bitts using the bitter pin, which should be able to be released from outside the locker to "slip" the anchor. This would occur if the windlass brake has slipped (in a storm, for example) and the cable has reached "the bitter end". This is the origin of the term "to the bitter end". It originally applied in sailing vessels where the cable was a rope, and the windlass or capstan was powered by many sailors below decks. Gypsies and wildcats The wheels on either a vertical or horizontal windlass provide for either chain or line to be engaged. The wheel for line is termed a warping head, while the chain handling wheel is variously referred to as the gypsy (in the UK) or wildcat (in North America). For clarity in communication the generic term chainwheel is often used. On small craft a warping drum is sometimes used to handle both chain & rope, although particular care must be taken with sizing and compatibility of line, chain, and windlass, for this feature to work effectively. It is important that the chainwheel match the chain size (i.e. the link pitch) closely. Even a small difference in link size or consistency can cause undue wear on the chainwheel and/or cause the chain to jump off the windlass when the winch is operating, particularly during payout, a runaway condition sometimes referred to as "water spouting" should it occur at high speed. Nowadays, especially on large tankers and cruise ships, the windlass may be split into independent port and starboard units. In these cases they are frequently coupled with warping drums (as distinct from warping heads). In some of these the warping drums are of the self tensioning or constant tension type. Mechanical advantage The mechanical advantage of a windlass is derived from the pulling force being multiplied by wrapping the rope around the drum. The math for such force phenomena is described by the Capstan equation. The formula is where is the applied tension on the line, is the resulting force exerted at the other side of the capstan, is the coefficient of friction between the rope and capstan materials, and is the total angle swept by all turns of the rope, measured in radians (i.e., with one full turn the angle ). While many modern windlasses require an external power source, many remain manually driven in the same manner as most sailing boats'