Yosemite Bowline not safe for climbing





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Published on Jul 14, 2012

There have been some rumors regarding the Yosemite bowline, saying it can open up during climbing, or that the bowline underneath disappears.
This video comes to show what might happen to the Yosemite bowline (as given by Wikipedia, without backup) during climbing.

In detail:
The Yosemite bowline is the only prominent tie-in knot which depends on the way you set it.
If you pull it tight by pulling on the main rope first, it becomes the Yosemite bowline that we all know.
If you pull on the free end first, the bowline underneath might open up and become undone.
Please note that this will happen regardless of how tight your final knot is.

When the bowline is undone, you still have a figure 8 with a loop in it that should hold (according to postings on ukclimbing.com, thanks jimtitt!).
If the climber's rope straightens up like in the video, the loop is gone too, and only the figure 8 is holding you. This happens specifically by getting force on the climber's rope side and unbalanced force on the harness side (see Video, you can pull on both ends, just more on the climber's rope). This sounds unlikely, but can it happen? It could happen when we re-arrange the harness, hang into a stand, turn around, fall to a side.

In case the free end slides back one step through the knot (which can happen to any knot): before the bowline is gone, you are safe. The Yosemite finish just opens up to be a bowline. But when the bowline is gone, there is no backup knot that holds you, as shown in the video (for comparison, with the re-threaded bowline knot, the free end must pass multiple times through the knot to open it).

Note that you don't need to tie anything the wrong way, or thread anything wrong. You can do everything correctly, and still get this result simply because of the way you tighten the Yosemite bowline.

If you make your figure of 8 correctly and tighten it, it will never fail! There is no way to change a figure 8. Same for the bowline.

But if you make your Yosemite bowline correctly, the knot can change to different knots as shown, and the bowline underneath, the fail-safe backup of the knot, could be gone. Even if unlikely, there is still a risk.

You can never forsee nor test all eventualities. In the end it comes down to statistics, that we do not have. If we hadn't found a number of negative reports about the Y-Bowline on the internet, we wouldn't have looked closer at the climbing knots like we did, and we wouldn't have started this discussion. The intention of this video is to help you understand this knot and its risks.

You may join the discussions on supertopo.com and ukclimbing.com.

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