Every boat of a World Sailing Class shall carry on her mainsail and, as provided in rules G1.3(d) and G1.3(e) for letters and numbers only, on her spinnaker and headsail
the insignia denoting her class;
at all international events, except when the boats are provided to all competitors, national letters denoting her national authority from the table below. For the purposes of this rule, international events are World Sailing events, world and continental championships, and events described as international events in their notices of race and sailing instructions; and
a sail number of no more than four digits allotted by her national authority or, when so required by the class rules, by the class association. The four-digit limitation does not apply to classes whose World Sailing membership or recognition took effect before 1 April 1997. Alternatively, if permitted in the class rules, an owner may be allotted a personal sail number by the relevant issuing authority, which may be used on all his boats in that class.
Sails measured before 31 March 1999 shall comply with rule G1.1 or with the rules applicable at the time of measurement.
National letters and sail numbers shall be in capital letters and Arabic numerals, clearly legible and of the same colour. Commercially available typefaces giving the same or better legibility than Helvetica are acceptable.
The height of characters and space between adjoining characters on the same and opposite sides of the sail shall be related to the boat’s overall length as follows:
Minimum space between characters and from edge of sail
Under 3.5 m
3.5 m - 8.5 m
8.5 m - 11m
Over 11 m
Class insignia, national letters and sail numbers shall be positioned as follows:
Except as provided in rules G1.3(d) and G1.3(e), class insignia, national letters and sail numbers shall, if possible, be wholly above an arc whose centre is the head point and whose radius is 60% of the leech length. They shall be placed at different heights on the two sides of the sail, those on the starboard side being uppermost.
The class insignia shall be placed above the national letters. If the class insignia is of such a design that two of them coincide when placed back to back on both sides of the sail, they may be so placed.
National letters shall be placed above the sail number.
The national letters and sail number shall be displayed on the front side of a spinnaker but may be placed on both sides. They shall be displayed wholly below an arc whose centre is the head point and whose radius is 40% of the foot median and, if possible, wholly above an arc whose radius is 60% of the foot median.
The national letters and sail number shall be displayed on both sides of a headsail whose clew can extend behind the mast 30% or more of the mainsail foot length. They shall be displayed wholly below an arc whose centre is the head point and whose radius is half the luff length and, if possible, wholly above an arc whose radius is 75% of the luff length.
Other boats shall comply with the rules of their national authority or class association in regard to the allotment, carrying and size of insignia, letters and numbers. Such rules shall, when practicable, conform to the above requirements.
CHARTERED OR LOANED BOATS
When so stated in the notice of race or sailing instructions, a boat chartered or loaned for an event may carry national letters or a sail number in contravention of her class rules.
WARNINGS AND PENALTIES
When a protest committee finds that a boat has broken a rule of this appendix, it shall either warn her and give her time to comply or penalize her.
CHANGES BY CLASS RULES
World Sailing Classes may change the rules of this appendix provided the changes have first been approved by World Sailing.
Racing Rules of Sailing for 2013-2016; Version 6
Racing Rules of Sailing for 2017-2020
Great Britain - RYA has declined to grant a license for prescriptions and cases.