A boom vang (US) or kicking strap (UK) (often shortened to "vang" or "kicker") is a line or piston system on a
sailboat
A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture.
Types
Although sailboat terminolo ...
used to exert downward force on the
boom
Boom may refer to:
Objects
* Boom (containment), a temporary floating barrier used to contain an oil spill
* Boom (navigational barrier), an obstacle used to control or block marine navigation
* Boom (sailing), a sailboat part
* Boom (windsurfi ...
and thus control the shape of the sail.
The
Collins English Dictionary
The ''Collins English Dictionary'' is a printed and online dictionary of English. It is published by HarperCollins in Glasgow.
The edition of the dictionary in 1979 with Patrick Hanks as editor and Laurence Urdang as editorial director, wa ...
defines it as "A rope or tackle extended from the boom of a fore-and-aft mainsail to a deck fitting of a vessel when running, in order to keep the boom from riding up".
The vang typically runs from the base of the
mast to the
boom
Boom may refer to:
Objects
* Boom (containment), a temporary floating barrier used to contain an oil spill
* Boom (navigational barrier), an obstacle used to control or block marine navigation
* Boom (sailing), a sailboat part
* Boom (windsurfi ...
. Due to the great force necessary to change the height of the boom while a boat is under sail, a line-based boom vang usually includes some sort of a
pulley system. Hydraulic piston vangs are used on larger sailboats and controlled by manual or electric hydraulic pumps.
By controlling leech tension, the boom vang is one way of controlling
sail twist
Sail twist is a phenomenon in sailing where the head of the sail is at a different angle of incidence from the foot of the sail in order to change the lift distribution with height. Twist is measured by comparing the angle of a straight line betw ...
. The boom vang may also be used to flatten the mainsail on
dinghies
A dinghy is a type of small boat, often carried or towed by a larger vessel for use as a tender. Utility dinghies are usually rowboats or have an outboard motor. Some are rigged for sailing but they differ from sailing dinghies, which ...
.
On small sailboats and some cruising sailboats a vang may be omitted. If a vang is not installed, then the
mainsheet
In sailing, a sheet is a line (rope, cable or chain) used to control the movable corner(s) ( clews) of a sail.
Terminology
In nautical usage the term "sheet" is applied to a line or chain attached to the lower corners of a sail for the purpos ...
has to try to control both horizontal and vertical angles of the boom. When the boom is near the centerline, the mainsheet is nearly vertical, and can exert downward force on the boom. As the mainsheet is loosened to increase the horizontal angle of the boom and sail, the mainsheet becomes horizontal and exerts less downward force. A vang works with the mainsheet to apply the downward force on the boom at all horizontal angles, allowing the mainsheet to be used to control the horizontal angle of the boom effectively.
While under sail, the opposite force to the vang is supplied by the sail itself. When the sail is furled, a
topping lift
The topping lift (more rarely known as an uphaul) is a line which applies upward force on a boom on a sailboat.
Part of the running rigging, topping lifts are primarily used to hold a boom up when the sail is lowered. This line would run from nea ...
supplies the upward force on the boom. Some line vang systems incorporate a piston to provide the topping lift force and to damp oscillations. Hydraulic vangs can inherently act in the topping lift role.
A gnav (the word ''vang'' spelt backwards) is an inverted vang. It is a rigid strut that extends obliquely upward from the boom to the mast, exerting a force that pushes down on the boom. As the fixing point of the gnav on the boom is hauled inwards towards the mast, the downward force on the boom increases. A gnav offers more uncluttered space beneath the boom when compared to a vang.
References
{{DEFAULTSORT:Boom Vang
Sailing rigs and rigging
Shipbuilding
Sailboat components
Sailing ship components
Nautical terminology
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