The J-Class was developed by Nathanael Herreshoff” as Universal Rule for racing boats. Two years after it was agreed between Britain and America that the Universal Rule would be used for large boats, where the International Rule would be used for 12mR boats and smaller. As a result, the 1930s America’s Cup races were all fought in the J-Class.
The J-Class was adopted for America’s Cup competition in 1928, looking forward to the next regatta in 1930. The Class itself, though, dated back to the turn of the century when the Universal Rule was adopted.
The Rule used a yacht’s various dimensions to calculate an equivalent rating in feet. Boats of equal rated lengths could then race against each other directly without making other allowances for time or distance sailed. Even though one yacht might have a longer length or another yacht a larger sail area, their overall configurations had to produce a rated length that met the Universal Rule for that class. J-Class yachts were the largest constructed under the Universal Rule. The Rule actually includes provisions for an even larger type of boat, the I-Class, though none were ever built. Inquiries made in the 1930s for a Defense in the smaller K-Class were rejected.
The J-Class were the first yachts in an America’s Cup match to be governed by a formal design rule. Previous defenders and challengers were only restricted by minimum and maximum lengths set forth in the Deed of Gift. Sir Thomas Lipton, challenging in 1930 for the fifth time, had held earlier discussions with the New York Yacht Club in hopes of adopting the Universal Rule for the previous America’s Cup match, intended for 1914 but delayed until 1920. Though an agreement to use the rule was not reached for that match, the 1914 boats, Vanitie and Resolute, still roughly followed J-Class parameters
There were only 10 J-class yachts designed and built. Additionally, several yachts of closely related dimensions, mostly 23-Meter International Rule boats, were converted after their construction to meet the rating rules of the J-Class.
Only the purpose-built Cup yachts, though, could compete in the America’s Cup. The “converted” J-Class yachts, while acceptable for Class racing events, were not admissible for America’s Cup competition. Responding to issues that surfaced in earlier defenses, the America’s Cup rules required that all boats had to be sailed to the event on their own bottom. Some critics pointed out the possibility that the challenger might, as a result, be disadvantaged by being of heavier construction than the defender. In order to avoid a situation that could be perceived as an undue advantage, the NYYC eventually agreed that all America’s Cup J-Class yachts would be built to Lloyds A1 standards, ensuring that defender and challenger met the same minimum construction specifications (the nautical term is “scantlings”). Most existing yachts were not built to such standards, so the Cup-eligible boats thus ended up heavier than the ineligible J’s.
(The issue of challengers having to build heavier boats due to the ocean crossing was a popular, if uncertain, explanation in the British press for the long string of American victories. In practice, a number of challengers added internal bracing for the crossing, which was then removed before racing. And on a few occasions defenders subsequently made the crossing in reverse in search of competition following their successful defense. The rule requiring that the challenger sail to the event on her own bottom was actually instituted in response to a super-lightweight challenger towed to the match through canals and rivers from Canada. )