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

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
This is why:

Me: “What’s the difference between double ropes and twin ropes?”

Dave: “Double ropes are most properly called “half” 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 point—this 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 mass—this 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!