|America's Cup Racing Yachts
Evolution of a Design - The Magnificent J-Class
W. Starling Burgess & Owlin Stephens' J-Class Ranger
Although they became recognized the most beautiful yacht design in the World, only 10 J-Class yachts were ever built - 6 in the USA and 4 in the
UK. Most of these competed in trials for the America's Cup, or competed in the Cup itself. Other yachts (pre J-Class) were converted to meet the
rule requirements. http://www.jclassyachts.com/history.html.
Name Built Designer AC Role LWL LOA Beam Draught Disp't SA
Enterprise US 1930 W. Starling Burgess 1930 Defender 80ft 120ft 9in 23ft 14ft 6in 128 tons 7583
Whirlwind US 1930 L. Francis Herreshoff 86ft 130ft 21ft 9in 15ft 6in 158 tons 7335
Yankee US 1930 Frank Paine 83ft 126ft 22ft 6in 14ft 6in 148 tons 7288
Weetamoe US 1930 Clinton Crane 83ft 125ft 9in 20ft 15ft 143 tons 7550
Shamrock V UK 1930 Charles Nicholson 1930 Challenger 81ft 1in 119ft 1in 20ft 14ft 9in 134 tons
Velsheda UK 1932 Charles Nicholson 83ft 127ft 6in 21ft 6in 15ft 160 tons 7541
Endeavour UK 1934 Charles Nicholson 1934 Challenger 83ft 6in 129ft 6in 22ft 14ft 9in 143 tons
Rainbow US 1934 W. Starling Burgess 1934 Defender 82ft 127ft 6in 21ft 15ft 141 tons 7535
Ranger US 1937 Burgess & Stephens 1937 Defender 87ft 135ft 21ft 15ft 166 tons 7546
Endeavour II UK 1936 Charles Nicholson 1937 Challenger 87ft 135ft 6in 21ft 6in 15ft 162 tons
where R = rule length (76 ft), L = LWL (ft), S = Sail area (sq-ft), D = Displacement (tons)
The J-Class had a maximum rating of 76 feet and a maximum allowable waterline length of 87 feet. During the 1930s, it was found that the
longest-waterline boats were the fastest. Both Ranger and Endeavour II were built to the maximum waterline length of 87 feet. Owlin Stephens
undertook a model-testing program during the development of Ranger. The models were given design numbers 77-A through 77-F, and 77CE.
While the models all had 87-foot waterlines, they had different beams, displacements, longitudinal centers of buoyancy, prismatic coefficients and
wetted areas. As with modern America's Cup Class yachts, the J-Class designs were optimized for the conditions they were expected to sail under.
The final lines for Ranger were derived from model 77-C which was believed to be the best suited for racing off Newport, RI (where the America's
Cup races were held from 1920 through 1983) where summer winds are light and seas relatively small. Ranger's final lines were modified from the
model 77-C lines most noticeably in the 'hooked bow' that can be found on the 1937 America's Cup winner.
The J-Class was based on the American Universal Rule which took into account length, sail area and displacement. Roughly,
R = 0.18 L square-root(S)/cube-root(35D)
Ranger J5 in