The Admirality Pattern, Stocked or Common Anchor
This anchor is illustrated in fig together with the names of the various parts. It is fitted with a stock, which should be of an approved design and weigh one-quarter of the specified weight of the remainder of the anchor. It is renowned for its excellent holding qualities, and even today some designs of patent stockless anchors are no more efficient, so far as holding properties are concerned, than the common anchor of one hundred years ago, assuming anchors equal in weight. It is no longer required to be carried on merchant ships.
When the anchor strikes the sea-bed the stock, being longer and heavier than the arms, assumes the horizontal position as soon as the anchor is stressed, thus causing the lower arm and fluke to become embedded. The stock gives the anchor great stability, i.e. it prevents it from rotating under heavy load or a stress applied other than in line with the shank. The anchor will turn in a horizontal plane quite easily as a ship swings with the tidal stream or wind. There are no moving parts to become choked with sea-bed material, so that should the anchor be accidentally broken out its holding position it remains efficient for re-anchoring.
The upper fluke, which protrudes from the sea-bed, contributes no holding power and may become fouled by the cable as the ship swings. Further, in very shallow water, or where the sea-bed dries out, small craft may become impaled on this fluke. The common anchor is difficult to show with the stock in position. In merchant ships it is usually found as a light (non-compulsory) kedge anchor with the stock stowed parallel with the shank, or as a lifeboat anchor. As a kedge anchor it is likely to weigh up to 2 tonnes, dimensions for this weight being roughly 3.9m overall length; 3.7m length of stock , and 2.5m width of arms.
The steel common anchor of today has a holding power of roughly three to four times its weight, depending upon the sea –bed. It is of surprising historical interest to note that admiral lord Nelson’s anchor (H.M.S Victory), with its buoyant oak stock, had a holding power of 2.8 times its weight. Efficiency improvements have therefore been small since then, and are only just developing.
The spheres or enlargements at the stock extremities serve two purposes: they assist rotation of the anchor when biting, and prevent, to a certain extent, sinking of the stock into the sea- bed when it is providing stability under load.
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