Climbing on a Single Half

Submitted by pony on Wed, 02/15/2006 - 22:16
[b]I posted this on the Canadian Mnt. website and thought it might make for an interesting chat.[/b] Given the fact that when climbing with half ropes (where your clipping alternately) only one rope takes the force of a fall, one could do an entire climb with a single half rope. This would be especially useful on alpine climbs where weight reduction is essential. For rappels, you make your V-Thread but instead of threading it with a piece of cord, you thread one end of the half rope and attach it to a locking biner along with a 60m peace of 7mm cord. The biner keeps it from pulling through the V-Thread and at the bottom of the rappel you simply pull the cord to retrieve the half rope. If there?s a chance that the rope could ice up in the V-Thread, then thread it with cord and add a small rap ring to the cord and thread the half rope in the same manner through the ring. Depending on the weight of the climber, you may need to add some additional friction to the rappel system. I realize this might sound a bit dicey, but hey, were talking about Extreme Alpinist!

That is exactly opposite of how I know it. Doubles (1/2 on the rope end) get clipped singly, and twins (with the two linked circles) get clipped together. I have led alpine rock, especially simul climbing easy rock, on a single half rope several times. I get leery of this when I have crampons on, tho. One bad step and you're off-belay. I have never used twins. [url]http://www.highonropes.com/climbing_rope_glossary.asp[/url]

UIAA 101/EN892 delineates dynamic ropes into three categories; Single Ropes, Twin Ropes and Half Ropes. Single Ropes Dynamic climbing rope, capable of being used singly, as a link in the safety chain to arrest a person's fall Usually found in diameters from 9.5mm to 11mm. Twin Ropes Dynamic climbing rope, which is capable, when used in pairs and parallel in each piece of protection, of arresting a person's fall These are generally smaller diameters from 7.5mm to 8.5mm. They have the added safety factor of a two-rope system and can be useful when doing long rappels. Half Ropes Dynamic climbing rope, which is capable, when used in pairs, as a link in the safety chain, of arresting a person's fall. Generally smaller diameters from 8mm to 9mm, this system reduces rope drag, allows for longer rappels, offers better safety for the "second" and greater versatility in the field. Single, Half, and Twin Ropes This next section is off the Blue Water's website. A single rope must sustain on one strand a minimum of 5 test falls with a drop weight of 80 kg without breaking. Single ropes are recommended whenever a fall on a single strand can occur. They are safe in the event of a fall and are used in situations with potentially high fall factors. Half ropes must also sustain 5 test falls on a single strand with a drop weight of 55 kg. They can be used as a single rope when the fall factor is less than 1. In the event of a serious fall, the necessary safety factors can only be achieved when the rope is used double. The double-rope technique is where each strand is clipped separately through different runners, giving two distinct very light single ropes. The greatest advantage of this technique is it provides less risk of total rope system failure. Twin ropes are tested with a drop weight of 80 kg on two strands together and must survive 12 test falls. The twin-rope technique, when used correctly, provides the highest safety margin in event of a fall. In this technique both ropes are clipped together through the same karabiners where they act as a stronger, safe single rope. In reguards to the "7mm" cord, I ment to say; a 3mm cord rated at 181kg and weighs only "7g" per meter vs a 7.8 Twin that weighs 41g per meter. Hope this clears it up!

you may want to test the actuall breaking strength of that 3mm cord before relying on it as a "pull" string, consider how much force you might have to apply if the biner lock and knot freeze to the ice. I'm guessing you could easily put 400 or 500 lbs of pull on it with a good heave. also consider that you may seriously comprimise the strength of the v-thread by side loading the pillar your pulling on, the inward compression of the biner plus this side loading might cause some concern. you might want to test that out. good luck, Tobias

If it's still up check out Steve House's solution used on Nanga Parbat, its on the Patagonia website, he also waxes on other thing ultralight. I think he used a 50 m single with a 55m pull cord, either 5 or 6mm

climbing on a single double is pretty common for lightweight trips. you just have to realize that you don't have as big as a safety net. as for the v-thread idea, i would be pretty leary of rapping off of such a rig. the side loading would worry me. i like the even distribution of force that a real thread provides. also, have you tried threading an 8 mm? it seems like this would be very hard to do. it seems equally hard (and more time consuming) to thread a thin cord and try to pull the 8 mm. that's my two cents.

As I recall, the Tested Hopes team did substantial testing on V-threads, as did the pro?s during the Bozeman Ice Fest. Tested Hopes did several live falls on both 22cm deep and 17cm shallow V-threads removing ice in between in an effort to weaken them to the point of failure, and they still held. The pro?s did a similar test during the festival; removing ice in between and having the participants jerk on it in an effort to get it to fail, again with no success. I understand there?s a certain amount of anxiety associated with V-threads, I know I got a little rattled the first time I raped of one. Personally, I know if the ice is sound, V-threads are bomber. Withstanding the impact forces exerted in a lead-fall far exceed that of a rappel. However, if side loading is a concern then construct the V-thread with a vertical orientation. This of course places an inward force on the ice. Another option is to construct the V-thread in a typical manner with the addition of a rap-ring attached to the cord. Run the rope through the ring and tied into a locking biner at one end with the pull cord attached at the opposite axis. This eliminates the risk of the rope icing up inside the V-thread under wet conditions at the expense of the weight and cost of a few rings.

darn it logged me out too... Has anyone ever done research on how much 1 twin rope will hold? Just out of curiousity... I can't really picture my 8mil snapping, but I can't imagine falling on it alone either...

If I recall correctly, the guy?s at the Ice Festival conducting live test-falls were doing most of them on a single Blue Water Ice Floss. The rope was like seven or eight years old and has taken something like twenty falls!
Spray