Marlow's Viper Cord and Other Cover Only Flexible Splices

[dmonn]

Should I leave the core or remove the core for the buried section?

 

[Brocky]

I would remove it. Some cords, like the Furler, have been designed to be able to make a continuous loop for sail boat usage, the core is removed for a section and the cover replaces it, for little, or no diameter change. The core in your cord might be more to help keep it round though, with how small it is, kind of like Icetail.

 

[dmonn]

Would the continuous loop be made by using a double brummel with both tails buried? Could that technique be used for a prussik loop?

 

[Brocky]

That would work, you would need to decide if you want to have the tapered overlapping covers, or the cover and core overlap. Locked brummels would be possible with the rebraiding the second tail method.
Another way would be to remove the core and run the cover around until it meets itself, some stitches and wraps around the end. Seems like it would give twice the strength of the cord, plus no tapering or struggles to get a consistent diameter.
Did your cord expand enough for a bury?

 

[Brocky]

Finally got around to sending some in for testing. The top two and bottom right were spliced like the top drawing, all broke at about the same spot. The bottom left was done different, which should of done better, but I think the cover was reduced too quickly to half diameter, to make it flexible.

 

[Joeybagodonuts]

Nice job Brocky. I've been waiting to see someone give this a shot... I wonder how euro companies making these similar hitch cords are achieving higher breaking strengths. Are they using a technora vs vectran, but with similar splices? The euro ones im thinking of, are indeed, all breaking over 5k, right? Forgive me, I'm drawing a blank on the company I'm referencing above...

Either way, pretty cool bud.

 

[Brocky]

I think they use the bottom design, mine might have broke early from reducing too quickly trying for the most flexibility. Gleistein Ropes is one that I’ve seen.

 

[Brocky]

After some more testing, the cover only splice gets close to the break strength of the cover itself. I only buried through the opposite side eye, and not further like the above drawing shows. Using the same splice on single braid that I knew the rated break strength led me to this conclusion. There is very little expansion near the eye, even with the cover tail bury, so it remains flexible eye to eye.

Another idea is to use small diameter core, 1.75mm in my testing, with multiple loops of it formed from a single loop, so it only needed an end to end splice. The core is independent of the cover so it can self equalize when loaded. The 1.75mm Vectran used has a break strength of 800 lbs., from testing, each strand has 560 lbs. when made into a hitch cord. This also makes them flexible end to end.

 

[Brocky]

Had some testing done to see if a gradual tapers, or if both tails were half diameter for most of the bury would be stronger for cover only hitch cords. Used NER 3mm Endura single braid dyneema with a break strength of 2300 lbs. The half diameters broke at 2288, not much loss. The gradual tapers broke at 3447, throws off my previous theory that this type of bury would only be strong as the cover’s break strength. Guessing the “cover” and buries worked together, like a double braid, to hold the load.

Also tested a Tuck-Bury splice, the one on the left,compared to a locked brummel, next to it, 2758 vs 2610. Have been doing rebraids for the second covered eyes, but it looses fifteen percent more strength than a locked brummel. The Tuck-Bury is stronger and easier to do and gives a smoother finished bury.

 

[Brocky]

The second cord from the bottom has the TuckBury on the top eye, no bulge from the brummel.

 

[Brocky]

Correction on the break strength of 3mm Endura, it’s 2,800 lbs.