Climbing-line "rope-thimbles", unsure how to utilize these (got several 1/2" 'steel rope thimbles' with my climb-rope!)

Question

I got some 1/2" steel-thimbles for my climbing-rope but sadly I'm not sure how to safely use them, I'd thought "I can just tie a knot at just the right spot so that the thimble is securely nested in the end-of-line loop" but, having since learned about knots & knot-failures (stuff like capsizing a knot), I'm now unable to use these thimbles because I'm unsure how to safely do so and if one failed it could be disastrous (maybe you're not even supposed to use these as part of any lifeline? Doubting that but not sure!)

Here's a link to the specific product, I got the 1/2" ones to go with my 11.7mm Blue Moon rope, with the intention of using (2) of them on either end of a 6' section I'm going to cut-off of my climbing line (to make into a general-purpose sling/lanyard), and using one knotted to the end of my climbing line so that, when rigging a basal anchor with a running bolan (or whatever knot is best here), the rope-on-rope friction would be eliminated as well as the start of the standing-leg of rope takes a very sharply-angled bend and this is blunted a bit by the thimble as well :D

Thanks a ton for any advice on using these, I got them both to keep my rope's integrity up there for longer, as well as to have a stronger climbing-system once I've rigged everything up and my "weak points" have these steel thimbles at the contact points instead of rope-on-rope!

I'm pretty confident that I need to stay-away from using any cinching-knots here because when under-load they'd want to 'squeeze-off' the thimble, but so far as I can see I should be OK to use them if the knotting is 'fixed' and doesn't cinch-down, just unsure what to do and can't use them til I know for sure of course!

Again thank you so much for any advice on this one!!

Answer 1

These thimbles are primarily used for fixed point attachment. They're used on yachts and sailing dinghies for stays, halyards and jib mounts. Spliced onto the end of the rope they're for loops and semi-permanent anchors, or where you need to attach two very different materials via a D-shackle or equivalent.

Climbers use rope-carabiner-rope for their equivalent job, you should never be rope on rope. Climbers like everything to be temporary, they like to inspect every knot every time. They like knots because they can be inspected every time. Sailors like splices because they're permanent and don't need to be inspected much.

While splices are stronger and more permanent, knots are "safer" because they can be checked.

The important thing to remember is that if a spliced rope on a thimble and D-shackle fails for a sailor it's mighty inconvenient, but that's about all. If it fails for a climber, it can be fatal. It requires expertise to be able to inspect even a twisted rope splice, with kernmantle rope you're on "if in doubt chuck it out" territory and you'll be throwing out a lot more rope than you would if you stuck to tying knots and using carabiners.

That's not to say you can't do it.

There are standard commercial products that do exactly what you're asking, though using the nylon thimbles which are more suitable for this rope type. They're designed for people who aren't experts, such as builders and scaffolders where they don't want to be spending half their time checking knots. Like any safety equipment there'll be guidance on how much and how many times they can be loaded before discarding. They don't expect you to be able to inspect the splice (beyond checking the stitching if stitched), you just discard as soon as you see any damage.

Why nylon not steel

Rope flexes, it twists and shifts, steel doesn't under these loads, nylon can. As the rope moves it will abraid against any edges on the steel. The closer wear characteristics and greater flexibility of the nylon thimble reduces this effect meaning that your rope has a longer working life.