Anchoring

Revised by BoatUS Magazine editors in April 2012

With so much investment literally riding on your anchor, your boat's ground tackle system is no place to cut corners. Your choice of anchor depends on the size and type of your boat, and the weather and anchoring conditions you generally encounter, although you should always be prepared for the worst. Boats with heavy displacements or superstructures that present a lot of wind resistance often need heavier gear. Boats with underbodies that are affected more by the current may need heavier gear than relatively flat bottomed boats. Heavier gear will be needed by cruising yachts that brave a wide variety of conditions and may sometimes have to anchor in open water. Even if you're a confirmed fair weather boater, remember that the true test of your ground tackle will come in adverse conditions when you need it most. You never know for sure what the weather will do or when you will have a breakdown. So, when talking anchors, bigger is better, and there's safety in numbers. No anchor can be all things to all bottoms, so have aboard at least two anchors of different designs to handle varying conditions. Finally, keep an anchor stored in a way so that it’s ready to go. There are stowage systems available for every type of anchor. These include brackets, bow rollers and chocks. Don't let convenience outweigh common sense if it means your primary anchor has to be assembled before it can be deployed.

Which Anchor?

Fluke (Danforth-type) or Light-weight

DanforthThis popular burying anchor has wide, sharp flukes. Its excellent holding power-to-weight ratio means it can be lighter than some other types of anchors used for the same conditions. As with any type of anchor, there are some negatives. The projecting flukes can be fouled by seaweed, shells, etc., preventing the anchor from setting. They are also somewhat unwieldy. Also, if tide or wind cause the boat to drift in the reverse direction from which the anchor was set, pulling the rode over this type of anchor in the process, it is possible for the anchor rode to foul in the anchor, pulling it out of the bottom. Setting two anchors can normally stop this from happening. Keeping watch when tide or wind reverses can also help with this problem. Further, if the anchor is buried deep enough in the bottom, this is less likely to happen. However all anchors have one or more drawbacks, and this type of anchor has been very successful over the years.

High-tensile strength aluminum models such as the Fortress are relatively light but can, as does the Fortress, have excellent holding power. Some models like the Fortress are not only quite light but can also be disassembled for easy stowage or quickly re-assembled. Thus a large model of this anchor could serve as an ultimate storm anchor. Fluke-type anchors hold very well in soft bottoms like mud and sand, but tend to slide on grass and skip on rocks, as do most anchors. In very soft mud or hard sand these anchors will often hold well when few other anchors will. The angle of attack of the fluke on the Fortress can be set with a plate to better accommodate mud or sand.

Plow

An efficient anchor, the plow features a single swivel at the shank base which inhibits it from breaking out when the direction of pull changes. The original patented CQR, made of steel forgings, is the favorite of many long term cruisers because of its construction, versatility and reliability. The plow will have difficulty holding in hard sand or other hard bottom, as is true of most anchors. The plow is usually effective in light grasses, and usually very effective in sand, and mud. Few anchors, including the plow, will hold well in heavy grass. In heavy grass it is more likely to hold (as is true of other types) if you are lucky enough to find a sand or mud hole which is bare of grass, but any anchor which appears to be holding in grass may suddenly break free in the middle of the blow as the last root of grass lets go, leaving the anchor to slide across the bottom with a clump of grass impeding its ability to reset. This anchor can be handled easily with bow rollers. And because it has no projecting fluke or stock, it is less likely to foul in the anchor rode.

Claw

A relative newcomer features a three-claw scoop design. It sets in most conditions in which other anchors will set.  It is reported to set in gravel. It has one-piece construction. It is usually stowed on rollers.

Herreshoff Anchor

Also often known as the Fisherman’s anchor, this anchor is better than most for holding in rocks, marl and hard bottom with small holes into which it can hook. It also frequently does better than other anchors in heavy grass, although beware the false security mentioned above whenever you anchor in grass. Many serious cruisers carry an anchor of this type for the limited times they may have to anchor in such bottoms. However, this anchor is somewhat prone to pull out of rock or grass or become fouled on its rode if the direction of boat swing reverses.

Other Designs

New designs are appearing on the market and some may hold great promise. However it’s important to thoroughly check out any new design by relying on knowledgeable experience rather than by merely reading advertisements or product reviews written by people who haven’t had a great deal of long term real life experience with the anchor, as well as with other types and with anchoring in general and in severe weather over varied bottoms. If an anchor fails to hold it may be at the worst of times with very serious consequences.  Many seasoned cruisers prefer tried and true anchors known and used for many years and in many conditions.

Ground Tackle Holding Requirements

Now that you have an idea about the type of anchors you may need, check the chart to determine the holding power you require. Since modern anchors are so efficient, it's their holding power, not necessarily their weight that proves their adequacy, although weight usually helps. In the chart below, find your boat's length or beam, whichever produces the greater load. Also, compensate liberally for relevant variables. For example, a houseboat may need the load capability for the next larger powerboat size. Next, match it to your intended use for the anchor (lunch hook, working, or storm anchor) to determine the minimum holding power you need. Cruising boats should consider carrying all three categories of anchors. However, always remember that there are few certainties when it comes to anchoring and overkill is always best. And this table is for guidance only. Always get the recommendations of the product manufacturer.

Boat Dimensions Horizontal Load (lbs.)
Length Beam (Power)Beam (Sail )Lunch HookWorking AnchorStorm Anchor
10’5’4’40160320
15’6’5’60250500
20’8’7’90360720
25’9’8’125490980
30'11'9'1757001,400
35'13'10'2259001,800
40'14'11'3001,2002,400
50'16'13'4001,6003,200
60'18'15'5002,0004,000
Anchor Rode

Depending on the size and type of your boat, your choices are either a combination rope/chain rode, or all chain. Rope should be nylon, either three-strand or braided, although most serious cruisers prefer three stranded. Nylon rope has elasticity which makes it a great shock absorber for sudden loads caused by wind and waves. Three-strand line should be medium lay, which has more twists per foot than soft lay. This is particularly important for use with a windlass, as the soft lay strands can untwist and separate, fouling the equipment. It is also important as to abrasion and tears while moving across the bottom. Three-strand rope can eventually become awkward to handle, especially when hardened by salt saturation or stiffened by constant exposure to the sun and weather. At this point it is usually best to get new line rather than take a chance with aged line. Braided line, which many consider to be excellent for dock line, often has a tendency to deteriorate from snags and abrasion when used for anchoring, although it is generally stronger and easy to work with. Remember that what you can’t see on the bottom can be very damaging to rope. (See Choosing the Right Rope).

Don’t scrimp on your anchor line.  All nylon rode will be more likely to foul on your running gear or keel or rudder if you have reversing currents or winds, because it is more likely to briefly float as the boat moves around and reverses its pull, while a chain is heavy and drops quickly to the bottom. Chain, used alone or in combination with nylon line, offers great benefits: It decreases the angle of pull on the anchor allowing it to set and hold more effectively, it's unaffected by chafe from rocks or sharp surfaces on the bottom, it helps to keep the boat from sailing about in winds, its weight forms a curve that, because of the catenary effect, helps to absorb shock loads in heavy weather, and, in the case of all-chain rode, it may require less scope for the same holding power as rope. If you use an all chain road, as do many, use also a nylon snubbing line. This will have one end secured to a strong cleat or other point at the bow and the other attached to the chain, at least several feet from the bow (preferably more), by a chain hook or some other means. (Some suggest that a chain hook will impair the galvanization on the chain, but this seldom occurs on quality chain which must sustain constant abrasion from obstructions on the sea floor.) After the anchor is set the snubbing line is attached and then the chain is played out so that there is a loop of chain between the point where the chain leaves the prow (as on the roller) and the point where the snubbing line is hooked to the chain.  This arrangement adds the elasticity of the nylon snubbing line to the rig and also increases the catenary effect of the chain because of the weight of the loop.

All chain is not created equal, however. Due to the inconsistent quality and often substandard galvanizing of many imported chains, we recommend that you buy chain made by North American companies unless you are sure of what you’re getting. Proof coil is one commonly used chain for anchor rodes. Made from low-carbon steel, it is identified by "G-3" imprinted on each link, and is adequate for many marine applications. BBB chain is slightly stronger than proof-coil, and has short links allowing a snug fit into windlass chain wheels. BBB is also preferred by many cruisers using all-chain rode. Hi-test chain is made from higher carbon steel that has been surface-hardened. It has a higher strength-to-weight ratio than proof coil and is favored by the weight-conscious, as it can in theory reduce the weight in the bow by up to 30% without sacrificing strength. But remember, within reason, the heavier your chain the more likely your anchor will set and hold well. Whatever chain you get, make sure if fits the cogs in the chain wheel on your windlass. This is best done by taking that wheel off the windlass and to the store so that you can lay the chain on the wheel, or taking a short length of the chain to the windlass on the boat.

Suggested Minimum Working Rode Sizes*

(For winds up to 30 knots.)

L.O.A.
Beam (Sail )
Beam (Power)
Nylon Rode
Chain Rode
10'
5'
5'
125’-3/16”
3/16”
15'
7'
7'
150’-3/8”
1/4”
20'
8'
9'
150’-3/8”
1/4”
25'
9'
10'
150’-3/8”
1/4”
30'
10'
11'
200’-7/16”
5/16”
35'
12'
13'
300’-1/2”
3/8”
40'
13'
14'
400’-5/8”
7/16”
50'
14'
16'
500’-5/8”
7/16”
60'
16'
19'
500’-3/4”
1/2”
*Suggested sizes assume fair holding ground, scope of at least 5:1 to 10:1, and moderate shelter from high seas. Boats that operate generally in shallow waters, as on the East Coast of the United States, may get by with shorter rode lengths.
Setting the Anchor

For a firm set and a good night's sleep, follow these simple guidelines:

Choose your spot carefully, considering the shelter it offers, whether it's a good holding bottom, and the proximity of other boats and obstructions both above and below the water. Remember that boats of different sizes may swing to a different scope than yours, so give other boats as wide a berth as possible to avoid any wee-hours fending off. Don’t anchor where your swing radius will intersect that of another boat. Never assume that all boats will swing the same direction at the same time. Circle the area where you plan to drop the anchor to be sure that there are no shoals into which you might swing as the tide and/or wind changes.

Approach your spot slowly, and put the boat in reverse when you're over the desired location. When the boat begins to gather sternway, lower the anchor to the bottom, and gradually pay out the rode. Be very careful to avoid injury to hands, feet or other injury. Take a turn around the bitt or cleat if you’re using nylon rope or secure the chain by a nylon snubbing line, progressively snugging up the rode and causing the anchor to "bite" and dig in as you continue to back down. Then pay out the rest of rode to the appropriate scope, backing down again. The amount of power used in backing down to set your anchor will depend on your boat, prop, engine and many other circumstances. Use enough power to be sure you’ll hold in a blow, but not so much that you’ll damage your equipment or cause injury. Finally, check the set of the anchor by sighting two stationary objects (preferably ashore) that can form a range, and check your position periodically, as you continue to back down and also at later times, in relation to the objects. Any change in their bearings means you'd better try again.

In most circumstances setting only one anchor will suffice. However, if you anchor in an area of strong reversing currents and poor holding or if you expect a storm with strong clocking winds, or in some other circumstances, it may be much better to set two anchors. This requires special tactics which are beyond the scope of this article. If you set two anchors and other boats near you only have one, you may be setting up a collision because they will swing in a much wider circle than you. And deploying two anchors may create other problems. For example, if your rodes twist together from boat swinging this makes it very difficult to get the anchors free and on the boat quickly—which is sometimes very important.

Determining Scope

The amount of anchor rode paid out depends on many things including the type of rode you're using and the weather and bottom conditions. Scope is the ratio of rode paid out to the depth of the water. The key is to keep the angle of pull on the anchor as close to horizontal as possible. Heavy weather or adverse anchoring conditions demand longer scope; however, keep in mind how you'll swing in relation to your neighbors and obstructions, including nearby reef and shoals. A widely used rule of thumb is to pay out at least 5 to 7 times the distance from the point where the rode leaves your prow (as, for example, the roller) to the bottom.  However this can vary with circumstances. For example, expectation of bad weather may dictate much more scope. A soft muddy bottom may require much more scope. You may be able to use slightly less scope with some anchors and an all chain road in settled weather and a good bottom. Less scope may be necessary if you’re in a crowded harbor, but it’s best to avoid this situation. As a general rule, the more scope you use (within reason) the greater your likelihood of holding, but you must keep the location and swinging radius of other boats in mind, as well as the location of obstructions and shoals and reef.

Retrieving the Anchor

Break out your anchor by powering up to it slowly (with your engine, not your windlass), taking in the rode as you go. (See Anchor Windlasses.) Once over the anchor, if you have a small boat, it may work to move all the crew to the bow, snub the anchor rode, and move aft. You should be able to lift it vertically. If it resists or if your boat is too heavy for this method, take in the rode until you’re over the anchor, snub the rope around the bitt or cleat, or secure the chain with a strong snubbing line to a strong cleat or a chain stop (not with the windlass) and power forward slowly so that you pull the anchor up in the opposite direction from that in which it was set. Take care not to carve up your topsides. A handy device for some boats is an anchor retrieval system, which uses a sling which you slide down the rode to help break the anchor free.

Some prefer to use anchor buoys, claiming that they help with retrieval. This involves tying one end of a line to the forward end of the anchor and the other to a float. They then snag the float with a boathook and pull up the anchor backwards. However, anchor buoys are seldom a good idea. First, other boats passing in the night may snag them, not only damaging the other boat, but pulling your anchor free. Secondly, it isn’t unusual for the boat deploying the anchor buoy to swing during the night as the wind and/or current changes, and snag the buoy and its line on the boat’s prop, rudder or keel.  This can then pull up the anchor.  If the buoy and line is snagged on the prop, as occurs more often than you might think, you wake up in the middle of the night, realize you’re dragging, hit the ignition switch and shift into gear to keep yourself off the reef or the bank or the nearby boat, and pull up your anchor and disable your boat all at the same time.

Whatever system you choose, remember that your boat's ground tackle system is a very important part of its safety equipment. Buy the best and check the gear often for signs of chafe and wear. With so much at stake, don't let the anchor and chain or chain/rope combination be your system's weak link.

 

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