Chockstone Forum

      Sponsored By
      ROCK
   HARDWARE

Chockstone Photography

Australian Landscape Prints

Chockstone Forum - Gear Lust / Lost & Found

Rave About Your Rack Please do not post retail SPAM.

Author

Double rope diameter/ratings

oldgranite

14-Jul-2011
9:07:16 AM

Hi,
So I am thinking about trying this double rope thing. I have tried it with my single 10.5 tied into the middle and like it, and want to try it on longer routes. I have done a lot of reading online including the tech tips page but can't find the specific answer I'm looking for.

My question is this: Can I use double rope technique with ropes of different diameter/rating? For example, to save me buying a whole new set of double ropes, could I keep using my 10.5 and pair it with another single (say a 9.5) or a 'double' rated rope (say a 9 or even a 8mm?). Will the difference in stretch and rope diameter cause issues?

I understand (I think) the difference in ratings, but am interested to know if this would create real world issues when two ropes of different elongation/rating/diameter are used together in a double (or twin) rope system. Also, are the ratings of ropes setup so that 'single' is always 'better' ie: would using two 'single' ropes, of the same rating/diameter/manufacturer in a double or twin system be generally better than using ropes rated for that purpose.

I have used a tag line when canyoning with a biner block to abseil the single line, and figure this would be the way to go when abseiling with two ropes of different diameter, so you abseil on the 10.5 and pull the 8mm double as a tag line. Or would a well tied and stoppered overhand be sufficent?

Eduardo Slabofvic

14-Jul-2011
11:05:36 AM

I have no idea what the text book will say, or indeed what the technoweenies will say, but I've been using different diameter twin/double (which is which I don't know) for years and am still here to type about it. I say go for it.

My current double rope set up is a 9mm and a 8.5mm. this is because i look at those 7.5 or 8mm ropes and think they look like really long shoe laces.

Sabu

14-Jul-2011
11:28:47 AM

I doubt it would negatively influence safety much. Although I'd still pay close attention to belay techniques (given one rope might have less friction than the other) and knots when tying them together for a rap (I have no idea how different diameters interact with certain knots).

gfdonc

14-Jul-2011
1:02:45 PM

My honest and correct answer is: I don't know.

I think one of the manufacturers and certainly sometimes online retailers will advise "must be bought in pairs". The drop testing for half ropes is done on one strand with reduced weight, so in theory two different ropes that meet the standard can be used together. I've often thought this test was flawed since in many real-world situations one strand will take most of the force.

My advice is, going with a slightly thicker rope never seems like a bad idea, except when using twin (rather than double) rope technique (due to increase in impact force).

I regularly climb on a thin single (9.7mm) with a half-rope (8.1mm these days). Refer Eduardo's comments.

GriZZly

14-Jul-2011
1:09:52 PM

As Ed noted hes still alive and generally there wouldnt be an issue in climbing on one half rope (or one double) and a single rope as its almost impossible to fall on both equally if youre clipping different gear with different ropes.

The main difference is that thinner half ropes generally have a lower impact force and as such climbing on 2 singles means that there is a higher impact force transmitted to you, but as above its unlikely you cop much more impact force due to generally only falling onto one rope at a time.

The main reason people dont climb with singles in a half rope format is theyre too bloody heavy.

I wouldnt recommend abseiling on an overhand with different sized ropes as theres a much higher chance of them slipping through each other but as always you make a decision in the particular situation. If theres no edges for it to get caught on a double fishermans is a better bet.

citationx

14-Jul-2011
1:13:39 PM

On 14/07/2011 GriZZly wrote:
>I wouldnt recommend abseiling on an overhand with different sized ropes
>as theres a much higher chance of them slipping through each other but
>as always you make a decision in the particular situation. If theres no
>edges for it to get caught on a double fishermans is a better bet.

This was the only point that I had. I don't know where i got the info (doubt it was in a text book, though) but if you have very different diameters you can have troubles with the EDK slipping a bit. If I do use an EDK with two greatly different diameters I pull each and every tail (all four) in the knot individually, sometimes twice, to make sure that the knot is really nice and snug. Having said that the biggest difference I've ever used would be around the 8.5mm and 10.2mm diameters... (thinking about what ropes i've had)

mikllaw

14-Jul-2011
1:21:59 PM

On 14/07/2011 GriZZly wrote:
>The main difference is that thinner half ropes generally have a lower
>impact force and as such climbing on 2 singles means that there is a higher
>impact force transmitted to you, but as above its unlikely you cop much
>more impact force due to generally only falling onto one rope at a time.

Until i got a pair of free 9mm ropes on facebook (being discarded as they looked thin) I climbed on a 10mm / 8.5 mm combo and had no issues except
1) the thinner rope slips more when belaying, don't clip the first piece with the thin rope
2)Abseilling the thinner rope will slip more and can cause know shift
and
3) below

>I wouldnt recommend abseiling on an overhand with different sized ropes
>as theres a much higher chance of them slipping through each other but
>as always you make a decision in the particular situation. If theres no
>edges for it to get caught on a double fishermans is a better bet.

3) I've used an EDK pulled tight with another EDK straight behind it.

oldgranite

14-Jul-2011
1:27:58 PM

Thanks for all the replies. Good to know a few people have done it and lived to type the tale.

Forgive my ignorance, but when you talk about twinning the ropes causing issues with increasing the shock load to the climber (which I get) does the same thing happen when you 'mix and match' styles - ie first few bits of gear twin the ropes, then clip seperately - in my head this doesn't have the same effect - it would seem to be that whatever the last bit of gear that was clipped is most important, so if you clipped seperatly, then twinned them, and fell, you would be causing that shock load issue?

Fish Boy

14-Jul-2011
2:46:10 PM

the rope speeds will be diff if you fall, so if changing between twin and double rope technique, always clip ropes through seperate biners to prevent meltdown.

MichaelOR

14-Jul-2011
3:27:36 PM

On 14/07/2011 Fish Boy wrote:
>the rope speeds will be diff if you fall, so if changing between twin and
>double rope technique, always clip ropes through seperate biners to prevent
>meltdown.

Absolutely correct! I used doubles for years - particularly useful when climbing at Araps.

Different diameters (even different brands of rope with same diameter) will stretch differing amounts. Also, if used as doubles (not twins always clipped into the same gear, every piece) then differing lengths of each rope will invariably be in use - climb and gear wanders. That means different amount of stretching even if ropes identical.

So in a fall the two ropes stretch differing amounts. IF they are clipped into the SAME biner then you will have rope rubbing against rope in the fall. This is not what you want. This could be a problem particularly if ropes are together in the last bit of gear.

There are 10 messages in this topic.