Pull Testing Stitching in Webbing

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I decided to do some testing on the strength of different stitches in webbing.

I built a simple fixture to hold the come-along, scale and test piece. The come-along is rated to 2,000 lbs and the scale is rated to 10,000 lbs and in calibration. The load was always steadily applied, not shock loaded
Pic 1

All the test pieces were 1.25 inch light weight polypropylene from Strapworks rated at 600 lbs. All the thread is Synthetic TEX 30, 3.5 breaking strength from Speer Hammocks. The box stitch was 1 inch square with an X in the center, 11 stitches per inch. For the bar tack I set the machine to Zig Zag, .2 inch wide and 34 stitches per inch. The box and bar tack were both double stitched. I tried a single stitch but it failed under very light loads.

The first test was a single bar tack. It failed at a light load by the webbing pulling out of the stitching.
Pic 2

The second test was 2 bar tacks.
Pic 3
It failed at 200 lbs. Again it failed by the webbing pulling out of the stitching
Pic 4

The third test was 3 bar tacks.
Pic 5
This test the stitching held at 600 lbs.
Pic 6
Failure didn’t occur until about 700 lbs and then it was a slow tearing of the webbing.
Pic 7

The box stitch held at 600 lbs.
Pic 9
Again the webbing failed a about 700 lbs and it was with a slow tearing of the webbing.
Pic 10

I now have a much more easy feeling laying in my hammock.
Let me know what you think.

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