Language: jargon: sailing
- A u-shaped piece of metal secured with a pin or bolt across the opening.
Shackles are used all over a sailboat! The primary types include pin shackles, threaded shackles, and snap shackles.
- 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. Because pin shackles are secured using something else, usually a cotter pin or seizing wire, they are definitely more complex to work with while hanging in a bosun's chair on halyard 20-40 feet above the deck. You're usually wishing you had a third hand.
- Threaded shackle
The pin is threaded and one leg of the shackle is tapped. The pin may be 'captive', and not able to be dropped into the drink. (There are few sounds more depressing than the ping - plonk as the pin hits the deck and bounces overboard while you're hanging from the masthead...) A threaded pin may also have a hole into which a cotter pin can be inserted. The threads may gall if over-tightened or have been corroding in the salt air, so a liberal coating of lanolin is not out of place on any and all threads, and a shackle key or metal marlin spike are useful tools for loosing a tight nut. Unlike the pin shackle, a threaded shackle can stay together just with threads, but it doesn't mean it will. Don't trust your life or rig to one unless it has been wired or cotter pinned.
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 (a potential safety hazard, but also 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.
The shape of a shackle is related to its use. One which is narrow like a loop of chain is strong and can take high loads from any angle, and is often called a 'D' shackle. Long and thin u-shapes can take a linear load, but may twist or bend with side and racking loads. The specialty headboard shackle is a variation on the type, with an additional pin in the loop to help absorb side loading. A shackle shaped like an 'o' in the loop is known as a bow shackle, and while weaker than a D is able to smoothly take loads from many directions. An anchor shackle needs to be very over-sized; it needs to be as strong as the chain at the very least so the chain breaks before the shackle would.
Some of the usual uses for shackles include attaching blocks to the spars or deck of a boat, attaching a sail to any line but especially halyards, and attaching any line (sheets, tether, cable/rode, life lines, etc.) to a fitting.
- Edwards, Fred; Sailing as a Second Language; International Marine Publishing Company; © 1988 Highmark Publishing Ltd.; ISBN 0-87742-965-0
- Marino, Emiliano; The Sailmaker's Apprentice: A guide for the self-reliant sailor; International Marine; © 1994 International Marine/Ragged Mountan Press; ISB 0-07-157980-X