By gaining the first two races for the America’s Cup in 1920, Shamrock IV needed only one more race to win. In the design of his first challenger Charles E. Nicholson produced a bulb-keel skimming dish of an extreme form and elaborately unusual construction, with mainly triple-skin wood planking and longitudinal framing, reinforced by widely spaced steel-web transverse frames.
Though the two headsail rig was often carried, a single headsail with a club along its foot was set sometimes, as may be seen in the photograph. The toprnast was socketed into the lower.