Omnisling webbing is a coarsely-woven nylon webbing with pockets placed in the webbing in the manufacturing process. The webbing is 1-1/4" wide and 3/16" thick. The pocket opening is about 1-3/4", and the woven-together section between pockets is about 3/4".
The Omnisling is sold as a product by BlueWater Ropes, though other vendors may be available. BlueWater cuts it to length and securely bartacks the ends, so that the "last pocket" can be used. They sell it in various lengths. Mine is eight feet long and weighs 10.2 ounces. Mine is the dark color which seems to be stiffer than the orange color, which I think is desirable.
Rumor has it that the webbing style was developed for getting a clean release when dropping nukes out of B-52s. It was recently de-classified, and the mill that makes it has been trying to find a market for its special properties, with only limited success. Omnislings are obscure, and can be difficult to locate for purchase.
The Omnisling is wrapped around a solid object and the rope rigged in a self-toggle/macrame style that allows it to release with a stout tug or two on the "cleaning" side; and the rope with Omnisling attached is pulled down to the waiting canyoneers. The Omnisling requires a solid object that will allow the detached side of the sling to pull from around it without getting stuck; and it requires a drop that is clean enough that the jumble of webbing and ropes is unlikely to get stuck.
The great advantage of the Omnisling is that the secure object need not be close to the edge of the drop. The distance to the object is limited only by the amount of rope you have available, and the friction on the cleaning rope from rock edges up to the anchor location. A fair amount of force is required to release the Omnisling, so the cleaning-line path needs to be fairly direct so that friction crossing rock edges does not diminish the cleaning-line force transmitted to the anchor too much. In many cases, it is advisable to do a test pull to make sure the release will occur.
Rigging the Omnisling
There are several different ways to rig the Omnisling. This method (the double-self-toggle) is the one I have found provides the best security and the most reliable release. Security depends in part on the loop of rope blocking the toggle-pull-through. Indications are that well-used, soft 8mm rope may be too easily pulled through to offer sufficient strength. Please avoid soft, small-diameter ropes.
On the other hand, as the rope gets thicker, it may require more force to release. A stiff 9mm rope might be too big and stiff to easily release. Become familiar with the attributes of your chosen rappelling rope and how it works with the Omnisling in a safe environment.
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Find a sturdy object that allows for a clean retrieval of the Omnisling. Pass the sling around the object, carefully selecting the side for the rappel-side that gives the cleanest removal. Let's designate one side of the Omnisling the 'working side' = 'A'; and the other side of the Omnisling the 'clean slide'. All the action takes place on the 'A' side, while the 'B' side remains straight and clean throughout the process.
Set the rope length and tie-off a loop. Attach this to the end pocket of the working ('A') side of the Omnisling using a rapid link or small locking carabiner. Designate one side of the ROPE the rappel (rap-side) and one side for cleaning (cleaning-side).
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Create a toggle by folding the working side of the Omnisling, and inserting the toggle through the end, or second from end, slot on the clean ('B') side of the Omnisling.
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Insert a second toggle in the adjacent slot.
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Insert a bight of the cleaning side of the rope into the toggle. Be sure there is plenty of slack between the attachment knot and the toggle-bight. Do not make the bight too big.
A bight that is too big, when pulled, can tend to twist and then become difficult to pull through, the last bit.
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With the two rope-bight toggles in place, pull firmly on the rappel-side of the rope, and tighten the whole rig up.
This completes the RIGGING of the Omnisling. Now let's discuss the sequence of events for using it responsibly.
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