How strong is it? ANCHORS (Part 1)
Premium Members can read the entire article here:
This section of my website is where I satisfy some of my curiosities (and hopefully some of yours) about the actual breaking strength of anchors, gear, and knots.
If you're new to this part of my website , I suggest you start at the overview page, and then bounce back here.
What's on this page?
How strong is an overhand knot anchor in a nylon sling?
How strong is an overhand knot anchor in a Dyneema sling?
How strong is a girth hitch master point anchor with Dyneema?
How strong is a girth hitch master point anchor with Dyneema, if one strand gets cut?
How strong is a girth hitching a Dyneema sling to a carabiner?
How strong is a girth hitching a Dyneema sling to a bolt hanger?
How strong is basket hitching a Dyneema sling to a bolt hanger?
1 - How strong is an overhand knot anchor in a nylon sling?
About 26 kN.
Source / testing: YouTube, You aren't supposed to tie a knot in this, Startaround 15:50
One of the most common ways to make an anchor. Simple, easy to check, fast, redundant, and probably hard to untie.
2 - How strong is an overhand knot anchor in a Dyneema sling?
About 21 kN.
Source / testing: YouTube, You aren't supposed to tie a knot in this, Startaround 11:00
While many people prefer to avoid tying knots in Dyneema, many folks think it's no problem. Again, this is a common and simple way to make an anchor.
Dyneema is less strong than nylon, but it's still #SuperGoodEnough for climbing. (Just don't expect to ever untie it . . .)
Takeaway:
If you double a sling like with the basket hitch, you get double the strength.
When you tie a knot in the doubled sling, you reduce the doubled strength by about half. So in the end, that leaves you with something close to the MBS for the original material.
We see this in both the nylon and Dyneema sling in the last two examples.
3 - How strong is a girth hitch master point anchor with Dyneema?
About 27 kN.
Source / testing: YouTube, Are climbing master points made with a girth hitch or clove hitch REDUNDANT??? Startaround 7:00
The girth hitch master point is a modern standard for many climbers. Good to know it's super strong! And yes, it's redundant if one strand gets cut. Read my whole article on it here.
4 - How strong is a girth hitch master point anchor with Dyneema, if one strand gets cut?
About 7 kN
Source / testing: YouTube, Are climbing master points made with a girth hitch or clove hitch REDUNDANT??? Start around 13:20
It's still pretty strong, but not nearly as strong as the anchor when things don’t get cut.
However, this only is going to fail in the following extremely unlikely situation: 1) a sling gets cut, 2) is then subjected to a very large (6-7 kN) load, and 3) that load is continuously applied. This is probably less likely would happen than you being struck by lightning when you're climbing, so personally, I wouldn't worry about it.
How strong is a girth hitching a sling to a carabiner?
What about girth hitching a sling to a bolt hanger?
What about basket hitching a sling to a bolt hanger?
