Shackles
A
shackle is a U-shaped piece of metal secured with a pin or bolt across
the opening, or a hinged metal loop secured with a quick-release locking
pin mechanism. They are used as a connecting link in all manner of
rigging systems, from boats and ships to industrial crane rigging
Pin
shackle
A
pin shackle is closed with a clevis pin. Primarily used above the deck,
pin shackles used to be the most common shackle used aboard boats. Pin
shackles can be inconvenient to work with at times because they are
secured using something else, usually a cotter pin or seizing wire.
Threaded
shackle
The
pin is threaded and one leg of the shackle is tapped. The pin may be
"captive", to prevent it from dropping loose. The threads may
gall if over-tightened or have been corroding in the salt air, so a
liberal coating of lanolin or a heavy grease is not out of place on any
and all threads. A shackle key or metal marlinspike are useful tools for
loosening a tight nut.
Snap
shackle
As
the name implies, a snap shackle is a fast action fastener which can be
implemented single handed. It uses a spring activated locking mechanism
to close a hinged shackle, and can be unfastened under load. This is a
potential safety hazard, but can also be extremely useful at times. The
snap shackle is not as secure as any other form of shackle, but can come
in handy for temporary uses or in situations which must be moved or
replaced often, such as a sailor's harness tether or to attach spinnaker
sheets. Note: When this type of shackle is used to release a significant
load, it will work rather poorly (hard to release) and is likely to have
the pin assembly or the split ring fail.
D-shackle
Also
known as a chain shackle, D-shackles are narrow shackles shaped like a
loop of chain, usually with a pin or threaded pin closure. D-shackles
are very common and most other shackle types are a variation of the
D-shackle. The small loop can take high loads primarily in line. Side
and racking loads may twist or bend a D-shackle.
Headboard
shackle
This
longer version of a D-shackle is used to attach halyards to sails,
especially sails fitted with a headboard such as on Bermuda rigged
boats. Headboard shackles are often stamped from flat strap stainless
steel, and feature an additional pin between the top of the loop and the
bottom so the headboard does not chafe the spliced eye of the halyard.
Twist
shackle
A
twist shackle is usually somewhat longer than the average, and features
a 90° twist so the top of the loop is perpendicular to the pin. One of
the uses for this shackle include attaching the jib halyard block to the
mast, or the jib halyard to the sail, to reduce twist on the luff and
allow the sail to set better.
Bow
shackle
With
a larger "O" shape to the loop, this shackle can take loads
from many directions without developing as much side load. However, the
larger shape to the loop does reduce its overall strength. Also referred
to as an anchor shackle.
Swivels
Swivels,
eye and eye are applied in applications where a quick swivel assembly
with a hook or quick link is required.
Swivels, Jaw and Jaw are applied in applications where quick assembly
onto a closed end chains is
required.
Information
courtesy of Wikipedia.org