VESSEL REVIEW | Gracious – Twin-rig prawn trawler for operation in North Sea off Scotland

Macduff Shipyards of Scotland recently handed over a new fishing vessel to local company MV Gracious.

The vessel, also named Gracious, was designed by Macduff Ship Design for twin rig trawling. It will be used primarily to catch prawns in the North Sea off Scotland.

Upon initial discussion of the newbuild, the decision was taken to develop a new hull form with the aim of providing good sea keeping qualities, high propulsion efficiency, as well as improved living conditions for the crew.

To achieve these objectives, Macduff Shipyards, in conjunction with Macduff Ship Design, set out to develop the new hull form, which would have a waterline length of 25 metres (82 feet), a registered length of just below 24 metres (79 feet), and a beam of 7.5 metres (25 feet).

Custom hull design coupled with noise-reducing features

The hull was compared against previous designs by the Wolfson Unit in Southampton, who utilised CFD technology to assess the hull resistance at a range of different speeds, as well as visualise where the major resistance was occurring.

With this information, progressive design alterations were made to further reduce the resistance, and improve the wake generated by the propeller. The initial results from sea trials were very encouraging, with a good speed to power witnessed, and the vessel punching effectively into head seas with little effect on speed.

As well as the hull form, the general arrangement of the vessel was carefully considered and set out to increase crew comfort, with a focus on reducing noise levels in the living spaces.

Given the generous length of the hull, and the yard’s experience with noise assessments on board vessels, it was decided to arrange the vessel with the crew cabins fitted amidships, between the engine room aft and the fish hold forward. By placing the cabins amidships, they were moved away from the propeller, which is one of the primary noise sources on board.

The galley and mess area were meanwhile situated athwartships, above the cabins below, with no part adjacent to the engine room.

Another effort to reduce noise was to route the engine exhaust pipes up the trawl gallows, instead of near the wheelhouse where they would traditionally be placed. During sea trials, the noise levels were measured and a noticeable reduction in dB was witnessed, with an absence of any propeller noise or vibration in living compartments.

Lower emissions for minimal environmental impact

Gracious features a steel hull and an aluminium wheelhouse and mast. The vessel is powered by a Caterpillar C32 IMO Tier III-certified main engine, rated 559 kW (750 hp) 1,800 rpm. This is coupled to a Masson Marine W7400 gearbox, with a large reduction ratio of 9.077:1, which drives the 2.5-metre diameter propeller fitted within a high thrust nozzle.

The selective catalytic reduction system and ancillary equipment for urea dosing and NOx monitoring were supplied by Caterpillar. A stainless steel urea tank is situated in the engine room and has a capacity of nearly 2,000 litres (440 gallons). Cooling for all engines, as well as the hydraulic system, was provided by using closed loop fresh-water systems with Blokland Non Ferro supplying the box coolers.

Gracious features a new design of rudder blade, developed by the yard, with CFD analysis conducted by the Wolfson Unit in Southampton. The rudder features two blades of aerofoil profile, driven by a Scan Steering MT 1000 unit. The system features no linkages and was built to be simple to fabricate and maintain.

Main hydraulic power on board is provided by a Hyundai 4AD086 auxiliary engine with a power output of 199 kW at 1,500 rpm and drives two Kawasaki swash plate hydraulic pumps. In addition to this, two 45kW electric motors are fitted, each driving an independent hydraulic pump, which can be utilised as a net retrieve system, or for using hydraulic equipment in the harbour with only one generator set running.

The hydraulic system is a load sensing type system, with electric control valves and remote joysticks fitted to the machinery. This system delivers power only when requested, with the system running idle when not in use, saving fuel and reducing noise throughout the vessel.

The deck machinery package was supplied by the yard, with a triple barrel trawl winch fitted with a Hagglunds CA210 motor, as well as two split net drums each with two Hagglunds CA70 motors.

Comprehensive trawling and processing suite

Thistle Marine supplied the MFB8 landing crane, along with a BK13 powerblock crane, both with slew ring base. A dynamic S45 gilson winch is fitted for lifting the catch onboard, and a small Rotzler hoisting winch is fitted to assist unloading the catch at the end of the trip.

Electrical power onboard is provided by two Mitsubishi generators, each with 98 ekW in power output and capable of running the ship’s power in addition to one of the 45kW hydraulic motor pump sets. If two pump sets are required, the second generator can be started to run it.

The electrical system on board was designed and manufactured by R D Downie, who supplied the switchboards, frequency drives for motors, starter panels for the machinery, fire/bilge/gas alarm panels, and battery systems.

The fish processing system was designed by the yard, with the catch handling system built by Northeast Fabricators, all from marine grade stainless steel.

The fish hold refrigeration system was designed and installed by Premier Refrigeration, which also supplied and installed the Geneglace 2.5-tonne ice maker. The equipment is all housed in a dedicated room situated between the sorting area and the winch room forward.

The fish hold was finished off with gel-coated FRP panels and insulated to a high level to save energy and retain cold. A dedicated, fixed, fish hold access ladder was integrated into the walls of the fish hold, to improve crew safety.

The vessel was painted to a high standard, using quality paint provided by International Paints.