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Banquo
Trad climber
Morgan Hill, CA (Mo' Hill)
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Topic Author's Original Post - Dec 11, 2010 - 02:48pm PT
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I like a center mark on a rope but I don't like what bi-color ropes cost so I thought I'd check the influence of some different markers on rope strength. My results should be considered preliminary and I think there are some problems with them. This is my first effort at testing rope and I had to debug test fixtures and had some uncontrolled, non-quantified variables. I thought I would post what I got anyway even though the results were highly variable and inconsistent. I did not measure the resilience, brittleness or the energy absorbed by the rope. Being an old rope, there was certainly variation in condition from piece to piece.
Being cheap, I used an old (15 or 20 years) rope that has been doing garage duty for some years. It looked to be in pretty good shape and wasn't even fuzzy. I've climbed on worse looking ropes and possibly older ropes. I don't recall using it as a toprope or that it took many falls but that it was retired due to age. I had used it mostly in the alpine, backcountry environment. It is a full dynamic rope of uncertain diameter and I'm not sure but believe it to be a dry rope. I don't know what manufacturer.
I cut 16 pieces from the rope and tested half of them tied in a loop with a double fisherman's knot and the other half as a single strand tied at each end in a clove hitch.
For each type of test I did two pieces unmarked, two marked with Sharpie, two marked with Rub-a-Dub (a fabric marker by the same people that make Sharpies) and two marked with a Marvey fabric marker. I totally covered the surface with the marker, much more so than you would actually do to a rope.
I believe sharpie is solvent based but don't know for sure.
Rub-a-Dub is marked as non-toxic and I think is water based but I don't know.
The Marvey/Uchida markers came in a 6 pack of primary colors with "bold tip" and were labeled as non-toxic but doesn't say water based or non-acidic.
For the clove hitch tests I marked the part of the rope that would be in the knot at each end. All clove hitch tests all broke at one of the knots.
For the loops, I marked the section that would pass over the 1/2 inch pins at each end. All of the loops broke at one of the pins, not at the knot.
My hypothesis was that solvent based markers (sharpie)and water based acidic markers would reduce the strength. The Rub-a-Dub is supposed to be non-acidic but I don't know for sure. Marvey makes markers labeled as non-acidic but they didn't have any at the local fabric store so the ones I used may or may not have been acidic. Blue Water suggests using Rub-a-Dub to mark ropes:
http://www.bluewaterropes.com/home/faqs.asp
My results are all over the place but it looks like markers do reduce the strength. I won't suggest you mark ropes but if you do have a mark on a rope, I would advise you not to tie loaded knots at the mark or have the mark at an anchor. Anything you do to a rope can only reduce its strength, the question is how much.
If I ever redo this type of testing, I would make sure to try a water based, non acidic marker. I would also use new rope. I would measure the energy absorbed by the rope or do impact testing.
Loop test video
http://www.youtube.com/watch?v=ivNFHUP9_ks
Clove hitch video
http://www.youtube.com/watch?v=3Wr_vtR3DMk
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murcy
climber
sanfrancisco
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Dec 11, 2010 - 09:31pm PT
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Cool!
I loosely weave dental floss into the sheathes of my ropes at the center point, which is just as visible as ink and not much chance of rope damage. The floss breaks and frays, which makes it even more visible. Plus if you have stuff in your teeth mid-route, you have floss.
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Banquo
Trad climber
Morgan Hill, CA (Mo' Hill)
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Topic Author's Reply - Dec 11, 2010 - 10:47pm PT
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QITNL - Yep, the stuff stretches more than I expected. To do dynamic tests you would need to have enough drop to allow for stretch. I have a 1200 lb steel block and a Peck & Hale "quick release hook" of 4500 lb capacity. The hook is pretty neat and allows you to drop a load by yanking a cord:
http://www.shipserv.com/ShipServ/pages/attachments/64057-ma/0114MA0610w.pdf
Just pick up the block with a forklift and hang the rope sample from a load cell. I just need an overhead anchor that is high enough, strong enough and stiff enough.
I haven't written off rub-a-dub yet since my results are pretty scattered. I don't think it will make your rope stronger though.
MURCY - I have a couple ropes with yarn woven through the sheath at midpoint. I use an blunt embroidery needle to weave it in. For yarn I use a strand worked out of the sheath of an old climbing rope which is pretty tough and comes in bright colors.
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SteveW
Trad climber
The state of confusion
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Dec 11, 2010 - 10:54pm PT
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Banquo
I'm curious how your test might work with pre-marked ropes,
like Beal. (I'm not quite ready to retire either of mine),
but it'd be interesting to know how they came out
compared to your tests.
And even though you used sheltered ropes, I wonder about
using younger ropes too.
Thanks!
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jstan
climber
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Dec 11, 2010 - 11:39pm PT
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This Crimmons guy is pretty sharp. I can't remember the number of times I have needed floss - when the leader is midpitch. On occasion I have even had to drop belay because of this.
These tests being all on ruined old ropes, I am going to go put floss into my ruined old ropes. That's the advantage ruined old climbers have over everyone else.
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jack herer
climber
Veneta, Oregon
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Dec 11, 2010 - 11:57pm PT
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I've heard that Marks-A-Lot brand pens are good for marking ropes.
Does any one know if this true?
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bmacd
Trad climber
100% Canadian
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Dec 12, 2010 - 01:03am PT
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It's best to mark ropes, like you mark your territory, by pissing on them
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Trad
Trad climber
northern CA
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Dec 14, 2010 - 12:01am PT
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Thanks for posting! It's always interesting to see actual numbers.
If you do more tests, I'd be curious to see results for a water-based acrylic paint.
Some background:
In the olden days when rec.climbing was the only climbing forum, sometimes it seemed like one of the most popular/successful trolling topics was ANYTHING related to rope marking.
But occasionally things appeared that seemed to make sense, one of which was a post that I copied, saved and, amazingly, could still find after all these years:
The recommendation: do not mark your rope with any kind of felt pen. Water-soluble acrylic paints are apparently safe. No information is available how long they stay on.
(I can paste in the entire post if anyone is interested.)
Anyway, the water-soluble argument seemed plausible to me and several years ago I got some acrylic paint from a local arts supply and marked my 70 m rope. (According to the time stamp on this picture, it was actually 5 years ago. I think I intended to post about this on ST at the time but, obviously, I'm a good procrastinator. Especially since the original rec.climbing post was from the mid-90's!)
However, I never considered the possibility that there might be acids in a water based paint. Anyone know anything about acrylics?
I guess the real the question is:
Was I gonna die?
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Clint Cummins
Trad climber
SF Bay area, CA
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Dec 14, 2010 - 02:43am PT
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If we assume an additive linear model, even with the small sample,
you are close to getting statistical significance for Marvey at the usual 95% level:
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bhilden
Trad climber
Mountain View, CA
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Dec 14, 2010 - 02:50am PT
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Banquo,
Bob Culp at the old Boulder Mountaineer recommended the Sharpie T.E.C. (Trace Element Certified) marker for ropes. You might want to test one of those next time around.
Bruce
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Karl Baba
Trad climber
Yosemite, Ca
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Dec 14, 2010 - 03:59am PT
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How long did you leave the marks on the rope before testing.
I have to imagine that weakening substances often take time to weaken. Battery acid after an hour on a rope is different than battery acid on a rope for years
Peace
Karl
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Banquo
Trad climber
Morgan Hill, CA (Mo' Hill)
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Topic Author's Reply - Dec 14, 2010 - 11:35am PT
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I forgot to add a couple details. The ropes were all marked on 11-17-2010 and tested on 12-9-2010. The results are in pounds.
I considered water based paint since I think a non-acidic water based product will be the best but hard to say if a paint is acid free. I think it would be best to stay away from a generic category since not all paints are equal.
Best bet might be an archival, acid free India ink. Faber-Castell makes an archival, acid free, India ink marker called "PITT big brush artist pens," probably worth the $2 for something that is not generic and probably has reliable chemistry. They also claim to be waterproof.
I would be willing to test more pieces, anybody want to donate some new rope? Perhaps even cut, tie and mark the pieces. I spent way more time scribbling on ropes that I did testing them. Talk to Clint but I would think three to five samples with and without marks might be a good idea. My gut feel is that the loop test will have less variability and that I should test with a standard carabiner. The loop test is pretty hard on the rope since as the knots tighten, the rope drags over the edge. Since the rope works over the edge, you also have to mark a fairly big section.
Clint- I need a little math lecture, I didn't do any sort of statistical analysis other than to observe that the scatter was big and the sample small. What do you conclude from your analysis?
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Brian in SLC
Social climber
Salt Lake City, UT
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Dec 14, 2010 - 12:11pm PT
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Best bet might be an archival, acid free India ink. Faber-Castell makes an archival, acid free, India ink marker called "PITT big brush artist pens," probably worth the $2 for something that is not generic and probably has reliable chemistry. They also claim to be waterproof.
Can recall researching into this awhile back, when it came up on wreck climbing and thereabouts.
Seem to remember that one reason folks couldn't rely on Sharpies, and various other pens, was that they used different solvents as carriers, and, some were worse than others for nylon. Some benign, while some degraded nylon. Same pen, different solvents. Can't recall which were bad, which were ok.
I think there's too much spread in your data to make any solid conclusions, but, its interesting for sure. No surprise that the clove hitches broke at the knots. Probably not much of a surprise that the loops broke at the 1/2" pin. I would think the loop test would have more fidelity for what you're trying to see, as, a clove hitch might have more variation in results just due to using a clove hitch. Big spread in both your control samples in both tests.
What I think would make an interesting test, is, to find a couple of fair sized pins, say, 3 to 4 inch in diameter, to wrap the rope ends around, apply your sharpie (etc) to the middle of the strand, and, pull to failure. In other words, try to eliminate the variability of the hitch and 1/2 radius bend as the weak spots, and, pull to failure the rope with and without marking.
Also, looks like you're just failing the sheath. I wonder if you could bump up the test speed, and, get the whole rope to bust?
Neat stuff. Thanks!
-Brian in SLC
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Ghost
climber
A long way from where I started
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Dec 14, 2010 - 12:31pm PT
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This whole debate is so last century.
Just get a bic lighter, fuse the two ends of your rope together. Then every point on the rope is the middle and you can stop worrying about it.
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mawk
Big Wall climber
Hugo, MN
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Dec 14, 2010 - 01:01pm PT
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Just a thought.
Since the question is: Does marking a rope weaken it?
Why do you have to use 10-11mm (normal) climbing ropes? Why not use 5-6mm (or smaller) cord? Seems like you could run more samples at lower cost.
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Greg Barnes
climber
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Dec 14, 2010 - 01:15pm PT
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How about the adhesive from climbing tape? A fair number of people wrap climbing tape around rope mid-points (repeatedly since it falls off sooner or later)...
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bhilden
Trad climber
Mountain View, CA
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Dec 14, 2010 - 01:27pm PT
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One other thing worth looking at is the penetration of the ink into the core of the rope. Is the marker just affecting the strength of the sheath or does the ink also penetrate to the core?
I think this is important because, as I understand the design of kernmantle ropes, the sheath is just supposed to protect the core while the core is supposed to be what provides the strength and elasticity to hold falls.
Bruce
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Seamstress
Trad climber
Yacolt, WA
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Dec 14, 2010 - 01:52pm PT
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The data is interesting to me. First is the concept of weakening the rope by marking it. We stopped that practice a few years ago given an article published about that weakening the rope. However, I didn't recall seeing any data.
Another question for me was the effect of aging and use on rope. Rescue teams get into huge dabtes about their soft goods reitrment policies. We are engaged in one now about when we should retire our ropes. There isn't a lot of published data.
Curious - what kind of rope did you test and do you know the original strength?
Thanks
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Banquo
Trad climber
Morgan Hill, CA (Mo' Hill)
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Topic Author's Reply - Dec 14, 2010 - 03:31pm PT
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Seamstress - It's just an old rope I had. I don't recall who made it, what diameter it is or if it was dry. I have pictures of me using it nearly 20 years ago.
From the white dork thread:
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kurthicks
climber
Washington
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Dec 14, 2010 - 03:49pm PT
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how many of the marked samples actually failed at the mark?
It seems to me that's the real question here.
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Ain't no flatlander
climber
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Dec 14, 2010 - 04:02pm PT
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Kurthicks is right, failure anywhere other than the marked section is irrelevant. The only way the DAV could get their test to show any "problem" was to place the marked section of the rope directly on the orifice of the drop rig. Even then, the difference was pretty minimal. Have yet to hear of a real-world case of rope failure at a middle mark. There seems to be no reason not to use a Sharpie for marking ropes.
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nutjob
Trad climber
Berkeley, CA
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Dec 14, 2010 - 04:28pm PT
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I usually end up cutting my ropes for self rescue or accidentally leaving the tails hanging out of my trunk on the way home, so age-related rope statistics just don't catch up with me.
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Trad
Trad climber
northern CA
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Dec 14, 2010 - 09:16pm PT
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Intrigued by this thread and being the science nerd that I am, earlier today I checked the pH of the acrylic paint and it came out neutral. Whew. ;) I don't know why I never thought of that before.
(I'm not joking, out of curiosity I really did check it this morning - I hadn't seen RURPS's posting at the time, but I'm sure he/she will be relieved!)
Banquo if you decide to test acrylics and want some litmus paper let me know...
Tom
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Clint Cummins
Trad climber
SF Bay area, CA
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Dec 15, 2010 - 01:59am PT
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Dan,
I concluded the same thing you did - it looks like there is a negative effect, but there were not quite enough observations to detect a statistically significant result.
The p-value on the t-statistic for MARVEY needs to drop below .05 to do that, and it's at .061 .
I think if you had 3 observations in each combination instead of 2, that would be enough to do it.
When I ran the linear regression, I used levels (pounds).
Your analysis was in terms of ratios (% of unmarked), which is also good.
I could reproduce your results by using log(pounds) as the dependent variable in the regression.
All the methods reduce to differences in means (or ratios of means, which is differences in log means) of the groups.
The linear regression is just convenient because it quantifies the variation or dispersion and gives you a single test statistic to check.
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bhilden
Trad climber
Mountain View, CA
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Dec 15, 2010 - 02:21am PT
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Banquo,
if you run more tests, I think it would be interesting, as another poster said, to put the treated piece of rope between the two pins and see if there is a difference in breaking strength. That seems to be a much more probable situation that will occur in climbing. It is very improbable that the marked section of the rope will be drawn across the radius of a carabiner given a 200 foot rope and a 9" marked section.
Bruce
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Clint Cummins
Trad climber
SF Bay area, CA
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Dec 15, 2010 - 02:47am PT
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Bruce,
I think the ideal test would be (as others have mentioned) with the rope ends wrapped around two large diameter objects, but this requires a more complicated testing rig with lots of room for such objects between the pullers.
The current setup at least tests how much the marker weakens the rope at the conventional failure point (knot or bend over small diameter object).
The marked section could be put in the middle, but unless the marker weakens the rope more than the knot or small diameter bend, you don't get a measure of what the marker did.
This could be an argument that the marker doesn't weaken the rope "enough", but it would be nice to know how close the comparison is.
For example, if the loop over the steel ring weakens the rope by 1000,
and MARVEY weakens the rope by roughly 510, it will usually break at the ring, and we would not be able to detect if MARVEY weakened the rope by 800 or by 100.
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bhilden
Trad climber
Mountain View, CA
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Dec 15, 2010 - 03:04am PT
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Clint,
Obviously some of the testing is going to be theoretical, but I think the test should mimic the most common climbing situations which for me means seeing what happens if the marked section is not running over an edge. If, in this situation, the knot breaks first then we can rule out about 99% of all climbing situations. No need creating any panic if it isn't necessary.
Bruce
ps - I tend to rule out the "over the edge" testing because the shape of the edge(blunt, sharp, jagged, etc) is such a huge factor in the results.
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Jay Wood
Trad climber
Fairfax, CA
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Dec 15, 2010 - 03:20am PT
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Here's a test for ink bleeding through to core.
Inked liberally, cut several hours afterward.
No noticeable ink on core. Sheath is stiffer where inked.
Maybe the test needs to be double-blind.
Results influenced by expectations of tester?
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jstan
climber
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Dec 15, 2010 - 03:39am PT
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When wrapped around a small diameter object like a biner with a bend of 180 degrees about 1/3 of the force on the other side is lost to sliding friction. When I went to a larger diameter pulling fixture I could not keep everything from getting equally stressed. But how about this?
I don't show it but the rope could be wrapped around each pin several times giving an exponential increase in sliding friction. The rope that is not so heavily stressed could be run off a distance so that its elasticity permits sliding. Note the pins would need some sort of texture to increase friction. With polished pins everything just got strained when I did it.
Tensile machines don't have a lot of travel so you can't go very far off to the side.
I may be failing Mechanics 101 here but I don't see it off hand.
Want the break at the mark. Going to have to have a very good sized control group.
I think Murcy's idea of using dayglow orange dental floss is the way to go.
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Banquo
Trad climber
Morgan Hill, CA (Mo' Hill)
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Topic Author's Reply - Dec 15, 2010 - 11:54am PT
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Large diameter testing is certainly the way to find the strength of a rope - which is not really what I am trying to do. My understanding is that in any real scenario, the rope will break at a knot or where it passes over an anchor and it is the reduction of that strength that I am interested in quantifying.
Black Diamond marked rope tests suggest that a mark will not reduce the strength enough to be an issue if the mark is not at a knot.
http://www.blackdiamondequipment.com/en-us/journal/climb/qclab/qc-lab-can-i-use-a-sharpie-to-mark-the-middle-of-my-rope
Like Clint says, the reduction in strength of the rope due to marking is probably too small to cause a break in the rope someplace other than at a knot or anchor. If my initial data turns out to be reliable, I might expect about a 15% reduction in static strength. So, if that is the case and I test a rope with a mark in either of my test configurations, I would expect it to break at the knot or anchor regardless of where the mark is. This is what the BD tests indicate.
Yes, it is unlikely in the event of a hard climbing fall that a center mark will be at a loaded knot or anchor. Unless the mark is at a knot or anchor, it may not matter if the rope is marked. One thing to consider is that in a fall, quite a bit of rope might pass over an anchor due to slack and stretch.
In a normal lead scenario, it is pretty hard to load the center of the rope at an anchor, to do so the leader has to fall a half rope length above his anchor. A full rope length out and a half rope past the last good anchor is not a fall I plan to take but I suppose it happens and you will want all the rope strength you can get if it does.
This, like all risk analysis, becomes a probability analysis. Will a lead fall occur? Will a lead fall generate high enough force so that a 15% reduction is significant? Will the center mark be at a knot or anchor when the fall occurs?
A better loop test might be to make samples like the BD ones with a figure eight at each end and then fold it in half so it is a symmetric loop and the rope doesn't have to drag over the pin so much. I think it would still break at the pin but maybe not. In my loop tests the upper pin is a bolt which did rotate but had some friction resistance.
All my tests of marked ropes broke at the mark. All clove hitch tests, marked or not, broke at a clove hitch. All loop tests, marked or not, broke at one of the pins.
Even though I was really generous in applying the marker, I didn't see any color on the core. It might bleed through over time though.
All tests broke the sheathing first and then the core. The highest load achieved was always when the sheathing broke. The core had quite a bit of strength but less than the whole rope which I suppose makes sense.
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kurthicks
climber
Washington
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Dec 15, 2010 - 01:56pm PT
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Yes, it is unlikely in the event of a hard climbing fall that a center mark will be at a loaded knot or anchor. Unless the mark is at a knot or anchor, it may not matter if the rope is marked.
True, but the mark can be at the belay device...
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Seamstress
Trad climber
Yacolt, WA
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Dec 15, 2010 - 02:16pm PT
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May I conclude that I should avoid "dropping" onto a rappel when the middle is marked - otherwise I need not concern myself with the very low probability of falling and stressing that rope segment.....
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bhilden
Trad climber
Mountain View, CA
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Dec 15, 2010 - 02:32pm PT
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I think there are some interesting things coming from the tests and the resulting discussion. As I said before, I was always under the impression that the sheath was not designed to add strength to the rope that it was the core which was the load bearing entity.
If, was we have seen, that the marker ink does not penetrate to the core, but the strength of the rope is potentially compromised, then it appears that the sheath does help bear some load. That could be a big wake up call for anyone who has some significant sheath wear on their rope.
I think it would be every interesting to ask someone at a rope company how they view the role of the sheath in a climbing rope.
Bruce
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Hummerchine
Trad climber
East Wenatchee, WA
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I have posted this elsewhere before...
So what if marking weakens the CENTER of the rope? The center of a rope is the part that strength matters the least. There is simply no way to cause a large stress to the rope here! It's near the ends that matters. Even if marking the rope reduces the sheath strength to zero, it's still plenty strong enough at the core. I'm not aware of a single rope failure due to this. BUT, there are quite a few instances of death by climbers rappelling on ropes that were not centered on the rap anchor. I recommend marking the center of your rope by whatever means possible...of course bicolor ropes are the best option!
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Magic Ed
Trad climber
Nuevo Leon, Mexico
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A few years ago Craig Luebben did a bunch of research and concluded that Sharpie and Magic Marker brands were safe for marking ropes. His results were published in one of the climbing magazines, I forget which.
Desnivel, the Spanish climbing magazine also did some research and concluded that the safest way to mark a rope was with a water-based latex paint. I tried that and found that the paint flaked off pretty rapidly so I went back to using a Sharpie.
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chusmacha
Trad climber
Bozeman, MT
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"The recommendation: do not mark your rope with any kind of felt pen. Water-soluble acrylic paints are apparently safe. No information is available how long they stay on."
The paint doesn't stay on very long. It is gone after a few climbs, especially if you're doing lots of rappelling where ropes are pulled through a ring, webbing a tree or whatever. The paint should be re applied just before the last of the old mark is gone saving the hassle of re identifying the center.
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Dingus McGee
Social climber
Laramie
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Circa 1973? Larry Peneberthy, Seattle, of his then recently formed company Mountain Safety Research (MSR now owned by REI?) tested makings on ropes. His conclusion was that paint and magic marker marks have negligible effects of rope strength. In fact a rope he had manufactured for sale had a paint line along its entire length. These ropes were somewhat cheaper than the European kermatle and I purchased one.
He published his findings in a newsletter. Another one of his studies established that wooden ice axe handles are not adequate for belaying falls. Does anyone have some of his newsletters on rope makings? Those that forget the past are condemned to repeat it.
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scuffy b
climber
Three feet higher
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I don't have any of his bulletins though I used to read them.
He contracted with Sampson Cordage, I believe, to try and make the choice
of a kernmantle rope more obvious.
At that time there were still plenty of people using Goldline or other
laid ropes because of cost, and it drove him crazy. He was bothered by the enormous
difference in rope stretch under body weight (which translates to how far
you have to Jumar before you actually get off your ledge, and how far you
go if you fall toproping) and by the vague criteria for retiring ropes.
He sold the ropes uncolored, and recommended using Rit dye to color your
own. A friend had one that was blue on one half, and red and white bands
on the other.
Penberthy also sold ropes unshrunk, with instructions for boiling them to
shrink them and make them dynamic.
Regarding the use of floss as a mark, if you pick out some of the bright
yarn from a scrap of rope or accessory cord, once your mark fuzzes up a
bit, it can be seen at a distance of at least half the rope.
That is, the leader can look down and actually see the middle mark at the
belayer.
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