The majority of cruising and racing yachts at FSC race in Q or U class. Both of these classes are 'dual'-scored with IRC ratings and Byron (By) Numbers.


IRC is a rating rule to handicap different designs of keelboats allowing them to race together; unlike a performance handicap a rating is not altered between races according to the individual boat's performance, but is based on the physical measurements of the boat.

An IRC rating is calculated by RORC (Royal Ocean Racing Club) using measurements of the boat; her length, weight, draft, rig size, sail area, and specific characteristics and features. The methods and formulæ used for the calculation of IRC ratings are not published. This prevents designers taking advantage of the rule when designing new boats and very substantially increases the competitive lifetime of IRC rated boats.

IRC is not an acronym, the letters don't stand for anything!


Byron (By) is an attempt to emulate the now-defunct (but much loved) RYA Portsmouth Number handicap. Like an IRC rating it takes a number of measurements from the boat, cranks the handle, and out pops a handicap. The original thinking was that it allowed incomers who may not have an IRC rating to take part in racing until they obtain one. In reality some, especially in U class, just race under Byron.

To find out what your Byron handicap would be, consult the list. Alternatively, Byron Software will calculate a handicap for you, on completion of an online form. And if you make a small donation, the results will come back quickly.

In the published results, the Rating system will be shown as PY rather than By. This is a feature of the scoring software that we use where it is hard wired into the published form. Since the formulæ for calculating finish times from By and PY are identical (only the handicap changes) nothing untoward is going on (honest).

Handicaps in Q and U classes

These are the latest IRC and By ratings available. IRC certificates are issued annually. The formula is tweaked slightly (doubtless in some smoke filled room) and the rating changes, although usually only by a small amount. Byrons don't change, unless the configuration changes (and you tell us).

A list of all Q class who are currently registered to race at FSC together with their IRC and Byron handiaps (where available) is available here. A corresponding list for U class is here

Mel Sharp

Q class captain: Mel Sharp

Mandy Owens

U class captain: Mandy Owens

IRC logo
Q start line
finishing with spinnakers