Destrictive testing of bridge hammock suspension

[Lancem]

In preparation for making a new bridge hammock, I did some crude destructive testing of various DIY suspension components. In particular, I wanted to test different methods for accepting the spreader bar tips. Components included 1/2" nylon tubular webbing, 7/64" Amsteel, 1"x1.5"x.125" aluminum, and a 3/16"SS bow shackle. The aluminum failed at 900#. Bar tacks using Gutermann sew-all failed at 1000# and 1100#. Hopefully the attached pictures speak for themselves.

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-Lance

[Levi Tate]

Nice first post. Thanks for sharing.

Do you have any pics of the bartacks before destruction?

What stitch pattern did you use?

Which method do you think you'll go with?

[Lancem]

Yea, first post here. Been at BPL for years, but this is the go-to place for hammock stuff.

The zig-zag stitch bar tacks were hastily sewn. I could have done a better job and used better thread. Four tacks 1/2- 3/4" apart.
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The bar tacks that failed were on the loop attached to a shackle which opened up the loop a bit. I speculate that created a bit of peel force that wasn't present at the business end of the webbing.
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I'm inclined to go without any hardware where the webbing, Amsteel and bar tip come together.

-Lance

[Lancem]

Two more tests. This time with 1/2' Mule tape.

The first test piece had a loop sewn with 5 quick bar tacks using Gutermann sew-all thread at one end and a loop created with a figure eight on a bight at the other end. The mule tape broke at the figure eight at around 850 pounds. The bar tack end was stretched.

The second test piece had loops at both ends sewn with X-boxes using Gutermann Mara 70. The first loop exploded at around 1100 pounds.



Teaser from above:


-Lance

[shipsgunner]

Excellent work. Appreciate the info!

[c0wb0y84]

Just to add some thoughts to the discussion, a knot tied in a line or webbing will pretty much always be the weak point as it will, depending on the form of the knot, reduce the breaking strength of the material anywhere from 35-55% whereas a properly spliced eye (line) or properly stitched eye (webbing) will only reduce the breaking strength 5-10%. In your situation a figure eight knot will reduce the BS by about 45%. Also bending the material over sharp edges is a different animal in BS reduction. If possible radiused edges are far better than 90 degree edges. Break out the Dremel!