What is the primary purpose of a capstan?

The primary purpose of a capstan is to bring tension to the mooring lines. A capstan is a vertical-axis rotating machine used on ships to handle heavy lines such as mooring lines and towing cables. It provides the mechanical advantage necessary to apply significant force when securing or releasing these lines, ensuring that the ship is properly moored and remains stable alongside a pier or during operations at sea. This capability is essential for maintaining safety and operational integrity, especially in varying environmental conditions.

Handling mooring lines includes controlling the tension on the lines, which is critical during loading and unloading operations, as well as in maintaining the vessel's position against wind and waves. The effective use of a capstan ensures that the vessel is securely moored and able to safely navigate off and on the pier.