How to Build a V-Thread Anchor
Rappelling on ice, when there are no manmade anchors, requires a bit of ingenuity. You can use ice screws or nuts/cams if there’s rock, but then you are forced to leave your gear behind. Not only does this take a toll on your wallet and junk up the wilderness, but after enough rappels, you will find yourself out of gear, maybe even before the rappelling is over.
The key to rappelling multi-pitch ice in the backcountry, then, is the V-thread, or Abalakov thread. While the thought of using ice as a rappel anchor seems initially daunting, scores of in-field tests and observations have shown that a properly constructed V-thread placed in good blue ice provides more than enough strength and support for safe rappelling.
Here’s the run-down for constructing a V-thread ice anchor as pictured and instructed by San Juan Mountain Guide Pat Ormond.
Make your V-Thread in thick, blue ice. Any other frozen medium, such as verglas (very thin ice sitting on a rock slab) or neve (hard, old snow) needs to be entirely avoided as only good, solid ice should be trusted to support your body weight on rappel.
Once you’ve found a solid spot, smooth out an area with the adze on your ice axe, chipping away the brittle ice sitting on the surface to reveal the stronger ice beneath it.
Take a 22cm ice screw and begin the first hole somewhere between 45 degrees and 60 degrees from the plane of the ice (60 degrees offers the maximum volume of ice between both channels, although a 45-degree angle is plenty sufficient). After completely burying the first screw, back it out a few cm, but not all the way. The first screw will serve as a guide for the next placement.
Take another 22cm ice screw, and begin the next hole to the side of the first one, also at a 45-degree angle, aimed toward the other screw placement. Given that ice tends to shear along a horizontal plane (side to side), begin the second screw slightly higher than the other. Line up the placement, and bury the screw as far as it goes, intersecting the first channel.
You can now back out both screws and clean the holes with your ice tool. Ice tools for fishing out the cord/rope can either be purchased pre-made and are basically a skinny wire with a hook on the end, meant for grabbing the tip of the rope. Or, for a cheap but effective alternative, you can make one with a clothes hanger. Simply cut a branch off a clothes hanger, and bend one of the ends to form a hook. If you cut the end at a diagonal, the sharp point will make it easier to catch the tip of the cord/rope.
Once the channels are cleaned out, you have two options for anchoring into the V-thread. First option is to fish a length of accessory cord through the channels. If you use this method, tie the cord together with a double fisherman’s knot to ensure your ends stay together. You can then run the rope through the chord and prepare the rappel. In this situation, you will complete the rappel, pull the rope through, and leave the cord in the V-thread.
The second option is to fish the rope itself through the V-thread. As you did with the accessory cord, use your ice tool to finagle the rope through the hole. Then pull the rope until its middle is sitting within the V-thread. Using this method allows you to completely clean the route, leaving nothing behind except for the V-thread.
Once you have rope through either the accessory cord or the V-thread itself, sink an ice screw above the V-thread with a quickdraw attached. The purpose of the ice screw and quickdraw is to provide a back-up anchor, just in case the V-thread fails. You don’t want the quickdraw to be weighted in any way when the first person rappels, since ultimately you are relying on the ice to hold your weight. Once it is the last person’s turn to rappel, the screw and quickdraw are removed and placed back on that person’s harness.
Before fully committing to the rappel, pull on the V-thread with enough force to ensure it is able to withstand a person’s body weight. As long as it checks out, with the back-up ice screw and quickdraw in place, have the heaviest person in the group go first on the rappel—this offers the group feedback on the strength of the V-thread.
When it comes time for the last person to rappel, as previously mentioned, the back-up ice screw is removed and the rappel is completed. The rope will then be able to easily slide through the channels as it is pulled free for either the next rappel or for the walk home on flatter terrain.
Keep in mind that when constructing a V-thread anchor, even on a single-pitch rappel, you can always set up two V-threads in the same station to provide extra security. As mentioned, set them vertically to each other, seeing as you do not want both V-threads to fail simultaneously on a horizontal plane of ice.
Before doing anything in the backcountry where your life depends on the construction of the V-thread, practice on an ice patch next to the parking lot where you won’t need to rappel. Have multiple people pull against the thread while chipping away at the ice to get an idea of how strong or weak the thread can be. Practice as much as possible so that when it comes to using a V-thread on a climb, you will feel dialed.