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redpoint_dog
Feb 6, 2007, 11:03 PM
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When using double ropes sport climbing would it be better to clip both ropes in to each bolt, or would it be better to alternate form bolt to bolt?
(This post was edited by redpoint_dog on Feb 6, 2007, 11:18 PM)
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overlord
Feb 6, 2007, 11:11 PM
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it would be better to alternate. that way you get a softer catch and you actually dont have much slack in the system (while pulling the slack to clip, youre pulling the strand from the second highest bolt and not the one directly below you).
offcourse you can clip both strands, but then you must do so all the time (or you risk some serious friction between strands), and youll get a higher impact force. that turns the double into a slightly heavier, more redundant single rope (or, if were more precise into a twin rope).
(This post was edited by overlord on Feb 6, 2007, 11:15 PM)
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redpoint_dog
Feb 6, 2007, 11:13 PM
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Sweet as. Thats what I thought I just wanted a second opion. Cheers
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metrogroaz
Feb 6, 2007, 11:16 PM
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http://www.gunks.com/rock/double_ropes/dropes_intro.htm
More information than anyone should type about double ropes
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robdotcalm
Feb 6, 2007, 11:32 PM
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Alternate. The time I best like double ropes is when I'm clipping the 2nd bolt and don't have to pull a lot of rope past the 1st bolt.
rob.calm
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sterlingjim
Feb 7, 2007, 12:42 AM
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If using half ropes they should be alternated or at least clipped separately. If using twin ropes they should be clipped together.
On a side note: contrary to popular belief half ropes do not deliver a lower impact force than single ropes.
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pylonhead
Feb 7, 2007, 2:29 AM
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metrogroaz wrote: http://www.gunks.com/rock/double_ropes/dropes_intro.htm More information than anyone should type about double ropes
I couldn't get your link to work, but searching google found:
http://www.gunks.com/...smGroup=2&smID=4
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sterlingjim
Feb 7, 2007, 2:51 AM
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I have to confess a pet peeve of mine. Officially speaking double ropes do not exist. There are half ropes and twin ropes. The definitions and functions of each are different. So when talking about double ropes it is important to understand which type is being discussed.
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metrogroaz
Feb 7, 2007, 2:57 AM
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Thank ya
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kixx
Feb 7, 2007, 2:30 PM
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SterlingJim,
You said that a double rope does not deliver lower impact forces than singles - this is contrary to what I believe and I'd like to hear more about it. Are there any good papers or articcles from your company or third parties that you know of which talk about impact forces on double ropes versus singles.
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brent_e
Feb 7, 2007, 9:58 PM
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kixx wrote: SterlingJim, You said that a double rope does not deliver lower impact forces than singles - this is contrary to what I believe and I'd like to hear more about it. Are there any good papers or articcles from your company or third parties that you know of which talk about impact forces on double ropes versus singles.
agreed,
I'd like to hear about it, too.
Brent
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cchildre
Feb 7, 2007, 10:47 PM
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kixx wrote: SterlingJim, You said that a double rope does not deliver lower impact forces than singles - this is contrary to what I believe and I'd like to hear more about it. Are there any good papers or articcles from your company or third parties that you know of which talk about impact forces on double ropes versus singles.
Basic:
Twin Rope: 5.2 kN for an Edelweiss Oxygen 8.2mm
Double Rope: 9kN for an Edelweiss Duolight 8mm - Twin Rope
Single Rope: 8.2kN for an Edelweiss 'Laser' 9.6
You need to understand how the physics work and what you need to achieve with each rope system. Typicall reasons: and correct me if I am wrong here please.
with twins, your looking to lower the chance of a cut rope on a ledge or fallen block. Redundancy is key
with half, your looking to lower impact force and rope drag, with limited redundancy.
Single, is what it is
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overlord
Feb 7, 2007, 11:11 PM
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cchildre wrote: kixx wrote: SterlingJim, You said that a double rope does not deliver lower impact forces than singles - this is contrary to what I believe and I'd like to hear more about it. Are there any good papers or articcles from your company or third parties that you know of which talk about impact forces on double ropes versus singles. Basic: Twin Rope: 5.2 kN for an Edelweiss Oxygen 8.2mm Double Rope: 9kN for an Edelweiss Duolight 8mm - Twin Rope Single Rope: 8.2kN for an Edelweiss 'Laser' 9.6 You need to understand how the physics work and what you need to achieve with each rope system. Typicall reasons: and correct me if I am wrong here please. with twins, your looking to lower the chance of a cut rope on a ledge or fallen block. Redundancy is key with half, your looking to lower impact force and rope drag, with limited redundancy. Single, is what it is
well, oxygen is a double rope, not a twin rope. and duolight is a twin rope.
doubles are tested with only one strand at a time, while twins are with boths strands at the same time. its logical that a single strand of a double rope has a lower impact force than a single strand of single rope. but if you would clip a double as a twin, it would have a higher impact force.
(This post was edited by overlord on Feb 7, 2007, 11:12 PM)
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petsfed
Feb 7, 2007, 11:44 PM
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Oh forget it. I'm no Richard Feynman. I can't explain the math I've done to show it.
The short version is that using half ropes as twins effectively doubles the peak impact force on the system, whereas using twins as halves cuts the peak impact force on the system in two, but causes the rope to stretch so much it may not be able to absorb all the energy and so break.
(This post was edited by petsfed on Feb 8, 2007, 12:35 AM)
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phillygoat
Feb 8, 2007, 12:31 AM
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I'm just as confused as ever...
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ja1484
Feb 8, 2007, 1:25 AM
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Getting back to the topic at hand and the OPs original question:
It would be better to get a single line and stop futzing around with twins or halfs on sport climbs. That's exactly what you need on the phsyically challenging, technically demanding, highly gymnastic sport climbs: To be hauling twice as much line and taking longer to organize your clips.
*farting noise*
Get a relatively svelte single rope, something in the 9.8 - 10.2 range, and be happy. If you're climbing on sharp rock and worried about chopping a rope in a fall...pad the edges or climb somewhere else.
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sterlingjim
Feb 8, 2007, 3:34 PM
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Half ropes appear to have lower impact forces than singles because they are tested with 55kg instead of the 80kg used for single ropes and twins.
I did some quick tests on this issue last fall for a friend who was curious. Here are the results:
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.
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
I had posted this up someplace else but can't remember where. I think Will Gadd has it up on his blogg. It may also have been posted up in a discussion at Supertopo.com
Half ropes have to have all the same properties of single ropes with the exception of peak impact to compensate for the smaller mass. So even though the ropes are relatively thin they still have to offer enough resistance to not elongate more than 10% with the 80kg. Impact force is measured and reported only from the first drop in the series. I would like to point out that the impact numbers you see printed on the hang tags will not be accurate in the field unless the temperature and humidity are precisely the same as the lab test conditions. More over, all the published numbers for any given rope are basically void after the first use.
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brent_e
Feb 8, 2007, 4:55 PM
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sterlingjim wrote: Half ropes appear to have lower impact forces than singles because they are tested with 55kg instead of the 80kg used for single ropes and twins. I did some quick tests on this issue last fall for a friend who was curious. Here are the results: These drops were conducted without the regulation conditioning but complied with all other requirements and procedures. Relative humidity was 42%, temperature was 20�C for 48 hours. 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 I had posted this up someplace else but can't remember where. I think Will Gadd has it up on his blogg. It may also have been posted up in a discussion at Supertopo.com Half ropes have to have all the same properties of single ropes with the exception of peak impact to compensate for the smaller mass. So even though the ropes are relatively thin they still have to offer enough resistance to not elongate more than 10% with the 80kg. Impact force is measured and reported only from the first drop in the series. I would like to point out that the impact numbers you see printed on the hang tags will not be accurate in the field unless the temperature and humidity are precisely the same as the lab test conditions. More over, all the published numbers for any given rope are basically void after the first use.
so, pretty much what you're saying is that if one wants to have less force on them or a piece, use a single rope, or use double and screamers?
I guess that negates the idea that using doubles to lower impact force on an ice screw is pretty much bunk then. At least you still have 2 targets to hit with your tools or kick with your feet.
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scrapedape
Feb 10, 2007, 5:23 PM
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Jim, you posted these results in The Lab forum here in response to a question I had asked:
http://www.rockclimbing.com/...ring=double;#1394069
Someone else raised the question in that thread of whether half ropes might still provide a softer catch in lower-FF situations.
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rgold
Feb 10, 2007, 6:27 PM
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On pitches with wandering protection, properly used half ropes will run in straighter lines than a single rope. With the reduction in carabiner friction comes the availability of effectively longer sections of rope for energy absorbtion, and so an effectively lower fall factor than is available from the single rope configuration.
This might account for some of the general impression about half ropes providing softer catches.
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