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dynoho
Nov 29, 2006, 5:03 AM
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There are many reoccurring posts regarding ropes and when they should be retired. It is frequently debated that with time alone, the nylon core of a kernmantel dynamic rope will lose strength, elasticity and the ability to absorb impact force. Manufacturers recommend retiring a rope after 3-5 years of “light use,” 3 months with more sustained abuse and immediately after a huge whipper.
I had the relatively unique opportunity to test this argument. The test is very unscientific due to the extremely small sample size of the test and the fact that the rope was used a few times. Ideally, many more samples, from multiple manufacturers, of multiple types should be tested without ever leaving the warehouse. This is beyond the scope of this test. I submitted a very old rope, my first, which was used only a few times (light use), to the original manufacturer for testing.
Hypotheses:
Over time, dynamic ropes will lose their ability to protect a climber from catastrophic tragedy.
History:
Enduro made in the Spring of 1992 by Blue Water Ropes; considered their most “rugged and durable.”
Use:
The rope has been used on three occasions for a total of twelve routes. The routes were top-roped, single pitch, with several “takes” each. Each “take” had a minimum of 20 meters of line between the climber and belayer. The line was always redirected over the anchor point which consisted of at least two carabiners. The heaviest climber weighed 81Kg. The rock varied from monzonite quartz to sandstone; however, the rope was always protected from abrasion while lowering. The belay devices used were BD figure-eights.
Storage & Condition:
The rope has always been kept flaked in a bag; dry, dark and at room temperature. It has never been washed or wet. It has never been exposed to gasoline, acid, bleach, urine, bug repellant, sunscreen, corrosive vapors, beer, sharpie felt tip pen or excessive UV light. The rope looks new. It is not fat or fuzzy, there are no flat spots or irregularities and the hand is relatively supple.
Specs in 1992:
Diameter: 11 mm
Weight: 79 grams per meter
UIAA Falls Held: 10
Impact Force: 8.4 kN
Static Elongation: 5%
Dynamic Elongation: Not Calibrated at the time.
Sheath Slippage: Not Calibrated at the time.
Specs in 2006:
Diameter: 11.86077 mm
Weight: 87.73 grams per meter
UIAA Falls Held: 7
Impact Force: 8.85 kN
Static Elongation: 7.60%
Dynamic Elongation: Not tested.
Sheath Slippage: Could not be tested due to excessive diameter.
Specific Results:
Test Type:
Nicolet Sigma 60
Was the sample conditioned prior to testing? YES ( I don’t know what this involves. )
Drop Tests:
Volts lbf. kN
1 3.9794 1989.70 8.85
2 4.6119 2305.95 10.26
3 4.8958 2447.90 10.89
4 5.0027 2501.35 11.13
5 4.8113 2405.65 10.70
6 5.1458 2572.90 11.44
7 5.2888 2644.40 11.76
8 Failure at Orifice
Weight in Grams per Meter:
Core – 55.51
Sheath – 32.22
Total – 87.73
Elongation:
mm/Before – 1000 mm
mm/After – 1076 mm
percent – 7.60%
Knotabilitiy:
Reading – 10.5
Actual -.885271
Observation:
Clearly the rope has degraded over the years. This is quantified by the decrease in falls held and the increase in impact force generated. The rope was thicker in diameter and heavier per meter. I believe that the rope was also shorter in length; however, this could not be accurately determined because Blue Water cuts their ropes long and I never measured it originally. I suspect that the long fibers of the core may have contracted resulting in a shorter, fatter and heavier (per meter) rope.
It should be noted that the performance of this rope was still well within the UIAA minimum requirements of 5 Falls held and 12 kN impact force.
Theoretical Conclusion:
It is obvious from this test that this rope lost some of it’s important qualities that comprise a climbing rope. Due to the large margin of safety that is designed into a rope, it may not decompose completely while not in use. Since there was some degradation, I highly recommend sticking to the manufacturers stated guidelines for maximum useful life, and the common sense approach of “when in doubt, throw it out.”
Disclaimer:
The manufacturer and UIAA suggest that a rope should be retired within 4 years. This test in no way suggests that a rope can be used safely for a longer period. Using a rope beyond it’s useful life can cause injury or death. This was a single test on one product made by one company and does not necessarily represent predictable results for other ropes.
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drfelatio
Nov 29, 2006, 5:46 AM
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Thanks. That was some really interesting information. I wonder what the results would be like in a larger, more controlled, time lapsed study.
[edit] I wonder what happened during Fall #5. The impact forces for each successive drop increased except for that one. [/edit]
(This post was edited by drfelatio on Nov 29, 2006, 5:48 AM)
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moose_droppings
Nov 29, 2006, 5:49 AM
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Very interesting.
After your next rope with 12 routes on it, donate it to me and I'll put another 200 routes use on it and send it back to you after 14 years for testing. Would be very interesting to read the findings of that one too.
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knudenoggin
Nov 29, 2006, 6:09 AM
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Interesting, yes!
But one should ask: are (all of) the measurements comparable?
(And given the "Specs", one might wonder how the same testing would've
compared even in 1992!)
E.g., how was diameter measured before/after (by whom, using
what method)?
The increase of 10% weight impresses me, but maybe I'm missing
something--overall length reduction, perhaps, so per-metre increase
covers fewer metres?!
Thanks,
*kN*
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dynoho
Nov 29, 2006, 5:18 PM
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drfelatio:
"I wonder what happened during Fall #5. The impact forces for each successive drop increased except for that one."
That is peculiar, and I have no explanation for the lower reading.
moose_droppings:
I still have 100 feet left over. You want to put 200 routes on it, funny guy? I know what you mean though; sitting in a closet was a waste of rope and tests on a used rope would have been more conducive.
knudenoggin:
I believe testing was comparable. They (the manufacturer) only tested what they measured originally in 1992, which is how the "Specs" were derived. Diameter is measured (I believe) by taking a length of rope, suspending a weight for 5 minutes, and measuring while weighted. Finally, yes to the weight increase. The overall mass for the entire length would be the same. If contracted, it would be obviously shorter thus heavier and fatter per meter.
It should be noted that due to technological advances, this same model and diameter rope today is lighter and holds 60% more falls.
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sterlingjim
Nov 30, 2006, 3:55 AM
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The lower value at drop #5 is likely to be explained by one of two things:
slippage at the clamp
failure of some fibers of the rope.
I see this quite regularly.
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drfelatio
Nov 30, 2006, 3:58 AM
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sterlingjim wrote: The lower value at drop #5 is likely to be explained by one of two things: slippage at the clamp failure of some fibers of the rope. I see this quite regularly.
Makes sense. Thanks!
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alexmac
Nov 30, 2006, 5:08 AM
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Excellent report, thank you for sharing.
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curt
Dec 4, 2006, 2:43 AM
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dynoho,
Thanks for posting that information. Basically, I think this confirms that it is a ropes use, rather than its age, that determines when the rope needs to be retired. Your results are consistent with other such tests I have seen. The one puzzling item to me (which no one else has mentioned yet) is your opinion that the rope was actually shorter after 14 years of use. I bet it was actually somewhat longer. Part of the reason that impact forces on older ropes go up, is because the ropes become permanently stretched--and thereby lose some elasticity. I think the explanation for the diameter of the rope increasing lies elsewhere.
Curt
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dynoho
Dec 4, 2006, 5:50 PM
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curt wrote: dynoho, The one puzzling item to me (which no one else has mentioned yet) is your opinion that the rope was actually shorter after 14 years of use. Curt
Actually, this was really more along the lines of 14 years of "non-use." I agree that under normal conditions, a rope will become permanently stretched from use, but this was sitting in a closet. Also, curiously, static elongation increased and impact force was approximately the same.
I would speculate that a well used rope becomes "fat and fuzzy" due to the fibers loosening up; in other words, becoming less densely packed. When "permanent stretch" is accounted for, the rope should weigh the same per meter. In this instance, the rope not only became thicker, but substantially heavier / m. It was the combination of diameter and weight that led me to this conclusion.
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pastprime
Dec 4, 2006, 7:48 PM
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I've never seen actual test results, but in my bazillion years of dragging my carcass up rocks it has always been considered common knowledge that, counterintuitively, rope fibers bunch up with use, and the rope becomes fatter and shorter as it ages. My experience bears this out. I've always heard, (hearsay) that was why the manufactures give you more rope length than what is printed on the lable- so that your 60 meter rope will still reach on a 30 meter rappel even after it was well used and had shortened up.
I know back in the day when we slung our hexes on perlon, the cord would get fatter so you couldn't slide it through the holes when the piece was well used.
I've heard it said the fatness of an old rope comes from the fuzz on its surface. Think about that. That fuzz comes from fibers that were already there. Burn the fuzz off of an old rope with a lighter and the remaining diameter is still fatter than a new rope.
The same thing happens with other cord, too. I have very old packs and stuffsacks with drawstring clamps that almost won't slide anymore because the cord has gotten so fat, and the cord isn't fuzzy at all.
Back on the origional topic, I think this test shows yet again that age alone doesn't degrade nylon significantly. The rope is still fine. 7 falls, less than 9kn impact force, better than a lot of new ropes were for many years.
(This post was edited by pastprime on Dec 4, 2006, 8:06 PM)
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roy_hinkley_jr
Dec 4, 2006, 9:46 PM
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dynoho wrote: curt wrote: dynoho, The one puzzling item to me (which no one else has mentioned yet) is your opinion that the rope was actually shorter after 14 years of use. Curt Actually, this was really more along the lines of 14 years of "non-use." I agree that under normal conditions, a rope will become permanently stretched from use, but this was sitting in a closet. Also, curiously, static elongation increased and impact force was approximately the same.
A common fallacy. All climbing ropes will shorten with usage, typically around 5% but the range is 2 - 7%. Age should have no effect (but humidity could, which is what the conditioning is about). The increase in impact force of old ropes has been reported many times before and is certainly no surprise.
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climbnjump
Dec 4, 2006, 10:37 PM
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i stopped climbing back about 10 years ago. i have a 50m blue water 11 mil that i used ALOT, its held a couple falls, still well within limits, bought it probably around 91. when i stopped climbing, i picked up 2 more ropes, 50m 9.5 and a 60m 10.5, both of which are practically new, and it sux because im climbing again and i wont use them for anything but top roping now.
guess i just dont want to trust taking a big whipper on an old rope and hearing an i told you so if im still here to hear it.
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dynoho
Dec 5, 2006, 2:32 AM
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climbnjump wrote: i stopped climbing back about 10 years ago. i have a 50m blue water 11 mil that i used ALOT, its held a couple falls, still well within limits, bought it probably around 91.
It seems that the explanations for these results are becoming convoluted. Stretch vs. contraction, use vs. non-use, etc. It would be interesting to compare the same model rope, slightly older, much more used, to the same testing. I would guess that it still would pass UIAA requisites. If interested, please PM for details.
Edited to correct piss poor grammer.
(This post was edited by dynoho on Dec 5, 2006, 7:11 PM)
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pastprime
Dec 5, 2006, 7:27 PM
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Dynoho, this is one of those topics that comes up, and gets answered, repeatedly over the years. It should be put in frequently asked questions. For liability reasons, rope manufacturers are very cautious about what they say, but the fact is that age alone, in the absence of other damaging factors such as heat or chemicals, is not damaging to nylon. Mammut, for one, has tested ropes that were 10-15 years old, moderately used, and they were fine in that they still passed the UIAA requirements for a new rope. Performance was pretty much what you would expect from a newish rope that had had the same amount of use.
Even very used ropes don't break if they are free from damage. Ropes that have been used alot will be less absorbing of impact forces, which doesn't hurt them for rappelling or top roping, but if severe, matters when leading. Reduction in impact forces is caused, in most cases, by repeated sliding of the rope over a radius when loaded, as in rapelling or lowering. A few normal falls don't affect the rope much. Falls become damaging when they are frequent, especially if severe, as for a climber whose normal days consist of repeated falls as they work a sport route.
Keep in mind that ropes are expected to be used, and have a large safety margin built in when they are new. The specs of a new rope aren't the minimum that allows it to be safe. The are sufficient to allow a considerable amount of degradation and still be ok.
Consider that some of the extreme alpine routes these days are being put up on a single 8mm rope, and they aren't failing even with some huge falls.
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curt
Dec 9, 2006, 11:06 PM
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roy_hinkley_jr wrote: dynoho wrote: curt wrote: dynoho, The one puzzling item to me (which no one else has mentioned yet) is your opinion that the rope was actually shorter after 14 years of use. Curt Actually, this was really more along the lines of 14 years of "non-use." I agree that under normal conditions, a rope will become permanently stretched from use, but this was sitting in a closet. Also, curiously, static elongation increased and impact force was approximately the same. A common fallacy. All climbing ropes will shorten with usage, typically around 5% but the range is 2 - 7%. Age should have no effect (but humidity could, which is what the conditioning is about). The increase in impact force of old ropes has been reported many times before and is certainly no surprise.
I guess that only happens where you live. We have measured the lengths of a number of climbing ropes--and they indeed get longer with use, not shorter.
Curt
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chriss
Dec 11, 2006, 2:07 AM
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I'm sure this has been refered to before.
http://www.uiaa.ch/article.aspx?c=231&a=147
"During my work for the DAV (German Alpine Club), during 32 years, I investigated many old ropes from time to time, when I received them from climbers and mountaineers, who wanted to know whether their rope was still good. Some of these ropes were 15, 20, 25 and even 30 years old. They were tested by a UIAA-approved test laboratory. The result: All ropes hold minimum one fall on the Dodero-test-machine, most of them more than one fall; and no rope broke in the knot, always at the orifice."
chris
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