UKC

Why is it that if you have coiled a rope double, that if you chuck it on the ground and pull one end, then almost always the whole rope comes out without any tangles. This just seems incredible and completely counterintuitive to me, especially considering what a nightmare ropes coiled singly usually are to unravel.

Yes, that's pretty much my experience too, though I think I uncoil my doubled rope from the centre first then the end.

I've conducted a wee bit of an experiment tonight and although I agree it seems counter intuitive the geometry  ( topology) is subtly different. The rope wants to lie in figure eight coils (I'm not sure if this is to do with the rope weave or the repeated half rotations of your wrist as you coil?) . Coiling from the end  my hand grips the rope at the top of the eight, each eight has a rope length l and the twist continues in the same sense along the whole rope. Coiling from the centre I grip the rope in the central node of the eight and lay each lobe of the eight in a separate handful so the eight now has length 2l: the folding of the rope perhaps means that the sense of the coil is different on either side? 

I agree though that this is not in itself an explanation but maybe a first step towards one .

I wonder if it works coiling two separate ropes together and then pulling out one of them. Might try tomorrow.

I think part of it is down to the fact that both ends are the last bits to be coiled and therefore all kinks are 'driven' out of the rope.

I have no answer.  My observation is that tangles happen with about the same frequency with single and double coiling; certainly double coiling is no worse.

I think it possible that the biggest contribution to tangling is how the coil is situated with respect to the person pulling out an end, as tangling happens because a loop being drawn out captures other loops. 

If a round coil ("mountaineer's coil") is directly under the belayer's hand, tangling is very rare in my experience, whereas if the round coil is off to the side of the belayer so that loops are pulled through the coil, tangling is far more likely.

If a flaked coil (the sort you make by laying down loops alternately to the left and right) is bent into a C-shape with the C facing the belayer's hand, then the coils are pulled off the C without being dragged through the coil and, again, tangling is very rare.

If you double the rope and then coil it, there is no net twist (end-to-end) in the rope because one half is twisted clockwise and the other half anticlockwise (as seen from one end). So there's a twist from one end to the middle and then to opposite twist from the middle to the far end. Tangling tends to happen when there's not much tension in the rope (usually towards the end as you feed it out), but in a double-and-coiled rope the residual twist peaks in the middle and then drops to zero as you approach the end, hence less tangling.

Another puzzle is when you start coiling have found the precise middle, and having carefully coiled it the ends rarely match and one is often 6"to 9" longer than the other!?

Thanks for various replies. Some proper experimentation seems needed. Even if it eliminates kinking, it still seems very surprising that a doubled rope pulls out so easily.

One strand tends to get bigger radius?

Easily avoided, of course, by starting from the ends.

It that's how you actually coil your ropes, then the kink theory goes out of the window.

But I always coil from the ends, so the middle is done last!

Always start from the ends. Never get tangles. Magic innit?

Of course the other magic thing is that a rope always gets tangled if you did not coil it yourself. 

I never now risk it as my experience is otherwise i.e. there's a good chance pulling one end of a rope coiled double will produce a clusterf*ck.

I recall that after a late start on a route in the Cattinacio, with a number of abseils intermingled with scrambling on the descent, my partner did what you suggest and chucked his rope on the ground at each abseil. I silently seethed as he sorted each tangle, imagining it might lead to a cold night out instead of the pub and a cosy sleeping bag!

I do always "flake out" the rope. It's just that it usually turns out not to have been necessary if coiled double.

Tried that a couple of times and on the second go we ended up with the middles of each rope looped together. 

In reply to:

I double coiled for years, but now only coil from one end. There are far fewer tangles, and flaking out is usually unnecessary - we only do it for really critical leads. 

I'm amazed people have found the opposite to be true! 

Most tangles occur because of twists in the rope that cause the rope to coil around itself and catch loops.  The key to avoid this unpleasant behaviour is to avoid twists. Double coiling goes a long way to avoiding this by ensuring any clockwise twist in one end is countered by and anticlockwise twist in the other end. The origin of twists is easily seen if you 'mountaineer' coil a rope without reversing the process [ie just pulling it out] - you get one twist per coil.

It is very hard to avoid twisting a rope because we are handed [every wondered why phone cords coil up in such a mess? Because the majority of us answer with the right hand and speak holding the phone in our left so we can write, gesture etc. When we transfer hands we introduce a 1/2 turn which is nearly always in the same direction, hence the mess]. Double coiling is an effective counter measure to this.

I don't find one way better or worse than another for paying out but double lap coiling is a lot faster than single coiling !

A what?

Ah well, yes, quite right, I did wonder if a reference to phones with actual cables might lose some younger readers...

Me too, i have more success with single coils, but tbh i still do have a fair amount of birds nests to deal with!

Do you coil the back and forwards way or the circular way. I think it is circular coiling of any sort which is just asking for trouble. I find it hard to uncoil a circularly coiled rope one loop at a time without a tangle!

If I have just one rope separated from the other, I coil from the ends, middle last.  This can be quite a bit faster than searching for the middle.  But if the two ropes are in a pile together, I've found they have to be separated before coiling.  The fastest way to do this is for each climber to pull out and pile one end until they reach the center of the rope that they are dealing with, and from that point coil from the center of their rope until the two ends are reached.

The incredible thing (to me) is that this almost always works without tangles if you just pull out one rope - same principle as I'm talking about with pulling one end of a double coiled rope.

I presume, as a mathematician, you know the lovely little trick for facilitating finding the (unmarked) ends of a rope which is in a random heap

Fully agree I finding double coiling leads to more tangles.

I'm sure you'll have noticed that some ropes only have one end...

Me too, although the biggest factor is how new the rope is.

Same for me. I was a bit mystified as well. Wondering if I'd misunderstood. 

Yes that is a great way to avoid tangles with two ropes together. Only thing I do different is I single coil straight out of the pile.

As a borderline obsessive, I practice Safe End Management (TM) and so almost never find myself in a situation where both ends are lost in the pile.  That said, I'm sorry to find that my mathematics training has been deficient, as I have no "lovely tricks" for finding both ends of the rope in a pile, other than grabbing a random strand and treating it as if it is the middle of the rope and piling double from there, continuing on with a single strand after one end had been found.,

I have a little wrap of light-reflective tape on each end of my ropes.  This makes finding the ends in the dark by headlamp light immediate, but doesn't help much in daylight.  The reflecting tape also helps when rappelling in the dark with a headlamp, as the ends of the rope are highly visible even at a distance.

Let me repeat that if you make a circular coil and are able to place it on the ground directly under the belayer's hand, that the coils will lift off with no tangling.

Mathematically is it not due to degrees of freedom and the fact you're holding both ends therefore minimising this parameter?

The thread has been interesting but, probably because my OP was not clear enough, my original intended point may have become lost amongst all the other factors. So I shall rephrase it to cut away all the stuff about coiling, links etc:

You belay someone up a route. Afterwards the two ropes are heaped up on the ground in "parallel". What astonishes me is that if you pull the top end of one of the ropes, the whole rope will almost always come out with no more than the odd little shake of a minor tangle.

Think Konigsberg bridge sort of stuff

...unlike the other rope which becomes a complete nightmare?

Sure, the rope ends are the unique pair of vertices of odd order (if there is only one rope in the pile).  If the ends lie just right, they might just happen to make a vertex of order 3, but almost all of the time it will be of order 1.  So in order to find the ends, all you have to do is...look for the ends?

That's your mate's problem and I'm no way detracts from the astonishment.

This has not been my experience.  I've found that if the ends aren't pulled out of the pile simultaneously, some pretty big messes can occur.

Tease the rope out into, say, four piles. You have a 3/4 probability of knowing immediately which piles contain the ends. If unlucky, try again!

Well it worked for me a couple of times today. Though as Mike says, the second rope might then be a mess!

Thats why there is always a rush to get your rope pulled and coiled before your partner has a chance

It is fairly normal to try to pull the seconds ends together out of the heap at the same rate.

I was once told however to pull one leaders rope end and the other rope seconds  end, ie pull ropes apart from top and bottom of the heap as for some unexplained reason this always works.   

Even more astonishing. I want an explanation!

Easier to try it out, Bob.

Usually looks like it is going to FU about halfway thro then all is good towards the end.

I agree, and always flake out for the hedge trimmer

But I want a theoretical treatment, not empirical evidence!

I don't think there is much if any mathematical theory available.  Knot theory is mostly irrelevant, because most climbing rope tangles aren't knots (they are unknots, since they typically are formed without using the ends of the rope (any knot tied in a bight is an unknot mathematically).

There has been some work on knotting of jostled cords ( http://www.pnas.org/content/104/42/16432 )---it made the popular press---but again it is about the formation of honest-to-god mathematical knots and the conditions for their formation involve more jostling than most climbing rope piles would ever see.  Moreover, the theoretical version of jostling, which is a rope end randomly weaving its way over and under a bunch of essentially parallel strands, doesn't seem to me to correspond to what happens in a pile of climbing rope.

I suspect that climbing rope tangling is essentially a physics problem, because the material properties of the rope, eg diameter, stiffness, roughness of the surface, are probably significant determining factors in what actually happens.

It's the almost that is the problem.

It was the tangles that this caused that started me to try tandem coiling.

There is another factor here. Someone I know finds that the ropes he uses now are much more prone to tangling than the ropes he used before.

I agree. It makes some sense that it would work for an infinitely flexible, unkinkable, perfectly smooth ropes. So what amazes me is that it is not messed up by the imperfections.