History of the anchor
Until the beginning of the 19th century anchors were of imperfect manufacture, the means of effecting good and efficient welding being absent and the iron poor, whilst the arms, being straight, generally parted at the crown, when weighing from good holding-ground. A clerk in Plymouth Yard, named Pering, in the early part of that century (1813) introduced curved arms; and after 1852 the British admiralty anchor, under the direction of the Board, was supplied to H.M. ships, followed by Lieutenant ("afterwards Captain") Rodger's anchor. Rodger's anchor marked a great departure from the form of previous anchors. The arms were formed in one piece, and were pivoted at the crown on a bolt passing through the forked shank. The points or pees to the palms were blunt. This anchor had an excellent reputation amongst nautical men of that period, and by the committee on anchors, appointed by the British admiralty in 1852, it was placed second only to the anchor of Trotman.
Later came the self-canting and close-stowing Martin anchor, which, passing through successive improvements, became the improved Martin anchor made of forged iron. A projection in the center of the arms works in a recess at the hub of the shank; the vacancies outside the shank are filled by blocks bolted through on each side, and are flush with the side plates, which keep the flukes in position.
The introduction of cast steel in 1894 led to the improved Martin-Adelphi pattern, in which the crown and arms are cast in one, and, with the stock, are made of cast steel, the shank remaining of forged iron. A projection in the crown works in a recess (right image), and is secured in its place by a forged steel pin, fitted with a nut and washer, which passes through the crown and the heel of the shank.
Anchor
So named due to its resemblance to a traditional agricultural plough. Many manufacturers produce a plough-style design, all based on or direct copies of the original CQR ("Secure"), a 1933 design patented in the UK (US patent in 1934) by mathematician Geoffrey Ingram Taylor. Ploughs are popular with cruising sailors and other private boaters. They are generally good in all bottoms, but not exceptional in any. The CQR design has a hinged shank. Despite the widely held belief that this is to allow the anchor to turn with direction changes rather than breaking out, the actual purpose is to prevent the weight of the shank from negatively impacting the fluke's orientation while setting. Other plough types have a rigid shank. Plough anchors are usually stowed in a roller at the bow.