Writer’s Deep Dive: Anchors

A ship’s anchor is a critical piece of equipment. It allows the vessel to be secured in place when a dock or pier is unavailable. However, just like the hull and sail shapes, the anchor has a significant amount of technology in its design.

Now, let’s dive in!

Terminology

Shank – The long piece of an anchor between the ring and arms.

Arms – The crosspiece at the bottom of the anchor.

Ring or Shackle – The top of the anchor to which the chain is attached.

Fluke – A flange at the end of the arms that digs into the seabed.

Stock – A crossbar at the top of the anchor.

Rode – The chain, rope, or cable that connects the ship to the anchor.

Hawsepipe – A small hole through which the rode passes.

Types of Anchors

The earliest anchors were rocks, and many have been found dating back to the Bronze Age. [1] The most common design comprised a hole bored through the rock with a rope tied through it. The ancient Greeks used baskets of stones, sacks of sand, and wooden logs filled with lead as anchors. All these early types of anchors relied on the weight to hold the ship in place.

The biggest improvement to the anchor design was the introduction of flukes. This is the iconic shape that most people are familiar with. Roman ships from the 1^st century have been found with this style of anchor and 10^th century Viking vessels. In fact, the Romans added the stock at the top of the anchor early on. Different variations of the fluked anchor have been developed over the centuries, but the basic design has remained the same and is still in use today.

The Admiralty Pattern anchor is a common shape that was based on the ancient Roman designs. The stocks are set at ninety-degree angles to the arms. When the anchor has landed on the bottom, strain on the chain will cause the stock to dig into the bottom, canting the anchor until one fluke digs in. Although the design is effective, there is a tendency for the rode to tangle in the stocks as the vessel swings with the wind and currents. This tangling may dislodge the anchor and require it to be reset. Another drawback is the difficulty in storage. Commonly, the ring was secured to a timber sticking out from the bow, known as a cathead, while one fluke was hauled up and hooked over the rail. A variation of the Admiralty Pattern anchor was developed in the mid-19^th century, known as the Trotman Anchor, which had folding stocks. [2]

A stockless anchor was patented in England in 1821. [3] Although the Admiralty Pattern anchor had superior holding capabilities, it was unwieldy to handle and store. The stockless anchor could be stowed flat or off the bow of the ship.

Until the mid-20^th century, small vessels used either a scaled-down version of the Admiralty Pattern anchor or a simple grapnel anchor, basically a four tined grappling hook.

Early sailors commonly used rope as their rode but it became replaced almost exclusively by chain on large ships. The downside to hemp rope is that it absorbs water and can fray on rocks and coral. Today, small vessels commonly use either chain or nylon rope.

Anchoring Techniques

To anchor a ship, a proper anchorage is determined, the anchor is dropped, the length of the rode is let out, and the fluke is set. The anchorage should be approached from downwind or down current, depending on which is stronger. The ship is stopped, and the anchor lowered to the bottom. Then the ship may drift or else motor back slowly, keeping the rode straight. As the anchor digs in, there will be resistance and the vessel should be maneuvered backward to achieve a good set.

With only one anchor, the ship will swing with the wind and currents. Multiple anchors can minimize the movement of the vessel. A forked moor involves two anchors off the bow set at a 45° angle. A bow and stern moor involves an anchor off the front and back of the ship.

It is important to know the depth before attempting to anchor. It is recommended that the length of the rode should be between four to ten times longer than the water is deep to prevent the anchor from breaking out. [4] The measurement should also include the distance between the surface of the water and the anchor roller or hawsepipe.

Weighing Anchor

An embedded anchor must be broken out of the bottom in order to haul it up. The rode is taken in until the ship is directly above the anchor. This rotates the anchor and is usually enough to free it. If not, the vessel can move around to loosen it. When an anchor is aweigh, it means it is hanging from the rode but not resting on the bottom.

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Copyright © 2022 Rebecca Shedd. All rights reserved.

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[1] Johnstone, Paul and McGrail, Seán (1989). The sea-craft of prehistory. London: Routledge. ISBN 978-0-415-02635-2, p.82.
[2] https://en.wikipedia.org/wiki/Anchor
[3] "anchor" in The New Encyclopædia Britannica. Chicago: Encyclopædia Britannica Inc., 15th edn., 1992, Vol. 1, pp. 377–8.
[4] Safety in Small Craft. Ch 2. Royal NZ Coastguard Federation. Mike Scanlan. Auckland. 1994