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Animated Knots Was Wrong - Grog Loops Tested


My fellow Dyneema (HMPE) nerds: Grog loops are a continuous loop made using hollow braided rope like Amsteel, with a brummel type connection so, in theory, you don't need to sew the splice. We tested how short the buries have to be to be super safe enough (spoiler alert: not too short!) and we discovered you don't exactly get the theoretical 180% of the single strand rating like

Animated Knots estimated at in the "strength" section of their Grog Sling Knot Article.


"Tech Specs"

Here's a tech sheet on Amsteel Blue. See the minimum strength for 3/16" (5mm) and 1/4" (6mm) and see that 180% is not what we got.

It is recommended that the tail loops be 30 times the diameter of the material, which is fine if you don't care how big your loops is, but if you are trying to connect two things together like two slackline webbings, that limits how small a Grog Loop can be. We tested configurations with "smaller than recommended" tails to see if we can make small loops that are super good enough. Because the tails are not sewn in a Grog Loop it is important to check on the loops after repeated loading, and it's probably a good idea to sew them as an additional safeguard if you can.


Jake's Data


Jake Monaghan tested 5 grog loops made of 7/64 Amsteel. His results show that longer tails were stronger but his short tails did not slip out. One of his tests did achieve 180% MBS.




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Extreme Gear sells 3 different types of Dyneema: Sk75, SK78, SK99 max


Our Data

Jake made us six 5mm and six 6mm Grog Loops with Amsteel Blue (Sk75) with short burys, normal ones, and extra long burys.

We got a wide range of results. The Grog Loops broke below MBS where we didn't have 30x diameters. Don't splice your tails too short!!! We had a huge range of results from 158% to 111% but none got to the theoretical 180% we should have been getting.



Takeways

  • Make sure you have 30x tail to diameter for optimal strength

  • Keep an eye on Grog Loops to make sure they are not slipping after repeated loading, luckily they are easy to check

  • Our tests are not conclusive but they show how big of a range you can get when slow pulling dyneema. Don't throttle the line of safety when using dyneema. Especially if your life will depend on it, have a safety ratio from the "rate" minimum strength because you don't know what you don't know.


What's Next?

We tested a bunch of different taper recommendations and we found a surprise.






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Edutainment has been a great way to help people understand their gear, and know the true limitations of it.  Watching HOW gear fails is more important than the force itself, as almost all gear is super good enough.  It's more important to share information on how to stay safe than it is to have a paywall.  We hope our stoke is contagious.

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