Anchor

An anchor is a device, normally made of metal, used to connect a vessel to the bed of a body of water to prevent the craft from drifting due to wind or current.

Use / Function

The primary purpose of an anchor is to hold a ship or boat in a specific location.

• Mooring: Keeping a vessel stationary while waiting for a berth, loading/unloading cargo offshore, or resting.
• Safety: preventing a ship from being blown onto a lee shore or rocks during a storm.
• Navigation: In some historical contexts, used to help turn a ship (kedging).

Operating principle

Anchors work by resisting the movement of the vessel through two main mechanisms:

1. Weight (Gravity): Simple heavy objects (stones, blocks of concrete) that rely on friction and mass to hold the bottom. Effective for small boats or on hard bottoms.
2. Hooking (Shape): The anchor is designed to dig into the seabed. As the ship pulls, the flukes (points) bury deeper. This is much more efficient than pure weight.

The Catenary Effect: Crucial to anchoring is the “rode” (the rope or chain connecting anchor to ship). A heavy chain forms a curve (catenary). The weight of the chain keeps the pull on the anchor horizontal, which helps it dig in. If the pull is vertical, the anchor breaks out (trips).

How to create it

1. Primitive Anchor (The “Killick”)

• Concept: A stone trapped in a wooden cage or a forked branch with a stone lashed to it.
• Materials: A forked tree branch, a heavy stone, rope/lashings.
• Method: Use the fork as the hook, lash the stone for weight.

2. Stock Anchor (Admiralty Style)

• Concept: A T-shaped iron device. The “stock” (crossbar) ensures the anchor lands flat so one of the two flukes points downward to dig in.
• Materials: Wrought iron for shank and arms, wood or iron for the stock.
• Method: Forge welding iron bars to form the cross shape. The stock is set at 90 degrees to the arms.

Materials needed

• Stone: The simplest weight.
• Wood: For stocks or primitive hook structures.
• Iron: For strong, slender shanks and flukes that can penetrate sand/mud.
• Lead: Historically used for stocks to add weight in compact form.
• Rope/Chain: Essential to connect anchor to ship.

Variants and improvements

• Stockless Anchor: Modern anchors (like the Hall anchor) where the flukes pivot. The stock is removed so the anchor can be pulled up into the hawsepipe of the ship.
• Mushroom Anchor: Shaped like a mushroom, used for permanent moorings in soft mud.
• Danforth/Fluke Anchor: Lightweight with large flat plates, excellent holding power in sand/mud relative to its weight.

Limits and risks

• Dragging: If the wind/current is too strong, or the bottom is too hard/soft, the anchor may not hold.
• Fouling: The rope can get tangled around the anchor sticking up from the bottom, pulling it out.
• Loss: If the anchor gets stuck under a rock, the line may need to be cut, losing the anchor.
• Scope: You need a line length of 3x to 7x the water depth for the anchor to hold effectively.