A Knot Costs You Strength. A Splice Doesn't.

Every knot you tie in a rope is a discount on how strong that rope is.

Not a wee one, either. Tie a knot in a rope rated to 22 kN and you have handed a chunk of it straight back. Sometimes close to a third. The rope did not get weaker. You built the weak spot yourself.

I only learned this properly once I started cutting up retired rope for a living. Now I think about it every time I join two things together.

Why a knot is always the weak bit

When a rope is pulled straight, every fibre shares the load evenly. That is what the number on the packet assumes.

A knot ruins that. The rope bends round a tight corner, so the fibres on the outside of the bend have further to travel than the ones on the inside. A handful of fibres end up carrying far more than their share. The rope also squeezes hard against itself, which pinches everything.

Pull hard enough and it lets go at the knot. Nearly always at the knot.

A figure of eight, the knot most climbers tie in with, keeps roughly three quarters of the rope behind it. A bowline is a little less. A plain overhand is worse again.

None of that means stop tying knots. A figure of eight is still far stronger than anybody needs, it is quick, and you can get it undone afterwards. That is the trade you are making.

What an eye splice rope join does differently

A splice does not bend the rope round a corner at all. It buries the tail of the rope back inside itself.

Pull on it and the bury grips harder. The load spreads along a long stretch of rope instead of piling onto a few fibres at one sharp bend.

Done right, an eye splice rope loop keeps most of the original strength. On the right rope it is close to all of it. That is why sailors splice their sheets, arborists splice their rigging lines, and rope access gear turns up spliced from the factory.

The catch is those two words, done right. HowNOT2 pull-tested it recently and the numbers are worth sitting with. A five year old sailing sling with a poor splice slipped apart at about 8 kN. A properly buried one broke at over 22 kN. Same idea, same sort of rope, nearly three times the difference, and none of it down to the rope.

They flattened a myth in the same test, too. A brummel lock does not make a splice stronger. It stops the splice working loose when there is no load on it. The strength is all in the length of the bury.

And an honest bit, because I would rather tell you than sell you. Climbing rope is kernmantle, a braided sheath over a core, and it does not take an eye splice the way 12-strand Dyneema or a double braid does. If somebody offers you a spliced climbing rope loop, ask a lot of questions first.

So I stitch instead of tying

There is not a single knot holding my gear together.

Every recycled climbing rope belt I make is bar-tacked, which is a dense block of stitching worked back and forth through the join. Same principle as a splice. Spread the load along a length instead of stacking it all onto one tight corner. A knot would also sit as a great lump under your shirt, which nobody is asking for.

Same on the climbing rope keychains. That loop is sewn, not tied. Same on the climbing rope dog leads, because if a lead is going to get yanked by something with four legs and no manners, I want that pull spread out. Everything else on the bench gets the same treatment.

None of it is life support. A belt is never going to be asked for 22 kN. But that rope already did the hard job once, and I would rather not be the man who undoes all of it with a lazy join.

Stay classy and remember,
Make Waste Useful.

George