Anchors

06 Jul 2019

This week we will be looking a anchors for the smaller boat rather than ships.

Until quite recently anchors for smaller vessels were either a simple grapnel or scaled down versions of ship anchors. However, since the mid 20th century new designs with greater holding-power-to-weight ratios have emerged. Many are known by their original trademarked names.

Grapnel anchor

A traditional design, the grapnel is merely a shank with four or more tines (sharp point on the prong). It has a benefit in that, no matter how it reaches the bottom, one or more tines will be aimed to set quickly by hooking into the structure, but may be more difficult to retrieve. A grapnel is often quite light, and is relatively easy to move and carry, being easy to stow if a collapsing model is selected. Grapnels rarely develop much hold in sand, clay, or mud however,  it is quite possible for this anchor to find such a good hook that, without a trip line from the crown, it is impossible to retrieve.

CQR plough anchor

Now superseded by modern designs. plough anchors stow conveniently in a roller at the bow, and have been popular with cruising sailors and private boaters. Ploughs are generally good in all types of seafloor, though not exceptional in any. A plough anchor has a fundamental flaw. Like it namesake, the agricultural plough, it will dig in but then tends to break out back to the surface. Plough anchors sometimes have difficulty setting at all, and instead skip across the seafloor. By contrast, modern efficient anchors tend to be "spade" types that dig ever deeper.

Delta anchor

Developed in the 1980s for commercial purposes by British marine manufacturer Simpson–Lawrence. It is essentially a plough anchor with a rigid, arched shank. Described as self-launching, it can be dropped from a bow roller simply by paying out the rode (cable chain or rope attached to the anchor), without manual assistance.

Danforth anchor

This is a light, versatile, highly popular fluke-style anchor that uses a stock at the crown to which two large flat triangular flukes are attached. The stock is hinged so the flukes can orient toward the bottom, tripping palms at the crown act to tip the flukes into the seabed. The design is a burying variety, and once well set can develop high resistance. Its lightweight and compact flat design make it easy to retrieve and relatively easy to store. A Danforth will not usually penetrate or hold in gravel or weeds. In boulders and coral it may hold by acting as a hook. If there is much current, or if the vessel is moving while dropping the anchor, it may skate over the bottom due to the large fluke area acting as a sail or wing.

Bruce or claw anchor

This anchor was an evolutionary improvement in its day. It is most effective in larger sizes. The Bruce and its copies, known generically as "claws", have been adopted on smaller boats (partly because they stow easily on a bow roller) but they are most effective in larger sizes. It was intended to address some of the problems of the only general-purpose option then available, the plough. Claw-types do not always set quickly in most seabeds, but they have the reputation of not breaking out with tide or wind changes, instead slowly turning in the bottom to align with the force. Bruce anchors can have difficulty penetrating weedy bottoms and grass. They offer a fairly low holding-power-to-weight ratio and generally have to be oversized to compete with newer types. On the other hand, they have a reasonable reputation in boulder seafloors. 

Herreshoff anchor

This is essentially the same pattern as an admiralty anchor, albeit with small diamond shaped flukes or palms. The novelty of the design lay in the means by which it could be broken down into three pieces for stowage. In use, it still presents all the issues of the admiralty pattern anchor.

Northill anchor

Originally designed as a lightweight anchor for seaplanes, this design consists of two plough-like blades mounted to a shank, with a folding stock crossing through the crown of the anchor.

In summary, when chosing an anchor the first rule of thumb is to understand the sea bed type you will be looking to secure to. Once you know this then the type of anchor can be considered. Thought also needs to go into the size and type of boat (to determine weight of the anchor) with finally the length of chain and rope.