Last week the Dutch governmental shipping company Rijksrederij (part of the Dutch Ministry of Infrastructure and Environment, Rijkswaterstaat) took delivery of its scientific research vessel Tridens after an extensive refit at Damen Maaskant Shipyards Stellendam in the Netherlands.
Tridens underwent a major midlife conversion to boost the vessel’s multifunctional capabilities for fisheries research, including installation of an innovative ‘drop keel’, Damen informed.
The Rijksrederij is the custodian of the North Sea and manages a fleet of specialist vessels. The maritime research institute IMARES, in collaboration with other European fisheries institutes, employs Tridens (73.5 metres in length and 14 metres beam) to help determine fish stocks in the North Sea, among other duties.
Commenting on the project, Dirk Kuijt, Technical Manager at the Rijksrederij said: “We’ve worked with Damen Maaskant Shipyards Stellendam over many years for maintenance, but this is the first time we’ve completed a refit of this scale and the first time we’ve installed a drop keel. The cooperation with Damen has been exceptional. It was a very big project for us and we had a very tight schedule. Tridens is departing immediately for survey trials and will shortly represent the Netherlands in a four-week joint European survey, so we were all under a lot of pressure. I’m very pleased with how Damen completed the project according to plan.”
Drop keel installation and complete refit
During the refit, Tridens was fitted with a wide range of modern scientific research equipment, including the drop keel with broadband multibeam echosounder installed by IJmuiden-based WNL Marine Electronics. With the new equipment, Tridens can accurately track biomass and fish shoals in the ocean as well as conduct bathymetric surveys.
Deployed up to 3 metres of the hull, the drop keel eliminates interference from the air bubbles that normally form around the hull and can affect the performance of the echosounders.
Installing the drop keel had far-reaching consequences for the rest of the vessel, requiring extensive engineering of the ship’s design and layout in order to accommodate the trunk – a kind of elevator shaft in which the drop keel is lowered, the company explained.
The drop keel’s specialised engineering works lasted 27 days. But making Tridens future-proof for another 10 years of demanding mobilisations required a complete refit and modernisation.
This part of the project saw Damen refurbish cabins for the crew, and overhaul the main engines, all propulsion equipment and the steering apparatus. The refit included completely replacing the stern gantry and winches and maintenance of the stern mast, booms, A-frame and the corners of the stern of the vessel. In addition, a dedicated device was developed for safe hauling of otter boards.
Following successful delivery on 2 March 2015, Damen Maaskant Shipyards Stellendam concluded its largest refit project ever.