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    Changes to boats - Keeping Legal

    The Rating Office regularly receives questions concerning compliance with IRC Rules. We also often hear anecdotally that boats are (generally inadvertently) infringing IRC Rules.

    Here are a few commonly recurring issues to help you keep legal.

    Change of ownership
    • On change of ownership of a boat with a current IRC certificate, the certificate is automatically invalidated and the new owner must apply for re-registration.
    Similarly, while the boat may come with a full inventory of overlapping headsails, the boat may not be rated for the largest of these. Or it may be rated for a single furling headsail. Please check.

    Crew number and crew classification

    With effect from 2013, the default option is now that crew are limited by weight in kilograms calculated as IRC Crew Number multiplied by 85.
    • Unless therefore, as permitted by Rule 22.4.3, a Notice of Race says something different, then crew weight limitations will be in force.
    A Race Committee may, of course, amend this in its Notice of Race. Similarly, there are no restrictions on crew classification, again unless invoked by Notice of Race. For these issues, therefore, boats need to refer to Notices of Race.
    • IRC Crew Number is not variable by a boat and has no effect on TCC

    Changes to Boats
    • IRC Rule 8.9 notes that physical changes which might affect the performance of the boat shall be declared and may invalidate the rating certificate.
    Apart from obvious changes to rated data, sail dimensions, keels, rudders, etc, this also includes removal of furniture, internal ballast (removal or re-locating) or any other fixed item aboard the boat when she was weighed, measured, or on which the rating has been based. Additionally, Rules 22.1 and 22.2 specifically address fit out noting that Hull Factor may be affected by any changes.
    • So, removal of, for instance, the saloon table, doors, floorboards, locker doors, watermakers, galley units, or any other fixed item, is not permitted without first reporting the change to the Rating Office and requesting an amended certificate.
    In a similar vein, each boat’s IRC rating certificate notes whether the empty weight includes bunk cushions and batteries. If these are noted as included, then they must be carried, unless the Notice of Race permits removal of the bunk cushions as allowed by Rule 22.1.2.
    • ‘Loose’ items (bunk cushions, bunk boards, etc) aboard the boat when she was measured must be carried in their normal positions when racing.
    Adding a stern scoop or bathing platform will not only change Hull Length and overhangs, but also Age Date.
    Other changes which sometimes get forgotten: fairing creases/ bumps on IOR boats, fitting a new rudder, removing or changing the skeg, selecting an optional carbon rudder; adding more batteries.
    • We recommend checking with IRC-SEA before making substantial changes, and it is usually wise to run a trial certificate to explore rating effects.

    SAILS: If you have an IRC certificate or about to renew it, and you get some new sails built to exactly the same size as on your currentor last valid certificate, you must declare these.

    Any new sails that will be the largest used when racing must be declared, even if they are designed to be the same size as the last valid IRC certificate. If your certificate is Endorsed then those new sails must be officially measured by someone approved by the Rule Authority.

    Furling headsails

    Probably the most commonly ‘misunderstood’ IRC rule is Rule 21.8, Furling Headsails. Based on your application for rating, the Rating Office will determine your eligibility.

    • It is then your responsibility to comply while racing. 
    • Please see a seperate document in our downloads section for further details: Headsail Furling Allowance.pdf

    Sail inventory

    Rule 21.1.5 summaries the limitations on sails that may be carried.

    A particular point, often ‘misunderstood’ is the restriction in paragraph (d) of this Rule on changing sails during a regatta run on consecutive days. Paraphrasing this: the sail inventory that you carry for the first race is then the inventory for the whole regatta.

    So, no leaving the heavy sails ashore on light days and vice versa, swapping spinnakers for different weather or course conditions, changing to an ‘offshore’ mainsail, etc.

    The only exception to this is significant damage. Unless stated in a Notice of Race, there is no formal requirement to seek approval for a change of inventory after damage. A prudent skipper might nevertheless wish to advise the Race Committee to avoid potential future problems.

    We are sometimes advised by owners that they carry fewer than three spinnakers. IRC Rule 21.6.1 is clear that there is no rating credit for this, but that boats carrying more than three must declare this.

    One valid certificate only

    Rule 8.2 now says: A boat shall not hold more than one valid IRC rating certificate at any time except as permitted by Rule 8.2.1.

    Rule 8.2.1 then describes a short-handed IRC certificate. It is thus now possible to hold more than one certificate at a time BUT the second one may only be used for short-handed (ie maximum of two crew) races. It is still NOT permitted to hold a number of certificates and to pick the best one for the conditions of a particular race.

    Non spinnaker TCC

    Certificates include a second, non spinnaker TCC for all boats normally rated to use a spinnaker. This second TCC is only valid for races for which the Notice of Race includes a non spinnaker class.

    • What is definitely NOT permitted is calling up the Race Committee 10 minutes before the start of a windy race asking them to use the non spinnaker TCC!


    Mast and boom black bands

    In the absence of black bands on the mast and boom, IRC definitions of P and E say that P is measured to the bearing surface ofthe halyard shackle and E to the aft end of the boom. If you do not have bands clearly and permanently marked, that is what a measurer will do. Which will not help your TCC.

    • So, get out the paint brush or the magic marker (NOT tape), hoist the main fully, pull the clew out as far as it will go, and mark the bands.

    Please also note that P and E are rig dimensions, NOT sail dimensions. So, getting your sailmaker to measure the luff and foot of your mainsail will not help. It is the limiting dimensions of the rig that are needed. And remember, you cannot set your mainsail outside those P and E limits!

    Accuracy of rated data

    Rule 9, Rating Review, is explicitly clear that this Rule does not apply to equipment inspection (ie check measurement) at an event.

    Rule 8.10 lists rated data parameters which are maxima and those which are minima and then clearly states that when a boat is inspected and data is found to exceed a maximum or to be less than a minimum, then the boat is not in compliance with her certificate. 

    Notices of Race

    It is important to read the Notice of Race for an event carefully so as not to miss details, including but not limited to Rating Deadlines and Endorsement.

    If there is a deadline for rating changes it will be published in the Notice of Race, so do check this and comply with it. The Rating Authority may refuse to issue an amended certificate if there are suspicions that it is to take advantage of a particular weather forecast; and remember that at busy periods ratings can take up to a week to issue even with the Expedited (‘fast track’) fee.

    It will also be stated in the Notice of Race if an Endorsed IRC Certificate is required. This is often missed or ignored, resulting in a last-minute panic to get boats weighed or measured.


    • Please check the NoR as soon as you get it, and if you need an Endorsed certificate and do not have one then contact us at

    The full version of the IRC Rule is available in the Downloads Section of this site. A Simple Version is also available, however it is not comprehensive and intended as a guide only.


    References (8)

    References allow you to track sources for this article, as well as articles that were written in response to this article.
    • Response
      Aside from clear changes to evaluated information, sail measurements, keels, rudders, and so on, this additionally incorporates evacuation of furniture, interior counterweight or some other settled thing on board the vessel when she was weighed, measured, or on which the rating has been based.
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