A stellar career in fishing
… is what Shaun Andrew, 48 years old, co-owner of Alaskan Leader Fisheries, chose for his living. And it is the way to go for his newest longliner fishery vessel NORTHERN LEADER, which he decided to equip with a SCHOTTEL propulsion system. Already for a year the Northern Leader is busy out in the often rough Bering Sea with two SCHOTTEL Rudderpropellers SRP 1012 (1,000 kW) and a SCHOTTEL Transverse Thruster STT 170 (300 kW) on board.
Shaun grew up in Kodiak, Alaska. His father was a diesel mechanic for ships and Shaun followed suit and started his career on several fishery vessels as engineer and captain. In 1990, at the age of 24, he became captain of the newly built ALASKAN LEADER, named after the newly founded company in which he became co-owner some years later.
Propelling a versatile working profile
The fourth ship of the company, NORTHERN LEADER, was on the drawing board for some time. Its layout grew continuously and the vessel changed its length several times. A main concern was the maneuverability of the vessel, as Shaun explains, a long line vessel has to be very maneuverable at very slow speeds. “I was looking for a fitting propulsion system for quite some time, when finally a tugboat captain told me about his SCHOTTEL z-drives.” Shaun says. He met up with SCHOTTEL US and after discussing z-drives and conventional shaft lines, the advantages of a Rudderpropeller based solution were obvious for him. Today, NORTHERN LEADER is equipped with a diesel-electric z-drive propulsion system – the scope of delivery from SCHOTTEL included thrusters, electrical drive motors, frequency converters, the control system and the masterstick.
A longliner has a wide-ranging working profile: While travelling fast to the fishing grounds, the vessels travel at a very slow speed during laying and hauling in the lines. The operational profile of the vessel on a 30-day trip includes two days sailing out at about 12 kn and two days sailing back after off-loading in Dutch Harbor. In between, the vessel spends 8 hours per day setting the gear at approx. 6 kn, and 16 hours per day hauling the lines at 2-3 kn. The 56m long NORTHERN LEADER catches fish by laying a 72km line of 76,800 hooks that are fed automatically with bait fish. Thanks to this modern system it takes just 6 to 8 hours to lay the line.
Maneuverability at its best with masterstick controlled Rudderpropellers
The combined propulsion concept of two Rudderpropellers and a Transverse Thruster enable the vessel to keep its course precisely while hauling in the catch - even with changing weather conditions. The hauling proceeds at a fairly consistent course and speed, but there might always occur a reason to stop the vessel and maintain position without putting too much pull on the lines. In situations like this, a conventional direct shaft line system with rudders always requires additional power, as the propeller and rudder can only alter the direction of the vessel by forward momentum. The Rudderpropellers on the contrary, can change course flexibly with minimum power and without altering forward momentum more than needed. “Above all longliners want maneuverability,” says Shaun, ”In this regard the z-drives are matched by no other system. In really heavy seas you really know you have spent your money well, because it is so easy to keep the vessel on course while hauling gear. In my opinion, in a large vessel like ours it would be almost foolish to not choose z-drives.”
To facilitate thrust control, all three thruster units on board can be controlled via one SCHOTTEL masterstick lever which gives the captain immediate and intuitive control of the vessel. The masterstick differentiates two drive modes: “sailing” offers best manoeuvring possibilities during operation in the open sea at high speed and in “harbor” mode the bow thruster is activated additionally for manoeuvring, for example for transversal movements. Besides the manual masterstick control, the system can also be switched to “auto heading” mode. Here, the gyrocompass signal keeps the vessel on course automatically. In operation, the master stick biasing is always activated. Hence, a certain amount of thrust is applied to each propulsion unit at any time, even with lever in zero. This does not only keep away the fishing lines from the thruster by generating outflow, but also makes it easy to stop the vessel immediately. For Shaun the advantages of the masterstick are obvious: “Just imagine the following situation: You are hauling gear and heading forward at approximately 2.5 kn and suddenly there is a problem in the gear and you have to stop the vessel quickly without putting too much tension on the lines. In this case you just pull the masterstick lever to zero and the thrusters stop the vessel on their own without having to reverse thrust ,” Shaun explains. ” Our bias is automatically set at 100 rpm - and in auto heading it not only stops you but even keeps heading.” Thus, if the auto heading mode is activated the vessel can be controlled by one hand and one action only.
High performance maneuverability and propulsion efficiency go hand in hand on board of NORTHERN LEADER. The diesel-electric driven propulsion system easily adapts to the versatile operation profile of the vessel. “Diesel-electric propulsion is ideal for longliner operation. It allows us not only to run just the amount of kW we need in every situation, it is also very fuel efficient.” explains Shaun. In addition to the reduced fuel consumption because of the electric motor, the Rudderpropellers increase the fuel efficiency even further. For Shaun this is a clearly proved accomplishment. Looking at his vessels he says: “The NORTHERN LEADER is considerably larger then all our other vessels. The closest is the BRISTOL LEADER which holds 1 million pounds of fish while the NORTHERN LEADER holds 1.7 million pounds and consists of over twice the steel. But when you compare fuel numbers the NORTHERN LEADER only burns about 10% more fuel then the BRISTOL LEADER. We consider this quite an accomplishment.”