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An anchor is also:

• the name of the host of a television news program: see news anchor.
• the source and destination of a hyperlink.
• in psychology, sticking to a given reference point: see anchoring.

Ship's anchor

An anchor is an instrument of iron or other heavy material used for holding ships or boats in position and preventing them from drifting by winds, tides, currents or other causes. The anchor is dropped to the seabed, with one end attached to the ship by means of the cable or chain. Anchors are designed to fix themselves in the ground, there by holding the vessel fast.

The word "anchor" is also used figuratively for anything which gives security, or for any ornament or appendage which takes the same form. Owing to a vessel's safety depending upon the anchor, it is obviously an appliance of great importance, and too much care cannot be expended on its manufacture and proper construction. The word is from the Greek agkura, which Vossius considers is from ogke, a crook or hook.

Use of anchors

An anchor is one of the most important pieces of equipment on a ship. Although many modern vessels never anchor in normal service, the ability to anchor in the event of breakdown or other accident is essential to prevent the vessel drifting into further danger. Most ships will carry more than one anchor. The primary anchor (or anchors, where one is fitted on each side of the ship) is called the bower anchor. A secondary anchor, especially one mounted at the stern of a vessel, is called a kedge.

An anchor must hold the vessel in place. The larger the vessel, the more "holding power" is required to prevent the vessel from drifting. If the force of the weather and sea on the vessel exceeds the anchor's holding power, the anchor will drag, and if not reset the vessel will drift. The holding power of an anchor depends on its design, its weight and the type of seabed in which it is embedded. On some surfaces (e.g. weed) it may be very hard to get a good hold with many anchors.

There are several different designs of anchor in modern use. The "traditional" anchor is a fisherman anchor. Although they are extremely effective they need to be heavier than many modern designs to achieve the same holding power, and they are awkward to store on deck when the vessel is under way or moored. Anchors in common modern use include the CQR (pronounced "secure"), the Danforth and the Bruce.

To be most effective the line from the anchor to the ship must lie horizontally along the seabed, as any upwards angle will cause the anchor to "break out" of the seabed, and it will not hold. For this reason a ship will normally lay out a length of chain several times the depth of the water to the anchor. This means that the vessel is not fixed in a single position, but can drift in a cirle limited by the length of chain that has been paid out. This limits how close vessels can lie to each other in an anchorage.

History

The most ancient anchors consisted of large stones, baskets full of stones, sacks filled with sand, or logs of wood loaded with lead. Of this kind were the anchors of the ancient Greeks, which, according to Apollonius Rhodius and Stephen of Byzantium, were formed of stone; and Athenaeus states that they were sometimes made of wood. Such anchors held the vessel merely by their weight and by the friction along the bottom. Iron was afterwards introduced for the construction of anchors, and an improvement was made by forming them with teeth or flukes to fasten themselves into the bottom; whence the words odontes and dentes are frequently taken for anchors in the Greek and Latin poets. The invention of the teeth is ascribed by Pliny to the Tuscans; but Pausanias gives the credit to Midas, king of Phrygia. Originally there was only one fluke or tooth, whence anchors were called eterostomoi; but a second was added, according to Pliny, by Eupalamus, or, according to Strabo, by Anacharsis, the Scythian philosopher. The anchors with two teeth were called amfiboloi or amfistomoi, and from ancient monuments appear to have resembled generally those used in modern days, except that the stock is absent from them all. Every ship had several anchors; the largest, corresponding to our sheet anchor, was only used in extreme danger, and was hence peculiarly termed iera or sacra, whence the proverb sacram anchoram solvere, as flying to the last refuge.

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Porters/Trotmans 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 Admiralty anchor, under the direction of the Board, was supplied to H.M. ships, followed by Lieutenant (afterwards Captain) Rodger's anchor. This 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 admiralty in 1852, it was placed second only to the anchor of Trotman. Later came the self-canting anchor, which, passing through successive improvements, became the improved Martin anchor made of forged iron. A projection in the centre 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, 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. All the above anchors were provided with a stock, the use of which is to "cant" the anchor. If it falls on the ground, resting on one arm and one stock, when a strain is brought on the cable, the stock cants the anchor, causing the arms to lie at a downward angle to the holding ground; and the pees enter and bury themselves below the surface of the soil. To stow a stocked anchor on the forecastle, it is hove up close to the forefoot, and by means of a ground chain (secured to a balancing or gravity band on the anchor), which is joined to a catting chain rove through a cat davit, the anchor is hove up horizontally and placed on its bed, where it is secured by chains passing over a rod fitted with a lever for "letting go." The cat davit is hinged at its base, and can be laid flat on the deck for right ahead fire or when at sea. Ground and catting chains have been superseded in some ships by a wire pendant and cat hook; the anchor is then hove close up to the hawse-pipe. To avoid cutting away a portion of the forecastle, in the "Cressy," "Terrible" and "Diadem" classes of the Royal Navy, the anchors, secured by chains, are stowed a-cock-bill, outside the ship, with their crowns resting on iron shoes secured to the ship's side and the flukes fore and aft. A difficulty is experienced in stowing the anchors when the ship is pitching or rolling heavily. Fig. 4 illustrates an anchor with cat davit or anchor crane used in the P. and O. Company's steamers ("India" class, 8000 tons); for sea the anchor is stowed on board by the anchor crane.

Stockless anchors have been extensively used in the British mercantile marine and in some foreign navies. In 1903 they were adopted generally for the British navy, after extensive anchor trials, begun in 1885. Their advantages are:

• handiness combined with a saving of time and labour;
• absence of davits, anchor-beds and other gear, with a resulting reduction in weight;
• a clear forecastle for "right ahead" gun fire or for working ship.

On the other hand a larger hawse-pipe is required, and there appears to be a consensus of opinion that a stockless anchor when "let go" does not hold so quickly as a stocked one, is more uncertain in its action over uneven ground, and is more liable to "come home" (drag). The stockless anchors principally in use in the British navy are Hall's improved, Byer's, and Wasteneys Smith's. In Hall's improved the arms and crown of cast steel are in one piece, and the shank of forged steel passes up through an aperture in the crown to which it is secured by two cross bolts. Two trunnions or lugs are forged to the lower end of the shank. In Byer's plan the flukes and crown consist of a steel-casting secured to a forged shank by a through bolt of mild steel, the axis of which is parallel to the points of the flukes; one end of the bolt has a head, but the other is screwed and fitted with a phosphor bronze nut to allow the bolt to be withdrawn for examination. A palm is cast on each side of the crown to trip the flukes when the anchor is on the ground, and for bringing them snug against the ship's side when weighing. Wasteneys Smith's anchor is composed of three main parts, the shank and crown which form one forging, and the two flukes or arms which are separate castings. A bolt passes through the crown of the anchor, connecting the flukes to it; to prevent the flukes working off the connecting through bolt, two smaller bolts pass through the flukes at right angles to the through bolt and are recessed half their diameter into it.

Stern, stream and kedge anchors are usually stowed with special davits. A portable anchor suitable for small yachts is the invention of Mr Louis Moore; the shank passes through the crown of the anchor like the handle of a pickaxe and the stock over the head of the shank. At the end of the stock are loose pawls. There are no keys or bolts, and the only fastening is for the cable. The anchor takes to pieces readily and stows snugly. In 1890 Colonel Bucknill also invented a portable anchor for small yachts.

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Marine anchor

Iron buoy-sinkers, as used by the London corporation of Trinity House, weigh from 8 to 40 cwt (400 to 2,000 kg); the specified weight is cast on them in large raised figures, and the cast and wrought irons used are of special quality, of which samples are previously submitted to the engineer-in-chief.

The anchors supplied to ships of the Royal Navy are required to withstand a certain tensile strain, expressed in tons, proportionate to their weights in cwts. New anchors are supplied by contractors, but repairs are made in H.M. dockyards, a record of its repairs being stamped on each anchor. In the Anchors and Cables Act 1899 a list is given of authorized testing-establishments, with their distinctive marks and charges, and testing- houses for foreign-owned vessels are enumerated in Table 22 of Lloyd's Register of British and Foreign Shipping. Cast-steel anchors, in addition to the statutory tests, are subjected to percussive, hammering and bending tests, and are stamped "annealed steel."

In addition to keeping motionless, an anchor may be utilized as an instrument of propulsion in warping.

 This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. {{cite encyclopedia}}: Missing or empty |title= (help)