Non Destructive Testing (NDT) techniques are used across all sectors of marine inspection on metallic based structures through to composite components, which include carbon fibre, glass fibre monolithic and cored laminates. Using traditional NDT techniques skilled marine inspectors regularly test for common defects including Void Detection, Impact Damage, Skin to Core delamination and Crack Detection (ultrasound and dye penetrant).
Once in-service, sea going vessels are generally subject to regular inspections and it is here that NDT plays a crucial role. A recent collaboration between leading experts in the Marine Inspection industry, including Wavelength NDT and Marine Results, together with the DTI and MCA, resulted in the creation of the Marine Information Note (MIN) 417 entitled “Large Yachts: Examination and Inspection of Carbon Fibre Masts and Spars”. This report is a breakthrough in the guidance, information and planning for best practice and inspection in a largely unregulated industry sector.
MIN417 is directed at the large sailing yacht sector within the scope of the Large Commercial Yacht Code (MSN1792), and is relevant to those vessels with spars or major spar components constructed from composite carbon fibre material; a growing feature in yacht construction over the last 20 years. Such spar structures include masts, spreaders, boom(s), gaffs, spinnakers and other poles, bowsprits.Priority is often given to the mast structure, as the safety and commercial implications are critical. Target “user groups” for MIN 417 include yacht designers, manufacturers, surveyors, insurers, underwriters, skippers and owners; possibly classification societies.
This project was undertaken in direct response to the recognition by leading practitioners and bodies in the marine industries, such as the MCA, that there was a general lack of guidance available on how and when quantitative inspection methods should be applied to carbon fibre spars. The report addresses when a carbon spar needs repair or needs replacement in the event of damage. How does a manufacturing defect, or damage inflicted during installation or service affect the structural integrity of a carbon spar and lastly, how can it be determined if a carbon spar is still serviceable and safe?The report provides guidance primarily for ‘in service’ management of the structural integrity of masts and other major spars using monolithic, as opposed to sandwich cored carbon composite. It is also applicable for pre-service inspection of masts.
The MCA states “While the failure of large masts is rare, the safety and commercial implications of failure can be considerable. The research report offers an approach, which will assist in ensuring that owners are aware of the condition of their masts and are able to undertake remedial maintenance when this is required.”
Dr Richard Freemantle of Wavelength NDT added: "We are pleased that the findings of this research project have now been published. The Large Commercial Yacht Code (LY2) contains a general requirement for the rigs on sailing yachts to be monitored in accordance with a planned maintenance schedule: Marine Information Note 417 and the associated report provides valuable guidance in meeting this requirement for the safety of all on board these vessels."(quote of David Ralph - Principal Surveyor of Code Vessel Policy)