Shackles for Boats

What are shackles?

- Design and uses of these handy metal clips -

A shackle (also known as gyve) is a small, horseshoe or u-shaped loop that can be opened and closed as required.

This is done by inserting or removing a pin through both ends of the body, often held in place by a split pin. Most marine shackles are made of stainless steel, but some are made of brass, titanium, or even dyneema fibre.

There's now a large selection of different types of shackle available on the market, in all kinds of shapes and for varying applications. You can find straight shackles, twisted, long, bow shackles, or swivel shackles, secured with threaded pins or bolts, and many more.

Quick release sailing shackles allow you to attach and detach parts on board a boat fast. A further advantage of curved shaped shackles is that they provide a movable connection and, in addition, they cause twisted ropes or halyards to twist back automatically.

A vast array of materials and shapes

- One for every type of use -

They can be found on almost all boats - from small dinghies to luxurious sailing yachts. The demands placed on them are high: not only must they be able to withstand extremely high loads, they also have to last in tough weather conditions and resist corrosion caused by salt water.

In boating, they can be used to hold lines in place at the bow, stern and masthead, strengthen blocks at the foot of the mast or link halyards to the heads of the sails for hoisting. Whenever you need to connect a fixed part with a wire or chain, a shackle is the ideal means to this end. 

Please make sure to use only the highest quality products on board, as shackles that can bend or break pose a considerable risk to the ship and crew. Above all, ensure that the breaking load is sufficient for the respective working load. DIN 82101 defines various shackle shapes, such as snap shackles, twisted and key pin shackles.

The most common types are anchor or bow shackles (recognisable by their 'O' shape) or dee shackles (shaped like the letter D, also sometimes referred to as 'chain shackles'). These types of shackle are closed with a screw pin or a combination of bolt and nut with a cotter pin, or a round pin that is secured with a cotter pin. 

They are often made of stainless steel, galvanised steel or steel alloys. D shackles should be used for securing and hoisting where the centre line of the load coincides with the centre line of the shackle. Care should be taken that they are not side loaded, as transverse or radial loads can twist or bend the shackle. Depending on the load angle, the load-bearing capacity is reduced. 

The working load limit (WLL) of a shackle is decreased when the pull of the load is off vertical (not in-line), and at 45° only around two thirds of the original nominal load-bearing capacity will remain. At right angles, the maximum load bearing capacity is reduced by half.

Bow shackles, however, are better at handling side loads because of their rounded shape, allowing the line to slide and tensile loads to act on the shackle from different angles. Their disadvantage is that the overall weight tolerance is lower compared to equivalent straight models.

In shipping, 316L stainless steel (Niro) is the standard for steel shackles; it offers the best compromise between strength and corrosion resistance. However, you can also find so-called HR (High Strength) stainless steel shackles, which are made of 17.4 PH stainless steel. This alloy contains a small amount of carbon (0.07%), which increases strength but also reduces corrosion protection. 

Fans of high-tech products are likely to choose titanium shackles. Compared to 316L stainless steel, shackles made of titanium save up to 45 per cent in weight. For example, a six millimetre shackle made of stainless steel (316L) weighs 22 grams and one made of titanium only 14 grams. 

Furthermore, working loads are significantly higher with titanium: eight millimetre stainless steel D shackles, for example, have a working load of 1,000 kg, while titanium D shackles have 1,440 kg. Nevertheless, this advantage comes at a price.

The way the shackle is manufactured also has an impact on the quality of the product. For example, shackles that are made from cheaper cast metal have a grain structure that is coarser and more random, which results in lower strength. Casting can result in air bubbles forming in the metal, decreasing its strength.

Forging, on the other hand, produces a more homogeneous metal structure that can absorb loads better - forged shackles bend first before they break. Machining is the process of shaping a piece of metal by removing material, which can weaken the structure locally.

Important shackles

- Different needs require their own solutions -

Professional retailers sell shackles that come in various shapes and sizes, and there's a good reason for this. Not only will breaking and working loads determine which shackle to choose, the intended use is also detrimental to the choice of shape and design.

Screw pin shackles are not recommended for permanent or long-term installations, they are mostly used when slings and other hardware are often changed out. In contrast, designs featuring a nut and cotter pin are more suitable for permanent use and work reliably when the bolt could turn under load.

Snap shackles are secured by a spring pin and are quickly 'snapped' open or shut. They have a swivel eye or a fixed eye and are used, for example, as jib shackles. They can be opened from the side or top. Swivel snap shackles often have additional rings.

With the arrival of high-strength, high-tech lines, so-called Dyneema soft shackles or rope shackles are often used on board. To make a soft shackle for sailing, an eye is spliced at one end of a short piece of rope and a stopper knot (diamond) is tied to the other end. These strong, lightweight rope shackles (also called soft shackles or loop shackles) are often used on the rig to attach the ends of jib sheets to clew rings and thus avoid having metal parts flapping around in the wind for increased safety. Rope shackles are very flexible and their soft material doesn't scratch or damage things like the deck or other surfaces on board. 

The disadvantage is that they cannot be opened under load. But even after heavy loads, they can be easily loosened by hand. A further disadvantage is that they are not 100% resistant to abrasion and can be easily damaged by sharp edges.

For anchors and anchor chains, specialist retailers sell robust and durable high-strength shackles or offshore shackles (also heavy-duty shackles or chain shackles) in a curved shape.  These are particularly large and made of galvanised steel with a locking bolt and an additional cotter pin that prevents the bolt from unscrewing. These types of shackle are particularly suitable as anchor shackles.

What size shackle do I need?

- Pay attention to breaking load and working load! -

The nominal tolerance of a shackle is usually marked on the unit itself. It specifies the load capacity in tonnes (t), the so-called Working Load Limit (WLL).

A 0.4 shackle, for example, has a load capacity of 0.4 t or 400 kilograms. Safe working loads and breaking loads are often additionally specified in shackle product catalogues. Exceeding the breaking load will cause it to break.

Safe working load is usually estimated at around 40 percent of the breaking load of the shackle. Ultimately, however, it is up to you to operate within workload specifications. To play it safe, choose a breaking load that is four times the working load.

The working load of halyards and genoa sheets can be easily calculated using the sail area. Multiply the sail area in square metres by 30 (for spinnakers 13). Manufacturers specify breaking loads for stays, which can serve as a guide.

When using shackles on board, safety comes first!

Check the condition of your shackles regularly to avoid unpleasant surprises. They may make many tasks much easier and safer on board, but this is only the case if they are in perfect condition.

Shackles are often subjected to extreme loads, this is especially true in boat rigging. Therefore, it's very important to take safety precautions to make sure your shackle will reliably hold, in particular for prolonged use.

This means that the material should be checked regularly for wear, cracks and signs of fatigue. Weak points or breaks can occur in the body, the pin, or in the eye or pin holes. Make sure you pay particular attention to any signs of bending, distortion or twisting. If you notice any of the above, the shackle will not be able to hold the loads specified.

Bent shackles are a sign of excessive side loads, which (especially on D-shaped versions) can eventually lead to failure. Pins that are bent or broken must be replaced immediately. Even if a pin appears to be fully intact, it may not be sitting properly in the shackle. 

If it's only slightly out of place, the risk of breaking under load is higher. You should also never force pins into position or hammer them in. Under no circumstances should you use something else that is a similar shape to close a shackle. Only use pins that have been specifically manufactured for the purpose and type of product.

Well-equipped: Carabiners, shackles and ropes

You can also find a wide selection of rope shackles for different applications on board in our ropes section.

If you need other equipment for mooring, securing and attaching sails, you can also find a range of further, shackle-related products, including carabiners, tack snap shackles and snap hooks, as well as blocks, pad eyes and sails in our online shop.