Anchors are an effective berthing aid. Anchors can be used for berthing without tug assistance on ships without bow thrusters and, in an emergency, to stop any ship.
A dredging anchor will hold the bow steady while allowing a ship to move forward or aft. A bow anchor can be dredged from a ship going forward or astern. The advantages of dredging an anchor when moving forward are principally that the ship’s pivot point moves to the position of the hawse pipe and, to overcome the anchor’s drag, propulsive power is used giving good steering at low speed. When going forward, corrective action will be needed to prevent the bow from swinging to port or starboard.
The intention is for the anchor to drag and not to dig in. If the anchor does dig in, it could cause the ship to stop and necessitate breaking the anchor out again. Digging in can also damage the ship, anchor or windlass. It is therefore important to use as little cable as possible, typically a length of cable that is between one and a half and two times the depth of the water.
Local knowledge regarding the nature and condition of the seabed is important to avoid dredging in an area where the bottom is foul.
In an emergency, anchors can be very effective in stopping a ship, provided the anchor is lowered to the seabed and the cable progressively paid out. Initially, the anchor should be allowed to dredge and gradually build up its holding power until its braking effect begins to reduce the ship’s speed. Care should be taken when trying to stop any ship in this way, especially a large ship, as the anchor and its equipment may ‘carry away’ causing damage or injury, if the anchor should snag.