Splicing loops in Amsteel question and Improved Soft Shackle

[sargevining]

A lot of the testing for soft shackles do show an increase in strength vs base line strength. The question is how much.

A lot of the testing I've seen reports the diamond knot failing before the shackle it self. If you look at this document, you see the knot portion remains intact, so that can account for the discrepancy. Basically, because of the splicing, the knot portion is extra reinforced, and this style of shackle fails at a different area.


the 4 lines is such: to make a shackle you effectively pass the amsteel through itself. That makes 2 lines. Then when you close it and load it, you have 4 lines (2 in each side of the loop).

Tension with-in the loop is only equal to the load one side of the loop is holding. This is the same effect as if you have a line and pulled on each end with 100lbs of force. The line tension would only be 100lbs, not 200lbs like you might think.

An easier way to explain it is that, while making a knot weakens the line, splicing does not, and may increase its strength (although there are no absolutes).

[SilvrSurfr]

An easier way to explain it is that, while making a knot weakens the line, splicing does not, and may increase its strength (although there are no absolutes).

I would disagree with that assertion. A splice always weakens the line.

[Boston]

I would disagree with that assertion. A splice always weakens the line.

Yes, and no. Most splices do, because they create a geometry change where the bury ends in the rope. This create's an area where stress in the rope is locally higher. The geometry change is known as a stress concentrator. Sharper geometry changes create larger stress concentrators. This is why we taper the end, to make this transition as smooth as possible.

However, this weak point is where the splice ENDS, the rope in the middle of the splice is actually stronger, because there's more material to bear the load.

In the case of a shackle, however, we aren't saying "the shackle is stronger because it is spliced". We are saying it's stronger because there's more material to share the load.

It's the same as trying to lift a 100lb load. You can use a line rated to 100lbs (working load), or you could use two lines rated to 50lbs. (well, in reality I wouldn't cut it that close, but you should get the point).

[tobiusnc]

Thanks for the para-cord sheathing suggestion, it's is a really great idea. I remember reading about it a while back, but I had forgotten. That may be where I end up.

I'm not worried about the loop increasing my hang distance, it's already going inside my whoopie splices, and those are inside the length of my tarp ridge-line. Since I don't ever plan to hang without a tarp (at least in the near future), my minimum hang distance is just under 12' plus what the tree huggers add. That puts me at typically about 15', less if I marlin-spike the free end of the hugger.

Here's a picture of what I'm thinking for adding a loop to the main line. The loose end of the fixed eye is wrapped around the main line 3 times, passes back over (similar to taut-line hitch, then buried inside the main line under the loops. Hopefully it's enough to get my idea across.
Attachment 110609

Any one have any thoughts on this splice specifically? It seems like it would work and wouldn't damage the line, but I'm afraid I'm missing something.

BTW, the more I think about it, I don't need a fixed loop on the other end. A stopper knot is all I need. I could then larks head the continuous loop of the hammock around the line.

[lxzndr]

Just a note on this... the amsteel load ratings are for spliced line.

from the bottom of the sampson amsteel-blue page http://www.samsonrope.com/Pages/Prod...?ProductID=872

ISO strength specifications are for unspliced rope. All other strength specifications are for spliced rope.
Size 7/64" (2.5 mm) changes from 12-strand to 8-strand construction.

(does not apply to lash-it/zing-it, those are unspliced strength)

[SilvrSurfr]

Just a note on this... the amsteel load ratings are for spliced line.

from the bottom of the sampson amsteel-blue page http://www.samsonrope.com/Pages/Prod...?ProductID=872


(does not apply to lash-it/zing-it, those are unspliced strength)

I wish I understood ISO 2307 strength specifications, which is what they are referencing. For example, ISO 2307 strength (metric tons) for 1/8" Amsteel is 1.1. What exactly does that mean?

[tobiusnc]

I wish I understood ISO 2307 strength specifications, which is what they are referencing. For example, ISO 2307 strength (metric tons) for 1/8" Amsteel is 1.1. What exactly does that mean?

From the ISO.org site.
The breaking force is the maximum force registered (or reached) during a breaking test on the test piece, carried out on a tensile testing machine with constant rate of traverse of the moving element. The breaking force values given in the tables of rope specifications are only valid when this type of testing machine is used.

According to google, 1.1 metric tons is 2425lbs. Seems to line up with the other specs.

[Boston]

It means if testing using the method in ISO 2307 the rope breaks at 1.1 metric tons, which is ~= 2425 lbs, which is about the same as the average breaking strength reported.

[SilvrSurfr]

I still see this as an SLS, not as a whoopie sling and a structural ridgeline. The SLS is not very popular (only WV comes to mind), and it sounds way more complex than just doing whoopies and a structural ridgeline.

I'm not sure how you plan to integrate the SLS into the GT Skeeter Beeter Pro (if that's what you're intending), but that's likely to be an issue as well. It seems like stock solutions would be the best way to go, but that's just my opinion.

[octagone]

Guys, guys, some of you are missing the original question, the main request for help!
It seems to me that the original post is NOT asking about the popularity, merits or shortcomings of a SLS. Let's go over that in a different thread.
The original post is also NOT asking about the accuracy of some 3rd party's soft shackle testing. The PDF linked was just FYI, a public service announcement. (incidentally, juskojj posted a link to l-36.com where they also cite a 230% soft shackle -- same one?)

Instead, Tobiusnc's main point (and first half of this thread's title) is about amsteel: how to join a separate branch onto a main line, that will be loaded at an angle from the main line.

Tobiusnc, I think your idea of a Kleimholst with a buried tail is clever. Some thoughts:
1. As the hammock branch is loaded, it will tighten the coils around the main line. This will mostly happen when first loaded, less on subsequent loadings. But this motion compresses the main line while applying friction to its circumference (think "indian burn"), I think you'll see damage to the main line under the innermost coil. You might be better off with a simple stitched bury. The joint will get ugly and open up, but the fibers will freely align as they need to. I think that will preserve most strength.
2. The main load will be from the suspension to the hammock. Consider making that line continuous, and splicing the center "ridgeline" segment into the suspension lines. Behold my stupendous doodling skills:
IMG_20150618_151135.jpg
3. You'll probably be fine any way you choose to go on this one -- even partially crushed 1/8" amsteel should be ok for many nights. Try stuff out and post more photos of how it's working out for you, how the amsteel is holding up. Inquisitive minds want to know