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Yacht classification definitions

The GT Factor

The gross tonnage value (GT) is a key issue, not only as a reference for the registration fees applied by the different flag administrations, but also because it determines whether an international convention, rather than a particular safety standard, applies to a yacht.

The table below summarises how the conventions and relevant certificates come into force depending on the gross tonnage of the yacht. In particular, the following values may have a critical impact:

300GT: In many codes, when you reach this value the yacht must be certified in unrestricted service (stricter requirements regarding stability, load line and life-saving appliances).

400GT: This is the threshold for almost all the environmental conventions such as MARPOL and Anti-fouling System.

500GT: This is the threshold for the application of the SOLAS Convention, meaning stricter requirements on machinery, safety systems, materials of construction, fire protection, life-saving appliances and navigational equipment. Furthermore an external certified management company is requested for the ISM and ISPS certifications.

The tonnage issue could also arise on existing yachts when undertaking major refits or modifications, in that any change to the internal volumes of the boat – such as adding enclosed deckhouses or superstructures, or modifying the hull transom or bow – will modify the tonnage value with the risk of subjecting the yacht to stricter mandatory rules.

UPDATE: Since this article was originally published, LY2 has been superseded by Large Commercial Yacht Code Revision 3 (LY3).

Tom Isitt

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