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
sq-ft
Whirlwind       US 1930   L. Francis Herreshoff                              86ft          130ft               21ft 9in     15ft 6in     158 tons    7335
sq-ft
Yankee           US 1930   Frank Paine                                            83ft          126ft               22ft 6in     14ft 6in     148 tons    7288
sq-ft
Weetamoe       US 1930   Clinton Crane                                         83ft           125ft 9in         20ft           15ft          143 tons    7550
sq-ft
Shamrock V     UK 1930  Charles Nicholson          1930 Challenger  81ft 1in      119ft 1in         20ft           14ft 9in     134 tons    
7540 sq-ft
Velsheda          UK 1932  Charles Nicholson                                   83ft          127ft 6in          21ft 6in     15ft           160 tons    7541
sq-ft
Endeavour       UK 1934  Charles Nicholson         1934 Challenger   83ft 6in      129ft 6in         22ft          14ft 9in      143 tons    
7561 sq-ft
Rainbow          US 1934   W. Starling Burgess      1934  Defender   82ft            127ft 6in        21ft           15ft           141 tons    7535
sq-ft
Ranger            US 1937   Burgess & Stephens      1937  Defender   87ft            135ft             21ft           15ft           166 tons    7546
sq-ft
Endeavour II   UK 1936  Charles Nicholson          1937 Challenger  87ft            135ft 6in        21ft 6in      15ft           162 tons    
7543 sq-ft
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
1937