double rope question

7:10 a.m. on July 24, 2001 (EDT)
(Guest)

Hi!
As I know, big difference in diameters between two halfs of a double rope increases tangling.
Does anybody know, what difference is not too much? Say, is it okay to use 8.6+10mm or 9+10mm pair?

thanks in advance

Gr.

2:01 p.m. on July 25, 2001 (EDT)
0 reviewer rep
408 forum posts
Hmmm....

Quote:

As I know, big difference in diameters between two halfs of a double rope increases tangling.

Not that I've noticed. Why do you think this? What is the mechanism?

Quote:

Does anybody know, what difference is not too much? Say, is it okay to use 8.6+10mm or 9+10mm pair?

Question is, why would you? If you are worried about cutting one over an edge in a fall, then, double ropes make sense, at any diameter, and...for my money, heck, make 'em both 11.5's!

What situation do you imagine using a fat and skinny together in perfect harmony?

Brian in SLC

2:41 p.m. on July 25, 2001 (EDT)
(Guest)

ebony and ivory

Only one time I have heard of this mixing of diameters for climbing(crazy kids).

A couple of really techy aid climber friends of mine, and I mean techy on a higher level than you thought possible, used two different diameter ropes for hard aid climbs. They would clip the fatty into the bomber pro and the skinny rope only into the "sketchy" body weight type pro. Their resoning was that the greater elongation of the skinny rope(thus greater force distribution over time) would allow them to eek out a little more from the bad pro, thus making it less likely to rip out in a fall.

Seemed to work ok and the reasoning is sound. It just adds another system to an already overly burdensome aid system. As for free climbing like this.

I am with you. If you are doing something to risk cutting them, go fat. If you are alpine climbing, go as skinny and light as possible.

matt s

10:38 a.m. on July 26, 2001 (EDT)
(Guest)

Re: Hmmm....

Quote:

Quote:

As I know, big difference in diameters between two halfs of a double rope increases tangling.

Not that I've noticed. Why do you think this? What is the mechanism?

When descending on double rope, skinny half twists around fat half because of different elongation.

Quote:

Quote:

Does anybody know, what difference is not too much? Say, is it okay to use 8.6+10mm or 9+10mm pair?

Question is, why would you? If you are worried about cutting one over an edge in a fall, then, double ropes make sense, at any diameter, and...for my money, heck, make 'em both 11.5's!

What situation do you imagine using a fat and skinny together in perfect harmony?

Brian in SLC


I want to use them for alpine climbing. The idea is to use only single fat rope when moving simultaneously and switch to double rope when it gets harder. I've never heard about a technique like this, but it looks quite reasonable!

Gr.

11:12 a.m. on July 26, 2001 (EDT)
0 reviewer rep
408 forum posts
Yeah...

Quote:

Quote:

Quote:

As I know, big difference in diameters between two halfs of a double rope increases tangling.

Not that I've noticed. Why do you think this? What is the mechanism?
When descending on double rope, skinny half twists around fat half because of different elongation.

Might could but not with an ATC or like device. At least I've not experienced it. Perhaps with a figure 8. But...with a figure 8, could be any diameter...! But...I wouldn't thing a difference in elongaton would matter with regard to twisting...but...I guess you could see twisting in each rope and one might be more pronounced but I'd think more due to difference in diameter than elongation...and rap technique (how rope is fed thru the device).

I've descended bunches of times on two very different ropes, including the biggest elongation difference, a static with a thin dynamic (also, a 7mm polypro and a 7.8mm ice floss). Noticed no twisting. Sometimes, if I orient the rope into the ATC at an odd angle to try to increase friction, I notice a twist below the rap device but thats not related to elongation or difference in diameter.

Quote:

I want to use them for alpine climbing. The idea is to use only single fat rope when moving simultaneously and switch to double rope when it gets harder. I've never heard about a technique like this, but it looks quite reasonable!

I'd just save the weight and use two skinnies. But...yer method would work just fine too!

Brian in SLC

12:07 a.m. on July 28, 2001 (EDT)
(Guest)

Twist

As Brian, I never noticed any twisting descending on ropes of different diameter with ATC or Gi-Gi. With a figure eight, ropes get twisted in any case, any diameter any difference between them.

Your system has no problems thoretically, bu it could be redundant and imply loss of time. You can move simoultaneusly with a couple of half ropes too, whereas tying and untying and getting on and off the second rope needs time and work. Making up and unmaking ropes (I mean making and unmaking a skein to put the rope in the pack or on the back, sorry I don't know the right expression) will also give to tangling the best opportunities.

Fil K

10:43 a.m. on July 30, 2001 (EDT)
(Guest)

Many Times

I have for many years used a 9 and 10 mm combo for multipitch climbs and continue to do so regularly. Why, you may wonder? I like having the versatility of a single rope on hand. If I'm on a trip I'll normally use the combo but I can still take a day at the crags and sport climb or do 1-pitch routes on the 10. It also saves wear on our double-rope sets that I want to use when weight is a real issue. I normally use a 10 with an older 9. I also like the increased cut resistance of a 10 on harder rock routes. When climbing as a threesome, we can put the big boy on the 10 to follow so we're not as concerned about rope stretch and cutting. As for twisting, I try to be very particular about rigging belays so that the difference in friction doesn't become a problem. A straight run is important in any case. For different diameters I try to always use an oval carabiner for running the re-directed ropes through (for any ropes, really). This seems to keep side/twisting forces about equal. I have had no twisting problems as a result of rapelling (sticht plate)unless I accidentally rig it backwards, i.e. bottom-to-top. Weight and rope drag have not been problems. The only possible negative to this system is increased impact force during a fall, but I think this is a very minor consideration. Hope this helps.
RP

8:46 p.m. on December 19, 2001 (EST)
(Guest)

Quote:

Hi!
As I know, big difference in diameters between two halfs of a double rope increases tangling.
Does anybody know, what difference is not too much? Say, is it okay to use 8.6+10mm or 9+10mm pair?

I have used double rope technique for many years including at times with different size ropes.

First, just a caution that you should study and understand the system intimately before relying on it.

Second, once you master rope handling skills, double ropes are safer and just as quick and expedient.

Third and most important: I strongly suggest that when rapelling, the larger diameter rope be placed through the anchor with the knot on the small rope diameter side. From personal experience I know that if the ropes are placed with the knot on the big rope side, that as you rapel, the knot can "follow" you down the rapel because of the increased friction through the rap device by the big rope. (do an experiment in your basement. Think carefully about the implications please). Luckily,in my case I spotted it as I started the rapel. I know this can cause a slowdown on multiple sequential fixed station raps (can't beleive I said that) but a fatal fall off the end of the rope will cause permanent and severe metabolic slowdown.

November 20, 2014
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