Thirty years ago in 1988 the Channel Handicap System, now named IRC, introduced its own Safety and Stability Screening (SSS) system to help race organisers decide on a boat’s suitability for a race from a stability perspective. All IRC rated boats still have a calculated SSS value printed on the certificate, with a higher number indicating a more seaworthy boat.
The SSS value was never a pure ‘stability’ factor and CHS/IRC has never directly measured stability and avoids expensive inclining tests. The SSS calculation includes factors derived from principal dimensions and design characteristics that influence stability. One of the Rating Office Directors used to describe it as “How well would this boat take care of its skipper and crew in the event of an emergency?”.