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A boomkin on the HMS Surprise (in center of image)

A boomkin, sometimes referred to as a bumkin or as a bumpkin, consists of an exceptionally strong and usually wooden spar that projects forwards and often (though not always) downwards over the main head-rail of a traditional western sailing ship, one on either side of the vessel (not to be confused with cathead). The heel of this spar is usually either butted against a knighthead or is bolted to it (bolting being more common from the end of the 18th century forwards). The outboard end of such a spar is designed with a neck to hold a single purchase block through which the tack is passed.On modern sailing yachts, the term boomkin is used to refer to a spar extending aft from the stern of the boat which has a long main boom. The backstay is attached at the end of the boomkin[1]

History of development[edit]

From 1710 until 1850 the development of the boomkin in English sailing vessels generally proceeded thus:[1]

  • 1710-1730 CE: The first boomkins were usually square in cross section, and were generally only 6 feet (1.8 m) to 8 feet (2.4 m) in length. Their width was standardized at one inch per foot of length (a ratio of 1:12) and this was uniform throughout their length (that is, they did not taper at either end).
  • 1730-1780 CE: Four changes in the shape of the boomkin took place during this time frame. It was lengthened, its inboard end was turned into an octagon in cross section rather than a square, its outboard end went from a square to a circle, and it began to taper somewhat so that it was 3/4ths its initial diameter at the tip.
  • 1780-1805 CE: The only significant change during this time frame was that the boomkin often became circular in cross section from beginning to end.
  • 1805 CE: From this date onward the inboard end was generally bolted to the knighthead and was made half-round in cross section. Also, an iron band was now introduced which could hold eyelets for the boomkin shrouds, usually three in number.
  • 1825 CE: At around this time the boomkin regained its entirely rectangular cross section shape, and was usually one inch wider than it was high. It also gained an additional eyelet for the securing of a slip.

Over time the use of boomkins was extended to the stern of the ship as well to provide an attachment point for a backstay or the sheet of a mizzen.


  1. ^ a b Goodwin, Peter G. (1987). The construction and fitting of the English man of war, 1650-1850. London: Conway. pp. 223–225. ISBN 0-87021-016-5.