Capsizing a Bowline Knot

[bellows]

Speculation on the anchor failure accident on Kiddie Cliff earlier this winter included some comments on possible bowline failure which surprised me and got me looking at the knot a little more. When I was a kid it was one of the knots my dad taught me and I always thought it was bomb proof. Not so, this video was eye opening:

(fwd to 1:45 specifically)

 

When cross loaded without a stopper knot, the bowline capsized in the test and failed at ~400 lbs(!!!!). I’d like to think I’ve never clipped into a bowline through the loop as it’s tied around an anchor, and that I’ve always put a stopper knot in the tail, but can’t say for certain since it’s the same way you’d clip into webbing at a rap station. Obviously I’ve learned something new, and think it’s worthwhile to share. Stay safe out there!

 

[genepires]

are you sure the strain gauge measured in lbs? I imagine that they go in metric so it could be some other measure.

[bellows]

Yes, you're correct. The gage measured 184kg at failure in the video, I converted that to the more familiar pounds since I don't have an automatic feel for the magnitude of kilograms.

[JosephH]

Knot particularly useful tests in a climbing context; the knots would never be loaded that way.

[ScaredSilly]

I think the main observation here is that the tests show the knot being cross loaded. While possible that is rarely how the loads are applied. Further, when the knots came undone it was hard to tell which end pulled through. Again not how the knot is used.

 

As such, while worth noting, the tests are not really a reflection of what happens in practice. Pit Schubert and the DAV did knot tests years ago that were much more realistic.

[genepires]

would have been nice to see a euro death knot (overhand) done.

 

so how could this situation happen? Maybe if an anchor was made by a bowline around a tree, someone clipped into the loop with a daisy chain and took a short fall factor 2 fall. somewhat unrealistic but possible.

 

[kurthicks]

The relevant take away of these tests is this: don't belay from your tie-in knot.

[Buckaroo]

Actually if you think about it in regards to the Kiddie Cliff accident this is probably exactly how the knot was loaded.

 

They tied a (relatively) short section of rope around a tree with a bowline, and clipped into the resulting loop. It would have had two end tails just like the test also. You also have to wonder how tight the knot was set and how long the tails were.