Vertical caving terminology and methods > Knots > Alternatives and enhancements to knots
A way to connect ropes to each other or back to themselves, without using a normal knot. The most common use is to form a loop known as an eye splice in the end of a rope. The second most common use is to join ropes to make a longer rope without using a bend, known as an end-to-end splice, such as the short splice and long splice. There are several other less common splices which are tailored specifically to hawser laid ropes, such as to fold the end of a rope back on itself rather than tying a knot or melting the rope to prevent it fraying, known as a back splice or end splice. Loops can also be made while joining ropes, known as a cut splice or horseshoe splice. Specially shortened versions of the eye splice can be used to connect to chains and rings, known as a chain splice or ring splice.
With most types of splice, the individual strands of two pieces of rope, or two parts of the same rope, are woven around each other in such a way that the individual strands grip each other using friction, rather than the entire rope at once like a normal knot. They normally require the rope to be partially deconstructed and rebuilt into the splice. Because of this, a splice is not normally considered to be a type of knot, in British English. Almost all splices require the end of at least one rope to be used, so they cannot be used to make a loop part way down a rope, and they cannot be used to join two ropes part way along both of them. Although there are many types of end-to-end splice, most have the disadvantage that they make the rope much thicker, which limits their uses, though there are some that only make it slightly thicker, such as the long splice (which can only be used with hawser laid ropes). As a result, eye splices are more common than end-to-end splices. With most types of rope, splices are extremely time consuming to prepare, are designed never to be undone, and often cannot be adjusted after they are made, so they are never used for rigging. They might be used in rare cases with pre-prepared equipment such as commercial prusik tethers or fixed handlines, but they are much more common with arborist, highlining and sailing equipment, where abrasion is less of an issue.
With hawser laid ropes, the strands are woven through each other, using a tool called a "marlinspike" or "marlingspike". With braided/plaited ropes, it is normal for one of the ropes to be fed through a gap called a "neck" or "throat" into the hollow middle of the other rope, with a long length buried inside the other rope, relying on the Chinese finger trap effect from the outer rope to grip the inner rope (this is most commonly used with Dyneema cords). For end-to-end splices, both ends could be fed into the middle of the other rope. With braided/plaited ropes, splicing is used almost exclusively to create eye splices, so the two ropes are really just different parts of the same rope, at either side of the loop. The buried length is normally about 20-30 times the diameter of the rope, so for a 10 mm rope, the bury length will be about 20-30 cm, but it can be as much as 72 times the diameter of the rope with Dyneema. This is normally fed through the outer rope using a tool called a "fid". Some strands of the inner rope are normally cut to different lengths to produce gentle tapers instead of abrupt changes, to preserve more strength. Splices in braided/plaited ropes are often protected with a whipping made from thinner thread which is lock stitched through them and wrapped around them, to prevent the splice from slipping when not loaded, or when repeatedly loaded and unloaded. With double braided/plaited and kernmantel ropes, it is normal for complex picking and unpicking to be required, weaving the core and sheath of one rope separately into the other rope, relying on the same effect as the braided/plaited rope, but in several different steps. Again, this is used almost exclusively to create eye splices, and in many cases, the core and sheath are passed around the eye in opposite directions to each other.
There are many different variations of each type of splice, many of which are tailored to specific types of rope manufacture. Some will work only with ropes that have a specific number of threads making up their sheath or core. Some manufacturers specify their own recommended splices which perform best for specific rope products. Splices typically take up much more length than a knot, so it is not possible to make a short tether using them. The part of the rope taking part in the splice remains relatively thick and stiff compared with the rest of the rope, and loses most of its dynamic properties, which can be inconvenient for some purposes. Splices have the benefit that they retain about 80-90% of the minimum breaking strength of the rope, or 100% with braided/plaited Dyneema. Note that with hawser laid rope, the stated strength of the rope is typically tested with an eye splice at each end which itself retains about 90% of the strength of the rope, so a short splice in the rope is often said not to reduce the stated strength, even though it actually does (a long splice retains about 85-90% of the stated strength, so 77-81% of the actual strength of the rope). However this strength will depend on the specific splice being used, and how well it has been made. For example, the strength of an end-to-end splice is improved if the splice causes the tails of both ropes to be kept under tension, which improves that rope's grip on the other rope. Without that, a much longer splice is needed to obtain the required amount of grip. Natural fibre ropes such as hemp generally need shorter splices than synthetic fibres such as nylon, and slippery fibres like Dyneema need far longer splices.
Splices rely on the sheath of a kernmantel rope to grip the rope strands. As a result, a damaged sheath can cause the strength to be lost completely, which is a serious problem in high abrasion environments like caves. In general, kernmantel ropes are not considered to be good for splicing even in low abrasion environments, though a few splices have been developed for them. Splices are far more common with double braided/plaited ropes, since both the sheath and core braids can take part in providing the grip of the splice, but they are still significantly weakened by a damaged sheath, and are not really suitable for caving.
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