How to make a V-tread
by Dave Furman
More and more recently I’ve come across all sorts of gear left on ice climbs, left when people rap off or when people can’t finish a route and rap or lower off. In the interest of keeping the chat room posturing to a minimum and to help preserve everybody’s rack, here is how I place a V-thread and retreat from an ice climb. (I feel like I’m uniquely qualified to write this, as I have retreated off of ice climbs in fourteen states, including almost every route at lake Willoughby and in smugglers notch.) A V-thread is stronger than a screw because the surface area of the ice you are supporting your weight on is much greater than that of the threads on an ice screw. Many people don’t trust them however, so what follows is my method of backing up and testing rappel anchors in general, as well as directions for making a V-thread.
Once you’ve decided you’re done, whether you’re at the top of the climb or not, you’ll want to examine your options—if there’s an easy walk-off or if there’s a shiny new bolt station nearby, obviously it may be faster and easier to frig your way over there. That never seems to happen to me, but I do run into all sorts of sketchy looking fixed anchors attached to all manner of trees, shrubs, rocks, blocks, icicles, threads, pins, etc. Usually they have eleventeen different pieces of tat all semi-equalized somehow, and it still looks sketchy. My rule of thumb is always back up my anchor—but that may not mean leaving anything behind. Often what I’ll do is create my own separate anchor, unweighted by the rappel rope through the fixed anchor, so that I have the opportunity to vigorously bounce-test the fixed one. If anything rips, I’m protected by my backup, and then can start leaving all my own gear…more likely the anchor holds even my heavily aggressive more-than-double-my-body-weight testing, and I can safely clean my backup (after my partner completes the rappel) without leaving a thing behind. I do the same thing with fixed V-threads. Place a screw or two far enough away that if the thread rips it won’t undermine your placement, and clip it to the rappel rope as well—it’s important that the rappel rope does not weight your backup anchor, or you won’t be testing the fixed one. This way, any anchor you see on the ice, as well as most tree and pin anchors, can be tested to ensure their solidity. It doesn’t hurt to carry a small knife, some extra cord or web and a couple rings to replace (not just add to) the really ratty fixed stuff.
To place a V-thread, first find the area of solid ice that has the least air pockets or cracks through it. It helps to find a small pillar or convexity, as this will aid in placing the holes for the thread. Place the longest screw you can in the ice, at an angle and location that will allow you to drill another screw to meet the first hole (the convexity allows you to place a hole on either side of it, increasing the size of the ice column in between). It is nice to leave the first screw partially in the ice so you can use it as a gauge for the correct angle and location for the second screw. You will be able to see the second screw intersect the hole from the first. Push a piece of cord or 11/16’’ web through one hole, and pull it out the other with the hook you brought with you. (This can be either a homemade job from coat hanger, or a pre-fab one—several are available, Charlet Moser makes a good one that is easily available. See directions below to make one) Tie the ends of the cord together, and you’re done. If the hole is shallow, or cracked, or hollow ice, or you’re just into public service, place a second thread 18’’ or so above the first, so that the rappel rope weights the two cords equally. If you practice, this really only takes five minutes to make a double thread anchor—I’ve often been able to place a thread between the time that my partner finishes a pitch, calls off belay and finishes constructing an anchor, and when they put me on belay.
To make a v-thread tool, get one of the all-wire heavy-gauge coat hangers from your closet, and cut a piece of wire about fourteen inches long. Bend one end to form a loop that you can clip to a carabineer. Bend the other end into a hook that will easily fit through the inside of one of your ice screws, and sharpen the point of the hook with your file. You’re done. I fold mine into a loop, hooking the hook end through the loop so it doesn’t catch on my precious gore-tex, but be careful of this as the wire will fatigue and break before too long—luckily they’re really cheap! Good luck and be safe!
See an update from Dave, and comments below
Good info but Petzl’s field tests of the pull-out strength of ice screws and ice v-threads show different results than what you’ve stated. It’s from a couple of years ago but basically their tests show that ice screws are stronger than v-threads! Here’s a link to the English translated video version. As you would expect the results varied a great deal depending on the quality of the ice.
http://www.dailymotion.com/video/x7z2t1_ice-anchor-workshop_sport
Good info, however it is my understanding that convexities are natural areas of tension in the ice. When ice anchors fail (screws, threads) the majority of the ice that is pulled off comes from the area of increased tension. Also, surface ice should be cleared off to gain access to more solid ice underneath that hasn’t been exposed to as much sunlight, temperature variation, or effects of snow-cover. Ideally, then, a flat area should be cleared.
http://www.beverlymountainguides.com/file_download/5/Ice-Climbing-Anchor-Strength.pdf
Some interesting info on horizontally vs vertically oriented threads (v-thread vs A-thread)
I attempted to post a comment earlier and am usure if there is a delay in showing up.
The v-thread is a great piece of know-how to have. A few points on the above article though. It is my understanding that convexities in ice are weak points, as there is increase surface tension and studies have shown that when ice anchors (threads, screws) fail, the majority of the ice that is lost causing them to fail is lost from the zone of increased tension (above, in a downward pull) and next to no loss from the zone of compression. Or consider swinging into a bulge in the ice with a tool vs swinging into a concavity. Furthermore, when possible surface ice should be removed to expose the more homogenous ice below that isn’t as exposed to temperature variation, sunlight, and snow-cover; also providing a flat surface in in which to screw.
Also, some interesting reading can be found on vertical orientation of threads (‘A’-thread) vs horizontal orientatoin (v-thread).
http://www.beverlymountainguides.com/file_download/5/Ice-Climbing-Anchor-Strength.pdf
There was an article called Ice Climbing Anchor Strength: An In-Depth Analysis recently published in the AMGA Mountain Bulletin on placing screws in pre-drilled holes, but it also talks about v-thread strengths. I found the article online. Check it out.
http://www.rock-ice.com/index.php?option=com_content&task=view&id=191&Itemid=1
Hope it helps!
Wow, this was written eons ago…it lives. A few notes. Someone above commented that I “write verry good”…unfortunately my writing was not perfect and I think that lead to some misunderstanding.
First, on screw vs v-thread strength. I’ve seen the petzl video stuff and also seen a bunch of other testing. Most of it was done in lake ice or the “frozen slushy” ice in a bucket that used to get used for testing screws. My own experience is that many times the ice on the routes where I get scared is hollow, candled, full of air pockets, etc…I do not believe that the ice I have seen in the testing cited is comparable to the “bad areas” of ice on climbing routes that I’m referring to…so what I SHOULD have said is that a v-thread CAN BE stronger than a screw in SOME CIRCUMSTANCES. If the ice is good it probably doesn’t matter, they are both plenty strong–but if the ice is really bad, then my own non-scientific testing (i.e. placing a variety of gear in crappy ice and body-weight-testing to failure)has convinced me that the thread can often be the stonger option.
Regarding concavity vs convexity–again, I am going to claim it’s cicumstantial. Much of the testing done in this area is dynamic, i.e. a fall. I am a bonafide chickenshit so when I rappel from a crappy anchor (or anything in ice) I am darn sure I am not bouncing around, so I consider any force I put on the anchor a lot less dynamic. When I’ve played with weighting and bouncing around on threads in different ice, convexities like a pillar don’t seem to fracture much at all that way they might under the force of a real fall–and remember, we’re backing all of these up, right? I do. For this reason I place my threads around a convexity IF IT SEEMS APPROPRIATE simply as a matter of convenience when placing the thread, because all other things being equal I haven’t found that it makes a significant difference in real-world strength (again, tested unscientifically by placing lots of threads in various ice and bounce-testing to failure). At the end of the day though, the best place to put a screw or a thread is going to be in the best ice, and you are going to have to be the judge of that–that seems obvious but I should have mentioned it. I would encourage anyone who has read this far to go and experiement for yourself–I would argue that if you do it in a thoughtful manner you’ll learn a hell of a lot more than I or anyone else or any book or article can teach you.
Great…thanks for all the info and links…I changed the post to reflect the new information.
Pls what are some of the applications of vee screw threads?
This article has new data that supports threads being stronger than screws in many cases. I doubt anyone will find this page anymore, but just in case…
http://www.ukclimbing.com/articles/page.php?id=4315