Editing Anchor (section)

== Anchoring ==
{{sources|date=August 2020}}

[[File:Polarstern anchor-winch hg.jpg|thumb|Anchor winch, or windlass, on {{ship|RV|Polarstern}}]]

[[File:Chain markers.jpg|thumb|Colored plastic inserts on a modern anchor chain show the operator how much chain has been paid out. This knowledge is crucial in all anchoring methods.]]
[[File:Stockless anchor 2 NT.PNG|thumb|A stockless anchor being broken out]]
[[File:Akaroa Harbour jpeg.png|thumb|Holding ground in [[Akaroa Harbour]]]]

Anchors achieve holding power either by "hooking" into the [[seabed]], or weight, or a combination of the two. The weight of the anchor chain can be more than that of the anchor and is critical to proper holding.  Permanent moorings use large masses (commonly a block or slab of concrete) resting on the seabed. Semi-permanent mooring anchors (such as [[#Mushroom|mushroom anchor]]s) and large ship's anchors derive a significant portion of their holding power from their weight, while also hooking or embedding in the bottom. Modern anchors for smaller vessels have metal ''flukes'' that 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, [[chain]] or a combination of rope and chain. The ratio of the length of rode to the water depth is known as the scope.

Holding ground is the area of sea floor that holds an anchor, and thus the attached ship or boat.<ref name="practice">{{cite web |last1=Idzikowski |first1=Jerzy T. |title=Anchoring practice |url=https://navlib.net/wp-content/uploads/2017/11/Anchoring-Practice.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://navlib.net/wp-content/uploads/2017/11/Anchoring-Practice.pdf |archive-date=2022-10-09 |url-status=live |date=2001}}</ref> Different types of anchor are designed to hold in different types of holding ground.<ref>{{cite web|last=Burden|first=Tom|date=28 May 2020|title=Selecting the Right Anchor|url=https://www.westmarine.com/WestAdvisor/Selecting-The-Right-Anchor|url-status=live|website=West Marine|publisher=|archive-url=https://web.archive.org/web/20140706042515/http://www.westmarine.com/WestAdvisor/Selecting-The-Right-Anchor |archive-date=6 July 2014 }}</ref> Some bottom materials hold better than others; for instance, hard sand holds well, shell holds poorly.<ref name=seabed/> Holding ground may be fouled with obstacles.<ref name=seabed>{{cite web |title=Seabed – where to anchor |url=https://www.sailingissues.com/yachting-guide/seabed.html |website=www.sailingissues.com}}</ref> An anchorage location may be chosen for its holding ground.<ref>{{cite web |url=https://www.tc.gc.ca/en/services/marine/ports-harbours/understanding-anchorages-canada.html |title=Understanding anchorages in Canada |website=tc.gc.ca}}</ref> In poor holding ground, only the weight of an anchor and chain matters; in good holding ground, it is able to dig in, and the holding power can be significantly higher.
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 seeks a location that 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 (see [[anchor windlass]]). The vessel should continue to drift back, and the cable should be veered out under control (slowly) so it is relatively straight.

Once the desired scope is laid out, the vessel should be gently forced astern, usually using the auxiliary motor but possibly by backing a sail. A hand on the anchor line may telegraph a series of jerks and jolts, indicating the anchor is dragging, or a smooth tension indicative of digging in. As the anchor begins to dig in and resist backward force, the engine may be throttled up to get a thorough set. If the anchor continues to drag, or sets after having dragged too far, it should be retrieved and moved back to the desired position (or another location chosen.)

=== Using 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.<ref>Hinz, Earl R.; The Complete Book of Anchoring and Mooring, first ed., 1986, Cornell Maritime Press; {{ISBN|0-87033-348-8}}</ref> 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 reduces 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 do 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.<ref>{{Cite web|title=Major danger of anchoring a fishing boat from the stern?|url=https://pontoony.com/danger-of-anchoring-a-fishing-boat-from-the-stern/|access-date=2021-06-20|website=pontoony.com|date=28 May 2021}}</ref> 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 now swings 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 ===
[[File:Памятник Петру 1.JPG|thumb|Statue of [[Peter the Great]] in [[Voronezh]], Russia.  He is leaning on an anchor, symbolic of his contributions to modernizing and expanding Russia's navy (1860)]]

''Kedging'' or ''[[Warping (sailing)|warping]]'' is a technique for moving or turning a ship by using a relatively light anchor.

In yachts, a kedge anchor is an anchor carried in addition to the main, or bower, anchor, and usually stowed aft. Every yacht should carry at least two anchors – the main or ''bower'' anchor and a second lighter ''kedge'' anchor.{{clarify|according to whom?|date=June 2023}} It is used occasionally when it is necessary to limit the turning circle as the yacht swings when it is anchored, such as in a narrow river or a deep pool in an otherwise shallow area. Kedge anchors are sometimes used to recover vessels that have [[Ship grounding|run aground]].

For ships, a kedge may be dropped while a ship is underway, or carried out in a suitable direction by a tender or ship's boat to enable the ship to be winched off if aground or swung into a particular heading, or even to be held steady against a tidal or other stream.

Historically, it was of particular relevance to sailing warships that used them to outmaneuver opponents when the wind had dropped but might be used by any vessel in confined, shoal water to place it in a more desirable position, provided she had enough manpower.<ref>{{Cite web |date=2021-05-01 |title=Anchors Aweigh |url=https://www.usni.org/magazines/naval-history-magazine/2021/june/anchors-aweigh |access-date=2025-03-10 |website=U.S. Naval Institute |language=en}}</ref>

==== 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 (the ship's momentum prevents recovery without aborting the maneuver). <ref>Liardet, Francis (1849) [http://www.sjohistoriskasamfundet.se/LB/Nautica/Seamanship/Liardet/Liardet%281849%29_p72.html Professional Recollections on Points of Seamanship] {{Webarchive|url=https://web.archive.org/web/20101029213748/http://www.sjohistoriskasamfundet.se/LB/Nautica/Seamanship/Liardet/Liardet(1849)_p72.html |date=29 October 2010 }}, Discipline, &c.</ref><ref>[http://www.psych.usyd.edu.au/vbb/woronora/maritime/working.html General Principles of Working a Ship, from The New Practical Navigator (1814)] {{webarchive|url=https://web.archive.org/web/20040820184758/http://www.psych.usyd.edu.au/vbb/woronora/maritime/working.html |date=20 August 2004 }}. psych.usyd.edu.au</ref>

===Multiple anchor patterns===
When it is necessary to moor a ship or floating platform with precise positioning and alignment, such as when drilling the seabed, for some types of salvage work, and for some types of diving operation, several anchors are set in a pattern which allows the vessel to be positioned by shortening and lengthening the scope of the anchors, and adjusting the tension on the rodes. The anchors are usually laid in prearranged positions by an anchor tender, and the moored vessel uses its own winches to adjust position and tension.<ref>{{cite report |url=https://assets.publishing.service.gov.uk/media/5a7a2ac2e5274a319e77853e/SD_SEA2EandP.pdf |title=An overview of offshore oil and gas exploration and production activities |page=8 |date=August 2001 |publisher=Department of Trade and Industry, UK }}</ref>

Similar arrangements are used for some types of [[single buoy mooring]]s, like the [[catenary anchor leg mooring]] (CALM) used for loading and unloading liquid cargoes.

=== 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<ref>{{Cite web|title=To deploy or not to deploy Trip Lines (aka Anchor Buoys)|url=http://cruising.coastalboating.net/Seamanship/Anchoring/TripLines.html|access-date=2020-12-26|website=cruising.coastalboating.net}}</ref> attached to the crown, by which they can be unhooked from underwater hazards.

The term ''aweigh'' describes an anchor when it is hanging on the rope and 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 that 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.