Sheers
Encyclopedia
Sailboat
A sailboat or sailing boat is a boat propelled partly or entirely by sails. The term covers a variety of boats, larger than small vessels such as sailboards and smaller than sailing ships, but distinctions in the size are not strictly defined and what constitutes a sailing ship, sailboat, or a...
s and dockyards for tasks such as lifting mast
Mast (sailing)
The mast of a sailing vessel is a tall, vertical, or near vertical, spar, or arrangement of spars, which supports the sails. Large ships have several masts, with the size and configuration depending on the style of ship...
s and heavier parts of the rigging
Rigging
Rigging is the apparatus through which the force of the wind is used to propel sailboats and sailing ships forward. This includes masts, yards, sails, and cordage.-Terms and classifications:...
on board.
Unlike in a gyn
Gyn
A gyn is a form of three legged lifting device used on sailing ships. It provides more stability than a derrick or sheers, and requires no rigging for support. However, it can only be used for lifting things directly up and down...
, which has three legs and is thus stable without support, stability in sheers (and in a derrick
Derrick
A derrick is a lifting device composed of one tower, or guyed mast such as a pole which is hinged freely at the bottom. It is controlled by lines powered by some means such as man-hauling or motors, so that the pole can move in all four directions. A line runs up it and over its top with a hook on...
) is provided by a guy
Guy (sailing)
A guy is a term for a line attached to and intended to control the end of a spar on a sailboat. On a modern sloop-rigged sailboat with a symmetric spinnaker, the spinnaker pole is the spar most commonly controlled by one or more guys.There are two primary types of guys used to control a...
. Sheers comprise two upright spars, lashed together at their heads and their feet splayed apart. The heels of the spars are secured by splay and heel tackles. The point at the top of the sheers where the spars cross and are lashed together is the crutch, to which a block and tackle
Block and tackle
A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads.The pulleys are assembled together to form blocks so that one is fixed and one moves with the load...
is attached. Unlike derricks, sheers need no lateral support, and only require either a foreguy and an aftguy or a martingale
Martingale (rigging)
A martingale is a fore-and-aft stay lying directly beneath the bowsprit strengthening it and, if extended from the sprit a jibboom, against upward force created by the head stays....
and a topping lift
Topping lift
The topping lift is a line which is part of the rigging on a sailboat; it applies upward force on a spar or boom. The most common topping lift on a modern sailboat is attached to the boom....
. Being made of two spars rather than one, sheers are stronger than a derrick of the same size and made of equivalent materials. Unlike the apex of a gyn, which is fixed, the crutch of a sheers can be topped up or lowered, via the topping lift, through a limited angle.