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| Blindingly new gear. They seemed to have enough rope to tie around the tree like the one in the background. Instead,they tied a clove hitch they didn't trust, backed up with a figure 8 on a bight. |
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| A couple of half hitches around a 3" tree. |
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| Single strand webbing. |
Webbing strength is rated as a loop, not a single strand. With a single strand the strength is down in the range of loads that could be achieved. Webbing will cut like a hot knife through butter when holding weight. Carderock has sharp quartz nubbins that have cut anchors. An anchor that can fail is not redundant. Two anchors that can fail are not one good anchor, they are still two bad anchors.
ReplyDeleteIt seems like you're confusing sewn slings with plain old webbing.. 1" nylon webbing is sold open-ended, usually by the foot, and I'm pretty sure the rated strength IS for a single strand. It would make absolutely no sense, and it would be dangerously misleading, to rate it as you are describing.
ReplyDeleteStandard 1" climbing webbing is rated at 17.7kN by Bluewater- even with knots reducing the strength, that is still pretty damn strong: https://bluewaterropes.com/product/1-tubular-climb-spec-x-100-yds/
The primary objection to single strand webbing is cutting. BW gives you tensile strength which is not how the UIAA certifies webbing, it is certified for impact strength as a loop. Are tope rope anchors subject to impact loads? They shouldn't be but increasingly are as people don't know where to rig and get pendulum falls.
DeleteI agree that cutting is often (usually?) the biggest danger regarding the integrity of soft goods- but this applies to all kinds of slings and cords. Even thick ropes can be cut through remarkably quickly when dragged across a sharp edge while loaded.
ReplyDeleteI get that webbing seems, and probably is, more vulnerable since it doesn't have a protective outer sheath as with kernmantle cord, but I think people often forget that the outer mantle isn't just a passive covering- it comprises typically 35-40% of a ropes weight, and a significant portion of its strength - a rope with a cut mantle is extremely dangerous.
Perhaps more relevant to this conversation, is that a loop of webbing often isn't any more redundant than a single strand. Unless you have tied a stopper knot in two places along the length of the webbing, and it is cut in between the two knots, it will fail if either strand is cut. A common example of this is girth-hitching a sling around a tree and clipping the loop to something else- If that loop of webbing is cut anywhere, on a single strand, the whole sling will slip through. Perhaps you think slings should always be doubled around an anchor or carabiner and then tied (meaning 4 strands..But in that case, to be logically consistent, you should treat all slings which are not doubled and knotted, with equal contempt as you do with 'single-strand webbing'..
Bottom line to me is, anchor components should be redundant. (Though like everything there are exceptions: when a component is incredibly strong or exceedingly unlikely to fail in any conceivable circumstance, if it is not practically possible to make it redundant (i.e. your rope), etc..