by
Stuart M Roy
Naval Architect and Surveyor
Stuart M Roy
Naval Architect and Surveyor
YACHT & POWERCRAFT DESIGN SERVICES
Stability of Yachts & Boats
Stability investigations and evaluations are generally needed when an owner wishes to gain certification for a boat, but may also be required to satisfy insurers following a refit or rebuilding programme. Approval might be needed for an owner to operate the boat as a charter yacht or a company might want to prove that its new product meets the European RCD requirements. To gain such a certificate or approval it has to be shown that the boat is fully compliant with the specific regulations for the type of craft in question and meets all the stability criteria. This can involve the production of a “Stability Booklet”, a document which sets out in a standard form the results of various flotation and stability calculations, as required by the UK’s Maritime and Coastguard Agency (MCA) for many of the vessels which comply with their Codes of Practice. Alternatively for RCD compliance the boat may need to be assessed against the ISO 12217 Standard on Stability and Buoyancy.
I can carry out all the stability evaluation work necessary for you to gain the required certification for your yacht, motor cruiser, workboat, fishing vessel or large yacht. This work is likely to involve a study of the design drawings, a practical inclining test at small angles of heel, computer simulations of the vessel undergoing large angles of heel up to 90 or 180 degrees, plus careful consideration of the loading conditions of the vessel in service. In some cases the work will also involve an assessment of the damage survival characteristics of the craft to ensure that an appropriate level of safety is maintained when any of the watertight compartments are flooded as a result of hull damage. By simulating the effects of flooding or hull damage it is also possible to make recommendations for any improvements that are needed to the subdivision of the vessel.
Should it be necessary, all the information on the vessel’s flotation, stability and trim for a range of loaded, unloaded and other service conditions can be compiled as a Stability Information Booklet for submission to the appropriate authorities. One such Stability Booklet was produced for a beautiful one hundred year old Bristol Channel Pilot Cutter (top left) to enable her to be approved for operation as a charter yacht under the MCA Code of Practice for the Safety of Sailing Vessels in Commercial Use, known as the “blue code”.
Another Stability Booklet, produced for a 37‘ sailing catamaran, involved the creation of a 32-surface computer model (left) from the original designer’s paper drawings, extensive calculations and an inclining test carried out afloat. Similar work is also performed regularly for motor boats where the owner wishes to gain certification for the vessel under the MCA “yellow code” or for larger sailing and motor boats under the “large yacht code”. The photograph at the bottom shows an inclining test on a 31’ Survey Vessel being carried out as part of the MCA requirements for a certificate under The Code of Practice for the Safety of Small Workboats and Pilot Boats - also known as the “brown code”.
New MCA Code - The Small Commercial Vessel & Pilot Boat Code of Practice
The MCA have now finalised the harmonisation of the four Small Commercial Vessel Codes (known as the yellow, blue, brown and red codes) into a single code book covering all small commercial vessels including pilot boats. Part of this new regulation, covering subdivision, damage survivability and intact stability was issued in November 2003 as Marine Information Note MIN 153 and put into use for stability assessment. Later the new code was issued under Marine Guidance Note MGN 280(M) see Codes Newsletter on MCA web site.
Any vessels previously requiring stability assessment under one of the four colour codes can now be assessed using the new SCV code, which derives its standards from both previous codes and the ISO standard 12217. This link with the ISO standards and the RCD means that there is a route to commercial vessel certification for new recreational craft which comply with the ISO 12217 stability standard. I have been working with MIN 153 since November 2003 and with MGN 280 since the beginning of 2005. This work involved assessing the intact and damage stability of new and existing designs using both the MCA and ISO 12217 criteria for approval, so that the owners could operate their boats in the charter and commercial markets.
I can carry out all the stability evaluation work necessary for you to gain the required certification for your yacht, motor cruiser, workboat, fishing vessel or large yacht. This work is likely to involve a study of the design drawings, a practical inclining test at small angles of heel, computer simulations of the vessel undergoing large angles of heel up to 90 or 180 degrees, plus careful consideration of the loading conditions of the vessel in service. In some cases the work will also involve an assessment of the damage survival characteristics of the craft to ensure that an appropriate level of safety is maintained when any of the watertight compartments are flooded as a result of hull damage. By simulating the effects of flooding or hull damage it is also possible to make recommendations for any improvements that are needed to the subdivision of the vessel.
Should it be necessary, all the information on the vessel’s flotation, stability and trim for a range of loaded, unloaded and other service conditions can be compiled as a Stability Information Booklet for submission to the appropriate authorities. One such Stability Booklet was produced for a beautiful one hundred year old Bristol Channel Pilot Cutter (top left) to enable her to be approved for operation as a charter yacht under the MCA Code of Practice for the Safety of Sailing Vessels in Commercial Use, known as the “blue code”.
Another Stability Booklet, produced for a 37‘ sailing catamaran, involved the creation of a 32-
New MCA Code -
The MCA have now finalised the harmonisation of the four Small Commercial Vessel Codes (known as the yellow, blue, brown and red codes) into a single code book covering all small commercial vessels including pilot boats. Part of this new regulation, covering subdivision, damage survivability and intact stability was issued in November 2003 as Marine Information Note MIN 153 and put into use for stability assessment. Later the new code was issued under Marine Guidance Note MGN 280(M) see Codes Newsletter on MCA web site.
Any vessels previously requiring stability assessment under one of the four colour codes can now be assessed using the new SCV code, which derives its standards from both previous codes and the ISO standard 12217. This link with the ISO standards and the RCD means that there is a route to commercial vessel certification for new recreational craft which comply with the ISO 12217 stability standard. I have been working with MIN 153 since November 2003 and with MGN 280 since the beginning of 2005. This work involved assessing the intact and damage stability of new and existing designs using both the MCA and ISO 12217 criteria for approval, so that the owners could operate their boats in the charter and commercial markets.
Yacht & Powercraft Design Services Ltd
Email: info@yacht-designer.co.uk
Tel. 44 (0) 1489-583346 Fax. 44 (0) 1489-583346 Mobile 07803-724317
Email: info@yacht-
Tel. 44 (0) 1489-
