The windlass is used for raising and lowering the anchor; it does this by heaving in and running out the anchor chain. Raising the anchor is called “weighing.” The windlass can also tension mooring lines and can be used to move the entire ship by hauling on lines to the shore in an process called “warping.”
While the name windlass can be applied to any dedicated mechanism for this purpose it is specifically referring to a horizontal style rotating drum.
Motive power is supplied typically through hydraulic or electric means. At its simplest a windlass is a powered axle that can be engaged or disengaged from a rotating drum by clutching in or out a mechanical coupling where rotating lugs engage detentes.
The axle typically passes through a wildcat. This is a deeply-grooved drum with sprockets to engage the links of chain used to attach the anchor. An attachment called a stripping bar prevents the chain from fouling.
The end of the axle terminates in a gypsy head, a smooth drum designed for use with rope. To help prevent slippage some gypsy heads are equipped with raised sections called whelps.
If the winch should fail accidental reverse rotation is prevented by a riding pawl, a metal arm that operates like a ratchet over stationary cogs. A nearby hand wheel will operate the brake.
A vertical version of the windlass is called a capstan. It has many of the same parts and serves the same function.
A devil’s claw is a chain stopper. It consists of a turnbuckle and ends in a pelican hook or similar apparatus that allows release while under strain. Once the pelican hook is attached, the turnbuckle is taken up, or tightened, until the ground tackle is secure. This is applied to the anchor chain when the windlass is not in operation as an additional redundancy: when the windlass is not used, the anchor will be secured from lowering by the pawl, the windlass brake, and the devil’s claw.
Prior to letting go the anchor the deck crew should disengage the devil’s claw, check that the chain is clear for running, the anchor is clear of all obstructions, and that the wildcat is disengaged. This will transfer the load of the anchor onto the windlass brake; by controlling the hand wheel the deckhand can control the rate of descent. This is the quick way of letting go the anchor. Otherwise, the wildcat may be left engaged and the anchor can be “walked out,” or lowered slowly.
The most important safety equipment is eye protection. Chips of metal or rust can fly out at high speed causing injury.
While anchoring your vessel, the best time to let go the anchor is when the vessel is moving slowly astern over the ground. You can establish that the vessel has stopped her forward movement when the backwash of the propeller reaches amidships and an azimuth bearing on the beam remains steady.
The correct procedure for anchoring in deep water—over ten fathoms—is, while under power, to back the anchor out until it is near but clear of the bottom before letting it fall. Holding the anchor to about two fathoms off the bottom before lowering the rest of the anchor fall will prevent the chain from running away too violently and from burying the anchor when it makes contact with the sea floor.
When attempting to free an anchor jammed in the hawsepipe the simplest method of freeing it may be starting the disengaged windlass at high speed.
The first action in preparing to recover the anchor is to engage the wildcat, otherwise it will not spin when the capstan is operated.
If you are weighing anchor in a rough sea, it is recommended to leave it underfoot, below the water’s surface, until the vessel can be brought to run before the wind or in some fashion make the working deck safe for complete recovery of the anchor. A loose anchor in a seaway is a very dangerous prospect for the crew and the vessel.
Synthetic lines may slip when wet on the gypsyhead. Additional turns will give a greater degree of control and security should the situation arise.
Because of the great strains imparted by the windlass, it is of the utmost importance to be mindful of the positioning of your body. The first rule is to never step into a bight of line, which is worth minding in any deck operation. A loop of line may suddenly become taut and bar tight, trapping and breaking whatever is captured within it, or snapping with a sideways force anything next to it. The term also applies to areas that may pose a danger if a line or machinery fails.
When working around lines under strain you should avoid working or standing around them whenever possible. Try to place yourself standing at a right angle to the direction of strain, for if the line suddenly parts while under tension it will snap back with a surprising elasticity. The force will generally travel in the directions opposing the pull. The farther to the side of a line you are standing, the safer you are.