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    See also Common Confusions (PDF excerpt from yearbook), extra information and *new* Jargon translated!

    What does IRC stand for?


    IRC does not officially stand for anything! Originally, “IR” was International Rule. However, as the Rule at that stage was not International, that name was not permitted. We simply decided to keep the initials as the name, and even after IRC received International recognition the name remained as simply IRC.Some people do call it International Rule ‘Club’, but it is not our published name.

    For how long is my certificate valid?


    All Thailand Issued IRC certificates expire on 30th May (as printed on the certificate). You will be invited to renew your certificate when it has expired.


    Can I hold more than one valid certificate for different configurations?

    No, except in the case of ‘short-handed’ certificates, see Rule 8.2.

    Why are the rating formulae not published?


    We believe the confidentiality of the IRC formulae is it’s main strength. It helps to prevent designers and builders producing boats specifically to ‘cheat’ the rule, thereby disenfranchising the existing designs for which IRC was created to cater.

    My boat had an IRC rating in the last 2 years, do I need to complete the whole new form?

    No, please contact your irc-thailand for a revalidation form.

    My boat hasn't had a rating for a few years but I want to get a current one. What do I need to do ?

    Contact irc-thailand with details of the boat and we will let you know what we require and send you the relevant forms. For boats last rated more than 2 years ago we usually require a new application form completed.

    I've just bought a boat which has a current rating – do I have to do anything?

    Yes. The IRC certificate is invalidated by change of ownership, so you need to re-register the certificate. Some check measurement may be required.

    Do you hold standard data for designs?

    We hold complete data for IRC one-designs and standard hull data for many designs: contact your authority. For non-OD boats we always require actual rig and sail measurements.

    My boat has held an IMS/ORCi certificate - can I get all the information off that ?

    Yes, except: bow and stern overhang, y,h,x; LL & LLmax, FL. Please send a copy of the latest certificate and p.2 Measurement Inventory with your application.

    Does my boat have to be weighed and/or measured by an official measurer?


    No, unless you require an Endorsed certificate (see below), or your local Rule Authority or race organiser requires boats to be weighed/measured.

    What is an Endorsed certificate?

    An ‘endorsed’ IRC certificate is one for which the data on the certificate has been audited and if necessary verified by measurement or other methods. The 2005 IRC Congress agreed that a set of common standards for the IRC Rating Authority and Rule Authorities to apply when endorsing a boat’s IRC certificate should be developed and published. See also “Accepted sources of data

    Generally, IRC is a self-measurement system. There is thus no general requirement for an owner to have his boat officially measured or weighed unless either he chooses to do so, or his Rule Authority (ie his local IRC body) and/or an Organising Authority for a race requires official measurement, generally resulting in an endorsed IRC certificate.

    To apply for an Endorsed certificate contact your local Rule Authority. A payment may be involved.


    Check measurement may be required on change of ownership or at intervals after original measurement.

    Do all sails need to be measured, or only the largest ones?


    The largest ones, plus the longest luff length of any headsail and the largest headsail headboard.

    What changes on my boat need to be declared to the Rating Office?


    Any changes which may affect the performance of the boat (see rule 9.6 & 27.1.)

    Can I remove items like the saloon table?

    If items are removed, which are either standard on a production boat, or were included in the previous certificate, then this must be declared and may affect the rating. Removing table, doors, etc. will increase hull factor; we try to discourage this practice. See rules 22.1 & 22.2.1.

    How can I see what affect changes I want to make might have on my rating?

    You can run up to 6 trial certificates; these are not valid for racing. See limitations and conditions published on our website.

    I need to amend some measurements / I want to run a trial certificate, what should I do?


    Download the amendment/trial form from our website, complete and return to your Rule Authority with payment details.

    How do I get a copy of another yacht's certificate?


    Copies of any other boat’s certificate can be purchased for £10. However, please see limits published on our website.

    Can I see what measurement data was submitted for another yacht?


    Only the measurements and data shown on the IRC certificate are publicly available, by buying a copy of their latest certificate.

    How is age allowance applied?


    Age allowance is calculated and applied to the TCC automatically after 3 years. Age allowance uses the average of the series and age dates in it’s calculation.

    Will my rating be the same each year? Why has my rating changed from last year even though my boat hasn't?


    Your rating may go up, down or stay the same from year to year, depending on how it is affected by program changes. It will not automatically go down each year due to age allowance, although this is an integral part of the TCC calculation. IRC is a ‘live’ rule. By this we mean that the maths behind the calculation of TCC is continually adjusted on an annual basis to reflect changes in design, sailing practice, etc. The changes affect generic types and characteristics, not individual boats or designs.

    Why is my rating higher than a sistership's?


    Ratings are based on rated data; therefore any difference in measurements or other details may affect the rating.

    My boat doesn't have a proper sail number - does it matter?


    Yes, IRC rated yachts must have an approved sail number, in the UK you should contact RORC, the RYA or the Clyde Yacht Clubs Association. If overseas, contact your local Rule Authority.