Twelve Metre Class Rule Stability

by David Pedrick

David PedrickThe Class Rule for Twelves has changed very little since the time of the America’s Cup Jubilee in Cowes in 2001. The major change made prior to that event was Appendix E, created to categorize older yachts and grant rating credits for design obsolescence with age, including generational changes in appendage configuration. A Propeller Allowance was also created to give partial credit for the hydrodynamic drag of the propeller installation and the compromised weight distribution from the engine.

Prior to the 2001 Rule, the contents of the 1985 Rule for the final America’s Cup regatta in Twelves was substantially reorganized in 1994 and issued for the NYYC’s Sesquicentennial Regatta. The text format of the Rule has remained essentially unchanged since then, other than adding Appendix E in 2001.

Between 2001 and 2013, the principal Rule change was in sail materials for the Classics. Initially, Division C was defined solely as having a keel-hung rudder, with sub-divisions of C1 for post-WW II, C2 for pre WW II (under Rules 3 and 2), and C3 for the first Rule, gaff-rigged. The sail material specification for all of Division C had a maximum fiber modulus of 250 grams/denier. For reference, the modulus limit in the main Rule was 1000 gm/den, suitable for laminated Kevlar sails.

The Rule change voted earlier this year raises the permitted fiber modulus in the general Rule for Divisions A and B (Winged Keel and Modern) to 1550 grams/denier, proposed originally at 1400 gm/den. This allows the use of materials that have become more common generally in high-performance racing, notably carbon fiber.

Meanwhile, back in 2004, sail materials for the entire Classic Division C were restricted to be even more elastic, requiring woven construction and a maximum fiber modulus of 120 grams/denier, effectively limiting such sails to woven Dacron. The Rule declared the end of all use of existing 250 gm/den sails after 2004. This conservatism seems to have been driven by cost concerns within the Newport fleet.

However, the Northern European Fleet was quite happy with the 250 gm/den specification, and continued to build sails with materials and construction that had been allowed before 2004 by preference and without problems. This interest was confined to Division C2 (pre-WW II) – later changed to Division D, within which most of the active racing European yachts belong.

The 2011 revision of the Rule kept the woven-sail, 120 gm/den limitation for the newly designated Divisions C (post-WW II) and E (Rule 1 gaffers), and continued to accept the 250 gm/den fiber modulus for Division D, but in a peculiar way. It permitted the 250 gm/den modulus only for sails that had been measured before 2008 – an anomaly that was waived by fleet choice in European regattas. This was resolved in 2013 by eliminating the grandfather restriction.

Meanwhile, Classic Twelves in Divisions C and E are still limited to the woven-sail, 120 gm/den modulus limit from the 2004 Rule, while Division D has the 250 gm/den limit that was confirmed in 2013. It seems incongruous for Division C to require more elastic sails than Division D, inviting discussion about revising this for consistency with Division D before hosting the World Championship regatta in 2019.