Measured rope weights

As part of a recent purchasing decision, I compiled this spreadsheet of measured vs. claimed rope weights.  Thought it might be useful to some.

"Measured rope weights" are reported simply as the total weight of the rope divided by its stated length. These weights are mostly from mp posts and a few of my own ropes. I did not account for: 

• ropes being longer than claimed (apparently some brands will send you e.g. 62.5m for a 60m) 
• the fact that the UIAA weight test is done by weighing a section of rope that is 1m under 10kg of tension.

Some conclusions

• Ropes are usually ~5-15% heavier than claimed. This doesn't necessarily indicate dishonesty though due to the 2 factors mentioned above.
• Bluewater is especially accurate, Edelrid especially overweight
• Beal Opera probably really is the lightest single rope on the market 
  • Despite the fact that 4 measurements average to 11.8% overweight
  • For another rope to beat the Beal Opera would require it to be overweight by <5%, which would be unusual. 
  • Its closest competitors would be the Mammut Alpine Sender 8.7 (claims 51 g/m) or Bluewater Argon 8.8 (claims 52 g/m). I wouldn't consider Edelrid ropes to be in the running due to their track record of being overweight.
• A single rope plus tagline is lighter than double ropes. The best you can do with doubles is 82g/m, single+tagline 76g/m. That's not to say anything about any other advantages that double ropes may have besides weight.

Why write " claimed" everywhere, the weight is the measured value by the certifying laboratory.

Jim Titt wrote:

Why write " claimed" everywhere, the weight is the measured value by the certifying laboratory.

Idk, call it whatever you want, the point is I care about the actual real total weight of rope that I will be carrying on my back which is different from what's listed on the specs, to an extent that differs across manufacturers & models.

Worst, dataset, ever. Not even a whiff of consistency in methodology, test method or test conditions. 

1) Nylon hogs water out of the air & is sensitive to temperature change too. The UIAA test involves controlled temperature & humidity, without which results will vary wildly, as in 10s of percents. My recollection: 30% difference between Fairbanks Alaska in the dead of winter to Panama just before a tropical storm hits... Rope length is also affected by humidity/temperature and will exacerbate the water absorption effect on mass/length.

2) Ropes shrink with age, on the order of +/- 5%

3) Because ropes shrink with age, manufacturers add extra rope, on the order of 10%.

4) And gravity changes too, depending on where you climb. +/- tenths of a percent differences between Denali, Death Valley, Everest... 

5) Don't forget to include a factor for the buoyancy of air as you change elevation...

Take-aways: 

Determining the precise mass of a rope is a fools errand; similarly, determining the precise length of a rope is a fools errand.

The UIAA test offers a very good indication of the relative weights of different ropes. 

As Jim notes, there is no "dishonesty" on the part of manufacturers. 

Nice work. 

Slightly disappointed that you skipped trying to measure the length of packaged rope, but can't blame you - it is PITA trying to determine length of 60m+ rope.

that guy named seb wrote:

Worst, dataset, ever. Not even a whiff of consistency in methodology, test method or test conditions. 

Its MP, not a journal article. Chill tf out. 

Very interesting data. Wish BD ropes were on there (thats what i typically use).

This topic comes up fairly often. The work here has already been done, and more precisely. Here's a recent one that covered it well:

https://www.mountainproject.com/forum/topic/122810129/experiment-wrong-rope-weight-was-almost-completely-due-to-humidity

grug g wrote:

Its MP, not a journal article. Chill tf out. 

Very interesting data. Wish BD ropes were on there (thats what i typically use).

It's not interesting if it's practically meaningless.

Controlling a few known variables isn't too much to ask. 

All I did here is collect data from a bunch of MP posts into a spreadsheet (plus a few of my & friends' ropes). not claiming to have scientific methodology or even new data for the most part. It was useful enough for me to make a purchasing decision (concluded that it's unlikely that any other single rope significantly beats Beal Opera). I didn't measure lenghts because 1) most of these are just from MP posts who didn't measure lengths, 2) I don't really want to cut down my own ropes, so the most useful metric to me is just total weight regardless of length.  The list of caveats needed to preclude criticism would be a mile long. ¯\_(ツ)_/¯

that guy named seb wrote:

It's not interesting if it's practically meaningless.

Controlling a few known variables isn't too much to ask. 

Calm down dude.  Not everyone is running a laboratory and following the scientific method.  In the absence of rigorous standardized tests some Annecdata that he took the time to compile is still useful.  

This ain’t rocket science.  

Ellen S wrote:

apparently some brands will send you e.g. 62.5m for a 60m

Having measured a lot of ropes, I wouldn't count on brand (or even brand+model) as a predictor - in my experience it varies rope-to-rope.

But thanks for posting better data than anyone else so far.  Let's hope the flaws inspire somebody to do better.

Interesting question, though, as to what the "ideal" excess length would be.  I'm not sure it's 0 - a lot of "made it with a 60" route comments are unwittingly based on 63-64m ropes, and in my experience it's rare for "60" ropes to be shorter than 61.5.  Having climbed a bunch with ropes I've actually measured, I feel a rope shorter than 61-62 puts the user at a significant risk of unpleasant surprises.

BTW the shrinkage with age I've been seeing is much smaller than 5%.  More like 1% (I do use my ropes to a very rough condition).

On a side note: I just purchased a new 70m x 9.5 to replace my old fat "heavy" 70m x 10.2. For fun I weighed both and found that the new 9.5 is actually 0.4 lb (181g) heavier than the old 10.2. As noted above there could be several factors like humidity and extra length, but it's still odd. The new rope though is noticeably smaller when coiled.