The art and skill of rope splicing is old and established. A splice, whether it be in a manila three-strand or exotic fiber hollow braid, holds as a knot does, with friction. The difference lies in where and how evenly the friction is applied.
A common statistic applied to splices is that they retain 90 percent of the rope’s initial strength. Knots, however, often struggle to maintain 40 percent to 50 percent. A knot that retains 60 percent is indeed a gift and should be used often.
This is not to say one is better than the other, but only to emphasize that knots and splices, while different, serve the same purpose and share similarities. Each has its own advantages and disadvantages, limitations and strengths. This article will explore splicing as it pertains to arboricultural practices, and will look at a few common splices with an eye to advantage and limitation. The end goal is to develop a better understanding of splices and what they can and cannot do to help you become a better, safer, more-productive arborist.
Pieces and parts
Like knots, splices have specific parts that make up their whole. Unlike knots, there is not much familiarity in these terms. For the purpose of this article, I will lay out a basic nomenclature. This is not a researched terminology, just descriptive terms I have found most commonly used.
- Eye – The eye of the splice is the bite or termination formed. It is the interface between rope, splice and connecting link.
- Bury – The bury of the splice is the amount of cordage fed back into the rope to create friction to hold the splice together. The amount of bury is splice, cord and material-dependent. Remember that bury length is determined more by fiber type than construction. While Tenex and Amsteel (both Sampson rope products) have common constructions, the bury distance is hugely different.
- Taper – This is the section of the bury where individual strands are removed to allow for a snug bury and to reduce stress risers or possible weaknesses in the finished splice.
- Throat – The throat of the splice is the area of the bury that was not tapered. It lies immediately below the eye. In some splices, the throat also contains the crossover.
- Crossover – The crossover is the section of a double-braid splice where the core enters the cover and the cover enters the core. This is the thickest section of the bury and the one most likely to have discrepancies if not spliced properly. It also refers to the point in some hollow braid spliced products where the ends of individual tapers may cross. In either case, the crossover should be smooth and nearly undetectable.
- Lock Stitching – This is the added stitching after the splice is run home and firmed up. It is applied along the bury of the splice. It comes in as many shapes and forms as there are splicers, and is often the trademark of a specific technician. It keeps the eye from elongating under low load. It also prevents a splice from being teased loose when not under load. The greatest load provides greatest friction, thus a splice is most secure when loaded. Unloaded splices with fibers relaxed can snag on a branch or whatnot and possibly tease out. Lock stitching is vital on all arborist splices.
Types and configurations
We will look at spliced eyes and friction buries such as in “loopie” slings. While many other forms of splicing exist, they are not commonly used in tree work. End splices, while attractive and sometimes seen, simply serve as stoppers and function simply and elegantly, but are not worth in-depth discussion. In-line splices in main haul lines and double braids, common in the maritime world, are often too bulky to pass through blocks and/or too strength compromised to trust to climbing or rigging lines. In-line hollow braid splices are used by arborists to form endless loops. We will look at some of these.
Eye splices are so common as to be proletarian. Climbing lines, rigging lines, guy lines, throw lines all can and do have eye splices. Whoopie slings have emerged as useful rope tools combining two splices in one product that saves time and energy while retaining maximum strength.
As noted in the introduction, splices retain more of the rope’s breaking strength. This is often the most touted advantage of a splice over knots. However, arborists must be aware that improper use can compromise and diminish splice strength. Choosing the proper configuration of splice allows rope and splice to perform to the highest levels. The topic of strength loss and gain will be a constant in our discussion, but is certainly not the only advantage of a splice.
The strength of a splice comes from the internal friction of the outside of the cordage constricting on the inner bury. The longer, smoother and more gradual the bury, the more efficient and more widely this constriction is spread over the splice. Inconsistencies in taper, rapid changes in diameter or “lumps” and “bumps” in the bury and throat of the splice cause stress risers or areas of unequal stress. These disrupt the “Chinese finger trap” action of the splice and are inherent weaknesses. Understanding how splices hold is paramount in using them properly.
Types of eyes
In the case of eye splices, there are two types: long and short/tight. In many instances, the preference is entirely personal. It must be kept in mind that eye splices are meant to be loaded along the axis of the rope in the direction of the top of the eye. Setting up a splice to be used in any other way counteracts the very friction and tension that gives it its holding power.
A rapid direction change or bend in the throat or bury of a splice can cause a similar effect. For instance, a tight eye cinched around a small diameter limb may deform the splice, compromising its strength. This compromise might not be immediate, but will develop slowly and worsen through repeated improper application.
The eye of the sling is a bight of rope. Knots, hitches and bends can be formed, given an eye of sufficient length, without compromising the strength of the splice. Both sides of the eye should be loaded equally lest the splice become unbalanced. It should be noted that ropes and rope systems fail at the weakest link. If the eye of the sling is configured into a knot that is weaker than the eye splice itself, then failure of the knot may occur significantly before the ultimate strength of the splice is reached.
Before selecting a splice, be sure to determine how it will be used and select an appropriate eye length. Tight eyes are excellent terminations for a single attachment point that is to be loaded in the direction of pull, such as a climbing line. Tight eyes are clean and compact and resist the tendency of the attachment to side load or twist when not under load. Longer eyes can be used in this application, but it is recommended that the eye be girth hitched to the connecting link to avoid side loading.
Whoopies and loopies
Popular with some arborists are whoopie and loopie slings. These cordage configurations allow the user to adjust the length from a minimum to a maximum, all while using a simple basket hitch or girth hitch depending on configuration.
Whoopies were designed to attach a piece of hardware to an anchor point. They consist of a single eye, either short or long, that the hardware is attached to. The body of the sling is another spliced eye, but the splice is left open to allow for adjustment. The open splice must be of sufficient length to allow the splice to generate enough friction so it does not slip.
A loopie is an endless loop sling with a single open splice for adjustment. The hardware, typically a block, is attached in a floating configuration. The sling is then girth hitched around the anchor with the splice adjusted to keep the throat of the splice at the desired length. The same friction considerations as with a whoopie must be taken into account with a loopie. Loopies also have the advantage of being used as connecting links in “knotless” rigging systems, false crotches, redirects and many other uses besides hardware attachment.
Loops formed by knots or splices in cordage and/webbing material are extremely useful to arborists for any number of purposes. Footlock prusiks, slings, hitch cords, redirects and anchor points all come to mind. Endless loops can be configured in one of three ways: basket, straight or choked. Basket is the strongest, as it uses four parts of rope on the load with advantageous bending angles. Straight is next in strength, and it uses two parts of the sling on the load. Choked is the weakest as it has more bends, but has the advantage of cinching tightly to the load.
In all configurations, the splice should be on the leg or straight part of the sling. This keeps the bending and possible distortion to a minimum, which preserves strength as well as longevity. The exception to this is the loopie sling.
In a prusik, the splice should be removed from the knot to avoid interference with the functioning of the hitch. If alternate axis of pull are required, then knots or stitching may be the better option.
Splices are being used in a number of efficient and creative ways by arborists.
Knowing how and why splices are designed to work and employing them in appropriate ways helps tree workers work safely and efficiently while maintaining productivity. Splices will always have a place in arboriculture as long as rope does. Use them wisely and your work will improve.