twin/ half ropes

[Zenolith]

yes, erik, this has been discussed before, but i forgot and those searches are irritating.

in the new bd catalog they have the "ice line" and the feller i asked at bd said its a 1/2 rope. i wondered if it could also be clipped into one piece (a screw on a pure ice climb) and he said, "those ropes are new and i haven't tried them yet" which convinced me that he was an idiot, so i spat and hung up.

i would like to know if there is a 1/2 rope which offers enough stretch to be safely clipped to one peice as is usually done on ice climbs.

the "ice line" is 8.1, 8 falls, 4.9kN(55kg), 10% stretch, and pretty light at 42g/m.

because of the low impact force i wonder if it might be reasonable to do an entire ice climb with both ropes cliped to each screw. and then i wondered to myself, "what is the advantage to that, huh?" does anyone have an opinion?

[erik]

zeno

check out edelwiess ropes and i know mammut is/or has coming out with a super safe rope in a samller diameter......

enjoy

do you still want those screws too??

[jon]

http://www.cascadeclimbers.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=000254

[Zenolith]

thanks jon, i couldn't find that one. and erik, yes, yes i do want those screws.

[scott_harpell]

yeah i cant remember what brand...but there i like a new 9.7-8mm rope that is a 10 fall rope....i dotn know if that would suffice....

[Ibex]

quote:

---

Originally posted by Zenolith:

yes, erik, this has been discussed before, but i forgot and those searches are irritating.

i would like to know if there is a 1/2 rope which offers enough stretch to be safely clipped to one peice as is usually done on ice climbs.

---

Zeno,

quityerbellyachin and do a search. the tech-heads on here debate this about once a month.

In answer to your question, I beleive PMI makes a rope that can be used as EITHER a half or twin. check out www.pmirope.com and read up on it.

Cheers

Shawn

[verticalturtle]

The shortest answer is yes you can clip both, but the impact force will be greater.

vt

[Gerg]

PMI Verglas

UIAA Ratings - Half / Twin Weight (per meter), 40.9g. Number of UIAA Falls, 8 / 12 (single strand with 55kg load) (two ropes with 80kg load) Impact Force, 5.8 kN. / 8.4 Static Elongation, 10% / 8%Elongation after 1st fall 36% / 34% Sheath Slippage, 0 mm.

So verticalturtle's statement is correct, but the impact force of double clipping THIS rope is comperable to a larger diameter single strand.

g

[goatboy]

My understanding is simplistic, but here goes:

Clipping two 8 mm ropes into one piece is similar to clipping one 16 mm rope into the same piece.

It increases the force placed on the piece in a lead fall by reducing the dynamic properties of the ropes.

Still, there are times when it's best to do so, ie. protecting both seconds on a short traverse, when you want both ropes clipped in to each piece.

[chucK]

quote:

---

Originally posted by goatboy:

My understanding is simplistic, but here goes:

Clipping two 8 mm ropes into one piece is similar to clipping one 16 mm rope into the same piece.

---

It's not that bad. It's more like an 11.3mm rope. That is two 8mm ropes have about the same cross-sectional area as one 11.3mm rope.

[Gerg]

For comparison, here are some single ropes from Mammut. The numbers correspond to Impact force (kN).

Flash 9.2 (10.5mm)Galaxy 8.9 (10mm)Tusk 8.7 (10mm)

The stated impact force for the PMI Verglas when used as a twin rope is 8.4kN. This is actually better than the Mammut single ropes! But, having a dynamic belay can have the most significant effect on reducing the imact force, so perhaps this is all a moot point?

greg

[Gilles]

I used to own 2 Beal 8.1 ice-line bought in France. They are good, you can clip 1 or both ropes, they wear out fast - not to be used on rock. The waterproof coating degrades in no time.

I now own 2 PMI verglas 8.1. Same thing, either clip 1 or 2 ropes. They seem to resist more than the Beal (although if I'm not mistaken, PMI is a joint-venture of Beal and a US company). They're a bit more water-resistant, but I avoid the rock.

They all make nice spaghettis very easily.Gilles

[IceIceBaby]

What will be the best single line +(6mm) rap line combo

Im looking for the lightest single rope out there I heard that there is a 9.1 single line out there but Im not sure

[al]

Beal's Stinger, at 9.4mm is the lightest advertized single I'm familiar with. My alpine rope is a Beal Booster, 9.7mmX50M, at 62g/Meter and impact force of 680 daN.

Forget the 6mm. I went that route before and spent 30 minutes untangling it after the first throw. It'll tangle like fishing line. My extra/rap rope is a Beal 8.1X50M Iceline. Light weight for the second to carry, yet good enough for a third to come up on.

[freeclimb9]

quote:

---

Originally posted by scott harpell:

yeah i cant remember what brand...but there i like a new 9.7-8mm rope that is a 10 fall rope....i dotn know if that would suffice....

---

Bluewater Lighting Pro: http://www.bluewaterropes.com/Dynamic_Ropes/DynamicRopes-9.7mm.htm

[David Yount]

Zeno: because of the low impact force i wonder if it might be reasonable to do an entire ice climb with both ropes clipped to each screw. and then i wondered to myself, "what is the advantage to that, huh?" does anyone have an opinion?

Idea_Guy: Related to maximum impact force the ropes will place on belay system (the only concern is on the actual placement):You can use half-ropes by clipping them into each screw, together. The impact force will be safe, because the UIAA won't certify a half-rope unless the impact force of 2 half-ropes clipped together is less than the maximum impact force for a certified single-rope. That maximum impact force for a single-rope (or 2 half-ropes clipped into the same piece) is 12kN. Typically 2 half-ropes clipped together exhibit impact forces far lower than maximum allowable; the PMI 8.1mm half-rope named Verglas generates a maximum impact force of 8.4kN in the UIAA tests (when tested together). Whereas many single lines generate larger maximum impact forces than 8.4kN in the UIAA tests but 12kN is allowable.

If you would lead a route on a single line then you can lead on a pair of half-ropes clipping them together at every piece.

Related to sheath burning:If you are going to clip both half-ropes to every piece then you may clip them through the same biner. If you begin clipping them together through the same biner and then clip them alternately that is fine too (in regards to sheath burning). If at any point on a pitch you clip them alternately and later wish to clip them to the same piece then you need to use separate biners for each line (unless the rope line is nearly straight). If you take a fall on a piece with both lines clipped through one biner and formerly the lines were clipped alternately and took different paths then the two lines will rub against each other fiercely as you fall is arrested. The lines will rub on each other not because they are in the same biner, touching. They will rub because they have different amount of slack and different amount of total length between the belay and the climber. These 2 differences will cause one rope to catch the fall first and the other rope will be fairly slack. If there is enough difference (how much is enough? nobody knows) then the relative movement between the ropes may cause enough friction (nylon rubbing on nylon creates significant friction which generates heat and the melting temperature of nylon is low such that it can easily begin to melt from this mechanical friction heat) to damage the rope decreasing it's tensile strength and maybe even melt the rope until it breaks during the arresting of the fall.

Decreasing maximum impact force (the only safety concern really is regarding the placement):If you want to clip both half-ropes into a piece then the impact force will be greater than if you only clipped one half-rope. The PMI Verglas maximum impact force in the UIAA test is 8.4kN for both ropes clipped together and only 5.4kN for one half-rope. But there are ways to decrease the impact force (generated in arresting a fall) when clipping both ropes together. The simplest way is to clip one half-rope to an extension sling or a longer sling. Both ropes are clipped to the placement, one rope is clipped closer and the other rope is clipped farther away. It is important that the ropes do not share a biner if clipping in this way (see sheath burning, above). How would this decrease the force on the placement since both ropes are clipped to the same placement?

Differently lengthened slings on the same placement for clipping both half-ropes decreases the force on the placement. TECHNICAL ENGINEERING (very long and not necessary): the additional distance fallen (which creates more energy) is trivial compared to the additional time during the deceleration (which decreases energy). E = W * d / t where E is the energy required to stop the falling climber (measured in Joules), W is the weight of the climber (measured in kilograms), d is the distance it takes to stop the climber, this is not the total distance the climber falls, just the distance the climber falls while the rope(s) is(are) arresting his fall (measured in meters), t is the time it takes to stop the climber falling (measured in seconds). Our goal is to increase t even if it increases d, because E varies more as a function of t rather than d.

Let's say you're 5 feet above your placement and you fall. You'll end up at least 10 feet lower. After you stop falling and everything settles you'll be about 14 feet lower typically. Those extra 4 feet were caused by the dynamic stretch of the rope(s) which is typically about 30% and also maybe the belay shifted. The static stretch is usually about 7% The dynamic stretch acts a bit like a rubber band, it recoils some. But it does not immediately return to its original length. When a dynamic rope catches a fall it elongates 20% to 30% typically and then recoils some. Ropes can elongate dynamically 40%, 50% sometimes even more in a really really long fall that is also high fall factor. They typically break if there is still energy to absorb after they stretch 50%.

If you hang a 100 foot rope with 7% static stretch and tie yourself to the hanging end then you'll stretch it about 7 feet and be hanging 107 feet below the belay. But if you take a 200 foot fall on a 100 foot rope and assuming it doesn't break you'll end up hanging much lower than 107 feet below your belay. Maybe you'd be 130 feet below. The dynamic stretch recoils some but it takes about 20 min to 30 min of unweighted rest for the rope to regain most of its elasticity (some elasticity is lost forever every time a dynamic rope catches a fall). As you were coming to a halt the rope might have stretched to 140 feet and then recoiled to 130 feet. The elongation of the PMI rope directly after the UIAA test was 36% when testing one half-rope (they use a factor 1.73 fall?). The rope stretched more than 36% while stopping the fall, then recoiled some.

In this example you fell 240 feet maximum and ended up 130 feet below the belay after a slight recoil. The distance fallen during deceleration is 40 feet, the distance the rope maximally stretched. This is the distance the rope was having work performed on it, the distance the rope was absorbing energy. The time during deceleration was brief, very brief. About a second?

(very dangerous pseudo science follows: generalize the dynamic rope as an ideal spring with force of 8.4kN exerted on climber of mass 70kg, a = F / m and calculated acceleration = -120m/ss obviously a coarse approximation but likely it's much larger than earth's gravitational field and since d = 1/2 * a * t * t with d=40feet and a=9.8m/ss then time to freefall 40 feet calculate t = 1.6 seconds and since the deceleration of the rope at 120m/ss is much greater than the acceleration of gravity at 9.8m/ss it would take less time to stop a climber in 40 feet than it would take to fall 40 feet so the time during deceleration during those 40 feet seems like it would be less than 1.6 seconds)

NON-ENGINEERING:All of this science just to give insight that if we can allow the rope more time to absorb the fall, then the impact force it places on the protection will be reduced. This was discovered in testing with load limiting stitch-ripping devices.

John Yates with Pro Design USA designed screamers which are a stitch ripping device that allows forces to be decelerated over a longer time interval than they would be if the Screamers were not in the system. And the forces transmitted by the ropes on the belay system are decreased.

ENGINEERING:Some interesting things happen when you look at how much energy is absorbed in the system when a screamer is used. If the True absorption is measured in a completely static system, lets say doing a drop test with a steel cable and weight we will see that about 500-600 lbf was absorbed by the stitch ripper(Screamer). When a Screamer though is put in a system which uses dynamic climbing rope instead of static steel cable the amount of energy which is absorbed is increase by 25-40%. We see that the absorption of energy increases to 800-900 lbf. I can attribute this extra energy we see being absorbed to the fact that the Dynamic climbing rope in the system is allowed to elongate and remain dynamic for a longer time interval than it would be, if there was no screamer in the system.

An example: A dynamometer or load cell is placed on a bolt hanger. A climber takes a fall which generates a fall with a factor of 0.5. This generates a force of 2000 lbf as seen on the dynamometer. When a Screamer is hooked in the system below the dyno, the same fall only shows a peak force of 1200 lbf. We know from extensive testing that the Screamer can only absorb 500 lbf. So how do we account for the extra 300 lbf seen in this example??? Screamers limit loads and dissipate energy over an increased time interval.

NON-ENGINEERING:The increased time interval (duration) of the arresting phase of the fall allowed the climbing rope to be more absorptive! This increase in the duration of the fall is most important in a Dynamic systems because it allows the rope to do its job even better than it was designed to do.

So back to our differently lengthened slings on the same placement for clipping both half-ropes decreases the force on the placement. If both half-ropes were clipped together to the first placement (whether on the same biner or separate biners, it makes no difference related to impact force) and you fall, both ropes will catch you equally, which is fine. They will exert a force on the placement less than 12kN because they are certified by the UIAA, and actually they will exert a force just about the same as a certified single-rope which typically is about 9kN.

But if one half-rope was clipped to an extension sling 2 feet long to the same placement and you fell, the half-rope clipped closer would begin to catch the fall first. After it stretched 2 feet the other half-rope would begin to catch. The time it takes to stop you will be a bit longer. And this longer duration during the arresting phase allows the dynamic nature of the ropes to absorb more of the energy. The 2 ropes will place a lower force on the placement. You can realize this same additional energy absorption without the extra sling. When leaving the belay with half-ropes if you want to clip the first several pieces with both ropes then use separate biners and establish with you belay 1 of the half-ropes as loose. The belay can keep 2 extra feet slack with 1 of the lines.

Now back to the top. Just because a half-rope is certified by the UIAA means that it's impact force is less than 12kN when clipped together, but that does not mean that your pro will hold. Clipping both half-ropes into a placement will always generate more force than 1 half-rope. Even if you use the extension sling or loose rope method.

If climbing snow and ice with no rock edges then clipping 1 half-rope is quite safe. A half-rope is not going to blow out due to a fall. It's sharp rock edges that destroy climbing ropes in falls. And a half-rope is much easier cut than a single-rope, due to surface area of the rope (and volume to a degree as well). Surface area increases 3 times faster than diameter, a rope twice the diameter will have six times the surface area. Those old 11mm lines last forever because they have so much area to take the abuse. These new 9.4mm lines show wear much quicker.

And here's an extra dose of relief. The UIAA test is more severe than anything that could possibly ever happen outdoors (regarding the edge they use to simulate a biner) (notwithstanding pendulum falls scraping the rope(s) across an edge). When they specify a rope like PMI Verglas with it's rating of 5.4kN what that means is that in the lab the rope absorbed all of the falling energy except 5.4kN. And that remaining force was passed on to the belay system. It does not mean that every fall you take on that line will generate 5.4kN of force on your placement. Far from it. The rope absorbs lots and lots of energy, and the longer you it has to absorb the energy the better it is at absorbing energy.

The energy created when falling outdoors is far less than in the UIAA test lab, and the force transmitted to your pro is usually way below pullout, assuming your pro opportunity was good and your placement was good.

To excerpt Helmut Microys, National Delegate to the UIAA Safety Commission for the USA and Canada.

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.

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. And use separate biners for each rope unless you clip all pieces with both ropes.

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.

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.

Zeno:and then i wondered to myself, "what is the advantage to that, huh?" does anyone have an opinion?

Idea_Guy:Clipping both half-ropes into every placement offers redundancy and you won't need to consider criss-crossing the lines.

Goatboy:

My understanding is simplistic, but here goes: Clipping two 8 mm ropes into one piece is similar to clipping one 16 mm rope into the same piece.

Idea_Guy:Two 8.0mm ropes together are like one 11.3mm rope, sort of…. It's mostly a function of design characteristics, including the secret "bake" to set the rope, but next mostly a function of volume and not simple linear addition of diameters, like chucK said.

Gerg:But, having a dynamic belay can have the most significant effect on reducing the impact force, so perhaps this is all a moot point?

Idea_Guy:Like Gerg said. Dynamic belays save placements! Just read the excerpt below.

Dynamic Belay may be the single most important safety item.

Last winter Craig Luebben and I conducted some drop tests on ice. Craigpublished an article in Climbing Mag on some of these results and resultsof his static tests. I have also written an article on static tests Ihave conducted in the lab (email me if anyone wants a copy). Anyway, weset up our tests under the bridge in Ouray. This was in pretty bad iceactually and for the most part the gear did not hold. Our setup was witha static belay, a new 10.5 mm BD rope, fall factors in the 1.5 to 1.8range, and 185 pounds of steel. With this setup the only thing thatactually held was a 10 cm screw. Everything else ripped out OR carabinersbroke! I attribute this to the bad ice and that the 10 cm screw thatheld was probably in the only good ice we found.

We decided to conduct a series of tests where we used the same section ofrope over again. The first three tests the gear ripped out. On thefourth drop we about keeled over in disbelief. We had a Snarg as the testpiece connected to the rope with a draw with BD QS2 biners. A few feetbelow this was two equalized screws (BD and a Grivel). They were equalizedwith a single 24" sling and a locked Big Easy was connected to the rope.

The biner on the snarg broke, the hanger on the Grivel screw sheared alongits long bend, then the big easy locked biner broke! This is three piecesof hardware that broke on one fall. Now, I am assuming that these werenot defective products (a solid assumption based on my knowledge of allthe gear and the systems to produce it, and a review of the fracturesurfaces of the parts we actually recovered). This means that the forcesgenerated were well in excess of 5000 pounds (multiple times!). Now thetricky part. Conducting a static test on a new rope with the same diameterwith the same type of knots caused the rope to break in the 3500 poundrange. I don't know why the gear broke and why the rope did not. Therewas about one hour between drops so the rope had some reasonable time torecover.

Now the good news. When we placed an ATC in the system (i.e. some dynamicaspects) every test we conducted held except for a couple of tests withSpectres.

What does this mean? Dynamic belays are your friend! Climbers have knownthis for about a century now. Many climbers today do not understand thisvery well. This is why I am relating these types of info to this newsgroup. I am purposely trying to get this group to discuss this stuff indetail and learn something from it.

[IceIceBaby]

Holly Shit,

Is that an essay or what… great info!!! Thanx

[Crackhead]

Whoa! that's an answer!

here's to ya'

[IceIceBaby]

What A Deal,

Black Diamond/Beal 9.4 Dry for $115 after shipping I have got one just now

[Zenolith]

good Idea! send that to a publisher!