Selecting the Right Anchor
Manson Supreme is a state-of-the-art scoop with roll bar to self-right and a slot for easy retrieval.
The type of bottom—mud, grass, sand, coral or rock—will dictate different choices of anchors, as will the size and windage of the boat, the wind conditions and the seastate. Some anchoring situations also call for more than one anchor to be used simultaneously.
You sometimes need to set two anchors in a crowded anchorage, with anchors at the bow and stern of the boat to limit its ability to swing. Two anchors set from the bow at a 60° angle are another good way to improve security against swinging and dragging, and they allow you to shorten the rodes and use less scope. In heavy weather conditions, where one anchor may not have enough holding power, setting a second anchor may be critical to staying put. Remember that as the wind speed doubles the force on the boat (and the ground tackle system) increases by four times.
Anchor styles for different bottom conditionsWhile the above cases show the need to sometimes set two anchors at once, having two anchors of different designs help ensure good holding in different types of bottoms. One anchor of the Danforth style and one plow anchor are typically all you need. Except for coral and rocks, where the old-fashioned Yachtsman anchor may work best, either a plow or a Danforth should hold adequately in most conditions.
The most popular anchor style is the fluke anchor, also called the Lightweight or Danforth. Light and easy to weigh, it stows flat and holds very well in mud or sand. Its excellent holding power–to–weight ratio means you can use a lighter anchor compared to other types, but it doesn’t hold well in grassy or rocky surfaces. Its flukes and stock (the wide crossbar at the top) are more prone to foul on rocks or the anchor line.
Plow and scoop anchors, the “single point” style represented by the CQR, Delta, Claw, Manson Supreme and Rocna, have the best all–around holding ability in varying bottom conditions. They generally reset themselves easily if the wind or current changes direction, and hold more effectively in grass, mud and sand. They do not have projecting flukes that foul easily, but their shape makes stowing them more awkward (a bow-roller or bowsprit is the best solution). Heavier powerboats and cruising sailboats often use plows as primary anchors.
Delta is a modern plow-style anchor that’s popular in boats with bow rollers.
How big is big enough?Sizing an anchor for your boat reinforces, with some limits, the “bigger is better” idea. If your engine fails and you are drifting toward a lee shore, having a properly sized anchor ready could save your boat. But raising the anchor by hand, with no electric powered windlass, calls for light and efficient ground tackle (and a strong back). Take the anchor manufacturer’s suggested sizes into account and consider your boating style. Do you typically anchor for two hours or for two weeks, in a lake or in the Atlantic Ocean?
The most outspoken advocate of big anchors is probably naval architect Steve Dashew. Just to stimulate arguments in the yacht club bar, we’ll quote his viewpoint. His advice: “Look at the average size of anchor in use for boats of your type, and double the size. After doing this, if you think you can swing it, add another 50 percent.” Of course, he is talking about bluewater cruising here, and standing up to hurricanes, not a day at your local lake.
Holding powerWhat you are looking for when buying an anchor is holding power, which may have little relation to the anchor’s size and weight. 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 coral bottoms anchors can’t dig in, but rather snag on protrusions and hold precariously. The holding power of modern anchors is remarkable, varying between 10 and 200 times the anchor’s weight. This means that some anchors that weigh only 5lb. can hold in excess of 1,000lb! But with the widely varying conditions in the real world, how do you select the anchor that’s right for your boat?
The Fortress, an aluminum-magnesium Danforth-style, has shown incredible holding power in 2006 anchor tests, with the 21lb. FX37 sustaining over 5,000lb. of load.
Anchor attributesIdeally, an anchor should possess the following attributes:
Assessing bottom conditionsAnchors need to develop enough resistance in the seabed to withstand the environmental forces on the boat—the wind and the waves. An anchor’s ability to develop resistance is entirely dependent on its ability to engage and penetrate the seabed.
Sand: fine-grained sand is relatively easy for anchors to penetrate and offers consistently high holding power and repeatable results. Most anchors will hold the greatest tension in hard sand. Pivoting-fluke anchors and non-hinged scoop anchors are the best types in sand. The Rocna performed excellently in anchor tests in sand.
Mud has low shear strength, and requires anchor designs with a broader shank–fluke angle and greater fluke area. This allows the anchor to penetrate deeply to where the mud has greater sheer strength. Mud is frequently only a thin layer over some other material, so anchors that can penetrate through the mud to the underlying material will hold more. Fortress anchors have greater holding power in mud because they can be adjusted from their standard 32° to a broad 45° fluke angle.
Rock and coral: holding power is most dependent on where you happen to drop the hook, rather than the type of anchor. 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, Delta, Rocna and Supreme.
Shale, clay and grassy bottoms: tough bottoms for all anchor designs, with the weight of the anchor, more than the design the most important factor in penetration and holding power. CQR, Delta, Rocna and Supreme anchors are thought to be good due to their ability to penetrate the vegetation. However, these conditions have a high probability of false setting, due to the anchor catching on roots and protrusions, rather than something solid.
Manson Supreme is a state-of-the-art scoop with roll bar to self-right and a slot for easy retrieval.
The type of bottom—mud, grass, sand, coral or rock—will dictate different choices of anchors, as will the size and windage of the boat, the wind conditions and the seastate. Some anchoring situations also call for more than one anchor to be used simultaneously.
You sometimes need to set two anchors in a crowded anchorage, with anchors at the bow and stern of the boat to limit its ability to swing. Two anchors set from the bow at a 60° angle are another good way to improve security against swinging and dragging, and they allow you to shorten the rodes and use less scope. In heavy weather conditions, where one anchor may not have enough holding power, setting a second anchor may be critical to staying put. Remember that as the wind speed doubles the force on the boat (and the ground tackle system) increases by four times.
Anchor styles for different bottom conditionsWhile the above cases show the need to sometimes set two anchors at once, having two anchors of different designs help ensure good holding in different types of bottoms. One anchor of the Danforth style and one plow anchor are typically all you need. Except for coral and rocks, where the old-fashioned Yachtsman anchor may work best, either a plow or a Danforth should hold adequately in most conditions.
The most popular anchor style is the fluke anchor, also called the Lightweight or Danforth. Light and easy to weigh, it stows flat and holds very well in mud or sand. Its excellent holding power–to–weight ratio means you can use a lighter anchor compared to other types, but it doesn’t hold well in grassy or rocky surfaces. Its flukes and stock (the wide crossbar at the top) are more prone to foul on rocks or the anchor line.
Plow and scoop anchors, the “single point” style represented by the CQR, Delta, Claw, Manson Supreme and Rocna, have the best all–around holding ability in varying bottom conditions. They generally reset themselves easily if the wind or current changes direction, and hold more effectively in grass, mud and sand. They do not have projecting flukes that foul easily, but their shape makes stowing them more awkward (a bow-roller or bowsprit is the best solution). Heavier powerboats and cruising sailboats often use plows as primary anchors.
Delta is a modern plow-style anchor that’s popular in boats with bow rollers.
How big is big enough?Sizing an anchor for your boat reinforces, with some limits, the “bigger is better” idea. If your engine fails and you are drifting toward a lee shore, having a properly sized anchor ready could save your boat. But raising the anchor by hand, with no electric powered windlass, calls for light and efficient ground tackle (and a strong back). Take the anchor manufacturer’s suggested sizes into account and consider your boating style. Do you typically anchor for two hours or for two weeks, in a lake or in the Atlantic Ocean?
The most outspoken advocate of big anchors is probably naval architect Steve Dashew. Just to stimulate arguments in the yacht club bar, we’ll quote his viewpoint. His advice: “Look at the average size of anchor in use for boats of your type, and double the size. After doing this, if you think you can swing it, add another 50 percent.” Of course, he is talking about bluewater cruising here, and standing up to hurricanes, not a day at your local lake.
Holding powerWhat you are looking for when buying an anchor is holding power, which may have little relation to the anchor’s size and weight. 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 coral bottoms anchors can’t dig in, but rather snag on protrusions and hold precariously. The holding power of modern anchors is remarkable, varying between 10 and 200 times the anchor’s weight. This means that some anchors that weigh only 5lb. can hold in excess of 1,000lb! But with the widely varying conditions in the real world, how do you select the anchor that’s right for your boat?
The Fortress, an aluminum-magnesium Danforth-style, has shown incredible holding power in 2006 anchor tests, with the 21lb. FX37 sustaining over 5,000lb. of load.
Anchor attributesIdeally, an anchor should possess the following attributes:
- Quick to set, and to reset when the wind/current shifts.
- Good holding in all bottom types: sand, mud, rocks, coral, and grass.
- Strong—able to handle high loads on any part of its structure.
- Good holding power, even at short scope.
- Easy to release from the bottom without damage.
- Compact to store on deck or in a locker.
Assessing bottom conditionsAnchors need to develop enough resistance in the seabed to withstand the environmental forces on the boat—the wind and the waves. An anchor’s ability to develop resistance is entirely dependent on its ability to engage and penetrate the seabed.
Sand: fine-grained sand is relatively easy for anchors to penetrate and offers consistently high holding power and repeatable results. Most anchors will hold the greatest tension in hard sand. Pivoting-fluke anchors and non-hinged scoop anchors are the best types in sand. The Rocna performed excellently in anchor tests in sand.
Mud has low shear strength, and requires anchor designs with a broader shank–fluke angle and greater fluke area. This allows the anchor to penetrate deeply to where the mud has greater sheer strength. Mud is frequently only a thin layer over some other material, so anchors that can penetrate through the mud to the underlying material will hold more. Fortress anchors have greater holding power in mud because they can be adjusted from their standard 32° to a broad 45° fluke angle.
Rock and coral: holding power is most dependent on where you happen to drop the hook, rather than the type of anchor. 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, Delta, Rocna and Supreme.
Shale, clay and grassy bottoms: tough bottoms for all anchor designs, with the weight of the anchor, more than the design the most important factor in penetration and holding power. CQR, Delta, Rocna and Supreme anchors are thought to be good due to their ability to penetrate the vegetation. However, these conditions have a high probability of false setting, due to the anchor catching on roots and protrusions, rather than something solid.