UKC

Hey folks, 

I am after a little bit of advice about my next rope purchase.

Background: for the last few years i have climbed on a pair of 60m triple rated 9.1s as general do it all workhorse and got on with this setup extremely well. I purchased these through a partnership my work has with a certain welsh gear company that i rate extremely highly and i got them for a very good price. This company seems to have stopped making ropes now and, after a bit of a run in with some extremely rough gneiss on the isle of Harris, I am now the proud owner of a 40m and a 20m triple. 

My question is this: now i have to pay full price for rope, do i really need triple rated? will half ropes do the job?

I climb as a 3 a lot and there is a bit of an ability gap between me and my regular climbing partners. I liked the extra security of a single rated rope when my second is dangling around on one line. Am i being over cautious here? i also feel like the thinner i go, the harder it will be to hold the weight of a person through a belay plate, but the extra cost and weight of triples vs halves is significant. 

With a group of 3 and rough rock, I’d stick with tripple rated ropes.

Or If the leader can cope with the weight, then thin singlen would also work. Penalty being the weight, pro being more robust and cheaper. 

Having a stab at this one...

The significant factor for triple certification is the 12 fall twin rating with 80kg rather than the 5 fall for single and half ( at 80kg &55kg resp.). Note the singles and half are tested as one strand and the twin as two strands in the test.

If you want a softer catch it's the half rope that has the lowest maximum impact force ( ie is stretchier - you want a low impact force- 8kN compared to 12kN in the other modes). How the 2 strands of a half rope will load up in a given fall is a mystery, but shouldn't exceed either figure. The ratings tables simply suggest that the triple rope will perform within the rating limit in each mode you could use it. No. of falls is 'invisible' in use, but real psychologically, so the choice comes down to how much you value the 1/2 rope's characteristically softer catch while having the reassurance of a 12 fall rating in the same system.

It must be a rope myths day today. There is hardly any difference between the stretch of a single rope and a half rope. Look at the stat "elongation at 80kg"

Mammut gravity Protect 10.2mm 7% Single rated

Mammut Galaxy Protect 10mm 6% Single Rated

Mammut Alpine Sender 9mm 7.5% Triple rated

Mammut Serenity 8.7mm 6% Triple rated

Mammut Genesis 8.5mm 7.3% Double/Twin Rated

Mammut Phoenix 8mm 10% Double/Twin Rated

Mammut Twilight Dry 7.5mm 6.7% Double/Twin Rated

So my point is that across the board, elongation (or stretch under load) varies inconsistently across diameters. Of course the higher the percentage stretch, the softer the catch. So for example you could use the Genesis and get a harsher catch than if you used an Alpine Sender. Or you could get a softer catch by using a 10.2mm Gravity Protect than by using the incredibly skinny Twilight Dry. Diameter simply does not map to catch.

To the OP, if you are mainly climbing with a single partner, just use doubles and save your cash. The difference you will see in friction between an 8.5 Genesis and an 8.7mm will be negligible. If you find it hard to hold a second, you'd be better off buying a higher friction belay device, for example the DMM plates are quite grabby by comparison to others on fat ropes and they will have been designed to be matched with thinner doubles. With a combo of for example a Mantis belay plate and a Phoenix pair of doubles, you could have the best of both worlds, soft catch and high enough friction to hold a second on a single strand.

Thanks Mike, fair points -though nobody suggested diameter was the dominant factor. For a softer catch the stretch on static 80kg load figures are less relevant than "stretch on first fall" figures. [BTW Mammut's rope page seems to have quite a few (self evident) misprints among the spec figures!] 

As per the point you make, and I've said elsewhere, the variations in specific ropes will be far more significant than the rating threshold limits used to define 1/2, twin and single ropes. Once you're aware of what the rating means in terms of impact force and fall numbers, you can read any rope spec and decide what you want from it.

Sure - I understand but this is a very common misconception which I regularly feel needs to be commented on. Half ropes are by definition smaller diameter than single ropes, and I feel as though people really don't understand the stats which come on the packet and that there is an assumption that by default Half ropes will give you a lower impact due to their higher stretch. This is absolutely not the case, as demonstrated above - the trend will broadly corrolate to the trend of impact force under similar lead fall conditions. I picked the elongation at 80kg because this is the closest to a slump onto the rope which is really what the OP was talking about rather than a full lead fall which would be closer to the stat you have cited above, there was a method to my madness I want people to really take the time to sit down and understand ropes because in most other areas people really make an effort to do so. Over on the other thread today (coincidence or something in the water?) there was all the usual, considerable amount of nonsense spouted...

Excellent Mike