Experiment: "wrong rope weight" was almost completely due to humidity

This has been discussed here before, but some ropes come out way heavier than their specifications, even if you take into account the manufacturer supplying an extra length %. 

The actual weight (as opposed to listed diameter) is a pretty good predictor of some characteristics and a nice way to compare ropes of a similar class between manufacturers. Sometimes, we're actually going to want ropes that are genuinely light too. I get that its not that important for everyone.. that's okay. I don't care that much about my cragging ropes weight either.

I'm a bit annoyed as I just got a new Mammut 8.7mm single rope which I wanted to be as light as possible for mixed free- and rope-soloing on big routes. It was supposed to be 51g/m but the actual weight, if you don't make any allowance for over-length is about 54.9g/m. Its about 7% difference, but what is more annoying is that it's basically a rope more comparable to others of a different class.

I can't see any reason why manufacturers will sort out this unless there is a little accountability. Maybe some manufacturers have more consistent manufacturing than others? It would at least be good to know the real weights of some of the ropes to help choosing the model I want.

The point of this thread is to start a record of real rope weights, to help use make better purchasing decisions. Also it may help to vent, or commiserate!

To kick things off:

EDIT: My rope as it came:

Mammut 8.7 Alpine Sender Dry* (60m, not measured, 3292g) should be 51g/m, actually ~54.9g/m (Not accounting for any over-length %)

EDIT: See post below.... it really is 51g/m

... stoked to be wrong :)

You are wasting your time.

Do you didn’t measure the rope to see if it was a few meters longer then 60? But your complaining about an additional 234 grams, that is 0.516 pounds.

I know I could loose half a pound of body weight if that extra 234 grams was going to be an issue on the send. 

First measure the rope. Then get the humidity as low as possible for a few hours. Then weigh it. Nylon is a pig for absorbing ambient moisture.

steve barrattwrote:

I get that its not that important for everyone.. that's okay.

John Pitcairn, hats off to you, sir!

Since I don't own an accurate rope length measuring device, I pulled through my new rope alongside some other 60m ropes I had to compare. This new rope mammut rope was pretty similar in length to them all when I factored in their histories. It was about half meter longer perhaps than a quite new 60m static tag line I had. Though I couldnt exactly know the exact length for sure, my new rope is was probably at least a little bit longer than expected.  

I decided to chop off 1m from the end (a length which I can accurately measure), and weigh it. It read in as somewhere between 54g and 55g, pretty much on the weight per meter which I originally mentioned. So, was I correct?...

I didn't believe John, but I could now test his point directly. It's been super humid here, so if a rope were really going to absorb water from air, now would be the time. Anyhow, I put the 1m length of rope in the oven set to 100 degrees C for a couple of hours to dessicate it. I weighed it again... 51g. Exactly on spec. 

I'm very happy to be proven wrong! 

It makes you also wonder the numbers behind the "Achieves < 1.5% in UIAA water absorption tests" 

Thanks so much for the useful input John!  May the ignimbrite gods illuminate all the good pockets clearly for you and the cow shits never appear below your projects.

Good on you for your testing. Interesting thread.

steve barrattwrote:

It makes you also wonder the numbers behind the "Achieves < 1.5% in UIAA water absorption tests" 

Isn't it <5% ?

https://theuiaa.org/home/new-uiaa-standard-developed-for-water-repellant-ropes 

To pass the test at a certified laboratory, the amount of absorbed water must not be greater than 5% of the rope’s weight. For comparison, a non-treated rope absorbs around 50% of water in this test, and ropes labelled as “dry” but lacking adequate treatments can absorb between 20% and 40% of water.

Dunking in water is quite different from the slow absorption of water from humid air

amariuswrote:

Isn't it <5% ?

https://theuiaa.org/home/new-uiaa-standard-developed-for-water-repellant-ropes 

Dunking in water is quite different from the slow absorption of water from humid air

Sorry, just to clarify I was quoting from the mammut website product page for the rope, not the UIAA standard.

And yes, very different.

steve barrattwrote:

May the ignimbrite gods illuminate all the good pockets clearly for you and the cow shits never appear below your projects.

There was plenty of cow shit below the ignimbrite today. Might be time to wash the rope.

Thanks for posting.  Interesting analysis for sure...I have an older mammut dry rope that also consistently measured higher that listed.   I wonder if certain companies treatments are more sensitive to absorption of ambient moisture than others.  They have battery powered fans for hands and holds now so maybe someone should start recommending pre-drying their rope for that hard send (not that I could remotely tell the diff).

 The UIAA testing is only for 900s of continuous water flow.  So maybe generally more of a shock test than a typical use one.

Ryan Pwrote:

I wonder if certain companies treatments are more sensitive to absorption of ambient moisture than others.

I wonder the same thing. I have a very short length of Beal Opera Golden Dry off-the-reel that I bought for something else that I might try out one day when I have some time.

It seems very counterintuitive to me that the dry treatment would make the rope absorb humidity, but who knows… maybe this is related to why they feel sticker than non-dry treated ropes sometimes (also counterintuitive). PTFE, often used, at least historically, is obviously highly hydrophobic, so again it makes little sense. It would be fun to do a test with the identical rope +\- dry treatment side by side. If dry treatment were always going to make ropes 5% heavier that would be useful to know. It would be a good reason to move away from dry treatment (often “forever chemicals”) in cragging ropes completely.

By the way I wondered how quickly the rope would reabsorb the humidity after drying.  Within a hour it was already halfway back to the original, higher, weight.. so the dry-to-send approach probably wont take over anytime soon! :D

This is the least informed thread I've seen in a long time, it even beats the recent bent wild country zero thread. 

Jim Tittwrote:

You are wasting your time.

And why is he wasting his time??

that guy named sebwrote:

This is the least informed thread I've seen in a long time, it even beats the recent bent wild country zero thread. 

What information am I missing? (Which you are informed about).

steve barrattwrote:

What information am I missing? (Which you are informed about).

Just typical mountain project shitposting/trolling.
I thought what you did was quite good - you noticed that the rope did not match manufacturer's specs, you ranted a bit, then investigated, noticed that the discrepancy can be clarified, and updated your post.Way better than a typical mp post.

amariuswrote:

Just typical mountain project shitposting/trolling.
I thought what you did was quite good - you noticed that the rope did not match manufacturer's specs, you ranted a bit, then investigated, noticed that the discrepancy can be clarified, and updated your post.Way better than a typical mp post.

Thanks, I appreciate it. I never fail to be exasperated by the negative bullshit on these forums.

was the info really worth cutting a meter off a new rope though?

steve barrattwrote:

What information am I missing? (Which you are informed about).

You're missing the biggest piece of the puzzle of all, how brands measure their ropes. Neither you nor I know how they measure their ropes, sure there is a standard for measuring the g/m of the rope but theres no guarantee that the manufacturers use this number.

Further more, every brand will have their own process this will be dramatically different. I've seen bag manufacturers be out by almost 400g for bag weight, I pointed it out then they changed it. 

The edelrid 19g are more often than not 20g, ropes are far from the only items that their weight is inaccurate. 

that guy named sebwrote:

You're missing the biggest piece of the puzzle of all, how brands measure their ropes. Neither you nor I know how they measure their ropes, sure there is a standard for measuring the g/m of the rope but theres no guarantee that the manufacturers use this number.

Further more, every brand will have their own process this will be dramatically different. I've seen bag manufacturers be out by almost 400g for bag weight, I pointed it out then they changed it. 

The edelrid 19g are more often than not 20g, ropes are far from the only items that their weight is inaccurate. 

Garbage, the test is clearly defined and performed by the independent lab that certifies the rope. The results can be seen at any time by the relevant authorities.

that guy named sebwrote:

You're missing the biggest piece of the puzzle of all, how brands measure their ropes. Neither you nor I know how they measure their ropes, sure there is a standard for measuring the g/m of the rope but theres no guarantee that the manufacturers use this number.

Further more, every brand will have their own process this will be dramatically different. I've seen bag manufacturers be out by almost 400g for bag weight, I pointed it out then they changed it. 

The edelrid 19g are more often than not 20g, ropes are far from the only items that their weight is inaccurate. 

The thing about criticising and calling people out, is that it is important to be actually correct, otherwise you will look foolish. For next time, you can check the UIAA standards online (an example). You will find that many UIAA standards reference European standards which are listed in the format EN 000000 . These EN standards are unfortunately paywalled, but you can often find them copied, sometimes slightly older versions, with a search like “EN 000000 pdf” and some digging.

Assuming that it is unusual here to have weighed equipment is rather naive. Over the years I’ve found some things to be very consistent with their advertised weights and some to be more divergent. In the case of my rope discussed here, it’s striking to me that when dry, it was was exactly on specification.

Finally, just because companies regularly advertise products to specification, but then supply an inferior product (in that specific regard), does not make it OK. We vote with their wallets and if a product actually has a different specification, we can as a community address that with corrected public info of what the real weight/performance/durability/whatever is. This works pretty well in other domains. That was the motivation behind my original post here. I’m happy I was wrong about my rope, but I still stand behind that principle.