Anchor: Encyclopedia II - Anchor - Designs of temporary anchors

Anchor - Designs of temporary anchors

The range of designs is wide, but there are actually trends in designs for modern anchors which allow them to be classed as hook, plow, and fluke types, depending on the method by which they set.

• Hook designs use a relatively small fluke surface on a heavy, narrow arm to penetrate deeply into problematic bottoms such as rocky, heavy kelp or eel grass, coral, or hard sand. Two of the more common versions of this design are the fisherman and the grapnel.

• Plow designs are reminiscent of the antique farm plow, and are designed to bury themselves the bottom as force is applied to them, and are considered good in most bottom conditions from soft mud to rock. North sea designs are actually a variation of a plow in how they work; they bury into the bottom using their shape.

• Fluke designs use large fluke surfaces to develop very large resistance to loads once they dig into the seabed. Although they have less ability to penetrate and are designed to reset rather than turn, their light weight makes them very popular.

In the past 20 years or so, many new anchor designs have appeared. Driven by the popularity of private pleasure boats, these anchors are usually designed for small to medium sized vessels, and are usually not appropriate for large ships. See modern designs.

Anchor - Fisherman

A traditional design, the fisherman, also known as a kedge, is familiar to people who've never used an anchor. The design is a non-burying type, with one arm penetrating the seabed and the other standing proud. The anchor is popular as the ultimate storm anchor, and has a good reputation for use in rock, hard bottoms, and kelp or eel grass covered bottoms. The three piece versions can be stowed quite compactly, and most versions include a folding stock so the anchor may be stowed flat on deck.

The primary weakness of the design is its ability to foul the cable over changing tides. Once fouled the anchor is likely to drag. In comparison tests the fisherman design developed much less resistance than other anchors of similar weight. It is difficult to bring aboard without scarring the topsides, and does not stow in a hawse pipe or over an anchor roller.

Anchor - Fluke

The most common commercial brand is the Danforth, which is sometimes used as a generic name for the class. The fluke style uses a stock at the crown to which two large flat surfaces are attached. The stock is hinged so the flukes can orient toward the bottom (and on some designs may be adjusted for an optimal angle depending on the bottom type.) The design is a burying variety, and once well set can develop an amazing amount resistance. Its light weight and compact flat design make it easy to retrieve and relatively easy to store; some anchor rollers and hawse pipes can accommodate a fluke-style anchor. A few high-performance designs are available, such as the Fortress, which are lighter in weight for a given area and in tests have shown better than average results.

The fluke anchor has difficulty penetrating kelp and weed-covered bottoms, as well as rocky and particularly hard sand or clay bottoms. If there is much current or the vessel is moving while dropping the anchor it may "kite" or "skate" over the bottom due to the large fluke area acting as a sail or wing. Once set, the anchor tends to break out and reset when the direction of force changes dramatically, such as with the changing tide, and on some occasions it might not reset but instead drag.

Anchor - Grapnel

A traditional design, the grapnel style is simple to design and build. It has a benefit in that no matter how it reaches the bottom one or more tines will be aimed to set. The design is a non-burying variety, with one or more tines digging in and the remainder above the seabed. In coral it is often able to set quickly by hooking into the structure, but may be more difficult to retrieve. A grapnel is often quite light, and may have additional uses as a tool to recover gear lost overboard; its weight also makes it relatively easy to bring aboard.

Grapnels rarely have enough fluke area to develop much hold in sand, clay, or mud. It is not unknown for the anchor to foul on its own rode, or to foul the tines with refuse from the bottom, preventing it from digging in. It is quite possible for this anchor to find such a good hook that, without a trip line, it is impossible to retrieve. The shape is generally not very compact, and is difficult to stow, although there are a few collapsing designs available.

Anchor - North sea

Designed originally for anchoring floating oil derricks in the North Sea, this versatile design has become a popular option for smaller boaters as well. The burying design acts similarly to a large scoop, and is known for the speed with which it digs in. Although not an articulated design, it has the reputation of not breaking out with tide or wind changes, instead slowly turning in the bottom to align with the force. Some versions of the design, such as the Bruce, are reputed to be easy to retrieve once broken out of the bottom, and some anchor rollers can accommodate their shank.

North sea designs may have difficulty penetrating weedy bottoms, rock, and coral. They can be particularly difficult to break out. Although they can be got aboard without scarring the topsides, they take up an inordinate amount of locker space. They cannot be used with hawse pipes.

Anchor - Plow

Several companies produce a plow-style design, and they are particularly popular with cruising sailors. Plows are generally good in all bottoms, but not exceptional in any. The CQR design has a hinged shank, allowing the anchor to turn with direction changes rather than breaking out, and also arranged to force the point of the plow into the bottom if the anchor lands on its side. Another commercial design, the Delta uses an unhinged shank and a plow with specific angles to develop very similar performance. Both can be stored in some anchor roller designs

The plow is heavier than the average for the amount of resistance developed, and may take slightly longer pull to set thoroughly. It cannot be stored in a hawse pipe.

Anchor - Modern designs

In recent years there has been something of a spurt in anchor design. Primarily designed to set very quickly, then generate superior holding power, these anchors (mostly proprietary inventions still under patent) are finding homes with users of small to medium sized vessels.

• The German designed Bügel has a sharp tip for penetrating weed, and features a roll-bar which orientes the anchor to the correct attitude on the seabed
• The Bulwagga is a unique design featuring three flukes instead of the regular two. It has performed well in tests by independent sources such as American boating magazine Practical Sailor. Manufacturer's website
• The Spade is a French design particularly popular with sailors. Although relatively expensive, it performs well, and features a demountable shank and optional aluminium construction, which means a lighter and more easily stowable anchor
• The New Zealand designed Rocna is a new anchor gaining popularity amongst cruisers. It too features a sharp toe for penetrating weed and grass, and has a particularly large fluke area. Its roll-bar is similar to that of the Bügel, and means the correct setting attitude is achieved without the need for extra weight to be inserted into the tip (an inefficiency common in other anchor types). Manufacturer's website

Adapted from the Wikipedia article "Designs of temporary anchors", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki