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Author Topic: Ropes (1/2, *2)  (Read 80 times)

cklein

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Ropes (1/2, *2)
« on: January 26, 2004, 10:58:42 AM »

Help.....Can somebody shed light on the subject of Double Ropes Vs. Half Ropes.  Ie....physical differences, clipping procedures, pros & cons.  Thanks
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Jim_Ewing

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Re: Ropes (1/2, *2)
« Reply #1 on: January 26, 2004, 12:21:34 PM »

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Jim_Ewing

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Re: Ropes (1/2, *2)
« Reply #2 on: January 26, 2004, 12:39:13 PM »

OOPS!  Sorry, that link only references the EN standards.

"Double rope" is the old term for what is now called "half rope".  Don't let anyone tell you it is OK to clip both at the same time.  "Half ropes" are designed to be clipped separately all the time throughout any given pitch. If you want to use a 2 rope system that you clip both ropes into every piece that is called a "twin rope".  The standards for "half" and "twin" ropes are distinctly different in that a "half" rope is tested in a single strand with a 55kg mass and a "twin" is tested with two strands with an 80kg mass.

There is a lot more to it than this.  If you want more information you should find a resource that spells out the differences in more detail.  If you really want to know the absolute last word on this you can purchase the standard EN892 from any one of the EN standards organizations such as the British Standards Institute (if you want it in English).
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DMan

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Re: Ropes (1/2, *2)
« Reply #3 on: January 26, 2004, 07:04:26 PM »

I do have a set of PMI Verglass 8.1mm ropes that were rated for twin and double use, meaning I could clip them either way.  If the climb was straight forward I would often clip them together, and seperate when it wandered.  I tried to find their website to no avail to verify it.
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MCarey

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Re: Ropes (1/2, *2)
« Reply #4 on: January 27, 2004, 09:45:40 AM »

Here's a quick look at EN892 Specs and Standards:

European Standard EN892 Mountaineering Equipment - Dynamic Mountaineering Ropes- Safety requirements and test methods

Terms and Definitions from the Standard:

1:      Single Ropes:  Dynamic Mountaineering rope, capable of being used singly, as a link in the safety chain, to arrest a person's fall.  

2:      Twin Ropes: Dynamic mountaineering rope, which is capable, when used in pairs and parallel, to arrest a person's fall.
 
3:      Half Ropes:  Dynamic Mountaineering rope, which is capable, when used in pairs, as a link in the safety chain to arrest a person's fall

testing requirements:  

1. Construction:  Kernmantle with core having a greater mass than the sheath

2. Sheath Slippage:  Must be less than 40mm over a 200mm sample or no more than 20%.

3. Static Elongation:  Tested using an 80kg weight for single and twin ropes and a 55kg weight  for half ropes
-      Single and Twin Ropes (using both strands):  Must be less than 8%.
-      Half Ropes (single strand):  Must be less than 10%

4. Impact Force: Tested during the first factor 1.739 fall (4meter fall on 2.3meters of rope).
-      Single Ropes: Impact must be less 12 kilonewtons (kN) using an 80kilogram mass.
-      Twin Ropes (2 strands parallel):  Same as Single ropes, but using both strands during the test.
-      Half Ropes (single strand):  Impact must be less than 8kN, tested using a 55 kilogram mass.

5. Falls Held:   Number of falls rope holds before breaking.
-      Single Ropes:  Must hold 5 falls of an 80kg mass.
-      Twin (two strands):  Must hold 12 falls of an 80kg mass.
-      Half (single strand):  Must hold 5 falls of a 55kg mass.  

Here's where it gets a little confusing.  UIAA 101 (Union Internationale des Associations d'Alpinisme) the UIAA standard for Dynamic Ropes uses most of the procedures and requirements set forth in EN892, with a couple of addendums.  
- They limit sheath slippage to no more than 20mm or 10% and
- they add in a requirement for Dynamic Elongation measured during the first dynamic drop of no more than 40% elongation.

Hope this helps,

Mike
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MCarey

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Re: Ropes (1/2, *2)
« Reply #5 on: January 27, 2004, 09:47:35 AM »

Sorry,  I forgot to answer the question.

It is possible for a rope to be tested and pass the requirements for both half and twin ropes.
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DMan

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Re: Ropes (1/2, *2)
« Reply #6 on: January 30, 2004, 01:12:49 PM »

Quote
It is possible for a rope to be tested and pass the requirements for both half and twin ropes.


If that's the case, which I believe my ropes are an example of such, I would recommmend to the original poster to find a pair of ropes like mine.  It's nice to have the choice to clip one or both depending on the situation.
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Jason

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Re: Ropes (1/2, *2)
« Reply #7 on: January 31, 2004, 07:16:37 AM »

Question for Jim;

I've been using 8.8 half ropes for a couple seasons. I've been clipping both ropes to my first piece, and then just one rope into each piece after the first.  Is this a bad habit?  

I understand the need to clip both ropes each time in a "twin" rope system.  What are the dangers/complications of clipping both "half" ropes to the first piece?  (or any higher pieces) Thanks!
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DMan

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Re: Ropes (1/2, *2)
« Reply #8 on: January 31, 2004, 08:28:20 AM »

Jim will probably give a better answer when he replies, but in the meantime I believe it has to due with how the ropes work together absorbing impact in a fall.  If half ropes are clipped in the same biner' they don't work as they should.  Maybe the friction of the two ropes against each other in a loaded biner has something to do with it.  Not sure how twin ropes get around the issue though...
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MCarey

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Re: Ropes (1/2, *2)
« Reply #9 on: February 04, 2004, 08:26:11 AM »

Clipping two-half ropes into one piece of gear is generally not recommended for a couple of reasons.

1.  As Dman noted the diameters of half ropes are generally larger and therefore do not fit as nicely in one standard sized biner causing increased rope drag and a greater chance of rope on rope abrasion.  This problem can be somewhat alleviated by clipping each strand into separate biners on the same piece of pro.  Still not really recommended because...

2.  half ropes are tested using a single strand and designed to be clipped into separate pieces of gear with the desired outcome of dispersing the load from a fall more equally through each piece of protection.  By clipping both ropes into one piece of protection you have the potential of overloading that individual piece causing it to blow.

3.  Regarding clipping the first piece and then clipping individual pieces:  Not recommended for both reasons above but also takes away the advantage of decreasing rope drag that half ropes provide.  Also not a good idea because you could overload that first piece causing it to blow and zipper your entire string of protection.

Twin ropes don't have these problems because their elongation, and impact absorbtion characteristics are designed and tested with the intent of using both strands together and parallel in each piece of protection.
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