Double ropes, twin ropes, and half ropes?

[Rodchester]

Well, I have head from two companies and below is their responses. Not much help. I have to ask myself, If they don't know who does?

First response from Scott Newell of Blue Water Ropes:

There is indeed no such monster as a "double rope". The UIAA designation is 1/2 rope. Two halfs make a whole. If you look at the last rope review in Climbing Magazine, they explain the difference. I believe "double rope" technique has been carried over to describe the ropes themselves. Half ropes are tested on the drop test tower with a single rope and a 55kG falling mass. Twins are tested with two ropes and an 80kG falling mass [the same weight as a single rope]. It is confusing when people look at specs for twins and half and the twin seems to have better specs. But, you are not comparing apples to apples due to the different testing technique. I have our current twin, the ice floss, at the testing lab right now. I am having it tested as a half as well as a twin and will post the specs and attempt to show the different results. The new website will be up in about two weeks. Hopefully the results from the certified test lab are back by then.

Scott Newell

Second response is from "Jeff" at BD. Even less help:

I'll respond to you and you can use my reply if you wish, or parts of

it.

Note B.D. is not a manufacturer of ropes...ours are made for us by either

PMI or Beal

Half Ropes and/or double ropes are the same thing. Generally you don't hear the term double ropes much anymore. These ropes are usually between 8mm and 9mm and must be used in pairs. They are versatile for long wandering routes because you clip them alternately and/or to the right and left to help prevent rope drag. As well they also have benefits when a long rappel may be in the works or falls where there is potential for sharp edge to chop a rope.

 

Twin ropes must be used as one, with both ropes clipped into each piece of pro. These are usually around 8mm or even smaller in diameter. Not as popular as the above.

Hope that clarifies a bit.

The Climbing Magazine Gear Guide 2001 has a great section on ropes and

the differences. You might check it out.

Regards,

-Jeff

 

[jon]

I’m not sure whether I’m restating what has already been stated or stating the obvious. Rodchester, if I understand your question you want to know what the physical property differences are between the half and double ropes. I don’t know really how they make the ropes and adjust the dynamics of the rope, but there has to be a difference between ropes. Here is my understanding based on physics. You Boeing and engineering guys feel free to chime in here.

Lets say you fall climbing with a single rope. The rope is designed to stretch and thus absorb a certain amount of your downward force so you don’t get hurt or rip out your top piece by having to large of a final impact force. Now lets say you are climbing with two single ropes, let’s say 10.5s same as above for comparison sake. If you fall, because two ropes are absorbing the force, they won’t stretch as much, and thus slowing you fall quicker, producing a larger shock load when the rope stops stretching. I don’t know if they have some equation for this, but there must be some relation between the fall force and stretch characteristics of the rope versus where the rope actually stops stretching.

So my assumption is that there is a difference in stretch characteristics between the double and twin. If my above example is right, the twins will have to stretch somewhere close to twice as much as a single to have the same minimal impact force as a single. Now with the double, because you would fall on either one rope alone or a combination of the two, but not two equally unless you clipped them into the same piece, there stretch would be comparable to a single, if not just a bit more. Someone stated that with twins you would be putting twice as much force on your pro. I don’t believe this to be correct. There might be more based on the rope stretch dynamics, but if they are designed right, there shouldn’t be a difference between twin and single. If all my examples are right, there should be a differences between the two.

I hope I’m somewhat correct and answers the questions.

word up

Jon

 

 

[Guest]

OK, great! Now I feel that I don't know s*** about the issue.

So there are ropes designated as half by the manufacturer. When climbing on half ropes using the double-rope technique we'll always fall on one, single rope. Why not then use just that one rope all the time? Would be much lighter to carry, right?

Of course it is easier to hit the ground falling from the first piece and possibly easier to cut through (is it?).

So basically does the "half" designation mean something about the strength or is just a suggestion that it's advantageous to use in a double-rope setup because of the weight savings? Or do they mean that the number of falls on "half" ropes is less?

Does "twin" mean one must NEVER clip them separately or they will break after a couple of falls? Or the stretch during the fall and stretching over the lifetime of the rope are undesirable but if I wanted to use a new pair of "twin"-s just once on a generally overhanging terrain it is just fine to use them in a double-rope setup?

Finally why would they test the "half" ropes with a lesser weight (55)? That distorts the comparison to "single" ropes.

Now I suggest coming up with a set of questions and sending it to the Climbing, BD and rope manufacturers.

[Guest]

OK, this is what I got so far from Helmut Microys, National Delegate to the UIAA Safety Commission for the USA and Canada.

(Sounds like those PMI 8.1 are a great deal).

First of all let me mention that the provider of the UIAA web site went bankrupt recently and it will be a while before a new one is operational. However, you would not have found the information you are looking for at this site.

 

The UIAA standard deals with three different rope types: single, half and twin. In the UIAA drop test the single rope is tested with an 80 kg mass, a single strand of half rope with a 55 kg mass and both strands of a twin rope with 80 kg. The single and half ropes must sustain at least five falls and twin ropes at least twelve to pass the standard. There are also differences among these ropes for elongation and impact force (single and twin < 12 kN; half ropes < 8 kN).

 

Single ropes are obviously designed to be used in a single strand.

 

Half ropes, or double ropes, are designed for (aid) routes with many runners at close spacing and are then clipped in alternately. The idea was to reduce friction, particularly in the days, when climbers used only carabiners and no sling extensions (the rope went zig-zag). These ropes should not be used in this way (i.e. clip in alternately), as often happens these days, for regular routes with runners further apart. Keep in mind that the rope is not tested with an 80 kg mass. A single strand of half rope, when new, may just hold one fall with such a mass.

 

The twin rope was designed to be used in the double strand and both strands must be clipped in every runner. Generally these ropes have a diameter of only 8 mm. The benefit of a twin rope is its essential safety and the advantage in the mountains for a full length rappel.

 

Present day ropes will not break at a runner or at the tie-in knot of the leader in a fall. This does not even happen with very old ropes. A rope fails when a sharp edge cuts it. As a rope is used, the capacity to hold a fall over a sharp edge decreases. Generally speaking, a rope which holds many falls in the UIAA drop test will resist cutting better than a rope which hold fewer falls.

 

A half rope used singly is, therefore, much more likely to be cut than a single rope. It could potentially be used for all climbing, but you better not plan on falling off. A twin rope is much safer, because of the higher capacity and the redundancy (only one strand may be cut). Using half ropes like a twin, clipping both strands in every carabiner is, of course, the safest solution (a pair of decent half ropes, tested like a twin rope will most likely hold over 30 falls).

 

The maximum allowable elongation for half ropes (10 %) is indeed larger than for single or twin ropes (8 %), but this would hardly be noticeable in most fall situations. Elongation is more often than not only a problem for a second with the rope out 100 feet. An 80 kg climber could drop eight feet under body weight even though the rope contains no slack.

 

Final advice: do not use your half rope as a single strand and when the runners are further apart, clip both strands. You only live once.

 

Ice climbers in USA routinely use the double rope technique placing gear (ice screws) very sparsely using half ropes.

So:

1. In this situation is the second half rope for backup purposes?

 

On pure ice faces and water falls, there are generally no sharp edges and the danger of cutting a rope are greatly reduced. A new half rope may be reasonably safe, although I would advice against it when there is a lot of dry tooling and runners are still far apart (I personally would not climb on it regardless of the situation). In the latter case it may be called a back up rope, because of cutting on an edge.

 

When the climber is on a water fall or smooth ice face, where there is no friction to speak of, the question can be asked, why not climb with a single half rope and clip all the protection. The result would be pretty well the same in a fall situation as having two ropes. If the rope breaks, it is because the fall energy was beyond the capacity of the rope. With two ropes clippped alternately and the runners the same distance apart, if the first rope breaks at the first runner and the second will fail on the one below.

 

One of the reason for two ropes on waterfall ice is that one must generally rappel and two ropes get you down faster and cheaper.

 

2. If I were to clip both half ropes together into one carabiner, wouldn't that increase the load on the protection beyond safety levels for the carabiners and protection as opposed to a single or twin setup?

 

Using two half ropes clipped in together will produce forces on the protection higher than when using a single rope. Twin ropes act like a single rope.

 

The forces in the system are, however, determined by the belay method. Any modern dynamic belay method will limit the forces inherent in the device. The impact force (the maximum obtained during the UIAA drop test) and provided on the rope tag, is of no consequence. Thus the forces generated, particularly in a near frictionless system, which may occur on a waterfall, are not very high.

 

These forces are, as a rule, vastly below the capacity of any equipment (carabiners, ice screws, pitons, slings, etc.). The problem lies in the holding capacity of the ice screw, piton, nut, etc. If the ice is of poor quality, a screw capable of holding 20 kN in good ice is no more helpful than a coat hanger, if that is the holding power of the ice.

 

So in a scary, poor ice, situation the only thing, which may be of value, is to put protection at very close spacing. That unfortunately is often not possible. But it would help to clip both ropes in the last bomber protection.

 

3. How soon/often do I have to retire the half ropes provided I take falls on them (very few climbers are 55kg and under, I am 90kg)?

 

If there are no sharp edges, a rope could most likely be used until the mantle starts shredding and can no longer be used in a belay device. This applies mainly to a single rope. The half rope is simply not designed to take major leader falls. But as mentioned before, the forces in the system are determined by the belay device. With a properly working dynamic belay, not much will happen to the rope. Do not belay with a static belay device such as a Grigri, which should be used for top roping only.

 

4. Is the conclusion that one just should not buy or use half ropes? Or they are still manufactured for cases where falls are not dead vertical, in alpine terrain wit lots of rope drag? Or perhaps they are manufactured out of inertia and for marketing purposes?

 

They are most useful in alpine terrain where lots of friction may result, if the ropes are clipped in all the runners. An additional advantage is that there is a backup rope of sufficient capacity, should a rope be cut by rock fall. Finally the rope offers redundancy in the case of sharp edges. Double ropes have more holding capacity over an edge to start with. Even if both ropes run over the same sharp edge, it is less likely both get cut because one will get loaded more than the other. In a retreat, being able to rappel the full length of the rope is invaluable.

 

The other option is to climb with twin ropes. Extra edge strength (remember twelve UIAA falls minimum), redundancy, lighter ropes, in a severe case the option of clipping in alternately, rappel convenience.

 

I personally have not owned a single rope for at least 25 years. I used to climb with two half ropes and clipped them together when it was suitable. Now I climb with twin ropes. I use these ropes in any terrain.

 

[dan_e]

That guy apparently knows what he is talking about and has confirmed that I have been using half ropes correctly. I have decided however to now climb mainly with twin ropes. Clipping alternately is a pain anyway and requires an even more attentive belayer. Like he mentioned in the post, the correct use of slings should eliminate or at least help reduce rope drag. Crossing half ropes is also a problem when clipping alternately.

 

[This message has been edited by dane (edited 04-03-2001).]

[goatboy]

For some great visual aids relating to all of this comparative rope technique analysis, see Freedom of the Hills (5th Ed) pp. 227-230.

Steve

[Zenolith]

Great job hunting down that information! Sounds like twins are the way to go for everything. I bet I'll get some odd remarks and stares at Smith when I'm climbing Moonshine w/ twins. Two more advantages of twins are the ability to divide up the weight more evenly on the approach and the need for just one twin for glacier routes.

[none_dup1]

This is very helpful, but makes me think I've been taking unnecessary chances. For several years I have climbed with a lone 9mm Stratos (a "1/2 rope") on everything from alpine 5.8 to slab routes like On Line. For harder routes I use the single 9.4mm Beal Stinger. If long rappels are expected, we carry a second rope in the pack, which makes belaying simpler and cleaner as you only have one rope to worry about. I have not been concerned about tying a 9.4mm to a 9mm for rappelling, and have even used the overhand knot (aka "European Death Knot"). Perhaps this has been foolish. What do you think?

Thanks,

John Sharp

[Guest]

To MrGoodTime:

1. Did you fall on your 9mm Stratos, what kind of falls and how many times? Just curious, because if no falls - no pro/con.

BTW, I rappeled from Online with a 10.5 and 8.0 tied with an overhand - knot was fine all the way down. The thin rope keeps feeding through the bealy device so knots at the end are important.

2. All the info from the topic hasn't given me an complete understanding of this seemingly simple issue. Twin ropes are easy - just like a single but 2 strands. The problems begin when you can't have all the different setups and in ice climbing where the leader more often than not moves quite a bit around. Not only twin on ice would then create excessive rope drag quite routinely but there is also that desire to reduce the fall force on the ice pro. This winter I climbed on 8.1 PMI and fell on one strand top-roping - it's a long fall. Belaying issues apart I think climbing on a thin rope is quite commiting and I personally am not comfortable leading on a 8.1. Above that it's the half-rope domain and the most uncertainty. So, as soon as I have some time I am going to actually test 2 9mm New England ropes I have with 80 kg at Ex38 and see what happens. I'll post the results. Anybody haas an appropriate dynamometer?

[This message has been edited by rafael (edited 04-05-2001).]

[none_dup1]

I have taken slab sliders on a 9mm, but no long falls completely in the air.

[Dru]

One thing I haven't seen mentioned at all on this thread refers to using half ropes and sketchy gear, and can be seen in Hard Grit or just about any shot of a Brit climbing (unless its on a boulder). When the gear is sketchy and may or may not fail in the event of a fall, you put in two pieces almost side-by-side and clip one of your two half ropes into each. Then if you fall and one piece blows but the other doesn't, you don't fall as far. Or you can climb on one (9.5 mm type) but use the other (8.5) as a directional, so that if you fall you get swung away from manky death pokers towards your directional piece. this is a little bit different than the "alternately clip each rope" scheme.

[Latch_Holeflaffer]

I am also considering going to half ropes, 8.6 mm Roca Fanatics, and I am concerened about a hard fall one one strand. Let's say you were looking at a good size runout and all you had to clip was one piece of gear. Now I know you don't want to clip them both into the same biner. Is their any reason you wouldn't want to clip a quick draw to one rope and a runner to the other off the same good piece? You use both ropes to catch the fall, but the catch would be softer because the second line would not come into play at the same time. What do you think?

[dan_e]

I would do that, as long as the ropes are not going through the same biner. The piece may indeed be loaded at different times. I would only do this on bomber pieces. I like the idea of clipping in each rope to a piece that's close together, I may start doing this more with those sketchy pieces.

[Nick]

There is an excellent and very clear exposition of these differrent kinds of rope, how they are used, and why, in Mark Twight's book "Extreme Alpinism". Everyone should read this book right now.

[Gerg]

I've begun actively looking at twin ropes. The lightest I found was the 7.5mm Twighlight by Mammut. But, this is below the recommended limit of my ascenders (8mm minimum). When I posed the question to Petzl, this is what they said:

 

Hello Greg,

There is no question that the handled ascenders will grab a Twilight rope.

However, Petzl has not done any testing on a 7.5mm rope. As a company line

we can only recommend a rope down to 8mm. If you use the rope grab on rope

thinner than 8mm you are doing so at your own risk and without Petzl's

recommendation. I would suggest that you take your rope to a good

specialty shop with the capability to allow testing of your setup before

purchase. I hope this helps Greg. And as always stay safe and know your

system.

Crandall Caughman

Petzl America

800.686.6206

ccaughman@petzl.com

 

Going to my local shop, I used a 7mm Beal rope to witness that a Petzl ascender would grab a rope that small (unweighted), but could not test a weighted rope. Even with an 8.1mm twin rope, this seems pretty sketchy with all the rope stretch and the probable amount of quickly induced ascender related wear on the rope.

So, is there a good way (prussiks) to ascend twin ropes in the event that the pitch is too difficult for the second to free climb?

If in doubt about the second being able to free climb the pitch, would half ropes (juggable) be recommended?

Greg

[dan_e]

I wonder how small ropes can get and still be safe? I don't think I will ever use anything under 7.5 mm as trying to hold ropes smaller than this in a fall would be like holding on to dental floss. I am actually going to stick with 8 mm as my minimum.

[Gerg]

Here's the official word from Mammut on their Twilight ropes and the use of ascenders.

-Greg

------- Forwarded message follows -------

From: "Bob Kennedy" <METOLIUS2/USER7>

To: METOLIUS2/USER3, METOLIUS2/USER4, METOLIUS2/USER5, METOLIUS2/USER12

Date sent: Tue, 10 Apr 2001 09:24:17 -0700

Subject: Re: some answers

Send reply to: bkennedy@metoliusclimbing.com

 

Information from Rene at Mammut:

 

2. Jumar on Twilight

>

> From what I know, there is no Jumar on the market which has the approval to

> be used on 7.5mm ropes.

> Also we wont advise to use a Jumar to often on a Twilight, since due to the

> lower amount of material in the sheeth the rope will tend to wear out much

> faster than other diammeter ropes.....just remember that the sheet on the

> twilight

> is made on 32 bobbins, compared to the previous line of twins (Genesis) which

> was made on 40 bobbins. So if you jumar on a twilight.....it simply wont

> last long, it's not recommended (at least run a seperate belay line to the

> person who climbs on the jumar) and it's also just not made for this.

>

> Take care and have a great day

>

> M A M M U T

> Alpine & Outdoor Sports

> Mr. Rene Meuli / Export Sales Manager

>

>

------- End of forwarded message -------

Chris Kratsch

Customer Service

Metolius Mountain Products

V: (541)382-7585

F: (541)382-8531