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Schottel just celebrated its 100th birthday. Located in Germany’s Rhine Valley, where the company began in 1921, Schottel continues to build its propellers to exacting standards.

Azimuth thrusters are a different stroke for new boats, but offer remarkable fuel effi ciency and maneuverability but offer remarkable fuel effi ciency and maneuverability

By Paul Molyneaux

he Washington-based seafood company Alaskan Leader Seafoods launched the 184-foot longliner Northern Leader in 2013, winning innovation awards for designer, Jensen Maritime. The Northern Leader was the rst diesel-electric shing vessel launched, using four Caterpillar C32s, two C18s and a C9 to power two Schottel rudder propellers type SRP1012FP at 1,000 kW each.

“They saved $500,000 in fuel the rst year. So their payback for going diesel electric was 4 to 5 years,” says Jonathan Parrott, senior naval architect at Jensen.

Three years later, in 2016, another Northwest shing company, Blue North, launched the 191-foot longliner Blue North. Designed by Norwegian naval architects and engineers, Skipteknisk, the Blue North is also powered by Cat gensets driving electric motors and Schottel Z-drive rudder propellers. The company reported impressive fuel savings, around 30 percent. Surprisingly few vessels

— newbuilds or major conversions — have picked up on the technology since then.

“There are definitely applications for the Z-drive and L-drive on longline vessels, even factory trawlers,” says Schottel’s West Coast Account Manager Ingi Huswick. “There are a lot of advantages. When you get to these larger vessels, one of the more complex things can be the long, complex shaft line that’s a maintenance headache, and it’s also going through your tankage and taking up space. With the Z-drive or L-drive, you have options for installation where you don’t have to build around the

— Ingi Huswick, Schottel

shaft line.”

Huswick explains that both Z-drive and L-drive are azimuth thrusters — able to rotate 360 degrees — the Z-drive requires two gearboxes, one up at the motor and one down in the propeller, while the L-drive the motor is mounted on top of the propeller

Washington state-based Wesmar has been turning out solid, reliable, and powerful bow and stern thrusters for the commercial fishing industry for more than 55 years. Bryan Thiemann, Wesmar’s account sales manager for the United States, said the company’s longevity and reliability have made their products ubiquitous across the nation’s fisheries.

“If it’s a commercial fishing boat, it potentially has our stuff on it,” Thiemann said.

Part of Wesmar’s success comes from their unique design, Thiemann added. Dual props increase thrust and efficiency.

Each Wesmar thruster has two counter-rotating fourblade Kaplan propellers. The dual-prop system raises efficiency by splitting power between two different gear sets, and the wash from the forward propeller is picked up by the aft, creating greater thrust. Wesmar bow and stern thrusters run from 5- to 500-horsepower, and the efficient dual propellers add up to more thrust per horsepower unit. This means space savings on smaller boats.

“For instance, with the Bristol Bay gillnetters, which is a big market for us, they’re often very shallow-draft vessels, so they don’t have a ton of space for a bow thruster. The Wesmar allows them more thrust in a smaller profile tunnel,” Thiemann said.

Gillnetters, Thiemann said, typically use thrusters with 8-inch propellers, but Wesmar offers 12 sizes running all the way up to 48-inch propellers, covering a wide range of boats across many fisheries. Solid stainless construction has been another key to Wesmar’s presence in the fishing industry.

“All of our thrusters, bow and stern, are full stainless steel construction. It’s 305 cast. We have stainless housings, gears, bearings, props. Everything we do is commercial duty… and manufactured in the USA. We’ve been doing it since 1965, and we make quality products that are built to last,” Thiemann said.

Thiemann noted that thrusters that are 25 or 30 years old often come into Wesmar’s shop in Arlington, Wash., and need just a simple seal and O-ring service to get back on the water. According to Wesmar, they use “the highest quality seals to the input and output shafts to prevent water ingress and oil leakage.” Service on the seals is simple because the thrusters do not have to be taken apart to swap out seals.

Wesmar’s two-bolt drop-in design makes retrofits simple for metric tunnels, with a couple models that can easily replace Max Power, Side Power, and Vetus thrusters. All Wesmar thrusters can be run on hydraulic power or a choice of DC 12-, 24-, or 48-volt power or AC variable speed. — Brian Hagenbuch

Wesmar and eliminates the need for the upper gear box.

“Our equipment maximizes efficiency,” says Huswick. “Eliminating the rudders, for example. Even when the rudder is turned a little, you start losing propulsion because you’re pushing against it. You can lose up to 30 percent efficiency when it’s turned hard.”

The system also gains efficiency in the way it manages power.

“There’s also a lot of redundancy in the system,” Huswick says. “With all those generator sets, you can run both drives with one or two, and the failure rate on an electric motor is much lower than on your typical diesel engine.”

According to Huswick, the system utilizes a load share module to shift loads between engines, enabling each engine to run at maximum efficiency.

“I may shut down some engines, or shift power where it’s needed,” he says.

Maintenance on the rudder propellers used on the Northern Leader is vital. Failure of the seals would wreak havoc on the units.

“We did our five-year ABS overall on it after six years of service,” says Huswick. “We replaced all the seals and bearings. It only took a day or two, but those technicians don’t

The Northern Leader was the rst big U.S. shing vessel to be equipped with azimuth thrusters, leading to fuel savings of $500,000 in the rst year.

come cheap, and it can be an expensive process.”

In spite of all the check marks in the plus column, Z-drives and L-drives remain rare in commercial shing eets. “I think shermen would rather stick with what they know, especially if they’re going to be out in the Bering Sea. We’re also not building a lot of new boats, and so we’re not seeing people move to the Z-drive.”

Keith Singleton, president of the value-added division of Alaskan Leader Seafoods, reports that the captain of the Northern Leader appreciates the maneuverability the Z-drive propellers give him.

“I know they like it mainly because they can stay on the gear when they’re hauling,” says Singleton. When asked if Alaskan Leader would use Z-drives on any future boats the company might build, Singleton is unequivocal. “Absolutely!” he says.

Paul Molyneaux is the Boats & Gear editor for National Fisherman and author of “The Doryman’s Refl ection.”

BRI DWYER PHOTO

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