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rocknice2


Aug 28, 2013, 8:57 AM
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Use 2 Ropes as Twin and Double in Same Pitch
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There are a few ropes out on the market that are rated for both Twin & Double.
I did some searching and found conflicting comments and no real data from the manufactures on this subject.

My question is:
In a single pitch can I use the 2 ropes as a Twin and a Double? Start out clipping the ropes together then separate them, then together again. And vice-versa?

I've heard you can start as twin but once you separate you can't join them again. Then I've heard the contrary as well.

Does anyone know of a manufacturer that shows if it is possible or not? I tried Beal, Mammut, Petzl and Sterling but none talk about mixed use in a single pitch


wivanoff


Aug 28, 2013, 10:27 AM
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Re: [rocknice2] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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http://www.rockclimbing.com/...post=2549877#2549877


rocknice2


Aug 28, 2013, 11:37 AM
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Re: [wivanoff] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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I saw that thread but I did miss this quote from Mammut via 'hascoituswithursa'

bearbreeder wrote:
heres the response from dead elephant

Hello (name deleted by me),

you had a question on your Mammut rope Phoenix 8mm and whether it can be used in twin and half rope technique in one single pitch. This is the case, you can always clip the two rope strands as twins, then split them as doubles, join again etc. This is exactly the advantage of half ropes compared to twin ropes where you always need to clip both ropes.

Hope this helps you,
best regards from Switzerland,

(name deleted by me)
Productmanager Climbing Equipment


bearbreeder


Aug 28, 2013, 11:42 AM
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Re: [rocknice2] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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in addition to that email from mammut above that i asked them about ...

if you watch brit climbers ... some experienced ones will use both twin and half clippings in the same pitch and even whip on em

from the Odyssey ... the amazing hazel findlay flashing E7 ... she splits the ropes then joins em back together at the last pin




james pearson on e8/9 ... he joins the ropes then splits em ... and even takes a fall latter ... doesnt die quite yet




Wink


budman


Aug 28, 2013, 11:57 AM
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Re: [bearbreeder] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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Tend to disagree. Twins as twins through the whole pitch! Doubles as doubles through the whole pitch! Reason being is that twins are clipped though every binner on the pitch, so if you fall both ropes move as one. On double rope lead left rope is clipped through it's own running belay and the right rope is clipped through it's own running belay. When you fall the left and right ropes move at different speeds and stretch at different rates. Possibility of one rope burning through the other if you mix and match twin technique with double technique.

Just because people have mixed the techniques doesn't make it the safest. Law of averages say you'll probably be o.k. if you do but it's the one time that it's not o.k. that counts.


bearbreeder


Aug 28, 2013, 1:10 PM
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Re: [budman] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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well personally id rather trust the manufacturer than some random RCer

which is why i asked them directly rather than going through the RC "yur gonna die" gongshow

i would think mammut would know what they are doing after 151 years in the climbing business

Tongue

Hello (deleted),

you had a question on your Mammut rope Phoenix 8mm and whether it can be used in twin and half rope technique in one single pitch. This is the case, you can always clip the two rope strands as twins, then split them as doubles, join again etc. This is exactly the advantage of half ropes compared to twin ropes where you always need to clip both ropes.

Hope this helps you,
best regards from Switzerland,

(deleted)

Freundliche GrŁsse / Kind regards
(deleted)
Productmanager Climbing Equipment
Mammut Sports Group AG, Birren 5, CH-5703 Seon
Tel. +41 62 769 81 32, Fax +41 62 769 82 47, www.mammut.ch



(This post was edited by bearbreeder on Aug 28, 2013, 1:13 PM)


Syd


Aug 28, 2013, 2:51 PM
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Re: [bearbreeder] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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Are the doubles are joined in the pic to minimise the clutter of two ropes at critical points, to make movement easier ?


Syd


Aug 28, 2013, 3:18 PM
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Re: [Syd] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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Just happened to find this:
http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?post=808503

Read beesty511's very long reply, with this:

"Conclusions:
What is to be learned from this accident? NEVER LET NYLON SLIDE AGAINST
NYLON! You should already know this. "


marc801


Aug 28, 2013, 4:28 PM
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Re: [Syd] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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Syd wrote:
Just happened to find this:
http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?post=808503

Read beesty511's very long reply, with this:

"Conclusions:
What is to be learned from this accident? NEVER LET NYLON SLIDE AGAINST
NYLON! You should already know this. "

Not applicable to the topic under discussion due to massive differences in variables, setup, rope types (static and dynamic), failure mode, etc.

Again, (re)read the response from Mammut for a directly relevant answer.


rocknice2


Aug 28, 2013, 5:59 PM
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Re: [Syd] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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Rope on rope friction is the leading argument for not joining ropes after they have been separated. The Dano case is totally different though.
In other to get a significant difference in stretch between the 2 ropes, one of them would need serious drag. In that case you wouldn't be clipping it. Furthermore the ropes would need to slide of over the other.

These are the 2 theories. Until I found the email from Mammut. One statement but from a reputable source.
Does anyone have a test or study to the contrary. There are a couple of blogs but again I think this is more theory than actual data.

Sure would like to know what Jim @Sterling has to say. :-)


(This post was edited by rocknice2 on Aug 28, 2013, 6:02 PM)


budman


Aug 28, 2013, 6:18 PM
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Re: [bearbreeder] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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Guess you could say I'm some random RCer. Been climbing most of my life and despite what a given manufacturer says about a product or it's use I'll go with my gut instinct and my climbing experience to err on the side of safety. Especially when the gain is minimal as in the mixing of twin and double technique. What you gain and the possibility of failure are yours to choose.

Personally I rarely climb on twins or doubles. Just go with a single lead with a thin tag but I understand both techniques and have climb with people who use both.


USnavy


Sep 3, 2013, 2:01 AM
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Re: [budman] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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You can start out using them as twins and then separate to halves, but do not join them back to twins once separated unless you use two different slings and biners. The problems is that once you separate the ropes, the amount of rope out for each strand and the amount of drag for each strand is different. Accordingly, when you fall the ropes can move at different speeds, which if allowed to contact each other could result in rope damage.


USnavy


Sep 3, 2013, 2:04 AM
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Re: [bearbreeder] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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bearbreeder wrote:
well personally id rather trust the manufacturer than some random RCer

which is why i asked them directly rather than going through the RC "yur gonna die" gongshow

i would think mammut would know what they are doing after 151 years in the climbing business

Tongue

Hello (deleted),

you had a question on your Mammut rope Phoenix 8mm and whether it can be used in twin and half rope technique in one single pitch. This is the case, you can always clip the two rope strands as twins, then split them as doubles, join again etc. This is exactly the advantage of half ropes compared to twin ropes where you always need to clip both ropes.

Hope this helps you,
best regards from Switzerland,

(deleted)

Freundliche GrŁsse / Kind regards
(deleted)
Productmanager Climbing Equipment
Mammut Sports Group AG, Birren 5, CH-5703 Seon
Tel. +41 62 769 81 32, Fax +41 62 769 82 47, www.mammut.ch
The guy that replied is likely just some grunt from marketing. If you spoke to the senior R&D engineer for Mammut I bet he would tell you something different. Send an e-mail to both Bluewater and Sterling, ask to speak to an engineer, then ask the question again. I bet you will get a different answer.


(This post was edited by USnavy on Sep 3, 2013, 2:07 AM)


rocknice2


Sep 3, 2013, 8:30 AM
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Re: [USnavy] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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USnavy wrote:
You can start out using them as twins and then separate to halves, but do not join them back to twins once separated unless you use two different slings and biners. The problems is that once you separate the ropes, the amount of rope out for each strand and the amount of drag for each strand is different. Accordingly, when you fall the ropes can move at different speeds, which if allowed to contact each other could result in rope damage.

I'll play devil advocate.
There IS different rope drag for each rope but how much is the question. If able to split and combine at will the rope drag will be significantly reduced. How much is too much if it's even applicable?
Then the ropes are BOTH passing through the biner, so it's not like one is stationary and the other passing over a single point at high speed. The weighted rope will most likely go to the bottom of the biner.

It's all conjecture though. I have believed as you for many years but with the new 7.8mm ropes out I'm looking deeper into it and finding surprisingly little in terms of actual data.


budman


Sep 3, 2013, 8:31 AM
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Re: [USnavy] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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You are quite right about starting them as twins and not rejoining them once they are split. The reason you would use doubles is to reduce rope drag as much as possible. Each double rope is rated for falls on it's own. So by clipping them together you lose a bit and for what gain?


bearbreeder


Sep 3, 2013, 2:25 PM
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Re: [USnavy] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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USnavy wrote:
The guy that replied is likely just some grunt from marketing. If you spoke to the senior R&D engineer for Mammut I bet he would tell you something different. Send an e-mail to both Bluewater and Sterling, ask to speak to an engineer, then ask the question again. I bet you will get a different answer.

product managers are required to know all the ins and outs of their products and the uses ... its not simply a marketing position

you can see the depth of their USA product manager here ... i bet he knows more than you on ropes

http://www.highinfatuation.com/blog/straight-from-the-mammoths-mouth-things-you-want-to-know-about-ropes/


id rather listen to MAMMUT directly than some RCer like you

not to mention the climbers that climb hard and fall more on doubles/twins than you ever will

someone DID email PMI and bluewater ... you can see the response they got

http://www.mountainproject.com/...vs-twin/107396265__2

remember that unlike RCers saying whatever they want, "safe" usage directions from a manufacturer such as mammut carries LIABILITY


Tongue


(This post was edited by bearbreeder on Sep 3, 2013, 2:32 PM)


USnavy


Sep 4, 2013, 1:05 AM
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Re: [rocknice2] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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rocknice2 wrote:
USnavy wrote:
You can start out using them as twins and then separate to halves, but do not join them back to twins once separated unless you use two different slings and biners. The problems is that once you separate the ropes, the amount of rope out for each strand and the amount of drag for each strand is different. Accordingly, when you fall the ropes can move at different speeds, which if allowed to contact each other could result in rope damage.

I'll play devil advocate.
There IS different rope drag for each rope but how much is the question. If able to split and combine at will the rope drag will be significantly reduced. How much is too much if it's even applicable?
Then the ropes are BOTH passing through the biner, so it's not like one is stationary and the other passing over a single point at high speed. The weighted rope will most likely go to the bottom of the biner.

It's all conjecture though. I have believed as you for many years but with the new 7.8mm ropes out I'm looking deeper into it and finding surprisingly little in terms of actual data.
This is a difficult question because it is like asking how many falls are required before a rope truly becomes unsafe. The answer is it depends. If you went a full pitch not clipping a half at all and then clipped both ropes as a twin on the last piece, then took a 50 footer on it, I bet something bad would happen. But if you clipped the first piece as a half, then used twins for the rest of the pitch and fell at the end of the pitch, I strongly doubt anything would happen.

It's really a variable question with a variable answer. But it is kind of a pointless question because who the hell climbs a pitch using twins, then halves, then twins, then halves and on and on? Once you switch out to halves there normally isint much of a need to use the twin method, except maybe while climbing over a ledge, in which case just use two separate draws and clip the rope as a twin. Problem (mostly) solved.


(This post was edited by USnavy on Sep 4, 2013, 1:06 AM)


USnavy


Sep 4, 2013, 1:16 AM
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Re: [bearbreeder] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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bearbreeder wrote:
USnavy wrote:
The guy that replied is likely just some grunt from marketing. If you spoke to the senior R&D engineer for Mammut I bet he would tell you something different. Send an e-mail to both Bluewater and Sterling, ask to speak to an engineer, then ask the question again. I bet you will get a different answer.

product managers are required to know all the ins and outs of their products and the uses ... its not simply a marketing position

you can see the depth of their USA product manager here ... i bet he knows more than you on ropes

http://www.highinfatuation.com/blog/straight-from-the-mammoths-mouth-things-you-want-to-know-about-ropes/


id rather listen to MAMMUT directly than some RCer like you

not to mention the climbers that climb hard and fall more on doubles/twins than you ever will

someone DID email PMI and bluewater ... you can see the response they got

http://www.mountainproject.com/...vs-twin/107396265__2

remember that unlike RCers saying whatever they want, "safe" usage directions from a manufacturer such as mammut carries LIABILITY


Tongue
Sure. I mean, its not like I work in the industry and climb with these said marketing guys and engineers or anything. As far as climbing hard, I have climbed grade V 5.12+ and multiple lines on El Cap--that's plenty hard enough. And only a Sharma stocker would actually think that climbing 5.14 gives you an engineering-level understanding of climbing gear. I know because I have climbed with a large sum of them. Some of them dont really know jack outside of how to dyno to a mono.

I am not saying that Mammut's staff are unqualifed. I am sure they all know a ton about climbing. But I have also spoken to Petzl employees that dont know their own Dragonfly rope is not UIAA certified as a twin, and Black Diamond employees that do not know that their pins are made out of chrome molybdenum steel, and the list goes on and on. Hell, the CEO of Sterling ropes isint even a rock climber (not that she needs to be, but one would assume)! So my point is not everyone knows everything about every subject and if a bunch of people are saying something other than what you think the correct answer is, you would be well off to further inquire using many references and sources instead of blindly believing the reference that best supports your opinion is gold.

Look, of course there have been climbers who have rejoined their halves and fallen on them without issue. Safety is a sliding scale. "Safe or not" is a question of your personal risk assumption. I am absolutely positive, no matter how many marketing guys say otherwise, that I could create a system in which you could get enough rope speed difference between the two ropes to cause a problem. I have blazed the sheath of a rope solely from the friction of a carabiner while taking a big space whipper. So if the carabiner alone can damage a sheath from friction, then two ropes in that carabiner, each moving at a different speed, certainly can cause problems under some conditions. Few people realize just how sensitive nylon is to heat (350F causes major strength loss) and how fast a rope can heat up under heavy friction while rubbing against other nylon components. I have seen a climber melt through the sheath of his rope, exposing the core, on a small lead fall because his tag line got caught in the lead line and rubbed against it during the fall. Crap happens.


(This post was edited by USnavy on Sep 4, 2013, 1:34 AM)


bearbreeder


Sep 4, 2013, 11:36 AM
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Re: [USnavy] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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USnavy wrote:
Sure. I mean, its not like I work in the industry and climb with these said marketing guys and engineers or anything. As far as climbing hard, I have climbed grade V 5.12+ and multiple lines on El Cap--that's plenty hard enough. And only a Sharma stocker would actually think that climbing 5.14 gives you an engineering-level understanding of climbing gear. I know because I have climbed with a large sum of them. Some of them dont really know jack outside of how to dyno to a mono.

I am not saying that Mammut's staff are unqualifed. I am sure they all know a ton about climbing. But I have also spoken to Petzl employees that dont know their own Dragonfly rope is not UIAA certified as a twin, and Black Diamond employees that do not know that their pins are made out of chrome molybdenum steel, and the list goes on and on. Hell, the CEO of Sterling ropes isint even a rock climber (not that she needs to be, but one would assume)! So my point is not everyone knows everything about every subject and if a bunch of people are saying something other than what you think the correct answer is, you would be well off to further inquire using many references and sources instead of blindly believing the reference that best supports your opinion is gold.

Look, of course there have been climbers who have rejoined their halves and fallen on them without issue. Safety is a sliding scale. "Safe or not" is a question of your personal risk assumption. I am absolutely positive, no matter how many marketing guys say otherwise, that I could create a system in which you could get enough rope speed difference between the two ropes to cause a problem. I have blazed the sheath of a rope solely from the friction of a carabiner while taking a big space whipper. So if the carabiner alone can damage a sheath from friction, then two ropes in that carabiner, each moving at a different speed, certainly can cause problems under some conditions. Few people realize just how sensitive nylon is to heat (350F causes major strength loss) and how fast a rope can heat up under heavy friction while rubbing against other nylon components. I have seen a climber melt through the sheath of his rope, exposing the core, on a small lead fall because his tag line got caught in the lead line and rubbed against it during the fall. Crap happens.

so mister RC "expert"

let me ask you this, how much TESTING have you done one mammut ropes, perhaps you can share with us the results

here you are slagging the mammut product managers .. perhaps you can share with us YOUR particular expertise with their rope products ... which so confidently leads you to proclaim that they are wrong with the usage of THEIR products

here you are bragging about el cap, 5.12, etc again ... but how much do YOU use and whip on halves in such a configuration

you arent putting down mammut on lack of REAL experience with the product in such a setup would you

Tongue


rocknice2


Sep 4, 2013, 1:22 PM
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I sent Jim an email and this was his response.

Jim Ewing wrote:
Hi Charles,

Sorry for the late response to your question. I was away on a short climbing vacation with my family.

So thenÖ

Indeed there has been lots of discussion on this topic and a pretty wide range of thoughts and opinions. Unfortunately the UIAA (the international mountaineering standards writing organization) does not clarify this point very well in the standard document. The standard, UIAA 101 (EN 892) merely states that a rope certified as half is suitable for use in pairs and clipped separately while a rope certified as twin is suitable for use in pairs and must be clipped together into the same carabiner as though they were a single rope. Currently there is no mention of how the ropes should be treated when it has a dual certification.

My personal opinion, as rope engineer and a climber, is that one should choose one technique before starting each pitch and stick with it to the end. Changing the technique back and forth mid pitch would likely create situations where the ropes have the possibility running unevenly (speeds) or even in opposite directions in the event of a fall. This could cause, as you stated, the potential for rope on rope friction, which we know can cause damage to the nylon. While Iíve never heard of a rope failure from such a scenario I see it as one possibility that can easily be avoided by sticking with one technique per pitch. That said, in 35+ years of climbing, and a huge amount of that time with half ropes and twin ropes, Iím certain I have mixed the techniques mid pitch many times without incident. I believe the point Iím trying make here, is to go with the best practices first but when thatís not possible you have to go with what works.

I know this does not clarify the issue much beyond your previous understanding but I hope it helps you make wise choices while you climb. If I can be of any further help feel free to contact me.

Best regards,

Jim

Jim Ewing
Product Engineer
Sterling Rope Company, Inc.

I also ask if he could do a non official test.

Jim Ewing wrote:
Iíve been trying to imagine some sort of test set up for this issue in years past but it never seems to become a very high priority, unfortunately. If you have some ideas feel free to share them and Iíll try to determine if it is possible to set up a test.


curt


Sep 4, 2013, 2:09 PM
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USnavy wrote:
You can start out using them as twins and then separate to halves, but do not join them back to twins once separated unless you use two different slings and biners. The problems is that once you separate the ropes, the amount of rope out for each strand and the amount of drag for each strand is different. Accordingly, when you fall the ropes can move at different speeds, which if allowed to contact each other could result in rope damage.

The "rule" against nylon on nylon contact is meant to prevent a scenario where a running rope crosses a fixed non-moving rope or sling, under load. The friction imparted to the fixed nylon piece can quickly melt through that piece--and this has been well documented.

The situation posed here, however, is quite unlike that. Frankly, I can't envision any scenario where one of the two ropes, upon being separated and then rejoined, would cross the other rope with either of the two ropes being fixed and not moving. As long as both ropes are moving (same direction and different speeds, or different directions) I don't see any problem.

Nylon on nylon contact under load is not always bad, per se. If that were true, Munter hitch belays would be uniformly fatal--and of course, they are not.

Curt


rocknice2


Sep 4, 2013, 2:35 PM
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curt wrote:
USnavy wrote:
You can start out using them as twins and then separate to halves, but do not join them back to twins once separated unless you use two different slings and biners. The problems is that once you separate the ropes, the amount of rope out for each strand and the amount of drag for each strand is different. Accordingly, when you fall the ropes can move at different speeds, which if allowed to contact each other could result in rope damage.

The "rule" against nylon on nylon contact is meant to prevent a scenario where a running rope crosses a fixed non-moving rope or sling, under load. The friction imparted to the fixed nylon piece can quickly melt through that piece--and this has been well documented.

The situation posed here, however, is quite unlike that. Frankly, I can't envision any scenario where one of the two ropes, upon being separated and then rejoined, would cross the other rope with either of the two ropes being fixed and not moving. As long as both ropes are moving (same direction and different speeds, or different directions) I don't see any problem.

Nylon on nylon contact under load is not always bad, per se. If that were true, Munter hitch belays would be uniformly fatal--and of course, they are not.


Curt
That last part is really interesting.


bearbreeder


Sep 4, 2013, 2:39 PM
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Re: [curt] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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thanks for the email from sterling

the relevant worry IMO is the difference in rope STRETCH between the two strands ... if you take falls on halves, IME this is fairly minimal ... of course i dont take a ton of whippers on halves at the full 70m rope length, but i doubt most RCer have such experiences either ...

on a perfectly vertical crack, ive noticed half ropes tend to overlap one another regardless, even with alternate clipping ... "burning" through should be as much a worry

a pic from UK climbing


the other thing to keep in mind is that different manufacturers will have different opinions on the use of a similar product ... for example all mammut half ropes are cleared for twin use, have been for years even though they were never officially rated as such till recently ... while other manufacturers will say its a no-no even though their halves have a lower impact force than the mammuts

then theres the famous DMM and dyneema issue .. while metolius goes and sells a dyneema PAS

IMO there are things that will likely kill you ... using halves and twins techniques in the same pitch aint one of them, just like the fear of crossloaded belay biners and the attempts to "solve" it

as you said, if we did worry about it, no one should use the munter

if anyone has any real testing, i would happy to contact mammut again and ask for their opinion ...

Wink


acorneau


Sep 4, 2013, 3:08 PM
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Re: [rocknice2] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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rocknice2 wrote:
I also ask if he could do a non official test.

Jim Ewing wrote:
Iíve been trying to imagine some sort of test set up for this issue in years past but it never seems to become a very high priority, unfortunately. If you have some ideas feel free to share them and Iíll try to determine if it is possible to set up a test.

I could imagine a test jig that would be easy to incorporate into a standard drop test tower, something like this...



This should allow the two ropes to stretch at differing speeds/amounts. Any wear would be witnessed where the ropes pass through the top combining "biner".


(This post was edited by acorneau on Sep 4, 2013, 3:10 PM)
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rocknice2


Sep 5, 2013, 8:18 AM
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Re: [acorneau] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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I think in your case the speed differential at the top anchor is minimal if you take a standard fall. If the fall is huge or if the climber continues higher placing more pro and then that will increase the speed differential.


I think the highest rubbing will occur at T1 not T final
The more you place L1 & L2 to the left the more rope drag is created. In that case I wouldn't clip rope L until pro T2 or T3 even.



I don't really see this scenario as a problem


(This post was edited by rocknice2 on Sep 5, 2013, 8:19 AM)
Attachments: Half Twin.JPG (15.8 KB)


bearbreeder


Sep 5, 2013, 10:47 AM
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Re: [rocknice2] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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rocknice2 wrote:
I think in your case the speed differential at the top anchor is minimal if you take a standard fall. If the fall is huge or if the climber continues higher placing more pro and then that will increase the speed differential.


I think the highest rubbing will occur at T1 not T final
The more you place L1 & L2 to the left the more rope drag is created. In that case I wouldn't clip rope L until pro T2 or T3 even.

[image]http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?do=post_attachment;postatt_id=6607;[/image]

I don't really see this scenario as a problem




the exact same fall scenario ... they take whippers, they dont die

Wink


verticon


Sep 5, 2013, 1:15 PM
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Re: [acorneau] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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acorneau wrote:
rocknice2 wrote:
I also ask if he could do a non official test.

Jim Ewing wrote:
Iíve been trying to imagine some sort of test set up for this issue in years past but it never seems to become a very high priority, unfortunately. If you have some ideas feel free to share them and Iíll try to determine if it is possible to set up a test.

I could imagine a test jig that would be easy to incorporate into a standard drop test tower, something like this...

[image]http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?do=post_attachment;postatt_id=6606;[/image]

This should allow the two ropes to stretch at differing speeds/amounts. Any wear would be witnessed where the ropes pass through the top combining "biner".

You're right, this looks like the worst case scenario. At the moment when the rope on the right will reach it's maximum elongation and stop moving, the other one will still be running for a while through the same biner (because it's longer and stretch is proportional to length).

And this is exactly the scenario Curt couldn't envision "where one of the two ropes, upon being separated and then rejoined, would cross the other rope with either of the two ropes being fixed and not moving"


curt


Sep 5, 2013, 2:48 PM
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Re: [verticon] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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verticon wrote:
acorneau wrote:
rocknice2 wrote:
I also ask if he could do a non official test.

Jim Ewing wrote:
Iíve been trying to imagine some sort of test set up for this issue in years past but it never seems to become a very high priority, unfortunately. If you have some ideas feel free to share them and Iíll try to determine if it is possible to set up a test.

I could imagine a test jig that would be easy to incorporate into a standard drop test tower, something like this...



This should allow the two ropes to stretch at differing speeds/amounts. Any wear would be witnessed where the ropes pass through the top combining "biner".

You're right, this looks like the worst case scenario. At the moment when the rope on the right will reach it's maximum elongation and stop moving, the other one will still be running for a while through the same biner (because it's longer and stretch is proportional to length).

And this is exactly the scenario Curt couldn't envision "where one of the two ropes, upon being separated and then rejoined, would cross the other rope with either of the two ropes being fixed and not moving"

Actually, when the shorter rope reaches its maximum tension, the climber's fall will be fully arrested and the longer rope will also stop running.

Curt


acorneau


Sep 5, 2013, 3:29 PM
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Re: [curt] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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curt wrote:
Actually, when the shorter rope reaches its maximum tension, the climber's fall will be fully arrested and the longer rope will also stop running.

Curt

Ah, but at that point the drop-test is ended; friction between the two ropes has happened and they're ready for inspection. Repeat as necessary.


verticon


Sep 5, 2013, 11:23 PM
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Re: [curt] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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You're right too :)

So, the Mammut guy is also right, it's safe to split and join the double ropes in the same pitch.


(This post was edited by verticon on Sep 6, 2013, 2:43 AM)


jktinst


Sep 6, 2013, 9:08 AM
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Re: [bearbreeder] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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On a Munter the parts of the rope that are rubbing each other are constantly changing, preventing any one spot from overheating. And if they are not changing, they are not rubbing either.

Iím very much on the fence as to whether there might be a potential safety issue with mixing half and twin techniques. I donít find the assertion of the Mammut product manager (that itís OK to mix) particularly convincing, especially in light of the other indications that this particular issue has simply not been tested by anyone yet. The argument that we have not seen accidents attributable specifically to this issue does not carry much weight with me either. As has been mentioned, thereís a variety of reasons why mixing is not a particularly widespread approach: the manufacturersí inclination to make, certify and market ropes for both uses, the rope path/friction considerations, the clearly fairly widespread belief that this is a safety concern, etc. (plus another potential reason below). On the other hand, I have a hard time imagining huge amounts of rope-to-rope friction from two strands running at different speeds through the same biner during a fall.

Iíve probably mixed the two techniques at some point in the past through carelessness or not knowing any better but, since I started paying more attention to my rope paths, length of slings and friction, I have not been tempted to intentionally mix. As others, I would tend to avoid it just to minimize friction. If I hit a straight stretch of route after a zig-zaggy one, I would still prefer to just keep clipping the two strands alternately for that reason. If I were facing a long runout section where I might really want both my strands to catch me at the highest possible pro, I would probably try to place two pros or, failing that, use two slings of different lengths on the same pro. One of the many things I like about half-ropes is the fact that one strand acts as a back-up for the other and it seems to me that they can do a better job of that if the two clipping paths are completely separate: less chance that theyíll both rub on that sharp edge that I failed to spot or that a falling flake will cut both of them.

If the two strands are still clipped in the same biner when you fall and both participate in the arrest, the only differential, as discussed above, would apparently come from greater stretching of the strand that follows the longer path. However, this also means that this longer strand will likely have more friction. So on the one hand youíd have a shorter strand whose stretching will be less impeded by friction (ie more able to stretch throughout its whole length) and on the other, a longer but more impeded strand. Iím not sure that there would be all that much difference between the two in how fast they would run through their shared biner(s). In addition, the Munter comparison makes me think that even if the two strands run together at different speeds or run in opposite directions (one strand slipping back down under its own weight while the other catches the fall ?), youíd just get the same kind of distribution of potential damage over different spots that you get with the Munter, ie no damage.

This would suggest that the main risk of rope-to-rope friction damage, would probably come from one strand running fast over/beside/against the same non-moving spot of the other strand. It seems that this situation would occur mainly if the strands are separated after having been clipped together and if, between the last shared clip and the point of the fall, only one of the strands has been clipped. Longer separated paths and longer falls would result in more rubbing and potentially more damage on that one spot. If testing were to be done to find out whether there really is a safety concern, I would suggest mimicking this situation as the potential worst case scenario before looking at other, less stringent conditions.

This could be yet another reason why there has not been a rash of accident reports from mixing the techniques: youíd have to take a whipper on a single strand after having clipped both together, fail to notice the damage on the other strand and then take another fall on that other strand (plus various other, less obvious conditions).


verticon


Sep 6, 2013, 10:42 AM
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Re: [jktinst] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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jktinst wrote:
This would suggest that the main risk of rope-to-rope friction damage, would probably come from one strand running fast over/beside/against the same non-moving spot of the other strand. It seems that this situation would occur mainly if the strands are separated after having been clipped together and if, between the last shared clip and the point of the fall, only one of the strands has been clipped. Longer separated paths and longer falls would result in more rubbing and potentially more damage on that one spot. If testing were to be done to find out whether there really is a safety concern, I would suggest mimicking this situation as the potential worst case scenario before looking at other, less stringent conditions.
So you mean that acorneau's rig should be modified like in the picture below, and the rope-on-rope damage might occur on the bottom biner, where we split the ropes and not on the tpo one. Right ?
Attachments: Twins-doubles2.jpg (58.0 KB)


jktinst


Sep 6, 2013, 7:56 PM
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Re: [verticon] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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verticon wrote:
So you mean that acorneau's rig should be modified like in the picture below, and the rope-on-rope damage might occur on the bottom biner, where we split the ropes and not on the tpo one. Right ?

No. More like this.


Partner rgold


Sep 7, 2013, 8:31 PM
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Re: [jktinst] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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It seems pretty clear to me that no one, including the rope manufacturers and experienced climbers, has a really clear idea about mixing twin and double technique. It also doesn't seem likely that anyone will have any clear idea very soon, because the circumstances that need to be tested are themselves far from evident.

Much of the "reasoning" offered doesn't sound very plausible to me. For example,

The problems is that once you separate the ropes, the amount of rope out for each strand and the amount of drag for each strand is different. Accordingly, when you fall the ropes can move at different speeds, which if allowed to contact each other could result in rope damage.

If the separated ropes are clipped together at the top piece, then the rate they run out is precisely the rate of the falling climber, and both ropes stop when the falling climber stops. The strand that wanders and is longer stretches a smaller percentage of its total length, and therefore absorbs less of the total fall energy than the other strand, but I don't see any issue with uneven speeds or different stop times at the top biner. This means that there is little to worry about in terms of rubbing in this situation, even from a theoretical point of view, other than creating a harder catch (which might be significant). But Hazel Findlay and others notwithstanding, there isn't much reason to clip two separate strands together. If you really don't trust a single strand to do the job, you shouldn't be climbing with half ropes to begin with. The only scenario I can think of offhand for clipping both strands is that there is a solid piece and something you might hit below. Clipping both strands should reduce the rope stretch and might keep you off the obstacle, at the expense of a higher impact to the pro and your body.

There is an issue with clipping separated strands to a single piece that is not the top piece that is worth mentioning: when loaded, this configuration will lift the draw. If the piece (nut or cam) is in a vertical crack, then it is going to move and could be extracted. If the piece is critical to a back-up role, then this would be reason enough to either not to join to strands there or else make sure the piece is secured from lifting. The lifting action of separated strands could potentially zipper a whole line of doubly-clipped pieces in this fashion if the lowest double-clipped pieces isn't held down.

This means that the potential for rubbing comes from the situation posted by jktinst, but even here the slack unloaded strand would have to be somehow pinned behind the running strand in order for there to be much or even anything in the way of damage. Perhaps this could happen if there was an unfortunate rock feature at that top double-clipped biner. A second possibility with this configuration is that the lower strand does become involved in stopping the fall, in which case you have ropes running in opposite directions through the highest double-clipped biner, a situation with the most potential for some kind of rope damage, although with both ropes running I'd guess the worst that could happen would be glazing of the sheath, which, by the way, has happened with the Munter hitch.

At the end of the day, the argument is very probably much ado about nothing, but that doesn't mean one can't comment on what seems to be the most rational procedure, understanding that it is very unlikely to matter one way or another. Personally, I'd go with the rope engineer and say that it is best in some abstract sense not to mix techniques. Moreover, there is almost never any good reason to mix techniques anyway. I mentioned one possibility above, other possibilities might arise when two seconds are following and one wants both ropes through a critical anchor, although one could still use slings of different lengths and avoid having both ropes together in a single biner. Meanwhile, I think the lifting issue is potentially far more problematic than any possible rubbing, so think carefully if you join separated strands about how your system will behave under load.


daveat


Sep 9, 2013, 8:19 AM
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Re: [acorneau] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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Kind of new to the forums, semi new to climbing and brand new to Trad... so maybe i'm making some stupid thoughts here.. BUT,

This is an interesting point to me.

rgold wrote:
There is an issue with clipping separated strands to a single piece that is not the top piece that is worth mentioning: when loaded, this configuration will lift the draw. If the piece (nut or cam) is in a vertical crack, then it is going to move and could be extracted. If the piece is critical to a back-up role, then this would be reason enough to either not to join to strands there or else make sure the piece is secured from lifting. The lifting action of separated strands could potentially zipper a whole line of doubly-clipped pieces in this fashion if the lowest double-clipped pieces isn't held down.

As that would apply, the piece on the left could/would likely shoot out of its placement.

acorneau wrote:
rocknice2 wrote:
I also ask if he could do a non official test.

Jim Ewing wrote:
Iíve been trying to imagine some sort of test set up for this issue in years past but it never seems to become a very high priority, unfortunately. If you have some ideas feel free to share them and Iíll try to determine if it is possible to set up a test.

I could imagine a test jig that would be easy to incorporate into a standard drop test tower, something like this...



This should allow the two ropes to stretch at differing speeds/amounts. Any wear would be witnessed where the ropes pass through the top combining "biner".


(This post was edited by daveat on Sep 9, 2013, 8:23 AM)


jktinst


Sep 9, 2013, 10:33 AM
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Re: [rgold] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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rgold wrote:
...A second possibility with this configuration is that the lower strand does become involved in stopping the fall, in which case you have ropes running in opposite directions through the highest double-clipped biner, a situation with the most potential for some kind of rope damage, although with both ropes running I'd guess the worst that could happen would be glazing of the sheath, which, by the way, has happened with the Munter hitch...

I still canít picture ropes running in opposite directions through a double-clipped biner other than if the slack/non-arresting one were to slip down under its own weight, which would probably not happen all that often. If the belayer manages to take up slack, run backwards, etc. during the fall, both ropes will run downwards together for a bit. If they are both involved in arresting the fall, they will both run up to, over and down from their respective arresting biner, no matter how far apart these two biners are.

Iíd also like to know more about the glazing of the rope by the Munter if anyone has more info. I searched both this forum and the Internet at large and didnít find a whole lot. The following statement from "Moutaineering Ė Freedom of the hills" is probably as authoritative as they come but it's not much: "After a big fall (on the Munter), the outermost layer of the sheath may be glazed Ė which is only cosmetic; this glazing, which also occurs to some degree with mechanical devices, wears off with use". Iím curious about the frequency and intensity of the glazing from the Munter compared to other devices. I also wonder whether dynamic vs non-dynamic arrests might give different results. Finally, it would be tricky to pry apart the two effects but I wonder how much of a part the heated biner plays in the glazing, compared to the rope-on-rope friction.


JimTitt


Sep 9, 2013, 12:06 PM
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Iīve seen some slight glazing on the rope when doing pull tests on the HMS/Italian Hitch (wrongly called the Munter by the way) but it is almost certainly from the rope/rope contact since the coeff. of friction at that point is so high. You get a certain amount of glazing with all devices (even though you probably canīt see it with the naked eye) and it is is of no concern anyway in real life. Itīs an annoying phenomenon though when your trying to do repeat pull tests as the friction in the plate with ATC/Tuber style devices drops if you use the same length of rope so you either have to take this into account or keep changing the section of rope being tested.


bearbreeder


Sep 9, 2013, 9:53 PM
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Re: [jktinst] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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jktinst wrote:
I donít find the assertion of the Mammut product manager (that itís OK to mix) particularly convincing, especially in light of the other indications that this particular issue has simply not been tested by anyone yet.

ahhh ... but it as been "tested" in real life by climbers falling ...

what i find interesting is that theres a very strong assertion by some climbers that it is "dangerous"... without any real proof, just theoretical conjecture

i would love for someone to produce and accident report where double ropes were used in the aforementioned way which led to an accident ... its something ill send back to mammut asking for clarification

personally id take the manufacturers word and climbers "testing" the setup buy whipping over intraweb theories anyday

Wink


rocknice2


Sep 10, 2013, 6:48 AM
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Re: [rgold] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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There have been many good points made in this discussion. One of the reasons I brought up this topic is, on a few occasions I've climbed a route where a double crack system converges to a single. In the past I have alternated clipping red/blue. When the ropes are running directly beside each other as in a single crack, I have found that sometimes I clip one around the other. This doesn't happen when the ropes are separated by a few feet or meters as in a double crack. The reason I think is that one rope will run over a knee and the other between the legs or over the other knee. Before anyone says just keep it organised, let me say that I do but in the real world shit just happens and I've been climbing on doubles for over 20 years.

rgold wrote:
There is an issue with clipping separated strands to a single piece that is not the top piece that is worth mentioning: when loaded, this configuration will lift the draw. If the piece (nut or cam) is in a vertical crack, then it is going to move and could be extracted. If the piece is critical to a back-up role, then this would be reason enough to either not to join to strands there or else make sure the piece is secured from lifting. The lifting action of separated strands could potentially zipper a whole line of doubly-clipped pieces in this fashion if the lowest double-clipped pieces isn't held down.
An excellent point and it's at this intersection that the highest differential in speed will occur.

I have done some [very, very] rough calculation and made some huge assumptions but it may be good for discussion. Please understand that this drawing is worst case and is not meant to mimic real world.
I made the blue rope shorter because for some stupid reason there is enormous rope drag at the blue triangle. the red triangle is the belayer.
Assuming a 10m fall on 15m of blue rope @ a dynamic elongation of 30% gives me a rope stretch of 4.5m. I divided that 4.5m by the amount of each rope at key points to find the rope travel at each point.
It's clear to see that the highest differential is at the point of convergence. Taking into account what 'rgold' said, the ropes would not be likely to rub there.




(This post was edited by rocknice2 on Sep 10, 2013, 6:56 AM)
Attachments: Half Twin_2.JPG (33.0 KB)


Partner cracklover


Sep 10, 2013, 9:05 AM
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Re: [rocknice2] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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rgold wrote:
There is an issue with clipping separated strands to a single piece that is not the top piece that is worth mentioning: when loaded, this configuration will lift the draw. If the piece (nut or cam) is in a vertical crack, then it is going to move and could be extracted. If the piece is critical to a back-up role, then this would be reason enough to either not to join to strands there or else make sure the piece is secured from lifting. The lifting action of separated strands could potentially zipper a whole line of doubly-clipped pieces in this fashion if the lowest double-clipped pieces isn't held down.

Just a point of clarification: I think you meant to say the *highest*, not the lowest doubly-clipped piece. As I'm envisioning it, in this scenario (unlike the normal zippering scenario) the bottom of a string of doubly-clipped pieces will actually be pulled *down*, while the top ones will be pulled up. And then, if the top one rips, the upward force will go to the next one down, etc.

Here's a quick pic to explain:



GO


(This post was edited by cracklover on Sep 10, 2013, 9:05 AM)
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rocknice2


Sep 10, 2013, 10:18 AM
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Lowest twin clip was referring to this pic



(This post was edited by rocknice2 on Sep 10, 2013, 10:18 AM)


jktinst


Sep 10, 2013, 11:56 AM
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When you posted your earlier diagram, I kind of lumped it with acorneauís. I saw that you made the point that the greater differential would be at the bottom of the double-clipped chain, not the top, but missed your assumption that the longer rope, because it had more friction, would behave as if it were shorter than the shorter one. I figured that you were simply disregarding the friction and that, as a result, you thought that it would be the longer rope that would run a greater distance through the lower double-clipped biner.

I get it now but Iím wondering if you might not be confusing what would constitute an enormous amount of rope drag for the leader to keep on climbing with what would significantly cut back on the ability of the rope to transmit the load of a fall to the belay. I think that the leader could easily arrive at a point where he cannot climb further, even pulling up slack two-handed before moving and yet, if he were to fall at that point, a few metres above his last pro, his belayer would still feel a reasonable yank.

My own experience and corner of a napkin estimates of how much tension is lost to friction at different bend angles suggest that in order to have the kind of severe friction that would make the longer rope behave as though it was significantly shorter than the other, you would already be in a situation where progress is impossible, never mind considering double-clipping.

(edited for clarity)

(This post was edited by jktinst on Sep 10, 2013, 2:06 PM)


rocknice2


Sep 10, 2013, 12:55 PM
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Re: [jktinst] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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Let me clarify.
This drawing depicts what I would consider real world. I'm not discounting amount of each rope out and differing rope speeds. The whole purpose is to reduce friction by splitting up the ropes. I'm just thinking now that it may not be that great a differential. IMO


Now this pic is total fiction or shall I say friction. It's a proposal that I came up with to show an absolute worst case. The blue rope is made shorter by tremendous rope drag. Notice that where the rope speed differential is greatest the strands are least likely to rub against each other.
Again NOT a real world scenario. Then again there will be one noob that will test it.



anarkhos


Oct 16, 2013, 4:50 PM
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Re: [rocknice2] Use 2 Ropes as Twin and Double in Same Pitch [In reply to]
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I made the mistake of clipping both doubles into one biner once. Never again. The ropes twisted in the biner and I ended up with horrendous drag. If I need both on one anchor for whatever reason (like a directional), I will use two biners.


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