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Using half ropes with twin technique?


Original Post
Michael Tilden · · Boise · Joined Aug 2016 · Points: 0

I know this has been discussed in other forums. Can you use half ropes with twin technique (clipping both ropes into one peice of gear)? There seems to be conflicting answers out there. It does not appear that the impact forced will be doubled, but rather multiplied by 1.2-1.6. ( according to Beal and Mammut) This would mean the impact force could be within acceptable levels (similar to beefy single lines impact force) But I could be wrong. Please educate me.

FrankPS · · Atascadero, CA · Joined Nov 2009 · Points: 275

I would think it depends on whether the specific ropes are also rated as twins. If not, don't use them as twins or accept added risk (sorry I don't have a scientific explanation - I just rely on the manufacturer's recommendations).

baldclimber · · Ottawa, Ontario, Canada · Joined Jul 2015 · Points: 1
Michael Tilden wrote: This would mean the impact force could be within acceptable levels (similar to beefy single lines impact force) But I could be wrong. Please educate me.

"Beefy" != higher impact force.  Completely unrelated.  Skinny ropes *can* have the highest impact forces.  See willgadd.com/single-and-hal…

Michael S. Catlett · · Middleburg, VA · Joined Oct 2014 · Points: 175

Unequivocally yes you can run them as twins.

Michael Tilden · · Boise · Joined Aug 2016 · Points: 0
Michael S. Catlett wrote: Unequivocally yes you can run them as twins.

That’s what I think also, but why is this and why so much conflicting information?

Kevin Mcbride · · Canmore AB · Joined Jan 2017 · Points: 160
Michael Tilden wrote:

That’s what I think also, but why is this and why so much conflicting information?

DONT USE HALVES AS TWINS!!!!, half ropes have a higher impact force than twins, there is a reason there is two different certifications for these ropes.

Mark P. · · Luzern, Schweiz · Joined May 2013 · Points: 730
Kevin Mcbride wrote:

DONT USE HALVES AS TWINS!!!!, half ropes have a higher impact force than twins, there is a reason there is two different certifications for these ropes.

So if I understand what you're saying: if you run half ropes (certified ONLY as halves) as twins, then you're unsafe because they together have less elasticity than would be desired - since both are catching you in a fall. Like taking a lead fall on static rope. Is that correct?

Greg D · · Here · Joined Apr 2006 · Points: 877
Kevin Mcbride wrote:

DONT USE HALVES AS TWINS!!!!, half ropes have a higher impact force than twins, there is a reason there is two different certifications for these ropes.

This is a bit alarmist. The numbers you have found are correct, approximately 1.4 times the force, not double. 


So, you just have to be aware of when this might be an issue, such as high fall factor falls.  High ff’s are most like early in the pitch or when really run out. Placing solid gear early and often helps to mitigate this. This was discussed a few years back. It turns out many people in Europe will alternate between half and twin technique even in a single pitch, even some well know pros. YMMV
Christopher Woodall · · Somerville, MA · Joined May 2015 · Points: 168

Only use your rope for what it is rated to. If you buy ropes rated as half and twins go for it. The only thing I would be cautious with is you probably shouldn't project with a triple rated rope.

Greg D · · Here · Joined Apr 2006 · Points: 877

Keep in mind, there are plenty of half rated ropes that could pass the twin test. There are fewer twin rated ropes that would pass the half rope test.  .  But, additional certifications are costly.  

So, you are probably ok, in most situation using halves like twins, but not the other way around. Maybe Jim Titt or rgold, both use two ropes, will chime in.

Michael Tilden · · Boise · Joined Aug 2016 · Points: 0

The ropes I’m particularly concerned about are the beal cobra 2s.

Alone they have have impact force rating of 5.1 kn. 
If twinned a fall should generate 7.14 kn according to the 1.4 force increase when both ropes are run through one peice of protection. (5.1 x 1.4 = 7.14) 
To me this seems more than acceptable considering many ropes generate impact forces of 8 and 9 kn. Again I’m trying to make sure.

Greg D · · Here · Joined Apr 2006 · Points: 877

(procrastinating house work)

Yes, what reboot said.  Keep in mind, those impact forces are test results of a very severe fall (1.77 FF, rigid 80kg mass), not what you would see in real life with a squishy body, deforming harness, movable belayer, etc.  You would have to work very hard to duplicate that scenario.  

rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526
Kevin Mcbride · · Canmore AB · Joined Jan 2017 · Points: 160

PAGING JIM TITT

Jeff B · · San Diego · Joined Feb 2018 · Points: 0
https://petzlsolutions.com/technicalsolutions/half-rope-vs-twin-rope

If you had a single line of protection to use it like a twin, why not just clip every other piece with alternating ropes so you are using your double as a double?
coppolillo · · Unknown Hometown · Joined Sep 2009 · Points: 70

Bunch of good ropes rated both twin and half----the Edelrid Apus 7.9mm and Skimmer 7.1 being two awesome examples. Functions perfectly as twin or half.....made in Germany, too! 

Jim Titt · · Germany · Joined Nov 2009 · Points: 490
Greg D wrote: Keep in mind, there are plenty of half rated ropes that could pass the twin test. There are fewer twin rated ropes that would pass the half rope test.  .  But, additional certifications are costly.  

So, you are probably ok, in most situation using halves like twins, but not the other way around. Maybe Jim Titt or rgold, both use two ropes, will chime in.

You will find it hard to buy a rope only twin rated nowadays, cant think of one at the moment.

Jim Titt · · Germany · Joined Nov 2009 · Points: 490
Michael Tilden wrote: The ropes I’m particularly concerned about are the beal cobra 2s.

Alone they have have impact force rating of 5.1 kn. 
If twinned a fall should generate 7.14 kn according to the 1.4 force increase when both ropes are run through one peice of protection. (5.1 x 1.4 = 7.14) 
To me this seems more than acceptable considering many ropes generate impact forces of 8 and 9 kn. Again I’m trying to make sure.

The impact rating on ropes is pretty irrelevant most of the time, considering the braking foce most belay devices generate with thin half/twin ropes obe is only happy to experience any sort of force at all if one falls off

Guideline #1: Don't be a jerk.

Trad Climbing
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