UKC

Once again my brain has struggled with the mathematical challenge of trimming the ends of a well used sports climbing rope. Start with an 80m length, measure and cut 8m from each end, then measure the remainder. New rope length is 62m plus two mini lengths of 8m. ????
This has happened to me three times over the years. Natural shrinkage through use or short changed when the ropes were originally bought?
With newer routes being put up at increasing lengths, verifying the actual, current length of your rope is important, but how many of us do?
Apart from measuring several times before applying the knife, I have also learned to mark the (possibly new) centre of the rope sparingly as the commercial product can dry to result in a section of stiff rope that jams in a belay device.

In reply to Stairclimber:

Ropes are very rarely the exact length (or diameter) that's marked on the packaging....

In reply to galpinos:


Luckily, routes too are very rarely the exact length that's marked in guidebooks

In reply to Stairclimber:

I thought you were going to say you had more rope than you expected, my half ropes are a few metres longer than they should be.

In reply to Stairclimber:

Sounds odd. As far as I knew ropes tend to be slightly over rather than under when bought and are surely more likely to be stretched rather than shrunk when older.

As far as rope length goes, whether I can lower off in one go or not is massively affected by stretch so if in doubt, eat more pies.

In reply to Stairclimber:

As a general rule nylon ropes shrink by up to 10% after the first couple of uses. Cavers know this and usually buy overlong lengths to allow for shrinkage. I wash my rope before use as this tends to shrink the sheath and length, and then re-measure it before marking it. Climbing rope manufacturers don't seem to mention this.

In reply to phizz4:

I thought that only applied to semi-static rope?

In reply to Stairclimber:

“Climbing ropes can and do shrink,” says Jim Ewing of Sterling Rope. “Nylon is a highly hydrophilic (readily absorbs water) and elastic material. Nylon yarns will change length with changes in moisture content as well as contaminants such as dirt. Nylon is also a plastic and ‘off gasses’ slowly over time as part of its normal aging process. The off gassing will, very slowly, dry out the nylon, causing it to shrink while also making it less elastic.”

Ewing further notes that you can restore some of a rope’s elasticity by soaking it in hot water (normal home tap hot-water temperatures), and that to allow for shrinkage, Sterling cuts its ropes three percent longer than marked. Most other rope manufacturers also trim their ropes so they are longer than advertised—you needn’t worry about a rope shrinking to the point that it will cause you to get dropped while being lowered. You have bigger things than shrink to worry about.

Interestingly, with almost all fiber ropes there is a certain amount of non-recoverable strain (stretch) in a new rope that results from the rope “bedding in” after a few load cycles, adds Josh Walls, also of Sterling. “The UIAA drop test requires the rope to be preloaded to the test mass for 60 seconds to both set the length of the sample,” says Walls, “and remove some of this non-recoverable strain prior to measuring impact force. A new rope has never been preloaded, so the first catch will likely be the softest for a given section of rope in the system. The non-recoverable strain will result in a slightly longer rope, however; this may be offset by shrinkage, as outlined by Jim.”

In reply to Stairclimber:

Thanks for the feedback folks. My new 64 and a half metre rope will continue to be tied into the rope bag while I climb on the other end.

In reply to GrahamD:

Great advice. Possibly the best, certainly the most welcome , that I've ever received. My wife too, will be so pleased to address this safety issue.