Operation of Anchors Using a Capstan or Windlass
Ships bow showing hawsepipes, with stdb anchor home; the port one being raised; courtesy of www.blueoceantackle.com.
Anchor chains are connected to a windlass that can either be of vertical or horizontal design. A vertical windlass is known as a capstan, and we shall describe the operation of the anchor and its components using a capstan.
The capstan has a drive wheel called a gypsy that is notched to suit the forged steel chain links.
The chain is fed from the capstan along the deck of the fo’c’sle head through a pawl and down through a hawsepipe pipe in the deck exiting at the ships bow. From here the chain drops downwards and is connected to the anchor using a shackle whose hardened steel pin passes through a hole drilled in the anchor central shank.
The anchor chain is stored in the chain locker; where its end is secured to a ring bolt welded to the chain locker bulkhead. This is known as the anchor chain’s “bitter end".
Whilst I was serving my time in Harland & Wolff of Belfast, I was working in the windlass room on a ship at the outfitting berth. I was being shown how to line-up the gearbox coupling on a capstan electric motor drive. One of the steel fabricators and a welder came in carrying a large steel ring and proceeded to weld this to the aft bulkhead. Curious as ever, I asked the men what it was for and, after a few ribald comments was told this was to secure the anchor chain and was known as the bitter end! Now, as a boy in the shipyard I was subjected to much ribbing being told some tall stories. So after the men had gone I asked my gaffer and he confirmed this was what it was called. He went on to tell me that the ring was a “bitt" and when the anchor chain was fully fed out it had reached its “bitter end" - the end of the chain.
Any I diverge; as I was saying, the vertical windlass or to give it its correct name the capstan, is fitted to the deck of the fo’c’sle head being driven from underneath by an electric motor and gearbox located in the windlass room.
A horizontal drum windlass or a combination of widlass/winch can also be used to operate the anchor chain; these are located on the fo’c’sle head and normally driven from a central motor.
Both windlasses and capstans have a safety device known as a devil’s claw. This is attached to a wire strop; the other end of the strop is secured to the base of the windlass/capstan, there being a bottle screw in the middle of the strop. When the anchor is home (has been raised against the hawsepipe) the claw is inserted into an anchor link and the strop tightened up using the bottle screw. This prevents any inadvertent or, accidental lowering of the anchor should the brake fail.
When I was at sea sailing as an Engineering Officer on large oil tankers most of VLCC’s had port and starboard capstans or windlasses driven by hydraulic motors; I seem to recollect steam driven ones as well, but I may be getting mixed up with winches on deck as this was over 45 years ago.
A sketch of a typical anchor operating system using a capstan, along with an image of a windlass and, anchor maintenance from Wiki Commons is shown below; please click on images to enlarge.