How long is an anchor chain?

It should be made clear at the outset that the length of an anchor chain should not be calculated in units of metres, but in units of nodes, which are most commonly used in navigation, and that the length of each node of an anchor chain is roughly 27.5 metres. It is necessary to explain here where this unit comes from.

The length of a knot in an anchor chain is not the same as a knot, which is the unit of speed used in sailing, but it is actually derived from the imperial unit, the English search. The length of a quintal is about 1.8288 metres, and because of the great maritime power of the British Empire, it became the international standard, and then the length of an anchor chain was unified to 27.5 metres. In practice, the anchor chain consists of a shackle between each section, and the sections are connected to each other by removable chain rings. The links are usually painted white so that the crew can tell how many sections of anchor chain have been launched.

The last link of the chain is usually painted red to warn the crew that they have reached the end of the chain. Normally, the anchor chain is fixed to the chain plate, and if the ship has not finished slowing down before the end of the release, the anchor chain is likely to break away from the ship and fly out. To prevent this from happening, the penultimate section of the anchor chain is usually painted yellow, similar to the use of traffic lights.

In international practice, a large commercial vessel usually has only 12 to 13 knots per anchor chain, which works out to between 330 and 357.5 metres in length. However, this is a vague standard value, and on a specific vessel it will depend on the vessel's outfitting numbers. The calculation of outfitting is complex and will not be repeated here, but it is important to understand that the greater the outfitting, the more the ship is exposed to winds and waves at sea, so heavier anchors, thicker anchor chains and cables, etc. will be required. Generally speaking, the outfitting number of a warship is higher than that of an ordinary cargo ship, but after the anchor chain reaches 13 knots it is not suitable to continue to lengthen it because it will prolong the time to retrieve the anchor, so it is necessary to thicken the anchor chain, or even to require more than one anchor chain to ensure stability.