The strongest ice anchor is also the simplest

The Abalakov or V-thread in ice is often the best choice for solid rappel anchors on multi-pitch ice climbs and as part of a belay anchor.  An Abalakov can be the strongest piece in any ice anchoring system and is considered stronger than an ice screw in the same location.

Named after its inventor, the Russian climber Vitali Abalakov, the descriptively named "v-thread" is much easier to pronounce than it's inventor, and it is one of the most simple yet genius contributions to the climber's "bag of tricks".   Every ice climber should know how to quickly build a solid v-thread and this article will review the commonly accepted standards for v-thread construction and use.    

                        Pitch two of the West Gully in the Glacier Gorge of Rocky Mountain National Park

The only tools necessary to construct a v-thread are a longer ice screw (22cm preferred) and a "hooker" for pulling the anchor material (webbing or cord) through the holes drilled in the ice by the long screw.   A steel "link" or aluminum carabiner are a good idea as well to serve as an attachment between the nylon anchoring materials and the nylon rappel rope.  Ice hookers can be constructed from aluminum coat-hanger wire which is easily cut with a pair of pliers, ideally to the 22cm length as well so that it can fit inside of the screw for transport.  The hook end can be sharpened with a file to get a better stick on the nylon.

The foundation of any anchoring system is the material in which the anchor is built (rock, snow, ice, moss, etc.) and ice can be one of the more difficult materials to accurately judge the strength of any given section.  Ideally the ice does not crack beyond a few inches when inserting the screw which should be in consistently strong ice upon it's entire insertion.   The first screw is inserted into the ice at a 45 degree angle to the ice on a horizontal plane. 

You are making as close to an equilateral triangle as possible which means that the three sides are of equal length and so the length of the 22cm screw should determine where the second hold is drilled.

Some folks like to keep a screw in the first hole to help line up the screw in the second hole.  Others prefer to "sight" down the first hole to ensure that the angle of the second screw is in-line.  Either way, the trick is to line up the screws so that the second screw intersects with the end of the first hole to make a 22cm equilateral triangle in the ice.  I like to put my lips to the ice and blow any scrap ice out of the holes to make for a clean pull of the nylon sling.

This is a two-handed maneuver but with a sharp hook it's pretty easy to grab the typical 6-7mm nylon cord or 1/2 inch nylon webbing and pull it through the hole.  Choice of joining knot is personal as there are many options.  Double fisherman and flat overhand are two of the more popular knots for this purpose and shown here are two "stacked" flat overhands joining together the ends of a 1/2 inch diameter x 60 inch length tubular nylon webbing.  The outer knot is tied first and tightened and the second knot tied on the inside of the first.

My ice climbing rack often includes a few of these slings pre-cut and attached to the long screw and hook on the same carabiner.  Often this set-up just lives in the bottom of my pack on long alpine routes, ready to be used if Plan A doesn't work out and going down is the best option. 

Once you have your solid, slung v-thread, it's time to attach the rope and the option is either to run the rope through the looped sling or put a piece of metal between the two nylon materials.  Although it's much more difficult to melt nylon in a below freezing environment due to the weighted rappel rope moving over the single nylon sling, thus cutting it and disconnecting you from the anchor. 

No matter how careful you are while rappelling to not let the two strands move at different rates through the rappel device, when ropes are wet  or frozen this is more likely to happen.  Because metal is cheap and life isn't, most of us elect to use either a steel maillon (screw) link or a carabiner as an attachment between the rope and nylon. 

Carabiners should be oriented with the gate away from the ice with the opening on the up side to reduce the risk of the rope becoming disconnected.  Tape is an easy remedy to ease fears of this real danger or doubling up carabiners is a more expensive but "bombproof" solution. 

Steel links that can be purchased in climbing and hardware stores are typically designed for industrial use and so the stamped strengths on their spine reflect only 1/3 of the full-strength of the link as industrial guidelines require this safety margin.  Limited testing of hardware store bought steel links in the 1/4"  5/16" and 3/8" by a reputable climbing manufacturer showed that many different types of steel links of the maillon style, all had breaking strengths 3 times that of the stamped strength- so the 880lb links, for example, were breaking at approx. 2500lb tensile strengths.  The aluminum rings popular in the 80's and 90's for rappelling purposes are rated at less than 700lb each and depending on the weight of your partner or his pack,  they are preferred in sets of two for extra security.

Another advantage of using metal is that it will make pulling the ropes down from below much easier with less friction and this can be one of the best reasons to rappel from a metal link.

If there is any doubt as to the integrity of the v-thread or just for extra piece of mind, a screw can be placed above the anchor, ideally at the length of a 24" attachment sling.  The carabiner that attaches to the rope should ideally have only 1/2" of gap once the rappel anchor is weighted so as to minimize any shock-loading in a worse-case scenario of the v-thread failing.  Once the first and heaviest rappeller is down to safety, the screw can be removed and the gentler rappeller can have the thrill of no back-up.

Often ice can be less predictable and either too cold and shattery or too warm and slushy and these can be signs that redundancy for an ice anchor is necessary.  All anchor pieces are strongest when attached together in-line with the forces that are being applied, and with v-threads, one above the other may also reduce the risk of a large horizontal crack taking out both v-threads.  (Ice seems to crack much more horizontally than vertically).  Often, I have  been 1000' off the ground and just prefer the stress relief of having an equalized, two v-thread anchor.  No worries, mate!

The flat overhand is also an easy knot to adjust, especially while wearing gloves and this can better facilitate the equalization of the two v-threads so that the pull on the steel link weights both as equally as possible. In the above photo, there was not enough non-sewn nylon material, so instead I used a 48" sewn sling through the upper v-thread and used the shorter red sling, tied with two flat overhands and attached directly to the steel link, to make these two v-threads "equalized".

                             John Ackelson rappelling off the top of the West Gully ice route in RMNP