Block (sailing)

In sailing, a block is a single or multiple pulley. One or a number of "sheaves" are enclosed in an assembly between "cheeks" or "chocks". In use a block is fixed to the end of a line, to a spar or to a surface. Rope or line is "rove" through the sheaves, and maybe through one or more matching blocks at some far end to make up a tackle.

The "purchase" of a tackle refers to its mechanical advantage. In general the more sheaves in the blocks that make up a tackle, the higher its mechanical advantage. The matter is slightly complicated by the fact that every tackle has a "working end" where the final run of rope leaves the last sheave. More mechanical advantage can be obtained if this end is attached to the moving load rather than the fixed end of the tackle.

There are various types of blocks that are used in sailing. Some blocks are used to increase mechanical advantage and others are used simply to change the direction of a line. Some blocks ratchet, which means that they turn freely when you pull a line in one direction but does not turn the other direction. This kind of block makes a line easier to hold especially on a windy day. They usually have some kind of a button or lever to turn the rachet block off turning it into a regular block that makes any lines that go into the block turn freely in both directions. Ratchet blocks are typically used on small keelboats and dinghies where the mainsheet is and jib sheets are located.

ailing terms in everyday English

; Chock a' block : Refers literally to the situation where pulling on the working line will not raise the load any further because the cheeks of one lifting block are already fast against the other. Figuratively this has come to mean that something is as full or as far as it can be.Fact|date=January 2008

ee also

* Block and tackle
* Two six heave
* Portsmouth Block Mills

References