Anchor

The anchor is one of the most fundamental pieces of ship equipment, allowing a vessel to hold its position at sea away from a berth, while waiting for a berth or orders, riding out weather, or lying at a designated anchorage. It works in combination with the anchor cable, the heavy chain that connects it to the ship. When the anchor is let go and the ship pays out cable, the anchor is designed to dig into the seabed, and much of the holding power actually comes from the length of chain lying along the bottom, whose weight and drag keep the pull on the anchor nearly horizontal so that it bites rather than breaks out.

Most large merchant ships use stockless anchors, whose hinged flukes fold to stow neatly in the hawse pipe and swing out to dig into the bottom when the cable comes taut. The anchors and cable are worked by the windlass on the forecastle, and the cable is measured in shackles, or lengths, so that the crew can control and record how much has been paid out. The amount of cable used, relative to the depth of water, is the scope; a greater scope keeps the pull horizontal and improves holding, and more is paid out in deep water or bad weather.

Good anchoring is a matter of seamanship and judgement. The officer chooses a suitable spot with good holding ground and enough room for the ship to swing around the anchor as the wind and tide change, avoids obstructions and other vessels, and pays out an appropriate scope. Once anchored, the ship keeps an anchor watch to guard against the anchor dragging (dragging is detected by watching the ship's position and bearings) and must be ready to use its engine or lay out more cable, or to weigh anchor and get under way, if the weather deteriorates. The anchor and its handling remain essential to safe ship operation despite all the advances in propulsion and navigation.