Overview
Anchors achieve holding power either by "hooking" into the seabed, or mass, or a combination of the two. Permanent moorings use large masses (commonly a block or slab of concrete) resting on the seabed. Semi-permanent mooring anchors (such as mushroom anchors) and large ship's anchors derive a significant portion of their holding power from their mass, while also hooking or embedding in the bottom. Modern anchors for smaller vessels have metal ''flukes'' which hook on to rocks on the bottom or bury themselves in soft seabed. The vessel is attached to the anchor by the ''rode'' (also called a ''cable'' or a ''warp''). It can be made of rope,Holding ground
Holding ground is the area of sea floor which holds an anchor, and thus the attached ship or boat. Different types of anchor are designed to hold in different types of holding ground. Some bottom materials hold better than others; for instance, hard sand holds well, shell very poorly. Holding ground may be fouled with obstacles. An anchorage location may be chosen for its holding ground. In poor holding ground, only the weight of an anchor matters; in good holding ground, it is able to dig in, and the holding power can be significantly higher.History
Evolution of the anchor
The earliest anchors were probably rocks, and many rock anchors have been found dating from at least the Bronze Age. Pre-European Maori waka (canoes) used one or more hollowed stones, tied with flax ropes, as anchors. Many modern moorings still rely on a large rock as the primary element of their design. However, using pure mass to resist the forces of a storm only works well as a permanent mooring; a large enough rock would be nearly impossible to move to a new location. The ancient Greeks used baskets of stones, large sacks filled with sand, and wooden logs filled with lead. According to Apollonius Rhodius andFluked anchors
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. This is the iconic anchor shape most familiar to non-sailors. This form has been used since antiquity. The RomanAdmiralty anchor
The Admiralty Pattern anchor, or simply "Admiralty", also known as a "Fisherman", consists of a central shank with a ring orStockless anchor
The stockless anchor, patented in England in 1821,"anchor" in '' The New Encyclopædia Britannica''. Chicago:Small boat anchors
Until the mid-20th century, anchors for smaller vessels were either scaled-down versions of admiralty anchors, or simpleGrapnel anchor
A traditional design, the grapnel is merely a shank with four or more tines. It has a benefit in that, no matter how it reaches the bottom, one or more tines will be aimed to set. In coral, or rock, it is often able to set quickly by hooking into the structure, but may be more difficult to retrieve. A grapnel is often quite light, and may have additional uses as a tool to recover gear lost overboard. Its weight also makes it relatively easy to move and carry, however its shape is generally not very compact and it may be awkward to stow unless a collapsing model is used. Grapnels rarely have enough fluke area to develop much hold in sand, clay, or mud. It is not unknown for the anchor to foul on its own rode, or to foul the tines with refuse from the bottom, preventing it from digging in. On the other hand, it is quite possible for this anchor to find such a good hook that, without a trip line from the crown, it is impossible to retrieve.Herreshoff anchor
Designed by yacht designerNorthill anchor
Originally designed as a lightweight anchor for seaplanes, this design consists of two plough-like blades mounted to a shank, with a folding stock crossing through the crown of the anchor.CQR plough anchor
Many manufacturers produce a plough-type anchor, so-named after its resemblance to an agriculturalDelta anchor
The Delta anchor was derived from the CQR. It was patented by Philip McCarron, James Stewart, and Gordon Lyall of British marine manufacturer Simpson-Lawrence Ltd in 1992. It was designed as an advance over the anchors used for floating systems such as oil rigs. It retains the weighted tip of the CQR but has a much higher fluke area to weight ratio than its predecessor. The designers also eliminated the sometimes troublesome hinge. It is a plough anchor with a rigid, arched shank. It is described as ''self-launching'' because it can be dropped from a bow roller simply by paying out the rode, without manual assistance. This is an oft copied design with the European Brake and Australian Sarca Excel being two of the more notable ones. Although it is a plough type anchor, it sets and holds reasonably well in hard bottoms.Danforth anchor
American Richard Danforth invented the Danforth Anchor in the 1940s for use aboardBruce or claw anchor
This claw-shaped anchor was designed by Peter Bruce from Scotland in the 1970s. Bruce gained his early reputation from the production of large-scale commercial anchors for ships and fixed installations such as oil rigs. It was later scaled down for small boats, and copies of this very popular design abound. The Bruce and its copies, known generically as "claw type anchors", have been adopted on smaller boats (partly because they stow easily on a bow roller) but they are most effective in larger sizes. Claw anchors are quite popular on charter fleets as their percentage set on the first try in many bottom types is very high. They have the reputation of not breaking out with tide or wind changes, instead slowly turning in the bottom to align with the force. Bruce anchors can have difficulty penetrating weedy bottoms and grass. They offer a fairly low holding-power-to-weight ratio and generally have to be oversized to compete with newer types.Scoop type anchors
Three time circumnavigator German Rolf Kaczirek invented the Bügel Anker in the 1980s. Kaczirek wanted an anchor that was self-righting without necessitating a ballasted tip. Instead, he added a roll bar and switched out the plough share for a flat blade design. As none of the innovations of this anchor were patented, copies of it abound. Alain Poiraud of France introduced the scoop type anchor in 1996. Similar in design to the Bügel anchor, Poiraud's design features a concave fluke shaped like the blade of a shovel, with a shank attached parallel to the fluke, and the load applied toward the digging end. It is designed to dig into the bottom like a shovel, and dig deeper as more pressure is applied. The common challenge with all the scoop type anchors is that they set so well, they can be difficult to weigh. * ''Bügelanker'', or ''Wasi'': This German-designed bow anchor has a sharp tip for penetrating weed, and features a roll-bar which allows the correct setting attitude to be achieved without the need for extra weight to be inserted into the tip. * ''Spade'': This is a French design which has proved successful since 1996. It features a demountable shank (hollow in some instances) and the choice of galvanized steel, stainless steel, or aluminium construction, which means a lighter and more easily stowable anchor. The geometry also makes this anchor self stowing on a single roller. * ''Rocna'': This New Zealand spade design, available in galvanised or stainless steel, has been produced since 2004. It has a roll-bar (similar to that of the Bügel), a large spade-like fluke area, and a sharp toe for penetrating weed and grass. The Rocna sets quickly and holds well. *''Mantus'': This is claimed to be a fast setting anchor with high holding power. It is designed as an all round anchor capable of setting even in challenging bottoms such as hard sand/clay bottoms and grass. The shank is made out of a high tensile steel capable of withstanding high loads. It is similar in design to the Rocna but has a larger and wider roll-bar that reduces the risk of fouling and increases the angle of the fluke which results in improved penetration in some bottoms. * ''Ultra'': This is an innovative spade design that dispenses with a roll-bar. Made primarily of stainless steel, its main arm is hollow, while the fluke tip has lead within it. It is very similar in appearance to the Spade anchor. *''Vulcan'': A recent sibling to the Rocna, this anchor performs similarly but does not have a roll-bar. Instead the Vulcan has patented design features such as the "V-bulb" and the "Roll Palm" that allow it to dig in deeply. The Vulcan was designed primarily for sailors who had difficulties accommodating the roll-bar Rocna on their bow. Peter Smith (originator of the Rocna) designed it specifically for larger powerboats. Both Vulcans and Rocnas are available in galvanised steel, or in stainless steel. The Vulcan is very similar in appearance to the Spade anchor. *''Knox Anchor'': This is produced in Scotland and was invented by ProfessorOther temporary anchors
* ''Mud weight'': Consists of a blunt heavy weight, usually cast iron or cast lead, that will sink into the mud and resist lateral movement. Suitable only for very soft silt bottoms and in mild conditions. Sizes range between 5 and 20 kg for small craft. Various designs exist and many are home produced from lead or improvised with heavy objects. This is a very commonly used method on the Norfolk Broads in England. *''Bulwagga'': This is a unique design featuring three flukes instead of the usual two. It has performed well in tests by independent sources such as American boating magazine ''Practical Sailor''.Permanent anchors
These are used where the vessel is permanently or semi-permanently sited, for example in the case of lightvessels or channel markerMushroom
The mushroom anchor is suitable where the seabed is composed of silt or fine sand. It was invented byDeadweight
This is an anchor which relies solely on being a heavy weight. It is usually just a large block of concrete or stone at the end of the chain. Its holding power is defined by its weight underwater (i.e. taking its buoyancy into account) regardless of the type of seabed, although suction can increase this if it becomes buried. Consequently, deadweight anchors are used where mushroom anchors are unsuitable, for example in rock, gravel or coarse sand. An advantage of a deadweight anchor over a mushroom is that if it does become dragged, then it continues to provide its original holding force. The disadvantage of using deadweight anchors in conditions where a mushroom anchor could be used is that it needs to be around ten times the weight of the equivalent mushroom anchor.Auger
Auger anchors can be used to anchor permanent moorings, floating docks, fish farms, etc. These anchors, which have one or more slightly pitched self-drilling threads, must be screwed into the seabed with the use of a tool, so require access to the bottom, either at low tide or by use of a diver. Hence they can be difficult to install in deep water without special equipment. Weight for weight, augers have a higher holding than other permanent designs, and so can be cheap and relatively easily installed, although difficult to set in extremely soft mud.High-holding-types
There is a need in the oil-and-gas industry to resist large anchoring forces when laying pipelines and for drilling vessels. These anchors are installed and removed using a support tug and pennant/pendant wire. Some examples are the Stevin range supplied by Vrijhof Ankers. Large plate anchors such as the Stevmanta are used for permanent moorings.Anchoring gear
The elements of anchoring gear include the anchor, the cable (also called a ''rode''), the method of attaching the two together, the method of attaching the cable to the ship, charts, and a method of learning the depth of the water. Vessels may carry a number of anchors: ''bower anchors'' are the main anchors used by a vessel and normally carried at the bow of the vessel. A ''kedge anchor'' is a light anchor used for warping an anchor, also known as ''kedging'', or more commonly on yachts for mooring quickly or in benign conditions. A ''stream anchor'', which is usually heavier than a ''kedge anchor'', can be used for kedging or warping in addition to temporary mooring and restraining stern movement in tidal conditions or in waters where vessel movement needs to be restricted, such as rivers and channels. Charts are vital to good anchoring. Knowing the location of potential dangers, as well as being useful in estimating the effects of weather and tide in the anchorage, is essential in choosing a good place to drop the hook. One can get by without referring to charts, but they are an important tool and a part of good anchoring gear, and a skilled mariner would not choose to anchor without them.Anchor rode
The anchor rode (or "cable" or "warp") that connects the anchor to the vessel will usually be made up of chain, rope, or a combination of those. Large ships will use only chain rode. Smaller craft might use a rope/chain combination or an all chain rode. All rodes should have some chain; chain is heavy but it resists abrasion from coral, sharp rocks, or shellfish beds, whereas a rope warp is susceptible to abrasion and can fail in a short time when stretched against an abrasive surface. The weight of the chain also helps keep the direction of pull on the anchor closer to horizontal, which improves holding, and absorbs part of snubbing loads. Where weight is not an issue, a heavier chain provides better holding by forming a catenary curve through the water and resting as much of its length on the bottom as will not be lifted by tension of the mooring load. Any changes to the tension are accommodated by additional chain bing lifted or settling on the bottom, and this absorbs shock loads until the chain is straight, at which point the full load is taken by the anchor. Additional dissipation of shock loads can be achieved by fitting a snubber between the chain and a bollard or cleat on deck. This also reduces shock loads on the deck fittings, and the vessel will usually lie more comfortably and quietly. Being strong and elastic, nylon rope is the most suitable as an anchor rode.Scope
Scope is the ratio of the depth of the water measured from the highest point (usually the anchor roller or bow chock) to the seabed, making allowance for the highest expected tide. The function of this ratio is to ensure that the pull on the anchor is unlikely to break it out of the bottom if it is embedded, or lift it off a hard bottom, either of which is likely to result in the anchor dragging. A large scope induces a load which is nearly horizontal. In moderate conditions the ratio of rode to water depth should be 4:1 – where there is sufficient swing-room, a greater scope is always better. In rougher conditions it should be up to twice this with the extra length giving more stretch and a smaller angle to the bottom to resist the anchor breaking out. For example, if the water is deep, and the anchor roller is above the water, then the 'depth' is 9 meters (~30 feet). The amount of rode to let our in moderate conditions is thus 36 meters (120 feet). (For this reason it is important to have a reliable and accurate method of measuring the depth of water.) When using a rope rode, there is a simple way to estimate the scope: The ratio of bow height of the rode to length of rode above the water while lying back hard on the anchor is the same or less than the scope ratio. The basis for this is simple geometry ( Intercept Theorem): The ratio between two sides of a triangle stays the same regardless of the size of the triangle as long as the angles do not change. Generally, the rode should be between 5 and 10 times the depth to the seabed, giving a scope of 5:1 or 10:1; the larger the number, the shallower the angle is between the cable and the seafloor, and the less upwards force is acting on the anchor. A 10:1 scope gives the greatest holding power, but also allows for much more drifting due to the longer amount of cable paid out. Anchoring with sufficient scope and/or heavy chain rode brings the direction of strain close to parallel with the seabed. This is particularly important for light, modern anchors designed to bury in the bottom, where scopes of 5:1 to 7:1 are common, whereas heavy anchors and moorings can use a scope of 3:1, or less. Some modern anchors, such as the Ultra will hold with a scope of 3:1; but, unless theAnchoring techniques
The basic anchoring consists of determining the location, dropping the anchor, laying out the scope, setting the hook, and assessing where the vessel ends up. The ship will seek a location which is sufficiently protected; has suitable holding ground, enough depth at low tide and enough room for the boat to swing. The location to drop the anchor should be approached from down wind or down current, whichever is stronger. As the chosen spot is approached, the vessel should be stopped or even beginning to drift back. The anchor should initially be lowered quickly but under control until it is on the bottom (seeUsing an anchor weight, kellet or sentinel
Lowering a concentrated, heavy weight down the anchor line – rope or chain – directly in front of the bow to the seabed behaves like a heavy chain rode and lowers the angle of pull on the anchor. If the weight is suspended off the seabed it acts as a spring or shock absorber to dampen the sudden actions that are normally transmitted to the anchor and can cause it to dislodge and drag. In light conditions, a kellet will reduce the swing of the vessel considerably. In heavier conditions these effects disappear as the rode becomes straightened and the weight ineffective. Known as an "anchor chum weight" or "angel" in the UK.Forked moor
Using two anchors set approximately 45° apart, or wider angles up to 90°, from the bow is a strong mooring for facing into strong winds. To set anchors in this way, first one anchor is set in the normal fashion. Then, taking in on the first cable as the boat is motored into the wind and letting slack while drifting back, a second anchor is set approximately a half-scope away from the first on a line perpendicular to the wind. After this second anchor is set, the scope on the first is taken up until the vessel is lying between the two anchors and the load is taken equally on each cable. This moor also to some degree limits the range of a vessel's swing to a narrower oval. Care should be taken that other vessels will not swing down on the boat due to the limited swing range.Bow and stern
(Not to be mistaken with the ''Bahamian moor'', below.) In the ''bow and stern'' technique, an anchor is set off each the bow and the stern, which can severely limit a vessel's swing range and also align it to steady wind, current or wave conditions. One method of accomplishing this moor is to set a bow anchor normally, then drop back to the limit of the bow cable (or to double the desired scope, e.g. 8:1 if the eventual scope should be 4:1, 10:1 if the eventual scope should be 5:1, etc.) to lower a stern anchor. By taking up on the bow cable the stern anchor can be set. After both anchors are set, tension is taken up on both cables to limit the swing or to align the vessel.Bahamian moor
Similar to the above, a ''Bahamian moor'' is used to sharply limit the swing range of a vessel, but allows it to swing to a current. One of the primary characteristics of this technique is the use of a swivel as follows: the first anchor is set normally, and the vessel drops back to the limit of anchor cable. A second anchor is attached to the end of the anchor cable, and is dropped and set. A swivel is attached to the middle of the anchor cable, and the vessel connected to that. The vessel will now swing in the middle of two anchors, which is acceptable in strong reversing currents, but a wind perpendicular to the current may break out the anchors, as they are not aligned for this load.Backing an anchor
Also known as ''tandem anchoring'', in this technique two anchors are deployed in line with each other, on the same rode. With the foremost anchor reducing the load on the aft-most, this technique can develop great holding power and may be appropriate in "ultimate storm" circumstances. It does not limit swinging range, and might not be suitable in some circumstances. There are complications, and the technique requires careful preparation and a level of skill and experience above that required for a single anchor.Kedging
''Kedging'' or ''Club hauling
Club hauling is an archaic technique. When a vessel is in a narrow channel or on a lee shore so that there is no room to tack the vessel in a conventional manner, an anchor attached to the lee quarter may be dropped from the lee bow. This is deployed when the vessel is head to wind and has lost headway. As the vessel gathers sternway the strain on the cable pivots the vessel around what is now the weather quarter turning the vessel onto the other tack. The anchor is then normally cut away, as it cannot be recovered.Weighing anchor
Since all anchors that embed themselves in the bottom require the strain to be along the seabed, anchors can be broken out of the bottom by shortening the rope until the vessel is directly above the anchor; at this point the anchor chain is "up and down", in naval parlance. If necessary, motoring slowly around the location of the anchor also helps dislodge it. Anchors are sometimes fitted with a trip line attached to the crown, by which they can be unhooked from rocks, coral, chain, or other underwater hazards. The term ''aweigh'' describes an anchor when it is hanging on the rope and is not resting on the bottom. This is linked to the term ''to weigh anchor'', meaning to lift the anchor from the sea bed, allowing the ship or boat to move. An anchor is described as ''aweigh'' when it has been broken out of the bottom and is being hauled up to be ''stowed''. ''Aweigh'' should not be confused with ''under way'', which describes a vessel which is not ''moored'' to a dock or ''anchored'', whether or not the vessel is moving through the water. ''Aweigh'' is also often confused with ''away'', which is incorrect.Anchor as symbol
An anchor frequently appears on the flags and coats of arms of institutions involved with the sea, both naval and commercial, as well as of port cities and seacoast regions and provinces in various countries. There also exists in heraldry the " Anchored Cross", or Mariner's Cross, a stylized cross in the shape of an anchor. The symbol can be used to signify 'fresh start' or 'hope'. The New Testament refers to the Christian's hope as "an anchor of the soul". The Mariner's Cross is also referred to as St. Clement's Cross, in reference to the way this saint was killed (being tied to an anchor and thrown from a boat into the Black Sea in 102). Anchored crosses are occasionally a feature ofSee also
* * * * *References
Bibliography
* Blackwell, Alex & Daria; ''Happy Hooking – the Art of Anchoring,'' 2008, 2011, 2019 White Seahorse; * Edwards, Fred; ''Sailing as a Second Language: An illustrated dictionary,'' 1988 Highmark Publishing; * Hinz, Earl R.; ''The Complete Book of Anchoring and Mooring, Rev. 2d ed.,'' 1986, 1994, 2001 Cornell Maritime Press; * Hiscock, Eric C.; ''Cruising Under Sail, second edition,'' 1965 Oxford University Press; * Pardey, Lin and Larry; ''The Capable Cruiser''; 1995 Pardey Books/Paradise Cay Publications; * Rousmaniere, John; ''The Annapolis Book of Seamanship,'' 1983, 1989 Simon and Schuster; * Smith, Everrett; ''Cruising World's Guide to Seamanship: Hold me tight,'' 1992 New York Times Sports/Leisure MagazinesFurther reading
* William N. Brady (1864). ''The Kedge-anchor; Or, Young Sailors' Assistant''. **First published as ''The Naval Apprentice's Kedge Anchor''. New York, Taylor and Clement, 1841.--''The Kedge-anchor''; 3rd ed. New York, 1848.--6th ed. New York, 1852.--9th ed. New York, 1857.External links