Ship Anchors: Parts, Types and Holding Mechanisms

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Published on Wednesday, 26 November 2025 05:26

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How stockless anchors work, chain types, and equipment specifications

QUICK ANSWER: WHAT IS A SHIP ANCHOR?

A ship anchor is a heavy metal device designed to secure a vessel to the seabed and prevent drifting caused by wind, current, or tide. Modern merchant ships use stockless anchors consisting of three main parts: the crown (which pivots and digs into the seabed), the shank (vertical shaft connecting components), and the joining shackle (D-type connection to the anchor chain). The anchor works by having its crown pierce the seabed slush, then gravity forces the shank horizontal so the flukes—two arm-like extensions on the crown—dig deep into the bottom. Four projections called tripping palms assist if the flukes initially fail to bite.

The anchor connects to studded chain cable measured in shackles, where one shackle equals 15 fathoms or 27.5 meters. Ships typically carry two bower anchors with chain lengths totaling 300-770 meters depending on vessel size. The amount of chain determines holding power—at least six times the vertical hawse pipe-to-seabed distance must be paid out to keep the shank horizontal. If the shank lifts just 30 degrees from horizontal, holding power drops by 50 percent. The chain's furthest end, called the bitter end, connects to the chain locker via an instant release mechanism allowing emergency anchor abandonment without entering the locker.

Anchor equipment specifications are determined by the Equipment Number (EN), a dimensionless parameter calculated from displacement, breadth, freeboard, and projected areas. Classification societies provide rigging tables matching EN values to required anchor weights and chain specifications. This standardized equipment is designed for temporary mooring in harbors or sheltered waters when awaiting berth or tide—not for holding off exposed coasts in rough weather or stopping moving vessels.

STOCKLESS ANCHOR CONSTRUCTION

The Three Main Components

Ship anchors are of the stockless type, eliminating the horizontal stock bar that characterized older anchor designs. This stockless configuration allows easier handling and stowing in the hawse pipe without requiring manual stock removal. The three essential parts work together to create holding power through mechanical advantage rather than weight alone. Understanding how these components interact explains why proper chain scope matters so critically for anchoring effectiveness.

Crown: The Digging Mechanism

The crown pivots about the shank in one plane, capable of making angles up to approximately 45 degrees relative to the shank axis. This pivoting action is essential for the anchor to orient itself correctly when dropped. At each of the crown's four corners sit projections called tripping palms—these act as backup digging mechanisms if the primary flukes fail to penetrate initially. The crown features two arm-like extensions called flukes that form the primary holding surfaces once buried in the seabed.

When the anchor drops, the crown pierces through the slush layer on the seabed surface. As the shank assumes horizontal position due to gravity and the weight of the chain pulling from above, the flukes angle downward and dig into the substrate. If initial penetration is insufficient—perhaps due to hard bottom or poor fluke angle—the tripping palms engage. These palms catch on the seabed and force the flukes downward through mechanical leverage, ensuring the anchor sets properly even in difficult conditions.

Shank: The Critical Connector

The shank is a long shaft positioned between the flukes below and the joining shackle above. It connects to the fluke assembly via a pivoting pin that passes through two holes in the crown (one on either side) and a corresponding hole through the shank itself. This pinned connection allows the necessary pivoting while maintaining structural strength to resist the enormous pulling forces exerted by the vessel through the chain.

The shank's orientation determines holding power effectiveness. An anchor holds well only so long as its shank remains horizontal on the seabed. It has been estimated that if the shank lifts up from horizontal by as little as 30 degrees, the holding power of the anchor reduces by 50 percent. This dramatic loss occurs because the pulling force changes from horizontal (which keeps flukes buried) to angled upward (which tries to extract the flukes). To ensure the shank stays horizontal during normal conditions, the amount of chain paid out must be about six times the vertical distance from the hawse pipe to the seabed.

Joining Shackle: Chain Connection Point

The joining shackle is a D-type shackle that connects the shank to the anchor chain, also called anchor cable. The shackle pin is oval in cross-section and slides into oval-shaped holes machined on the ends of the lug. This oval design prevents rotation and ensures the shackle maintains proper orientation. The pin is secured in place by a tapered wooden spile pin hammered tightly into a hole drilled through both the lug and the metal pin. An iron nail driven into the wooden pin ensures snug fit and prevents loosening, especially due to vibration when the chain is slack.

Opening such a shackle requires an anchor-shackle rod punch and a sledgehammer to punch out the shackle pin. The wooden pin and iron nail get sheared off in this process. This seemingly crude fastening method has proven reliable for decades because it combines simplicity with security—there are no threads to corrode or gall, and the wooden pin swells slightly when wet to maintain tightness.

❕ Important: The joining shackle connecting the anchor must always be a lug shackle because it requires a pin passing through a hole in the top of the shank—lugless shackles cannot perform this function.

HOW ANCHORS HOLD POSITION

The Two-Stage Setting Process

When the anchor is dropped, it falls through the water column with the crown leading due to weight distribution. Upon contact with the seabed, the crown pierces the slush—the top layer of soft sediment that overlays firmer material below. At this point the anchor has not yet set; it merely rests on the bottom. The actual holding mechanism engages during the second stage when the vessel drifts back or the windlass heaves in slightly, creating tension on the chain.

This tension pulls the chain taut, which in turn pulls the shank toward horizontal. Once the shank reaches horizontal orientation due to gravity and the catenary curve formed by the chain's weight, the flukes angle downward into the seabed. The flukes dig in because the pulling force is horizontal while the fluke surfaces are angled relative to that force—creating a wedging action that drives them deeper. The deeper they penetrate, the more seabed material they must displace to pull free, which means greater holding power.

Tripping Palms as Backup

In cases where the flukes fail to dig in sufficiently during initial setting—perhaps because they landed flat or the seabed is particularly hard—the tripping palms provide a secondary mechanism. These four projections at the crown's corners are positioned to catch on the seabed as the anchor is pulled horizontally. When they engage, they create a fulcrum point that forces the crown to rotate, which in turn pushes the flukes downward into the bottom.

The tripping palm mechanism demonstrates why anchor design is not purely about weight but about geometry and mechanical advantage. A lighter anchor with properly designed tripping palms will set more reliably than a heavier anchor without them. Once the flukes dig in through either primary or palm-assisted action, the anchor achieves its full holding power, which can be many times its own weight in good holding ground.

The Critical Horizontal Shank Requirement

An anchor's holding power depends absolutely on maintaining a horizontal shank angle. When the shank is horizontal, the pulling force acts parallel to the seabed, which keeps the flukes buried by driving them forward through the substrate rather than upward out of it. As soon as the shank angle increases from horizontal, the force vector gains an upward component that works to extract the flukes.

The 50 percent holding power loss at just 30 degrees of shank lift is not linear—it accelerates as angle increases. At 45 degrees the anchor may have only 30 percent of its horizontal holding power remaining. At 60 degrees it may be holding by friction alone. This is why proper scope is non-negotiable: without sufficient chain length to maintain the catenary curve that keeps the shank horizontal, the anchor cannot perform its designed function regardless of how good the bottom or how well it initially set.

✔ Holding Power Factors:
• Fluke penetration depth into seabed substrate
• Shank angle—must remain horizontal for maximum effectiveness
• Chain scope—minimum 6:1 ratio of paid out length to water depth
• Seabed type—mud and clay best, rock and coral worst
• Chain weight—creates catenary ensuring horizontal pull
• Tripping palm engagement if flukes initially fail
• Vessel movement—steady pull maintains set, jerking can break out

STUDDED CHAIN CABLE ADVANTAGES

Why Studs Matter

Anchor cables are usually studded chains where each link contains a crossbar called a stud welded across the link's interior. This simple addition provides three critical advantages over unstudded chain of the same diameter. Studded chain has become the universal standard for ship anchor cables because these benefits far outweigh the modest increase in manufacturing complexity and cost. The studs transform the chain from a simple tension member into a sophisticated anchoring system component.

Increased Weight for Catenary Formation

The studs increase the weight of the chain by about 15 to 20 percent compared to unstudded chain of identical link diameter. This additional weight causes a more pronounced catenary to form when the chain is deployed. The catenary—the natural curve the chain adopts under its own weight—is essential because it ensures that when the ship tries to drift away, the pull on the shank exerted by the chain is horizontal rather than angled upward.

With insufficient catenary, the chain would pull more directly on the anchor, creating an upward vector that lifts the shank and reduces holding power dramatically. The extra weight from the studs allows the chain to sag more deeply, maintaining horizontal pull at the anchor even when the vessel surges in waves or wind gusts. This is why heavier chain generally provides better anchoring performance even if the tensile strength is adequate—it's not about preventing breakage but about maintaining proper geometry.

Prevention of Link Deformation

When a link is subjected to tension, it tends to increase in length with a corresponding decrease in breadth—the link tries to elongate and narrow under load. The stud fitted across the link interior prevents the reduction in breadth, thereby preventing increase of length. This dimensional stability is very important because each stud has to exactly fit into grooves provided on the gypsy of the windlass and also on the compressor type of bow stopper (referred to as cable compressor).

If links deformed under repeated loading cycles, the studs would no longer align with the gypsy grooves, causing the chain to jam or ride up on the gypsy. The windlass would be unable to heave in the chain properly, potentially leaving the anchor stuck on the bottom or the chain hanging in a bight. The dimensional stability provided by the studs ensures that after thousands of deployments and retrievals, the chain still engages cleanly with the windlass mechanism.

Kink Prevention

Studs prevent kinks from forming in the chain. Kinks can form in unstudded chain when the chain is slack—two or more links can twist relative to each other, creating a compressed knot-like formation. When these kinks straighten out under tension, they do so with a jerk. A jerk causes a force which may be as much as six times the steady tension being exerted. This shock loading can break chain links, damage windlass components, or break out a well-set anchor.

The studs physically prevent adjacent links from rotating relative to each other in the manner that would create kinks. Even when the chain lies slack in a heap in the chain locker, the studs maintain link alignment. This is particularly important during anchor deployment when chain runs out rapidly—without studs, the violently moving chain could kink itself, then break when the kinks snap straight under the shock load of the anchor hitting bottom and the vessel continuing to drift.

CHAIN LENGTH AND SHACKLE UNITS

Standard Shackle Measurements

Anchor chains come in lengths of 15 fathoms each, connected by joining shackles. One shackle equals 15 fathoms which equals 90 feet or approximately 27.5 meters. Lengths of cable are thus expressed in shackles, with each shackle representing this standard unit. The shackle is an English measurement unit and all chain manufacturers globally make chains in one-shackle-length increments to ensure international standardization and interchangeability.

When classification rules require a specific total chain length—say 605 meters—this is increased to the nearest full shackle length to meet the rule requirement. For 605 meters: 605÷27.5 = 22 shackles exactly. But if the requirement were 610 meters, it would round up to 23 shackles (632.5 meters). For ease of operation, the total length is divided into two approximately equal halves, with each anchor connected to roughly half the total required length. One chain typically includes one extra shackle beyond the equal split—this extra length is the spare shackle required by classification rules.

The Bitter End Connection

The end of the chain furthest from the anchor is called the bitter end and is connected to a strong point in the chain locker. The most popular connection method is an instant release mechanism such as a senhouse slip which can be released from the forepeak store without requiring any person to enter the chain locker. This safety feature allows emergency anchor and chain abandonment if the windlass fails or the situation demands immediate release.

Provision must be made for securing the bitter end to ship structure with fastening capable of withstanding a force of not less than 15 percent and not greater than 30 percent of the minimum breaking strength of the as-fitted chain cable. This seemingly weak connection is intentional—the bitter end should be capable of holding the chain weight during normal operations, but it should be constructed so that it will break in case of emergency rather than damaging ship structure. If a dragging anchor cannot be recovered and threatens to pull the vessel onto rocks, the bitter end connection should fail before the chain locker structure tears out of the hull.

Spare Shackle Stowage

Classification rules require ships to carry one spare shackle of chain. This spare shackle is typically connected to one of the chains—making that chain one shackle longer than the other—because this is the most convenient stowage method. If kept in the forecastle stores, a spare shackle would occupy all available space and make it difficult to stow spare mooring ropes and wires. Hence on most ships either the port or starboard chain is longer by one shackle, and that extra length accounts for the spare shackle requirement.

The spare shackle allows repair of the working chains if a link becomes damaged or excessively worn. Rather than replacing an entire chain length, the damaged section can be removed and the spare shackle inserted to maintain required total length. This is far more economical than keeping entire spare chain lengths aboard, and the single spare shackle provides adequate redundancy for typical service needs between drydocking periods when chains can be thoroughly surveyed and replaced if necessary.

JOINING SHACKLES: LUG AND LUGLESS TYPES

Lug Shackle Construction

Joining shackles connect one chain length to another. They come in two types—lug (or D-type) and lugless. The shackle joining the chain to the anchor, usually referred to as the anchor shackle, can only be a lug shackle because it must have a pin which passes through a hole in the top of the shank. A lug shackle has two parts: a rounded part and a pin. The pin is oval in cross section and has a head at one end. The pin slides into the lug.

A tapering hole is provided through the lug and the end of the pin of the shackle. A tapered wooden spile pin is hammered tightly into this hole to prevent the shackle pin from coming out, especially due to vibration when the chain is slack. An iron nail is driven into the wooden pin to ensure a snug fit. To open such a shackle, an anchor-shackle rod punch and a sledgehammer are used to punch out the shackle pin. The wooden pin and iron nail get sheared off in the process. Though this seems primitive, it is remarkably secure and simple to maintain—there are no threads to corrode or seize.

Proper Lug Shackle Orientation

Lug shackles in the anchor chain must always be fitted with the rounded part towards the anchor. This orientation facilitates easy passage over the gypsy, cable compressor, and the top of the hawse pipe when the anchor is dropped. If installed backwards, the lug would snag on these components, potentially jamming the chain or damaging equipment. When lug shackles are fitted as joining shackles between chain lengths, the end links (first and last link) of every chain length would be an open link (without a stud) to allow the lug of the shackle to pass through.

Lugless Shackle Design

A lugless shackle consists mainly of four parts: two rounded sections, a stud, and a tapered steel pin. When assembled, a lugless shackle resembles a stud link, except that it looks thicker than a regular link. The two rounded parts slide into corresponding grooves to form an open link. The stud then slides into position by means of grooves provided for this purpose. There is a tapered hole into which the steel pin is hammered tight. Each end of the tapered hole is then plugged watertight by gently hammering in a suitable pellet made of lead.

Where lugless shackles are provided, there are no open links at the ends of chain lengths because there is no need for lugs to pass through them. This eliminates the structural weak point that open links represent. Lugless shackles maintain the same strength as studded links throughout the chain, providing more uniform strength characteristics. However, they are more complex to manufacture and somewhat more difficult to open for chain length reconfiguration or repair.

✘ Common Mistakes:
• Installing lug shackles with rounded part away from anchor—causes snagging
• Forgetting to drive iron nail into wooden spile pin—allows loosening
• Using wrong type of shackle at anchor connection—only lug type works
• Failing to secure lead pellets in lugless shackles—allows water ingress
• Not maintaining open links where lug shackles require them
• Mixing lug and lugless shackles without proper transition links
• Over-tightening or under-tightening wooden spile pins

CHAIN MARKING SYSTEM

Visual Length Indication

In most ships, all joining shackles are painted red. White paint and seizing wire are used as markers so that the amount of chain paid out can be determined at a glance from the forecastle deck. This marking system allows the officer supervising anchoring to quickly know how much chain is deployed without needing to count every link or measure with instruments. The system uses a progressive numbering scheme that encodes the shackle count in the number of marked links.

The Progressive Marking Scheme

First Shackle Marking:
• The first studded link on either side of the shackle is painted white
• Seizing wire or a jubilee clip is attached to the studs of those links
• This indicates one shackle (15 fathoms or 27.5 meters) paid out

Second Shackle Marking:
• The two studded links on either side of the shackle are painted white
• Seizing wire or a jubilee clip is attached to the stud of the second studded link on either side
• This indicates two shackles (30 fathoms or 55 meters) paid out

Third Shackle Marking:
• The three studded links on either side of the shackle are painted white
• Seizing wire or a jubilee clip is attached to the stud of the third studded link on either side
• This indicates three shackles (45 fathoms or 82.5 meters) paid out

This pattern continues progressively—four white links for the fourth shackle, five for the fifth, and so on. The seizing wire or jubilee clip always attaches to the outermost white link in the sequence, providing tactile confirmation of the count. Even in darkness or poor visibility, an experienced seaman can feel the number of white-painted links and the position of the seizing wire to determine how many shackles are deployed.

The red paint on the joining shackles themselves provides warning that a shackle is approaching—when red paint appears in the hawse pipe, the operator knows to slow the chain runout to avoid deploying more than intended. This simple but effective system has prevented countless incidents of running out the entire chain inadvertently, which would result in losing both anchor and chain if the bitter end connection failed as designed.

ANCHOR END COMPONENTS

The Turning Pendent

At the anchor end, a turning pendent is connected between the anchor and the connecting shackle. This turning pendent is provided to allow free rotation of the anchor when it is lifted out of the water without allowing the chain to twist. The need for this component becomes clear when considering what happens during extended anchorages. In a day, whilst at anchor, the ship drifts through one complete circle around the anchor caused by tidal changes. The anchor chain gets twisted by one turn per tidal cycle. If the ship is at anchor for 10 days, it accumulates 10 turns of twist.

When the anchor gets lifted out of the water, the stored twist energy in the chain is released, causing the chain to unwind along with the anchor. The anchor, being heavy, will gain high rotational momentum and hence will continue turning even after the chain has straightened. This continued rotation would hinder hauling the chain through the hawse pipe as the spinning anchor catches on the pipe lip or damages the hull plating. The turning pendent solves this by absorbing the rotation—it allows the anchor to spin freely without transmitting that rotation up the chain, acting as a swivel bearing.

Chain Stowage and Routing

The chains are stowed in two separate chain wells placed in the chain locker forming part of the forepeak tank. The chain is led out of the locker through a pipe with a bell mouth at the inner end—this pipe is called the spurling pipe. The bell mouthing is provided to enable the chain to move in a rotating fashion as it is being stowed while heaving up the anchor. This rotating motion enables the chain to be stowed properly without forming a heap that would jam on subsequent deployments.

The chain passes out of the spurling pipe, wraps around the cable lifter (the gypsy on the windlass), and enters the hawse pipe where it is connected to the anchor. The reason stud links are used is they reduce free movement of the links within the chain locker and thereby prevent kinking of the links. When kinking happens, the free flow of the chain is prevented by a lump of chain getting stuck at the bell mouthing, preventing free runout during anchoring operations. This can leave the anchor hanging with insufficient chain deployed to set properly—a dangerous situation in an emergency.

EQUIPMENT NUMBER CALCULATION

What Equipment Number Represents

The Equipment Number (EN) is a dimensionless parameter used to determine the size and number of anchors, chain cables, and mooring and towing lines for a new ship. It is calculated from the vessel's physical characteristics using a formula provided by classification societies. The EN serves as an index into standardized rigging tables that specify required anchor weights and chain specifications. This system ensures that vessels carry anchoring equipment appropriate to their size and wind-current exposure without requiring custom engineering for every ship.

However, it is important to remember that the anchoring equipment determined in accordance with the Equipment Number is intended for temporary mooring of a vessel within a harbour or sheltered area when the vessel is awaiting berth, tide, or similar short-term holds. The equipment is therefore not designed to hold a ship off fully exposed coasts in rough weather or to stop a ship which is moving or drifting. In such conditions, the loads on anchoring equipment increase to such a degree that components may be damaged or lost owing to the high energy forces generated, particularly in large ships.

The EN Formula

The equipment number EN on which the requirements of equipment are based is calculated as follows:

EN = K × ENc

where:

ENc = Δ^(2/3) + 2BH + 0.1A

• Δ = moulded displacement in tonnes to the summer load water line
• B = greatest moulded breadth in meters
• H = effective height in meters from summer load waterline to top of uppermost deckhouse
• A = area in square meters in profile view of hull, superstructures and houses above summer load waterline within Rule length
• K = factor depending on vessel type and service notation

Effective Height H Calculation:
H = a + Σhi

• a = distance in meters from summer load waterline amidships to upper deck at side
• hi = height in meters on centreline of each tier of houses having breadth greater than B/4

Service Factors and Considerations

The K factor varies by vessel type. For fishing vessels, K equals 1.00. For other vessels, K equals 1.00 for vessels of Unrestricted Service and 0.85 for vessels of Coastal Service. This recognizes that coastal service vessels generally operate in less severe conditions than unrestricted service vessels and may justify slightly reduced anchoring equipment.

In calculating H and A, sheer and trim are to be ignored. Parts of windscreens or bulwarks which are more than 1.5 meters in height are to be regarded as parts of houses when determining H and A. The height of hatch coamings and that of any deck cargo such as containers may be disregarded. These rules simplify calculations while capturing the primary factors affecting wind loading on the vessel.

The Equipment Number formula is based on assumed maximum current speed of 2.5 m/s, maximum wind speed of 25 m/s, and minimum scope of chain cable of 6 (the ratio between length of chain paid out and water depth). For ships with Rule length greater than 135 meters, the required anchoring equipment is also considered adequate for maximum current speed of 1.54 m/s, maximum wind speed of 11 m/s, and waves with maximum significant height of 2 meters. It is assumed that under normal circumstances a ship uses only one bow anchor and chain cable at a time.

❕ Important: The EN is given in the class certificate, so there is no need to refer to calculation formulas whenever EN is needed, such as when ordering new chain lengths after old chain has worn beyond rule requirements.

USING THE RIGGING TABLE

Matching EN to Equipment

Having found the equipment number, the details regarding anchor sizes and chain specifications may be obtained from the rigging tables provided in classification society regulations. These tables list EN ranges in the first column, with corresponding equipment letters, anchor weights, total chain lengths, and chain diameters for three grades of steel in subsequent columns. The process is straightforward: calculate EN using the formula, locate that EN value in the table's range column, and read across to find the required specifications.

As an example, consider the EN range 2380 to 2530. The corresponding equipment letter is J+, each anchor weighs 7350 kg (7.35 tons), and the total length of chains provided is 605 meters. Since chains always come in shackle lengths of 15 fathoms each, the rule length is increased to the nearest full shackle length to meet the requirement. For ease of operation, the total length of 605 meters is divided into two equal halves, and the nearest minimum full chain length in shackles per chain is given by: (605÷2)×(3.7878÷90) = 12.73 shackles. The nearest full shackle length is 13 shackles. Hence each anchor will be connected to 13 shackle lengths of chain.

Chain Grades and Diameter Selection

The chain links are graded according to carbon content in the steel and corresponding heat treatment. Three standards of link material are graded as CC1, CC2, and CC3—representing low strength, medium strength, and high strength respectively. Owners are free to choose any grade from the three qualities. Having selected a grade, the same grade must be used throughout the chain length for the full life span of the ship since the cable lifter slots are made per the diameter according to the grade selected.

Higher grade steel allows smaller diameter chain for the same strength, which means lighter chain. However, lighter chain provides less catenary for the same paid-out length, which can reduce holding power even if tensile strength is adequate. Many operators prefer the middle grade (CC2 or Grade 2 or Special Quality) as it balances adequate strength with sufficient weight for good catenary formation. The lowest grade (CC1 or Grade 1 or Mild Steel) is rarely specified for large vessels as it requires very large diameter chain that is heavy to handle and stow. The highest grade (CC3 or Grade 3 or Extra Special Quality) is common on modern large vessels where reducing chain weight is important for stability.

ANCHOR TYPES FOR DIFFERENT VESSELS

Beyond Stockless Anchors

While stockless anchors dominate merchant shipping, other anchor types serve specialized purposes. The stockless anchor's advantage lies in handling and stowing—it self-stows in the hawse pipe without crew intervention. But for vessels where these factors matter less, alternative designs may offer better holding power per unit weight. Small craft, yachts, and specialized vessels often use different anchor types optimized for their specific operational patterns.

Bruce Anchor: Features three claws that dig into the bottom. Sets easily but doesn't penetrate deeply, making it suitable for short stops in moderate conditions but unreliable for overnight anchoring above 6 Beaufort wind force. Popular for lunch stops and temporary holds.

CQR (Plow) Anchor: Uses a hinged plow-shaped fluke that digs in well, particularly in mud or sand. The hinge allows about 75 degrees of sideways motion each side, maintaining hold when wind or current changes direction. Penetrates better into weeds and grasses than some alternatives. Patented in 1933 and remains popular for yachts and small commercial vessels.

Delta Anchor: A variation on the CQR by the same manufacturer. The principal difference is the fixed shank without hinge, and altered shape allowing automatic deployment from bow roller. The flukes are improved for better initial penetration. The fixed shank provides more predictable setting behavior than the hinged CQR.

Danforth Anchor: Introduced in 1939 with low weight but incredible holding power in easy-penetrable seabeds except very fine sand. Features pivoting flukes at the bottom of the shank that bury themselves deeply. Considered the storm anchor par excellence when holding ground is suitable. The Fortress and Performance versions represent high-quality implementations of this design principle.

Spade Anchor: A modern design that sets and resets easily, self-launches off the bracket, and provides excellent holding in most bottoms. The concave fluke shape creates suction in soft bottoms while the pointed tip penetrates hard surfaces. Popular on cruising yachts.

Mushroom Anchor: Shaped like an upside-down mushroom and used widely as permanent moorings for lightships, dredges, and lighters. Relies primarily on weight and suction rather than fluke penetration. Not suitable for temporary anchoring as it requires time to bury itself through wave action and current scouring.

Good to Know

Kenter shackles are specially designed joining shackles with a double-hinged construction that allows them to pass smoothly over the cable lifter gypsy despite being thicker than regular links. They can be opened and reassembled without special tools, making them ideal for connecting lengths when reconfiguring chain.

Good holding ground is normally marked on nautical charts by an anchor symbol. The abbreviation indicates bottom type: M (mud), S (sand), Cl (clay), St (stones), R (rock), Co (coral), Sh (shells), Wd (weed). Mud and clay provide best holding, rock and coral provide worst.

Chain length on ships varies between 86 meters to 770 meters depending on the size and dimensions of the vessel, with very large ships carrying significantly more chain than the minimum required to allow deep-water anchoring.

Anchor weight ranges from 660 kg for very small commercial vessels to over 46,000 kg for the largest ships. VLCCs and ultra-large container ships can have anchors exceeding 20 tons each.

Hawse pipe design includes a recess at the hull to house the anchor when stowed, with internal reinforcement to withstand anchor impact loads during heavy weather when the anchor may surge in and out slightly.

Windlass arrangements may be split (separate windlass for each anchor) or combined (one windlass with two cable lifters). Combined arrangements save space but prevent simultaneous anchor operations.

Anchor dredging occurs when insufficient chain is paid out and the anchor drags along the bottom rather than holding. The officer on watch will notice the ship is moving relative to fixed points ashore or that the chain grows taut rather than maintaining a catenary.

Rock anchors are hook-like devices used to connect directly to rocks above water in some Mediterranean mooring situations, while helical screw anchors are manually screwed into sandy beaches in places like Greece and Turkey.

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