Offset overhand bend | |
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Names | Offset overhand bend, European Death knot (EDK), offset water knot, flat overhand bend, thumb knot, thumb bend, Creeler's knot, openhand knot |
Category | Bend |
Origin | Ancient |
Related | Overhand knot, water knot |
Releasing | Jamming |
Typical use | sewing, weaving, baling, climbing, rappelling |
ABoK | 246, 359, 1236, 1410, 1557, 1558, 3789 |
The offset overhand bend (OOB, ABoK No. 1410) is a knot used to join two ropes together end-to-end. It is formed by holding two rope ends next to each other and tying an overhand knot in them as if they were a single line. Due to its common use in several fields, this bend has become known by many names, such as thumb knot, openhand knot, [1] one-sided overhand knot or flat overhand bend (FOB), though the terms "one-sided" and "flat" are considered incorrect. [2]
The term 'offset' refers to the knot core being displaced from the axis of tension. This geometry allows the knot to more easily translate around an edge - particularly a 90 degree edge.
Long used by weavers to join the ends of yarn, the offset water knot is very old. It was one of the knots likely identified among the possessions of Ötzi the Iceman, who dates from 3300 BC. [3]
The knot is also tied in a slipped form by mechanical balers to bind straw and hay, but this bend is not practical to use as a binding knot when tied by hand. [1]
For mountaineers/climbers, there tends to be a strong preference for using knots that are perceived to be relatively easy to tie - even when fatigued or in a less than optimal frame of mind[ clarification needed ] - and so #1410 (Offset overhand bend) is favored. Climbers/canyoners need to retrieve their ropes after an abseil/rappel descent. The ability to retrieve ropes after an abseil descent is crucial - and in many cases, two ropes need to be joined to increase the distance that can be descended in one 'pitch'. The resulting knot that unites the two ropes needs be secure and stable, have a small footprint, and be resistant to jamming.
There is controversy over its safety, as it can fail by capsizing under high loads, [4] [5] [6] [7] and some American climbers refer to it as the European death knot, abbreviated to EDK, with some sources recommending against its use. [8] [9] Failure of this knot has been implicated in some accidents and near-misses - although post accident retrieval of ropes for examination are usually inconclusive because the ropes have separated (and hence there is no remnant knot to examine). [10] [11] [12]
Many sources argue that the name 'EDK' is a misnomer, and the knot is safe for abseiling / rappelling, since this does not generate as high forces as a fall. The nominal load during abseiling/rappelling is one person - generally around 1.0kN (approximately 100kg). If the system is configured so the ropes are doubled through the anchor, the joining knot will only be subjected to 50% of the load (ie approximately 0.5kN) - which is well below the instability threshold. With due diligence given to dressing and setting the knot, the risk of capsizing is highly unlikely. [13]
Several sources recommend adding a second overhand as close as possible to the first (a stacked overhand or double overhand) for most situations, which maintains most of the benefits, while preventing it from capsizing. [9] [13] [12] [11] [14] [15] [16] [17] This doubles the overall footprint of the knot, which might increase its likelihood of getting stuck in cracks, but does not harm its ability to pass over edges. There are several different choices of offset knots - all offering varying levels of advantages/disadvantages. Another option is wrapping the strands a second time before passing the tail through (a two-rope version of ABoK #516, also called a double overhand [8] or flat doubled overhand bend [9] ) but again, it increases the overall footprint.
Easily formed in most lines, the offset overhand bend is jam resistant at nominal loads of one person (approximately 100kg). In EN892 climbing ropes, the jamming threshold is thought to be in the vicinity of 3.0kN (300kg). The instability threshold is thought to be above 4.0kN (400kg) – that is, a capsizing event becomes increasingly probable as loads exceed 400kg. It is critically important to pay close attention to dressing and cinching of the knot before attempting to abseil. That is, climbers must exercise due diligence when tying this knot – by pulling firmly on each of the four rope segments – which is necessary to achieve a properly compacted and cinched dressing state. [18]
Despite questions about this knot's security, it does present some advantages for use in rappels. Because the knot is offset from the axis of tension, it can translate more easily over uneven surfaces and 90 degree edges than other knots; and it is quickly tied and readily untied. Since a stuck rope on a multi-pitch descent can be catastrophic for climbers, these advantages, along with ease of tying, have led to its popularity. As with all knots used in life critical applications, the tails must be of sufficient minimum length (never less than 200mm in offset knots), and be diligently dressed and fully tightened by pulling individually on all four rope segments. [19]
An interesting yet overlooked fact is that #1410 (offset overhand bend), can be rotated to induce a choking effect to trap and crush the tails. Virtually all testers appear to only examine this knot in its mid-rotation state.[ citation needed ] It is theorized that this mid-rotation state is in fact the orientation where the structure is most vulnerable to capsizing. In addition, when tying the offset overhand bend using different rope diameters, the thinner diameter rope must be positioned underneath the larger diameter rope. This tactic further inhibits any likelihood of capsizing.
The offset figure-eight bend, a similar knot using the figure-eight knot, has been used in the belief that its greater size and complexity brings more security. But testing and more than one fatal failure indicate the figure-eight variant to be less secure, more prone to capsize at lower loads, and in capsizing uses more of the ends than does a capsizing overhand bend. [13] [19] Moreover, while there is one proper dressing of the overhand bend, there are a couple of dressings for the offset figure eight bend. [2]
A knot is an intentional complication in cordage which may be practical or decorative, or both. Practical knots are classified by function, including hitches, bends, loop knots, and splices: a hitch fastens a rope to another object; a bend fastens two ends of a rope to each another; a loop knot is any knot creating a loop; and splice denotes any multi-strand knot, including bends and loops. A knot may also refer, in the strictest sense, to a stopper or knob at the end of a rope to keep that end from slipping through a grommet or eye. Knots have excited interest since ancient times for their practical uses, as well as their topological intricacy, studied in the area of mathematics known as knot theory.
A shank is a type of knot that is used to shorten a rope or take up slack, such as the sheepshank. The sheepshank knot is not stable. It will fall apart under too much load or too little load.
The figure-eight knot or figure-of-eight knot is a type of stopper knot. It is very important in both sailing and rock climbing as a method of stopping ropes from running out of retaining devices. Like the overhand knot, which will jam under strain, often requiring the rope to be cut, the figure-eight will also jam, but is usually more easily undone than the overhand knot.
The figure-eight or figure-of-eight knot is also called the Flemish knot. The name figure-of-eight knot appears in Lever's Sheet Anchor; or, a Key to Rigging. The word "of" is nowadays usually omitted. The knot is the sailor's common single-strand stopper knot and is tied in the ends of tackle falls and running rigging, unless the latter is fitted with monkey's tails. It is used about ship wherever a temporary stopper knot is required. The figure-eight is much easier to untie than the overhand, it does not have the same tendency to jam and so injure the fiber, and is larger, stronger, and equally secure.
Figure-eight loop is a type of knot created by a loop on the bight. It is used in climbing and caving.
The Flemish loop or figure-eight loop is perhaps stronger than the loop knot. Neither of these knots is used at sea, as they are hard to untie. In hooking a tackle to any of the loops, if the loop is long enough it is better to arrange the rope as a cat's paw.
A zeppelin bend is an end-to-end joining knot formed by two symmetrically interlinked overhand knots. It is stable, secure, and highly resistant to jamming. It is also resistant to the effects of slack shaking and cyclic loading.
A climbing harness is a device which allows a climber access to the safety of a rope. It is used in rock and ice climbing, abseiling, and lowering; this is in contrast to other activities requiring ropes for access or safety such as industrial rope work, construction, and rescue and recovery, which use safety harnesses instead.
Glossary of climbing terms relates to rock climbing, mountaineering, and to ice climbing.
Rock-climbing equipment requires a range of specialized sports equipment, for training, for aid climbing, and for free climbing. Developments in rock-climbing equipment played an important role in the history of rock climbing, enabling climbers to ascend more difficult climbing routes safely, and materially improving the strength, conditioning, and ability of climbers.
Abseiling, also known as rappelling, is the controlled descent of a steep slope, such as a rock face, by moving down a rope. When abseiling, the person descending controls their own movement down the rope, in contrast to lowering off, in which the rope attached to the person descending is paid out by their belayer.
The sheet bend is a bend. It is practical for joining lines of different diameter or rigidity.
The Munter hitch, also known as the Italian hitch, mezzo barcaiolo or the crossing hitch, is a simple adjustable knot, commonly used by climbers, cavers, and rescuers to control friction in a life-lining or belay system. To climbers, this hitch is also known as HMS, the abbreviation for the German term Halbmastwurfsicherung, meaning half clove hitch belay. This technique can be used with a special "pear-shaped" HMS locking carabiner, or any locking carabiner wide enough to take two turns of the rope.
Kernmantle rope is rope constructed with its interior core protected by a woven exterior sheath designed to optimize strength, durability, and flexibility. The core fibers provide the tensile strength of the rope, while the sheath protects the core from abrasion during use. This is the only construction of rope that is considered to be life safety rope by most fire and rescue services.
The water knot is a knot frequently used in climbing for joining two ends of webbing together, for instance when making a sling.
A Prusik is a friction hitch or knot used to attach a loop of cord around a rope, applied in climbing, canyoneering, mountaineering, caving, rope rescue, ziplining, and by arborists. The term Prusik is a name for both the loops of cord used to tie the hitch and the hitch itself, and the verb is "to prusik". More casually, the term is used for any friction hitch or device that can grab a rope. Due to the pronunciation, the word is often misspelled Prussik, Prussick, or Prussic.
A Yosemite bowline is a loop knot often perceived as having better security than a bowline. If the knot is not dressed correctly, it can potentially collapse into a noose, however testing reveals this alternative configuration to be strong and safe as a climbing tie-in.
A dynamic rope is a specially constructed, somewhat elastic rope used primarily in rock climbing, ice climbing, and mountaineering. This elasticity, or stretch, is the property that makes the rope dynamic—in contrast to a static rope that has only slight elongation under load. Greater elasticity allows a dynamic rope to more slowly absorb the energy of a sudden load, such from arresting a climber's fall, by reducing the peak force on the rope and thus the probability of the rope's catastrophic failure. A kernmantle rope is the most common type of dynamic rope now used. Since 1945, nylon has, because of its superior durability and strength, replaced all natural materials in climbing rope.
The South African Abseil or South African Double Roped Classical Abseil is a modern variation of the non-mechanical classical abseil method used by mountaineers and rock climbers to quickly descend steep terrain by sliding down a rope wrapped around their body to create controlled friction.
The offset figure-eight bend is a poor knot that has been implicated in the deaths of several rock climbers. The knot may capsize (invert) under load, as shown in the figure, and this can happen repeatedly. Each inversion reduces the lengths of the tails. Once the tails are used up completely, the knot comes undone.
The persistent use of the term 'flat' or 'one-sided' is incorrect and it is hoped that this paper will assist in correcting the nomenclature.
[2016 version:] The Double Overhand has the best all round performance. ... [2015 version:] The overhand is not a recommended bend for tying two ropes for live load due to the low break strength and failure by rolling. ... Double overhand is a recommended bend
Overhand EDK ... Not recommended for canyoning. ... – Max force is low well below 10kN, the bend rolls off the end, multiple major rolls. ... either the Double Overhand or the Stacked Overhand bend are recommended for canyoning
In one such rappelling accident in recent times (in the Tetons, September 1997), the flat overhand failed when it was sloppily tied with too short of a tail. ... For added security it can be easily backed up simply by tying another flat overhand above the first one, although this adds bulk.
AND THE BEST JOINING KNOT IS… the double overhand. ... During year I used the Simple Overhand Knot to rappel. But one day I almost saw my climbing partner falling because this simple knot.
Adding a safety by tying a second overhand on top of the first is probably a good idea.
As a result of all these findings I am convinced that what I term the Double Overhand is the best knot (if not the safest) to use when joining two ropes together for abseiling.
the preferred knot for connecting rope is the European Death Knot ... WITH a back-up knot.
Most guides tie a backup by adding a second overhand bend next to the first.
For normal abseiling, if the ropes are dry then I use a well-tied, neat, single overhand knot with ample tails (30cm). If I was double loading the ropes with 2 people at once, or if the ropes were icy, I use a double overhand knot.