- Sheers
Sheers are a form of two-legged lifting device, that were used by
sailboat s anddockyard s for tasks such as liftingmast s and heavier parts of therigging on board. [cite book|pages=97|title=Rudimentary Treatise on Masting, Mast-making, and Rigging of Ships|author=Robert Kipping|date=1854|location=London|publisher=John Weale]Unlike in a
gyn , which has three legs and is thus stable without support, stability in sheers (and in aderrick ) is provided by a guy. [cite book|title=Rudimentary Dictionary of Terms Used in Architecture, Civil, Architecture, Naval, etc.|author=John Weale|pages=142,403|date=1850|publisher=John Weale|location=London] 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 ablock and tackle is attached. Unlike derricks, sheers need no lateral support, and only require either a foreguy and an aftguy or a martingale and atopping lift . 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. [cite book|title=Admiralty Manual of Seamanship|author=Ministry of Defence (Navy)|date=1995|publisher=The Stationery Office|id=ISBN 0117726966|pages=3-192–3-194,3-203]References
Further reading
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