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Ashackle (orshacklebolt), also known as agyve, is a U-shaped piece of metal secured with aclevis pin orbolt across the opening, or a hinged metal loop secured with a quick-release locking pin mechanism. The term also applies tohandcuffs and other similarly conceived restraint devices that function in a similar manner. Shackles are the primary connecting link in all manner of rigging systems, from boats and ships to industrial crane rigging, as they allow different rigging subsets to be connected or disconnected quickly.
A shackle is also the similarly shaped piece of metal used with a locking mechanism inpadlocks.[1] Acarabiner is a type of shackle used inmountaineering.
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With a larger "O" shape to the loop, this shackle can take loads from many directions without developing as much sideload. However, the larger shape to the loop does reduce its overall strength. Also referred to as an anchor shackle.
Also known as achain 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.
This longer version of a D-shackle is used to attachhalyards tosails, especially sails fitted with aheadboard such as onBermuda 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 notchafe thespliced eye of the halyard.
A pin shackle is closed with an anchor bolt and cotter pin, in a manner similar to aclevis. It is for this reason they are often referred to, in industrial jargon, asclevises. Pin shackles can be inconvenient to work with, at times, as the bolt will need to be secured to the shackle body to avoid its loss, usually with asplit pin or seizing wire. A more secure version used in crane rigging features the combination of a securingnut (hardware) located alongside the cotter pin. Pin shackles are practical in many rigging applications where the anchor bolt is expected to experience some rotation.
As the name implies, a snap shackle is a fast action fastener which can be implemented single-handedly. 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'sharness tether or to attachspinnakersheets. 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.
The pin isthreaded and one leg of the shackle istapped. The pin may becaptive, which means it is mated to the shackle, usually with a wire. The threads maygall if overtightened or have been corroding in salty air, so a liberal coating oflanolin or a heavy grease is not out of place on any and all threads. A shackle key or metalmarlinspike are useful tools for loosening a tightnut.
For safety, it is common tomouse a threaded shackle to keep the pin from coming loose. This is done by loopingmousing wire or a nylonzip tie through the hole in the pin and around the shackle body. For pins that have a cross-hole in the threaded end a cotter pin can be used. One disadvantage of wire is that mousing can introducegalvanic corrosion because of material differences; it is especially bad when used in places where the shackle is exposed to air and water. Nylon is not recommended for use where significant movement of the shackle is expected.[2]
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 thejib halyardblock to themast, or the jib halyard to the sail, to reduce twist on theluff and allow the sail
Modern strong fibers such asPBO (IUPAC name: poly(p-phenylene-2,6-benzobisoxazole),aramids (Kevlar,Technora,Twaron),Vectran,carbon fibers,ultra-high-molecular-weight polyethylene (UHMWPE, Dyneema, Spectra) and othersynthetic fibers are used to make extra strong ropes which can also be tied into lockable loops calledsoft shackles.[3]
According to sailmagazine.com, "a soft shackle can handle just about every function performed by a metal shackle, in many cases better. Soft shackles articulate better, don’t rattle around when not under load, don’t chew up toe rails or beat up masts and decks, don’t hurt when they whack you on the head, are easier to undo and don’t have pins that fall overboard at a critical moment".[4] A modern rope can lift as heavy loads as a steel wire 3 times as thick and much heavier. Metal shackles may be preferred because soft shackles can be cut by sharp edges, burned, or deteriorate in some environments.
One disadvantage of soft shackles made of Dyneema and other modern fibers is their susceptibility to be weakened by heat, also heat caused by friction. It is advisable to subject it to medium level loads for a while to remove any slack that may cause friction heat when loaded to its maximum.
Thestopping knot of a soft shackle may be atrue lover's knot, adiamond knot, a double lineceltic button knot or achinese button knot (ABOK #600, ABOK #601, ABOK #603 doubled as one tail-end reverse-trails the other, emerging tail-ends preferably buried in the opposing main part as it emerges together from the knot forChinese finger trap attachment). Another preferred stopping knot is a two rope combined wall+crown+wall+crownknot (atwo string rose knot).[5] The latter ones with the added thickness of the returning tail ends have the advantage of less of a sharp curvature at their weakest spot, the eye around the neck of the button.[5]
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