For more than 5 years now, Working Group 22 of Technical Committee 188 of the International Standards Organization (ISO) has been developing a standard for the assessment and categorization of the stability of pleasure craft with a length up to 24 m. This work became necessary when the European Union decided to issue a Directive on Pleasure Craft, facilitating the export and import of pleasure craft to and from the various countries comprising the European Union. All newly-built pleasure craft up to 24 m in length, to be marketed in the European Union, must comply with the stability standard being developed, and some 50 other ISO standards, covering all aspects of structure, materials, equipment, etc, as of June 1998.
To support the work of Working Group 22, The Netherlands carried out a comprehensive study for Part 2 of ISO 12217, covering the stability of mono-hull sailing craft. Together with the French, Swedish and UK delegates, this work finally lead to the development of a single stability index. Working Group 22, in September 1996, unanimously agreed to adopt this concept for the assessment and categorization of the stability of mono-hull sailing vessels. This paper gives a description of some of the work that was carried out by the Netherlands in this regard and gives a description of the single STability Index (STIX) concept and the way the STIX value is determined from the various stability and buoyancy properties of sailing vessels.