Vertical caving terminology and methods > Prusiking systems, prusiking methods > Sit-stand systems
An uncommon sit-stand system for prusiking, which should be avoided due to its complete lack of safety features, and its serious limitations. The legs perform most of the work, and the arms are used for balance. It has almost none of the major benefits of the frog system, and it is far better to use the frog system instead. Cannot be used for prusik loops. This system is still sometimes used by arborists, often combined with doubled rope technique, where it still lacks safety features.
This system offers absolutely no safety features and no redundancy. The chest jammer is the only ascender that can be safely relied on. A failure of the chest jammer results in falling upside down, and hanging by the mar-bar attached to the foot jammer. The mar-bar is not attached to the sit harness in any way and can simply slip off the feet, resulting in plummeting down the pitch, head first. Many designs would not be able to cope with the weight of a caver on the straps, and would simply break under the strain, producing the same result. Even if the caver is somehow able to hold themselves by their feet, and their home made equipment is capable of taking their weight on the straps, the rope can pull onto the top of the foot jammer's cam, forcing it open. Although with most ascenders, the safety catch will prevent them fully opening, it results in the entire weight of the caver being put onto just a few of the teeth of the cam. They are not designed to be loaded that way, and could damage the rope, or simply fail to grip and cause the caver to rapidly scrape down the rope all the way to the bottom of the pitch, head first. Even if the teeth somehow manage to take the weight of the caver, they are left hanging upside down by their feet, a position that they have absolutely no way to recover from. While a safety carabiner can be used to reduce the chances of toppling over backwards, it still does not solve the lack of redundancy, and slipping out of the foot strap because of the sudden movement when the chest jammer fails, results in a fall until the safety carabiner slams into the top of the foot jammer, possibly breaking one of them, and once again resulting in plummeting down the pitch. This system does not satisfy even the most basic safety requirements.
This system is similar to the frog system when passing rebelays, but relies more on a cows tails to avoid toppling over, which could be very serious. It is inconvenient to use when passing deviations, especially for deviations that pull the rope a long way from vertical. It is almost impossible to perform a mid-rope changeover, depending on the descender and how it is locked off, so a small problem that could normally be solved by that manoeuvre results instead in being hung up. It cannot be used safely for passing a knot while prusiking because the cows tail has to be unclipped before the ascenders can be tested, though it can be used to pass a knot if that limitation is ignored. It is nearly impossible to use for passing a knot while abseiling, due to being unable to perform a mid-rope changeover. Reverse prusiking is very difficult and forces you to curl up almost upside down, due to the position of the foot jammer. Comical while practicing, much less funny when it is needed above a huge drop. At least it is not as bad as the another prusiking system. Bottom weighting is done by pulling the rope upwards while trying not to lose your balance. It is awkward for slightly sloping pitches, since both feet are stuck together, and cannot move independently to push away from a wall, but at least both hands can be used while leaning into a steeper slope. This system is identical to the frog system, in terms of energy transfer efficiency. Taking a rest is comfortable. Yay?
The foot jammer arrangement is very bulky to carry, and awkward in tight pitches due to its fixed width. Disconnecting the foot jammer to pass a knot, rebelay or Y-hang, or to fit through a narrow gap, brings the very real risk of dropping it down a pitch, and being hung up as a result. This system also does not work well for tandem prusiking, since the arrangement of the ascenders causes the caver to rock backwards and forwards when a caver beneath them moves on the rope, resulting in motion sickness.
Uses a chest jammer and a handled for caving foot jammer when used for caving. For arborists, a simple foot jammer may be used, connected to just one foot. For caving, the foot jammer is bolted to a mar-bar, so that the ascender sits between the feet, and the feet rest on the mar-bar. The mar-bar strap passes over both feet. This strap is what causes the foot jammer to be lifted when the feet are raised, and would be used to catch an upside down caver after a failure of the chest jammer. Since it is highly unlikely to be useful in that emergency, a safety carabiner can optionally be clipped to the D-ring, and around the rope between the ascenders. This may help to keep a caver upright, or to catch the top of the foot jammer in the event of a failure of the chest jammer. It is a highly recommended option, but it would be even better to use a top jammer above the chest jammer with a safety cord, turning it into the frog system. Or to put that in other words, don't use the inchworm, use the frog system. For ascending tight pitches or getting over a lip, the recommendation is to remove the foot jammer, attach it to the rope above the chest jammer, and use it for the hands instead, pulling up on it using the strength of the arms instead of the legs (this risks dropping it, and prevents the safety carabiner from working as a safety feature). This makes it the same as the frog system used without its footloop, and is nearly impossible to do when tired. The sit harness plays an essential role both as a main support and for safety. The chest harness is only used for efficiency.
French roofers and plumbers have been described using a knotted rope to climb buildings from as early as 1684, though the technique is almost certainly much older. It was later used by exterior decorators, and while it was not actually prusiking, it used the same basic approach as the Gérard Alpine technique, and would inspire prusiking techniques.
The inchworm system was invented by German inventor Ed. von Mengden in 1879, derived from the hands and feet system, using clamping jaws ascenders, with one of them held in a large housing on the chest attached to a full body harness, leaving the hands free for performing tasks such as building work. The foot jammer needed both feet to be used at the same time. In 1913, Austrian inventor Johann Machek reimagined the inchworm system with the body held in a boatswain's chair below the ascender, and this is likely to have been influenced by Ed. von Mengden's approach, even though he had used a different type of ascender. It is likely to have also been indirectly inspired by the existing method of climbing knotted ropes, since it was intended for use by exterior decorators, but it is more likely to have been inspired directly by the Texas system which had been adapted from it, since it uses an extremely similar approach. The foot jammer was connected to a pair of shoes, and gripped the rope when the shoes were tilted correctly. This system was then re-invented by American caver Charley Townsend in 1965-1966 in California, for use with mechanical ascenders, after a mishap during the 1965 American National Speleological Convention. Whatever that mishap was, it cannot have been worse than the potential for mishaps that this system offers. Presumably, he had been using the Jumar system in 1965, which at that point probably had no safety cords. In the original demonstration in 1966, it was called the "armless, double-foot and seat-chest sling ascending method", a mouthful which fortunately did not survive, as other cavers then came up with its more familiar name. In that configuration, it used the mar-bar, and could be used for the hands when needed. It was probably first used for caving by Charley Townsend. In 1987, the American National Speleological Society recommended having a long safety cord to the foot jammer, but this would mean a very significant 3 metre fall if the chest jammer fails, potentially damaging either the caver or the rope, following which it would be impossible to recover, since the foot jammer would be out of reach. While it is better than nothing, it would be better to simply not use the inchworm system.
This history section only covers the inchworm system. This article also has a detailed history of many of the other devices and techniques that are used for vertical caving.
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