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).

Boat Name Boat No IRC By Class
Aries 737 1078 U
Atalanta 9567 0.887 964 Q
Aurora 719 0.785 1078 U
Deep Purple 6226 1035 U
Encore 1663 0.919 912 Q
Excelle 4462 0.912 931 Q
Gap Year 705 0.778 1078 U
General Khaos 9233 0.970 940 Q
Ida 265 1094 U
Jackdaw 4243 1.047 810 Q
Kaimana 1152 0.840 1009 U
Les Beez Neez 11230 0.834 1030 U
Mary Boon 1202 0.771 1115 U
Minx 6902 0.937 905 Q
Moonshine 5780 953 Q
Popincoota 7170 1009 U
Scorpion 5592 0.891 980 Q
Temeraire 5508 0.911 930 Q
a little Trifle 8198 0.823 1039 U
Wilkie 7268 0.831 1034 U
Mel Sharp

Q class captain: Mel Sharp

Mandy Owens

U class captain: Mandy Owens

IRC logo
Q start line
finishing with spinnakers