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Arpège — an innovative demonstration trawler featuring diesel-electric propulsion — is now undergoing her first refit after completing 4000 hours of trial fishing expeditions conducted by owner Alexis Hagneré since delivery in October 2015. The boat (length overall: 24m; beam: 8.5m) was built by Socarenam. According to the project managers, Arpège has performed well and met the expectations of her owner/skipper who reports that the trials enabled him and his crew to learn not only how to work with the boat, but also how to use Danish seine gear which is new to this part of France.

A product of the ‘Ships of the future’ programme

Arpège was developed under France’s ‘Ships of the future’ programme to advance R&D and innovation that contribute to making vessels safer, more environment friendly, and more economical. The programme received €2 million in government funding and is estimated to have cost a total of around €8.2 million.

French boat- and shipbuilder Socarenam initiated the programme and acted as prime contractor. The programme partners included naval architecture firm Bureau Mauric, energy specialist ENAG for propulsion system customisation, maritime electronics specialist Marinelec for power optimisation and the development of the power management and control system, and iXBlue for the optimisation of the bottom-scanning sonar. Socarenam is based at Boulogne-sur-Mer on France’s Channel coast.

Power/displacement ratio

Arpège has a full-load displacement of 300 tonnes and a transit speed of 10 knots. The boat is powered by a pair of 221-kW ABB electric motors receiving electrical power from two Caterpillar C18 variable-speed diesel generator sets. The 10-knot transit speed meets the design specification despite the relatively low overall power rating of 442kW, confirming the design’s excellent propulsion power/displacement ratio. The results owe much to the optimisation of the electrical power system, the streamline hull and the bulbous bow. The hull’s slim ‘belly’ section ensures more efficient flow lines to the propellers than is the case with conventional trawler hulls.

Reliable, user-friendly control system

The programme engineers are happy with the efficiency of Arpège’s electrical systems, as well as their excellent reliability throughout the fishing trials. They proudly point to the simplicity of the operator interfaces and the excellent crew training programme. Remote maintenance is also available should the crew need assistance at sea. The energy management module collects data relating to onboard energy consumption as well as serving as a decision-making aid. This module also has an add-on routing function that suggests the minimum-energy route. Note that whereas most trawlers of this size have just one propeller, Arpège has two, chiefly to improve route tracking while trawling in cross currents and winds by enabling the boat to maintain its heading rather than ‘crab’.



(© Socarenam)

Lower fuel consumption

The fishing trials yielded an hourly fuel consumption that is 15 to 20% lower during transits at 10kts than that of comparable conventional trawlers. For complete fishing expeditions, the average daily fuel burn was 35 to 55% lower than for similar trawlers using conventional gear and 10 to 35% lower than for comparable Danish seine trawlers. “Arpège consumed just 45 litres of fuel per square kilometre of fishing ground covered. By comparison, other Danish seine trawlers burn 50 to 60 litres/, or up to 33% more, while conventional trawlers burn 250 to 300 litres/,” commented a programme manager.

While lower fuel consumption automatically implies less pollution, it should be noted that Arpège was also designed in compliance with zero domestic effluent and waste guidelines.

To duct or not to duct?

Arpège has two unducted fixed-pitch propellers. This design decision was based on trade-off analyses of bollard pull, pull rating at intermediary speeds, energy efficiency during transits and PME, an administrative maximum power rating. Doubts have been expressed, however, as to whether this is the best choice. This issue will be resolved when the design is reviewed after one or two additional winter fishing seasons. It may be necessary to modify both Arpège and other trawlers based on the same basic principles.

Big-boat volumes

Innovative naval architecture and space optimisation resulted in a design offering the deck space and internal volumes of Boulogne-based trawlers with a length overall of 28 to 35 metres, even though Arpège measures only 24 metres. The gear includes two winches, each holding 4000m of 44-mm textile-coated steel wire rope, two trawl drums for the seines and a third for pelagic trawling. The winches are powered by 130-kW electric motors. “The winch motors proved both efficient and reliable. They require hardly any maintenance, are quiet, and completely eliminate the risk of hydraulic fluid leaks on the main deck.”

Refit and design changes

The programme sponsors have noted, however, that certain improvements need to be made. Some of these changes are included in the refit now underway, beginning with modifications to the rope guide and trawling gear. During the first few months’ fishing, the crew found that the rope guide was too stiff and had too little travel while paying out and that the rope rubbed against the trawling gear resulting in excessive wear.

Better handling means better prices

In the sealed preparation room, the catch is cooled using liquid ice combined with pulsed air refrigeration which maintains a uniform temperature throughout the room. This ensures that the fish keep better and, as a result, fetch better prices at auction. While working in the preparation room, the crew is also sheltered from the elements.

Arpège is the first trawler of this size to have the sorting area and store on the same deck, a feature that significantly improves handling. The store has space for 950 crates, or around 25 tonnes. The overall design reduces catch handling while ensuring better working conditions for the crew. When the net has been hauled, the catch is transferred to a large locker then onto a conveyor where four crew members sort the fish at ergonomically designed workstations.

Zero-discard holding tank

The deck below the sorting area includes a 10-m3 holding tank ready to comply with anticipated zero-discard rules requiring fishing vessels to hold some or all of the by-catch.

Improved safety

Improved crew safety, working conditions and comfort were also key aims of the Arpège programme. The three-deck design offers a freeboard of over 2 metres, compared with just 40 to 80cm for conventional designs, ensuring a larger safety margin in big seas. The results recorded during the trials demonstrate 25% greater stability at large heel angles, thereby reducing crew fatigue and the risk of accidents. With a roll period of 9.5 seconds, Arpège rolls very gently.

The Arpège also features a snag hazard detector. “The trials demonstrated the capabilities of both the snag hazard detector and the sonar. The real-time bathymetric charts produced by the sonar and the associated software give the skipper an accurate representation to the seafloor ahead and generate automatic on-screen warnings and decision-making aids to help the skipper manage the boat and its gear as effectively as possible, especially when responding to hazards.”

Crew comfort

Like the fish processing area, Arpège’s other interior layout and fittings are designed for improved crew comfort. The living quarters have benefited from input by ergonomists and designers. The hull shape enabled the architects to allocate 25% more space to the living quarters compared with other boats of the same size while improving the separation between living and work areas in such a way that the former remain much drier. The wheelhouse is modern, high above the water and offers a panoramic view. The skipper has his own cabin, the mate and/or passengers or observers have a two-bunk cabin, and the five fishermen share a five-bunk cabin. There is also a separate mess.

Quieter too

Given that the high noise levels typically encountered on working trawlers contribute directly to crew fatigue, noise reduction was another of the Arpège programme’s chief aims. The success achieved in this respect is impressive. Measurements revealed noise levels of 70dBa in the mess, 64dBa in the cabins and 62dBa in wheelhouse. These values compare favourably with the specifications which called for 70dBa in the cabins and 66dBa in wheelhouse.

Written by Vincent Groizeleau, translated by Steve Dyson


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