In answer to Lipton's challenge of 1929 the Americans designed four J-Class yachts as possible defenders. Enterprise, Whirlwind, Yankee and Weetamoe were launched within a month of each other; Weetamoe and Enterprise from the Herreshoff yard and Yankee and Whirlwind from Lawley & Son's yard in Bristol. Whirlwind, the second J, was the most revolutionary of the four. Francis L Herreshoff had moved away from conventional yachts and designed a boat, which took the new rule to its extreme. Whirlwind combined many new ideas and Herreshoff experimented with hull shape and rig. She was the longest of the early J's at 86ft on the waterline and remained so until Ranger and Endeavour II were built in 1937. She was built of semi-composite construction (the other three American Js were built out of the highly expensive Tobin bronze), was double-ended and had a permanent backstay.