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CTruk Twin Hull FRP workboats built to demanding offshore DNV and BV Standards with Scott Bader’s Crestomer 1152PA structural adhesive.
CTruk Boats Ltd., located in the UK at Brightlingsea, Essex, designs and builds multi-purpose composite marine craft used as workboats for offshore wind farm support, as well as customised vessels for military, security, disaster relief and commercial applications. Established in 2010, the company has a clear business mission to provide safe, fast and highly flexible working vessels by taking an innovative design approach.
The company's patented modular pod system, initially created to meet the complex requirements of offshore wind support work, is an example of CTruk’s design approach to problem solving; the ‘moveable’ FRP deck pods enable an operator to change the vessel’s functionality in just a few hours. Vacuum resin infusion processing technology to minimise laminate weight and increase productivity, along with advanced composite materials are used by CTruk in preference to fabricating with aluminium. To meet stringent offshore vessel standards, only materials and processes that have been fully approved by Det Norske Veritas AS (DNV) and Bureau Veritas (BV) are used in production. This includes Scott Bader’s Crystic Crestomer 1152PA urethane acrylate structural adhesive, which is specified by CTruk for all FRP bonding.
FRP bonding advantagesTo further reduce weight, increase productivity and cut labour costs, the company uses a structural adhesive where possible for FRP-FRP joint bonding in its designs. Scott Bader’s Crystic Crestomer 1152PA is specified in all CTruk composite marine craft for structurally bonding in; hull stringers and bulkheads, transom sections, engine beds, deck sections and for hull to deck joints.
Published Scott Bader technical data for cured Crestomer 1152PA gives typical physical property values of 100% elongation at break and a maximum tensile strength of 26 MPa; the limiting factor is the fibreglass substrate failure, not the Crestomer adhesive joint strength. Crestomer 1152PA is MEKP cured, supplied to CTruk pre-accelerated in 25 kg pails, which is applied by hand. It offers a good level of application flexibility on the shop floor during the bonding assembly stage, as the Crestomer 1152PA grade has an open working time of up to 50 minutes (at 2% w/v catalyst, 25°C) and is suitable for gap-filling joints up to 25mm.
Design change approvalAccording to CTruk, depending on the application area and vessel specification, most FRP joints must also be over-laminated. However, as saving weight and production costs are key objectives, the CTruk design team is constantly looking to identify any new areas where it is possible to only bond with Crestomer. Any design change must comply with offshore vessel DNV and BV standards, therefore any new applications using only adhesive joints (with no over-laminating) must be submitted for approval, along with detailed calculations. Optimising safety with performance is critical and so the CTruk design team use Finite Element Analysis (FEA) to ensure that hull and deck structures meet rigorous strength criteria and comply with the relevant class specifications.
More information: www.scottbader.com - www.ctruk.com