To meet stringent offshore vessel standards, only materials and processes that have been fully approved by DNV and Bureau Veritas (BV) are used in the production of CTruk’s multi-purpose composite marine craft. This includes Scott Bader’s Crystic Crestomer® 1152PA urethane acrylate structural adhesive, which is specified by CTruk for all FRP bonding.
CTruk’s vessels are used as workboats for offshore wind farm support, as well as customized vessels for military, security, disaster relief and commercial applications.
To further reduce weight, increase productivity and cut labor costs, CTruk 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 structural bonding in of hull stringers and bulkheads, transom sections, engine beds, deck sections and for hull to deck joints.
Jim Cutts, CTruk’s Director of Engineering, commented: “As we manufacture vessels to full marine classification, the company must use materials that have gone through rigorous type-approvals. The CTruk design team only specifies proven products that are known to meet DNV and BV requirements with reliable and consistent results. Crestomer 1152 is one such product, giving the advantages of high-elongation, toughness and impact resistance at an economical cost.”
According 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.
Seb Shillaker, Head of Production, explained: “Whilst most of CTruk’s construction applications for Crestomer 1152 include an over-laminating procedure, we do also use purely bonded connections in a number of areas, such as some structural flanged connections. This gives us clear advantages, with savings on labor, materials and a lower overall vessel weight.”
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. Optimizing 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.
CTruk has successfully obtained approvals for certain FRP bonding only application areas, so that in the current craft build specifications the main deck beam, in spite of it being a high impact area, is now also joined only using Crestomer 1152PA structural adhesive, as well as some of the hull and deckhouse structural flange connections.
SC Falcon, which successfully completed sea trials in February 2014 and which is now in service, is the most recent CTruk offshore wind farm support vessel (OWSV) to be designed and fabricated using advanced composite materials and Crystic Crestomer bonding technology.