kapstan

Kapstan, commonly spelled capstan in English, is a heavy drum mounted on a vertical axle aboard ships that is used to apply controlled force to a rope or cable. The rope is wound around the drum, and sailors rotate the capstan to haul on the line, multiplying their effort through friction and mechanical advantage.

The capstan is usually located on the weather deck and may be driven manually with a capstan bar inserted into sockets in the capstan head, or powered by electric, hydraulic, or diesel motors. A pawl or brake system prevents the drum from running backward, allowing a crew to hold a load once the desired tension is achieved. In operation, lines such as mooring hawser or a portion of an anchor chain are secured and wound around the drum as it is turned by the crew or by the drive.

Variants include single and double capstans and units designed for manual or powered operation. Some ships use a pair of capstans in tandem to handle especially heavy loads; a windlass, a related vertical drum, is commonly used for anchor handling while the capstan handles mooring lines.

Capstans have been a staple of maritime work for centuries, evolving from purely manual devices to integrated deck machinery on modern vessels. They are sometimes named kapstan in other languages, reflecting transliterations of the same device.

Safety considerations include keeping hands clear of rotating parts, using proper belaying and line handling, and ensuring that lines are free of tangles to prevent rope burns or loss of control.