With so many anchor options out there, how do we know which ground tackle is best?
Usually, anchor manufacturer recommendations are based on a boat’s length or tonnage. Performance testing data of different anchor styles in various bottom types can be a good starting point to determine which type of anchor is appropriate for your boat. Tables for minimum anchor size and holding power performance are available online. But most importantly, do you have the right anchor for your sea bottom type?
What you’re looking for when buying an anchor is holding power, how it burrows into the seabed. Most cruising boats face varying conditions and opt for two (or more) anchors to ensure the right anchor is available for different bottom types. Well-prepared cruising boats also carry a large storm anchor and/or an anchor specifically for kedging off in emergencies. Dayboats, or local cruisers that encounter the same local bottom types, match anchor selection to the area’s most common bottom type.
If your boat is heavier than the average boat of that length, or if it presents more windage, you should select a larger anchor. The same holds true for the rest of your ground tackle; shackles, swivels, and rode. Boats used for long-distance cruising may need to anchor in rough weather, certainly requiring heavier gear. But a huge anchor is only as good as your ability to handle it. It must be manageable by your crew and your equipment and easily deployable at a moment’s notice.
When an anchor penetrates the surface of the seabed, suction created by the bottom material, plus the weight of the material above the anchor, creates resistance. In rocky or hardpan bottoms, anchors can’t dig in, but may snag on protrusions and have a precarious hold. The selection of a suitable bottom for anchoring is as critical as the design of the anchor. Whenever possible, avoid poor holding ground like hardpan, rocky patches or thick grass. The bottom type is on your charts. If you don’t already know them, learn to understand the bottom types and their chart symbols, and your anchoring success will be greatly improved.
Sand: A sandy bottom is relatively easy for anchors to penetrate and offers consistently high holding power and the best reliable results. Most anchors will hold the greatest tension in hard sand. Aim for sand! Pivoting-fluke anchors such as the Danforth are great in sand for smaller boats. Non-hinged scoop and plow anchors are the best types in sand for boats with bow rollers.
Mud: A muddy bottom requires anchor designs with a broader shank-fluke angle and greater fluke area to provide more surface area. This allows the anchor to penetrate deeply to where the mud has greater shear strength. Remember too, that soft mud often lays thinly over some other material, so anchors that can penetrate through the mud to the underlying material will hold better. Again, the Danforth performs in mud for smaller boats. Fortress anchors have greater holding power in mud because they can be adjusted from their standard 32° to a broad 45° fluke angle.
Clay, shale or grass: These are difficult bottoms for all anchor designs. The weight of the anchor, more than its design, may be the most important factor in penetrating these stubborn surfaces. If the anchor can’t dig in, it will never hold. An anchor style with a pointed tip such as the modern Rocna, Delta and Supreme anchors are ranked best due to their ability to penetrate vegetation. Keep in mind that your anchor may act like it’s holding, catching on roots or protrusions, then suddenly let go when the wind comes up.
Rocky: Holding power in rocky bottoms is as dependent on luck as it is on the type of anchor you have. You might just drop it in the right place, but the success of your anchoring will depend on your anchor’s pointy ends. Chain is necessary to resist abrasion and a trip line is recommended to release your anchor, just in case it hooks under a ledge or boulder. Plow-shaped or grapnel-type anchors, with high structural strength to sustain the high point-loads, generally work the best. These anchors include the Claw, CQR, Rocna, Supreme and the Fisherman.
Underwater debris or obstructions can foul even the best of anchors. I once anchored in a designated anchorage known for its holding ground, went ashore to buy groceries and returned—appalled—to find the boat had dragged across the harbor, even though it had fetched up initially. It took some doing to retrieve the 66-pound Bruce, but when it came up, so did a complex remnant of chain link fencing wadded up around the anchor.
Despite advertising claims to the contrary, no single anchor design is best in all conditions. Read the test results, compare features of each style and watch the videos to learn the pros and cons in varying conditions. Then make the best choice for your bottom conditions. The old standard Danforth anchor is a good choice for a smaller boat without a bow roller because it folds flat, is easy to stow and has great holding power for its weight. Its wide, sharp flukes sink into sand and hard-mud bottoms, but are less effective in deep mud or a grassy bottom.
Beware though, if the wind shifts and your boat rotates to the opposite direction from which the anchor was set, a Danforth anchor can pull free.
The single point plow and scoop styles, represented by the Manson, Mantus and Rocna, CQR, Delta and Claw, have the best all-around reputations for holding ability in varying bottom conditions. They generally reset themselves easily if the wind or current changes direction. The newest scoop designs include round “roll bars” that self-right the anchor, automatically turning it right side up. Plow/scoop anchors, even though they hold more effectively in grass, mud and sand have a shape that makes stowing them more awkward. That makes them more suitable for boats with bow-rollers or bowsprits, which is why heavier powerboats and cruising sailboats often use plows as primary anchors.
Sometimes you may have to select a particular anchor for a unique purpose. One season I was recovering from surgery, which prevented me from quickly and easily handling our anchor. Not wanting to give up single-handing, I opted for an aluminum Fortress anchor. It weighed a fraction of my Danforth, stowed easily and had superior holding power in soft bottoms. The downside? I quickly learned to avoid eelgrass beds—to my great frustration, the lighter anchor would swim above the grass and not set.
The right anchor for a dinghy? Most people opt for a folding grapnel or a small, plastic-coated mushroom because both stow nicely without damage in a small boat. I’ve always had the best luck with a grapnel placed strategically on the bottom. These small anchors are OK when you’re watching the boat, but for unattended anchoring, I recommend a nice little Danforth—a “lunch hook.”
Don’t forget about your rode. Three-strand nylon is normally the small boat material of choice, because its elasticity absorbs shock loads. To weigh down the anchor shank for better penetration and protect the rode against abrasion, a short length of chain can be shackled to an otherwise all-rope rode. For small boats, a general rule of thumb is a boat length of chain. For serious cruisers, all-chain rode and an anchor windlass is probably a better option.
Whichever anchor(s) you choose, proper setting technique will optimize the anchor(s) effectiveness. The pull of the anchor rode, acting on the leverage of the anchor’s shank, causes the flukes or plow tip to dig in deeper, thus creating additional resistance. The stock is designed to help the anchor dig in evenly, rather than roll or catch on one fluke alone. Using your anchor is an exercise in mindful seamanship. Stop the boat’s forward progress, lower the anchor to the bottom in a controlled fashion, then back away from it while letting out the rode. Never throw the anchor out through the air, Popeye-style, or dump a pile of chain on top of the anchor. Both are good recipes for fouling the rode around the anchor, which may prevent it from setting. After letting out the rode, snub it off and slowly power in reverse to bury the anchor. Many boaters make the mistake of not backing down hard enough to tension the rode sufficiently to bury the anchor. Three common things that will prevent the anchor from burying itself are trying to set the anchor on scope that is too short, reversing too abruptly, or failing to apply a reasonable strain on the anchor rode.
Most boating experts agree that, for greatest anchoring security, you should carry two anchors of different styles, one Danforth style and one plow/scoop variety. What you’re looking for when buying an anchor is holding power. Do your homework, know your bottom type and always keep your ground tackle ready to deploy at a moment’s notice. Remember, this is not gear you want to compromise on. Anchor in the right place for your anchor, run out plenty of scope and you’ll be confident in a big blow. If your boat becomes disabled, it’s the anchor that’s going to keep it from drifting into danger.
This article was originally published in the October 2022 issue.