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Posted
My knowledge is empirical while yours is theoretical. Or hypothetical. Or even fanciful. Geek_em8.gif

 

try it sometime. It's easier to get a flat sheet of ice to fracture than it is a rounded piece with a diameter equal to the width of the flat piece.

That is true if you are applying force with a pointed object. A cord is not a pointed object.
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Posted

I think the danger of the sharply-angled ice is not that it can actually "cut" the rope, but that the interior rope fibers cannot possibly be as strong when bent over an acute angle. The rope cuts itself.

Posted

Well I don't know, it's all a matter of scale, I mean if you increase the surface area of contact then you spread the shearing force over a greater portion of rope. And the minimum bend radius is longer, so your rope is less kinked at the point of contact. But that's probably 10-20 seconds of forceful cord-pulling at least.

  • 3 weeks later...
Posted

As a public service reminder i thought this to be an adequate forum to get my message across.

 

Here was the scenario, Awesome early morning (too early for the location) but felt like getting some climbs in before the the first climbers got to the area (Evan Thomas Creek). The morning was awesome good coffee awesome moonlight spirit was high.

Got to the base of the route feeling good. After my first route confidence was strong. By headlamp i enjoyed completing my second route before the light was good enough to illuminate my second rappel. The ice had been variable but good, a bit brittle in sections.

 

My first rap on the second route was relatively short i stopped at an Abalakov, the routes all had multiple fixed stations of the sort, I set a screw and clipped into both the screw and the "bomber" Abalakov. The knot was out of the ice and the ice was totally free of any visible fractures. After pulling my ropes through the anchor both ends were now on the ground. For a moment i hesitated, the anchor looked good, no it looked really good and i would be down in a short 30 seconds. However it could of been much quicker getting down if i had not back up my sytem. But i had no real time constraints or rush for safety i set a backup abalakov. I always back up anchors of this sort, had i had a partner we would of back up with a screw anchor. This time my system most likely saved my life. I leaned back and within a second or so a block of ice with abalakov intact was accompanying me on the rap. My anchor was set close to the initial Abalakov and the shock was not really noticeable.

 

After hearing that folks use the Abalakov routinely in this popular area and take them often as primary anchors i felt like i needed to say something. Maybe it was the quick change in temperatures that might of forced the ice to relieve some tension? Who knows, no visible or even location type flaws in the abalakov were noticed. On my hike out the colours were really bright, had a nice drive and enjoyed one of the best tasting coffees in my life.

 

 

Patrick Delaney

ASS. Alpine guide

 

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These observations and opinions are those of the person who submitted them. The ACMG and its members take no responsibility for errors, omissions, or lapses in continuity. Conditions differ greatly over time and space due to the variable nature of mountain weather and terrain. Application of this information provides no guarantee of increased safety. Do not use the Mountain Conditions Report as the sole factor in planning trips or making decisions in the field.

Please check out http://acmg.ca/mcr for more information.

Posted
... I leaned back and within a second or so a block of ice with abalakov intact was accompanying me on the rap...

 

That is creepy! No visual signs of fracture/weakness...

Good reminder for us to back up anchors!

  • 2 months later...
Posted

The ice season is nearing an end but for those still out and about please consider the following:

 

 

 

It is well known that the ‘V-Thread’ or the ‘Abalokov’ anchor is a standard practice for rappelling ice climbs. These types of anchors are used by most ice climbers these days.

 

I have seen quite a few ‘less than ideal’ methods and materials used for this practice as of late.

 

Some issues:

1. Diameter of Cord- It is ideal to use a minimum of 7mm cord for these anchors. Thinner diameter cord can certainly hold body weight but does not provide a very large safety margin. It should be known that cord or webbing can loose a significant amount of strength once a rope or two has been pulled through the cord. The pulling of the rappel rope through the webbing or cord often melts into the sheath and core of the material. I have seen many V-threads made with 5mm and even 4mm cord this year. I’m glad these are working for whoever is using them but I surely wouldn’t recommend using V-threads with this very thin material when you come along them on your decent. I climb with many advocates of ‘light and fast’ climbing but the wt. difference between 5mm cord and 7mm cord will not make or break your ability to ascend ice climbs. I often use pieces of an old 8 or 9mm rope to leave on climbs, which is stronger and takes longer to wear out than thinner cord and is a good way to recycle old ropes.

 

2. Type of Knot- I see a lot of small diameter cord used for V-threads tied together with a simple ‘overhand knot’. The standard knot for connecting cord in V-threads is a ‘fisherman’s (Single or double)’. The ‘overhand knot’ is popular for attaching (equal diameter) rappel ropes but only with large amounts of tale (1.5 - 2 feet is fine). Tests show that the ‘Overhand knot’ can roll or flip (essentially start to fail) more easily with icy or wet ropes, smaller diameter cord, dissimilar sized cord, or with knots that aren’t properly dressed. The cord within V-threads is often icy, thin, and large tails are not practical. Again, this knot (the overhand) obviously works for many people in this application but the safety margin is less and someday an accident will happen. See http://www.needlesports.com/advice/abseilknots.htm for some interesting ready on the ‘Overhand Knot’ for attaching rappel ropes.

 

 

3. Spectra or Dyeenema slings- Many of us use these thinner, light wt. sewn slings for ice and rock climbing (instead of bulkier and heavier nylon slings). These light slings are especially nice for winter climbing as they don’t absorb water the way that Nylon slings do. Ever notice that you can’t buy webbing made with these materials off the spool like you can Nylon? The reason for this is that the knot holding strength of these materials is much less than with nylon. These materials are slippery and the knots can easy slip and fail. I have seen several sewn Spectra slings that have been cut and then re-tied around trees or used in V-threads. Don’t do this. If you are desperate than use your climbing rope. There is ‘cord’ (generally 5.5mm) made out of spectra as well. This too is slippery. It is recommended to use a ‘Triple Fisherman’s’ knot when connecting this type of cord to prevent the slipping of the knot.

 

Remember to:

1. ALWAYS back up your V-threads or Abalokov anchors with an ice screw or two while the first climber(s) go down. Make sure the back up is through the rope and not simply through the anchor material in case the knot slips or cord breaks. The last person to go can remove the back up screw knowing that the V-thread has been tested.

2. It is good practice to go off of two V-threads, especially if you made neither of them. I will go of one if I made it myself but will almost always make another if there is just one old thread in place. Better safe than sorry!

3. Try not to litter the ice climbs (especially popular ones) with V-threads of poor quality, ie: marginal materials, they will only have to be backed up with another.

4. When adding a V-thread to be combined with an existing thread make them equalized so that both can be used. Having one thread a foot shorter than the one below nearly pointless.

 

 

Rob Owens

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