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scrapedape
Jun 9, 2006, 3:14 PM
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Is anyone aware of any tests in which half ropes have been tested according to the UIAA single rope test? i.e. with an 80 kg mass instead of a 55 kg mass? It seems to me that in many situations where one would use double ropes for reducing rope drag, the entire fall could be caught on just one rope.
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tradmanclimbs
Jun 9, 2006, 3:26 PM
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I would go out on a limb and say that in most common uses of doubble ropes a single rope would get the fall. the only way to avoid this is to place two pieces and then clip one rope to each piece. Some climbs I lead on just the red rope for 30m, go arround the corner and then finish the pitch on the blue rope. This is pretty common. that being said I also doubble up the gear and clip both ropes when the climbing is hard enough that a fall is likley.
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mother_sheep
Jun 9, 2006, 3:50 PM
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Not sure about the test results but keep in mind that there are places where you absolutely would not want to climb on a single half rope. I wouldn't be caught dead climbing on a single half in places prone to rockfall and sharp edges. You probably already knew that tho.
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tradmanclimbs
Jun 9, 2006, 3:58 PM
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I also do not recomend climbing on a single half rope although some pretty big name climbers have done it to save weight on alpine rts. I am however proposing that in many standard uses of the half rope system you are in efect climbing in a situation where a single rope is going to be the sole recipiant of a fall.
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tradklime
Jun 9, 2006, 4:00 PM
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This question has come up before in threads and, as I recall, no data was ever located. You could look at a rope like the Beal Joker, which is rated as both a sing and double (and twin for that matter), and get a sense of how ropes might perform. That said, there doesn't seem to be any consistentancy in rope characterisitcs (impact force, diameter, grams/m, etc.) that directly coorelate with fall numbers. So I dunno, but I'd love to see the numbers too.
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dirtineye
Jun 9, 2006, 4:18 PM
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falls on one half of a set of doubles are routine.
Remember the fall test is a factor 1.77 fall, not likely to see many of those on one of the ropes in a set of doubles.
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antiqued
Jun 9, 2006, 4:46 PM
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In reality, most people are usually falling on only one strand - but never for a FF2.
The Joker is rated for 6.5 falls, 8.2kN with 80kg, and for 25 falls (6kN)with 55kg. The Mammut Serenity is rated for 5 falls (9.5kN) with 80kg, and for 19 falls with 55kg (7kN).
It's only two data points, but the suggestion is that a rope will take about 4X as many UIAA falls with 55kg as with 80kg. If true, all of the half ropes would be expected to hold 1 UIAA 80kg fall, since they must hold 5 55kg falls to be certified.
The real question is how much do you weigh, and how fast can you shed heavy gear!
Examples with 55kg
Phoenix - 8 falls
Ice Line 9
Cobra 18
Sterling Biathlon 9
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tradmanclimbs
Jun 9, 2006, 5:14 PM
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Ice climbing with boots, tools, poons, extra clothes, 8 screamers w biners and 12 screws i am well over 200lbs but rope strength is a non factor when the belay rips out 8^)
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iceisnice
Jun 11, 2006, 5:09 PM
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i do most of my alpine routes on just one half rope. even though half ropes are rated as a "system" they are still taking "single rope" falls (obviously not including factor 2 falls.......which you shouldn't be taking anyway). for alpine, it is ok to use just one.....you just have to understand the limitations. on most alpine routes you are not taking high force falls. they tend to be off angle with lots of rope drag. there has always been an arguement against using them on routes that may have sharp edges. shit, that's most alpine routes. and honestly, even a larger single rope (which isn't that much larger in the first place) is just as prone to be cut on a sharp edge. as stated, this arguement is an old one and there is NO right or wrong answer except to say that there are some situations where it is ok to use one half rope and there are situations where it isn't ok. the more important thing is your knowledge and training
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scrapedape
Jun 12, 2006, 1:00 PM
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In reply to: the more important thing is your knowledge and training
Right.... which is why I posted in this forum, looking for specific data.
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iceisnice
Jun 12, 2006, 3:39 PM
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i've never asked you specific question but........when i've wanted technical data on stuff i've called the manufacturers themselves. petzel has been very helpful with that kind of data. BD is helpful too if it pertains to their specific product. i've found they are the best source. you can make an arguement that they are biased and it would be better to find an objective party that has they own tests and results, but i'm not familiar with anyone.
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rgold
Jul 15, 2006, 8:28 PM
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There have been some independent tests of half ropes with an 80 kg weight. I don't have the references, but think Clyde Soles might have done such a test. What I remember is that half ropes don't break on the first UIAA test fall, but may break on the second or third such fall. There are two things to remember about this, however. The belay will not be static, so the peak loads obtained in the test will not occur, and if half ropes are being used in pairs, there is a second rope to come into play in the exceptionally unlikely case that the first breaks.
The mathematical equations describing energy absorbtion by climbing ropes suggest that the peak load obtained in a UIAA test fall with a 55 kg weight will be the same as the peak load obtained with an 80 kg weight and a fall factor of about 1. That's the leader falling all the way back to the belayer (hitting the ground if it is a single pitch climb)---in other words a much bigger fall than usually occurs in practice. So the safety margins associated with the 55 kg weight can be viewed as applying to factor 1 falls on a single strand, and for almost all climbing situations (and all single-pitch routes) this is entirely sufficient.
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sterlingjim
Nov 30, 2006, 5:32 PM
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I just finished a series of drops on half ropes with 80kg at the request of Will Gadd.
Rope A. 80kg-7.35kN, 55kg-5.39kN, published with 55kg-4.85kN
Rope B. 80kg-8.15kN, 55kg-6.23kN, published with 55kg-6.3kN
Rope C. 80kg-8.23kN, 55kg-6.25kN, published with 55kg-6.5kN
Rope D. 80kg-9.22kN, 55kg-5.88kN, published with 55kg-6.1kN
These drops were conducted without the regulation conditioning but complied with all other requirements and procedures. Relative humidity was 42%, temperature was 20ºC for 48 hours. I also listed the published numbers from each manufacturer; I used ropes from 3 different ones.
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cracklover
Nov 30, 2006, 6:55 PM
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Cool! Thanks, Jim!
Interesting to note that these numbers are no lower than those you typically see from a single rope. In fact, in the case of rope D, they're even on the high side.
This belies the standard belief that a 1/2 rope will give you a softer catch... at least for a serious fall.
GO
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rgold
Nov 30, 2006, 8:03 PM
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Interesting, Jim. Did you, by any chance, find the number of UIAA falls these ropes could take with an 80 kg weight? Presumably fewer than five, otherwise the manufacturers would have trumpeted their dual rating.
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crotch
Nov 30, 2006, 9:26 PM
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Thanks Jim. Do you have any data as to whether half-ropes would pass UIAA twin tests across the board?
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sterlingjim
Nov 30, 2006, 9:53 PM
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I didn't do drops to failure though I'm 100% certain none would have made it to 5.
Ropes A and B are on the skinny end of the spectrum. Rope C the middle. Rope D is a burly 9mm rated only as a half.
I didn't do tests as twins but my hunch would be that rope A would pass, B and C maybe and D no way. They would all pass number of drops but the failing grades would come from high impacts.
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scrapedape
Dec 18, 2006, 4:23 PM
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Thanks, Jim, for sharing your results here.
cracklover wrote: Interesting to note that these numbers are no lower than those you typically see from a single rope. In fact, in the case of rope D, they're even on the high side. This belies the standard belief that a 1/2 rope will give you a softer catch... at least for a serious fall. GO
Indeed, which is why I asked in the first place!
Interestingly, yesterday I took what I expected to be a ~5 foot fall, only to find myself about 30 feet lower down the route, due to rope stretch. It was a very low factor fall with a good deal of rope out.
I don't take enough falls to know where I might have wound up if I'd been using a single. But, I am inclined to think that half ropes might still provide a softer catch than a single in low-factor falls, if not in a UIAA fall. But I guess in a low factor fall I probably don't need to be so worried about impact force anyways.
(This post was edited by scrapedape on Dec 18, 2006, 4:37 PM)
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rgold
Dec 30, 2006, 1:16 AM
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Jim, can you tell us
(1) which test you performed first, the 55 kg drop or the 80 kg drop, and whether you think that one of the tests would influence the results of the other?
(2) Whether the "conditioning" you didn't perform might have an effect on the numbers and if so, what that effect is likely to be?
The standard equation for impact loads, based on a Hooke's Law model of the rope as as spring, gives the following predicted 80 kg UIAA impact loads (*) for the ropes in Jim's tests. Jim's test values are recorded in parentheses. The units are kN for all numbers.
Rope A: 6.65 (7.35)
Rope B: 7.66 (8.15)
Rope C: 7.69 (8.23)
Rope D: 7.24 (9.22)
Except for Rope D, the measured values are about 6% to 11% higher than the predicted values, which does not seem to me to be surprising for a linear model whose behavior at very high or very low loads is expected to depart from the real curve.
The relatively low predicted values may account for the widely held belief that half ropes will have lower impact loads for all body weights
The Rope D value is 27% higher than predicted, a matter that begs for more of an explanation than just ``departure from linearity.''
(*) The values are predicted by first solving the standard equation with m = 55 kg and fall factor=1.78 for the rope modulus k, and then using that value of k to calculate the tension in the rope for m = 80 kg and fall factor = 1.78.
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sterlingjim
Jan 2, 2007, 4:21 AM
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Hi Rich,
I did the 80kg drops first but the order doesn't matter since each drop was done with a fresh sample. No sample was dropped twice.
The standard for conditioning is rather long but the simple answer is that the samples must be in an atmosphere of 20C and 65% relative humidity for 48 or more hours (sorry, I don't have the standard right here in front of me). The effect would be higher impacts across the board but it's difficult to say by how much. Dry treatments and other lubricants will inhibit the moisture uptake to differing degrees.
Rope D may be a bit of an anomaly since it was an old model of 9mm half rope. It was probably about 10 years old and never used but was not stored in a bag.
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stymingersfink
Feb 6, 2008, 1:02 AM
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sterlingjim wrote: The standard for conditioning is rather long but the simple answer is that the samples must be in an atmosphere of 20C and 65% relative humidity for 48 or more hours (sorry, I don't have the standard right here in front of me). The effect would be higher impacts across the board but it's difficult to say by how much.
Or IOW... is it better for me to "condition" my ropes (once they've dried out from the weekend) in a cold + dry location and drive to the ice with them in the pack in the back of the truck, than it woulb be to grab them outta the warm+dry basement and throw them in the backseat before driving to the ice?
I'm guessing stored cool+dry, with minimal temp fluctuation pre-climb.
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