Technically, IRC does not officially stand for anything. Originally, “IR” was an abbreviation for International Rule. However, since the Rule at that stage was not recognized under International Rule (sailing), that name was not permitted. So RORC simply decided to keep the initials as the name, and even after IRC received International Rule recognition, the name remained simply IRC.
The IRC rule is not published, meaning the only bodies capable of calculating an IRC rating are the RORC Rating Office and UNCL Centre de Calcul in Paris (they are joint owners of the Rule). This prevents designers from attempting to design 'to the rule'. The earlier IOR was published, and often amended, resulting in widespread criticism for several reasons. Firstly, as the rule effectively dictated the nature of boat designs, amendments to the rule could result in older designs gaining less favourable ratings compared to their real world speed, making racing competitively more expensive. Also, the pressure to produce designs which performed well under the rule resulted in designers producing yachts with certain dimensions intentionally extreme, in order to gain an unfairly favourable rating. The production of yachts which were excessively light and beamy - what became the classic 'diamond' plan form of the IOR - was believed to impact safety, and was cited as a factor in the 1979 Fastnet race disaster. In theory, the IRC avoids these problems.
An IRC yearbook is made available at the beginning of January each year to holders of certificates from the previous year together with a rating revalidation form. Apart from the IRC rule, the yearbook provides help to owners applying for their certificates by way of diagrams and definitions, race management recommendations, useful names and addresses, articles from invited authors and much other relevant information.
IRC can apply a rating to any mono-hull yacht. It considers such features as asymmetric spinnakers, carbon masts, canting keels, and water ballast, all of which have been permitted for several years. Furthermore, the rule is reviewed annually in light of new developments and past results. On this front, RORC seeks and actively welcome input and comment from the users.
IRC permits and encourages owner declared measurement data: self measurements. These will be maintained for the future, although some clubs and areas have always insisted that locally they should measure boats.
There are endorsed IRC ratings which require any sailing club, working under the auspices of the RORC, be satisfied as to the correctness of the rated data, generally by measurement by appointed measurers. Race Committees may require endorsed certificates for some events. Also, an IRC measurement manual is available on request to assist with local measurement if required.
Boat classes/models for which IRC Standards have been set in terms of LOA, overhangs, empty weight, beam and draft measurements only. Upon applying for base ratings (non-endorsed), one may elect to have standard overhang dimensions and a class weight used towards their IRC Ratings. Racers then need to submit rig, sail, ... to complete the application process. These standard overhang and displacement values reference the lightest boat in class.
IRC Rule and the information contained here is published with permission from the RORC Rating Office & Seahorse Rating Ltd. For additional information please visit http://www.rorcrating.com
IRC was essentially a rename of the Channel Handicap System (CHS) which was started in 1984 by RORC and UNCL. IRC came, in the early 2000s, to largely overtake the earlier IMS handicapping system. However, as of 2008 there is some movement globally for a new improved version of IMS, known as the ORC rule, to return to favour with racing clubs.