Straight From the Mammoth’s Mouth: Half Ropes Are Not Twins
Last month Dave Furman, Mammut USA’s hardgood expert, answered my question about sheath thickness of ropes.
Usually when leading with two thin ropes, I just call them double or twin ropes. This is a good idea when alpine climbing, since you want a second rope anyway for descending, so you may as well reduce the overall weight by using two thin ropes to lead on. It’s also a good idea if you have two people following your lead, or if you are rock climbing a very loose and/or wandery route that could create a lot of rope drag. In my brain, half, double and twin all end up being pretty synonymous.
But no, double (half) and twin ropes are not the same thing! So though you would still be leading with 2 ropes in all of those situations, you would want to select either “half” or “twin” ropes (which are two different things) depending on how you plan to use your protection, because they have different strength ratings. Which I may or may not have specifically known before đ
Basically, twin ropes need to be clipped through the same biner for each piece of pro. Double (or half) ropes can be clipped separately into different pieces. See, that’s not confusing at all đ
This is why:
Me: “What’s the difference between double ropes and twin ropes?”
Dave: “Double ropes are most properly called âhalfâ ropes by the UIAA. These ropes are designed so that the leader climbs on two ropes and clips each strand separately through protection, often alternating so that each rope is clipped through every other protection point in order to give better safety margin on routes where cutting a rope is a danger, to manage rope drag on complicated terrain, or to protect the second climber on traverses. Half ropes may be clipped separately or they can be clipped together so that both strands are clipped through every protection pointâthis is called twin rope technique. Dedicated twin ropes are lighter in weight and bulk, but should always be clipped so that both strands pass through every protection point.
It is notable that when people look at ropes in a climbing shop, the test results they see for single, double and twin ropes are all different, so they are difficult to compare. Single ropes are tested using a single strand and an 80kg mass. Half ropes are tested as a single strand under a 55kg massâthis is because the test assumes that under a fall the first rope will stretch enough that the second strand will absorb some degree of the force of a fall, but it means that the test results do not compare to the test results of any other ropes. Twin ropes are tested using two strands and the 80kg mass, so these can be compared to single-rope specifications.”
Thanks Dave! đ
I’ll just use a beefy single and protect well. I’m barely smart enough to comprehend the concept of cams. Plus, I have a feeling my poor little arms would get so tired running two lines of protection. I do like the redundancy though.
Thanks Steph.. I ran across this topic recently myself when looking into getting a set of alpine ropes. I just wanted to add that some new ropes are now coming out that are certified to half and twin, such as:
http://sterlingrope.com/product/149345/fp/_/Fusion_Photon
cheers
In continental Europe, outside of a few areas, fewer people use half-rope technique–most people use their half ropes with Twin technique clipping both strands togetherâconsequently most of the half ropes on the market will pass the test for both half and twin ropes, and this is common enough that it is assumed. All of Mammuts half ropes will also pass the twin rope test–here’s what Mammut has to say about the subject in our rope booklet: “…here you have the choice between twin rope technique, where both ropes run parallel through the protection and half rope technique, where the «left» and «right» ropes run separately through different protection points…”. (incidentally that is available here, there’s some good info buried within… http://www.mammut.ch/images/Mammut_Seilfibel_E_web.pdf ) Speaking only for Mammut, we generally don’t certify our ropes to more than one standard because there is a very real concern that people make assumptions about a rope based on the fact that it is marketed differently, that often donât really hold true. As an example, our Serenity 8.9mm single rope was initially introduced with both single and half rope specs and many people assumed that it was âmore durableâ than a thinner half rope, when the reality is that it was far less durable than our thinner Genesis 8.5mm ropeâthis was the subject of Steph’s blog post here: https://stephdavis.co/blog/straight-from-the-mammoths-mouth-things-you-want-to-know-about-ropes/ . In general we would rather steer people into using their ropes in the manner that will result in the greatest degree of utility for most people, which is why we have shied away from dual certifications like this. It isn’t right or wrong, but my sincere belief is that more people wind up with a rope that better suits their needs as a result. Hopefully that adds a bit of perspective, but please fire away if it raises still other questions.
[…] manager at Mammut and my gear-expert friend. He wrote some great guest posts here already about differences between ropes, and he knows a lot about specs and the more technical capabilities of cordage. Here’s what […]
[…] When I have questions about things involving physics and climbing gear, which require actual mathematical answers beyond me going “well, this is what I’ve always done and it’s always worked, so that’s what I can tell you,” I go immediately to Dave Furman, the hardgoods category manager at Mammut USA. He’s written some extremely informative guest posts here, and he is a great source of information. […]
What are the most proper techniques for rappeling with 7.7mm twin ropes? Are figure 8 atcs preferred over normal/v groove atcs?When cleaning the route at the end of the day Is it safe to have the four strands of 7.7mm rope doubled in each slot of your common atc when abseiling? I cant find much on the inter web about this!!!!
-Seb
Hi Seb, usually you want to take measures to make sure the rappel is not too fast with the thing ropes. One way is to turn the belay device upside down. Another way is to add a second locking carabiner. And it’s always good to have a “second hand” sling backup clipped to one leg loop.
With dual or triple rated ropes there’s something to said for picking EITHER half OR twin technique on any given pitch. When you run the rope through separate pro they travel different distances, and therefore in a fall, will move at different speeds. That’s all well and good until they then meet in one carabiner on one piece of pro, this can cause the two ropes to build significant friction and heat between them. This does not happen with twin ropes of the same make and model, as they are going to stretch and travel at the same rate (I have never heard of using twins of different models). Or am I wrong?