Ice Rappel Anchor Tips and Considerations.
The ice season is nearing an end but for those still out and about please consider the following:
I have seen quite a few ‘less than ideal’ methods and materials used for this practice as of late.
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.
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.