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Destructive Testing: Webbing Termination Methods

Original Post
20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,348

Today I ran through a quick test involving different webbing termination methods and I figured I would share the results. I explored five termination options: a webbing locker*, a carabiner line locker**, a bartack-sewn loop, an abnormal-stitch pattern and an overhand knot. The sewn loops were created with 4mm x 0.5mm bar tacks using size 92 nylon thread (about 15 lbf MBS).

The webbing I used was some generic, 1” flat nylon webbing which did not turn out to be nearly as strong as I expected.

Anyway, the photos!

The samples, from left to right—abnormal stitching pattern, sewn loop and webbing lockers:

Carabiner line-locker testing:

Web lockers:

In short, it seems as if this webbing is not overly influenced by termination methods, aside from knots. I suspect the main reason why different termination options are not influencing the webbing more than a few percent is because the webbing has a very high elongation relative to the webbing used in climbing and slacklining (nylon, polyester, polyethylene, Vectran, ect).

I was especially surprised to see that the abnormal stitching pattern did not influence the strength compared to the standard bar tack stitching pattern. I choose the pattern I used in the “abnormal stitching pattern” test because it distributes the load very inefficiently amongst the fivers, which would normally result in premature failure. However, the webbing elongation was so high that it did not matter either way. The following photo clearly illustrates how the abnormal stitch pattern causes circular uneven loading of the webbing’s fibers:

Last, I do not believe the results of this test can speak beyond the scope of the exact webbing I tested, and therefore I am going to repeat the test later with 1” climbspec. As I know someone is going to ask, I did not start with 1" climbspec is because it fails at around 4,500 lbf in a webbing locker and I do not have any extra webbing lockers to spare for destructive testing, so I choose to use a webbing with a low failure strength.
Allen Sanderson · · Oootah · Joined Jul 2007 · Points: 1,135

What was your stitch count? That is did you use the same number of stitches in each type of bar tack?

So for instance, with the abnormal stitch pattern it probably have held up simply because the number of stitches made up for the inefficient pattern. Thus you were able to obtain a test load that was similar to the more efficient bar tacks. Such result would not be surprising.

What would be more interesting is to use the same number of stitches for each and compare relative strengths. If the abnormal stitching was still similar to the more efficient tacking then at that point one can look at the quality tacking and what is required to have an efficient tack yet allow for abnormalities while over stitches making up for it.

Guideline #1: Don't be a jerk.

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