the waterjet’s Australian parent company in 2014. The Thrustmaster Doen waterjets are manufactured in Houston.

The DJ172 is also a new line of Thrustmaster Doen waterjets that’s rated up to 850 hp. The whale watch boat jets are a direct thrust model, which means that the inboard thrust bearing has been eliminated. “Because we have eliminated the inboard thrust bearing, direct coupling to the gearbox allows the builder to move things further aft in the hull,” said Jordan Tilton, Thrustmaster’s sales manager for waterjets. That reduces weight, cost and eliminates the traditional Cardin drive shaft. Boatbuilders like that feature.

A feature favored by the whale watch boat’s owner is the internal inboard hydraulics. “So there’s no risk of hydraulic fluid being exposed to the outside environment,” said Tilton.

DJ120 (510-hp) jets are going into some Navy boats. Tilton can’t disclose what the boats and their missions are, but said, “It’s a new approach for the Navy and kind of a different application for us.”

A feature that made the DJ120 waterjets particularly appropriate for the Navy project is their cavitation margin. There’s usually some cavitation as a boat starts to get on plane, but the way DJ120’s impellers are designed, “drastically reduces the cavitation margin when getting on plane,” said Tilton.

MJP

Not long after the Swedish company MJP Waterjets acquired Ultra Dynamics about five years ago, the company introduced its MJP Hybrid waterjet in the U.S. The Hybrid matches up MJP’s mixed-flow stainless steel pump with its UltraJet series easy-to-install aluminum frame.

The MJP Hybrid waterjet combines the best characteristics of the MJP DRB and MJP Ultrajet series. MJP Waterjets photo.

The MJP Hybrid waterjet combines the best characteristics of the MJP DRB and MJP Ultrajet series. MJP Waterjets photo.

The benefit of the mixed flow pump as opposed to the axial flow waterjet is more efficiency, said Jason Hill, product manager for MJP’s UltraJet series. Within the mixed-flow pump, the water accelerates more than with the typical axial-flow pump. “That allows it to generate more pressure, which is more speed and gives it higher efficiencies in the 25-knots-plus range,” said Hill. That also means better fuel economy.

A new product due out soon is a waterjet with a 400- to 600-hp mixed-flow pump that will be more economical and more competitive against traditional cast aluminum waterjets.

MJP’s new waterjet won’t be a 100% cast-aluminum jet. There will still be some traditional MJP components. The stator, for instance, will be stainless steel. “We don’t see the benefits of going to aluminum in that particular component because it sees the most abuse,” said Hill. “It catches the water off the pump, things that are being accelerated come in contact with it.”

NAMJet

NAMJet, the Denver-based waterjet company, has come a long way in the past four years. Back then it delivered 18 waterjets a year. Now NAMJet delivers an average of one of its five models every two days.

With its new product offerings, NAMJet should increase production output even more. One is the RaptorJet, available in both electric and hydraulic versions. “But the electric version is the first waterjet worldwide to provide the option of electric actuation,” said Phil Organ, NAMJet’s technical sales support manager. That means no hydraulic pumps, oil tanks, filters, plumbing, hydraulic maintenance or oil leaks.

For both the electric and hydraulic models, the operating systems for the jet’s steering and reverse are in the vessel’s interior. With the hydraulic RaptorJet, that means no oil in the water.

NAMJet’s 431HH was the first waterjet put into the RaptorJet series as the RJ431e (“e” denotes electronic version). A test boat outfitted with RJ431e jets and 480-hp diesels hit 40 knots, 5 knots faster than a standard 431HH.

Part of that increase is from NAMJet putting the RaptorJet through its new computational fluid dynamics program, which resulted in a smoother intake design.

About the author

Michael Crowley

Michael Crowley is a correspondent for WorkBoat Magazine.

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