Has anyone heard of a V- thread failure?

I'm a little paranoid of V-threads. How safe are they?

I think that the V-thread (aka Abalakov sandwich) is just dandy, and I have used them extensively. Just from looking at them, you get a feeling that they are just as bomber as the ice you are putting them into. I can’t say that I am an expert from any kind of technical knowledge, rather just a bunch of practical experience with having used them in all kinds of ice (i.e. alpine and water ice). While more than one V-thread is probably a good way to build a rappel anchor, I have rapped from a single V-thread on many occasions. Here is an interesting thread that I was able to find on these types of anchors that you may find useful. Cheers.

cascadeclimbers.com/threadz…

When drilled correctly, (ie) at least 5 inches apart, (the drilled holes) You will break the webbing before you break the ice.
Go drill some put a cord thru it and try to make it fail.

I like to make them, get two or more people on the cord, attached, pulling with all their force, and tapp, tapp, try to make the ice fail by chipping it away.

Do this test and you will be a believer.

"Has anyone heard of a V-thread failure?"

No, I haven't; the CMC'ers are teaching them as a viable anchor. Some of the ice-dudes & dudettes are taking along the longest of the long screws to install the anchor.

One of my thoughts: if the ice is solid, can't I just use a medium sized screw? I mean these v-threads are friggin solid; I bet I could use some of this 5.5mm dyneema and hold a full on factor 2. Why haul up a long screw?

Chris - man, having your feet blow off! dang, that's full-on Lincoln conditions baby!! I thought it's been fairly mild the times I jaunted up this season. Sh*t I wish I coulda been up there with ya; I love that place when it fires off like that; keeps the riff raff out.

Oh, Chris I had one more thought on this subject; if you feel suspect about the anchor. Have the first person to weight the station fire a screw (or two) in as a backup. If the V-thread holds, then the last one down pulls the screw as the anchor tests OK.

Yea it was frickin nasty and hear I'm all worried about V-threads.

Thanks Mark, I'm planning on doing some longer routes the nexted couple of months and they require V-threads to get down.

Question: What is the ideal length of screw to use for the best angle of strength. (possible question for the physics majors out there) Probably longer the better -- but at some point it may be overkill and not necessary.

Thanks in advance

Ten years ago or so I remember reading a good write up about testing of Abalakov anchors. Can not recall if it was in a climbing magazine or elsewhere. The take away from the article was that as temperatures drop the anchor becomes stronger. Failure could only be induced in slushy ice. Sub zero temps in what most ice climbers would say is "brittle ice" achieved the best results.

Kirra wrote:Question: What is the ideal length of screw to use for the best angle of strength. (possible question for the physics majors out there) Probably longer the better -- but at some point it may be overkill and not necessary. Thanks in advance

In good ice, the distance between the two holes at the surface should be at least 15 cm or 6 inches. Below that distance there is significant degradation of the strength of the Abalakov. Increasing the distance to 20 cm (8 inches) makes for a stronger anchor, but not by much, maybe 10%. Using thick cord (e.g., 8 mm) spreads the force over more ice.

thank brenta - the length of the screw is what I am also curious about. This would establish the distance between the top of the ice and the vertex..?? (correct term)

If A is the point to where the screw holes intersect, and B and C are the entry points of the screws. Distance from B to C should be >= to 6", does the distance between A and the half-way point between B and C matter also..?

The angle between the screw and the surface should be between 45 and 60 degrees. In the latter case, of course, you get an equilateral triangle. With a 22 cm screw, it's OK to separate the two holes by close to 20 cm. If you only have shorter screws to make your V-thread, you may want to decrease the distance between B and C accordingly.

I'll bet good money on Jim's idea.

These anchors get published with a superfluous safety factor. Anyone up for some experimentation (with redundancy, of course) to see where the failure plane occurs?

I forgot to add that the angle of 45 degrees maximizes the area of the triangle with vertices A, B, and C for a given screw length.

Mark Nelson wrote:These anchors get published with a superfluous safety factor. Anyone up for some experimentation (with redundancy, of course) to see where the failure plane occurs?

I don't have the data you'd like to see, and I'd be interested in them myself. Don't forget, however, that for a fixed angle, the strength of the V-thread grows quadratically with the length of the screw. The numbers I've seen quoted for Abalakovs in good ice are in the 10-20 kN range. Cut the screw length in half, and we are talking about 2.5-4 kN -- in good ice.

I've done Jim's idea of chipping away at a v thread: We girth hitched a sling through the holes which should have increased the force on the ice and used 4 guys anchored to the rope and bouncing against the v thread. It did not fail until the ice column was approx 2/3 of an inch in diameter. The ice was not what I call bomber ice either, but was sort of soft and wet...

I trust a V thread!

If you do a test similar to this make sure you back up your thread so the rope does not whip back at you, and you don't go falling down the mountain.

V-threads are usually extremely bomber, and are a welcome sight leading or at a belay. Use your gut feeling-if existing or one A-kov isn't enough, add another equalized one. With some practice, they should only take you a couple of minutes. Always take one long screw, even of your angles are slightly off, a long screw is more forgiving when constructing a A-kov sammy!

I've rapped off v-threads numerous times, generally on 6-7mm perlon cord. There are instructions and some test results in Craig Luebben's book "How to Ice Climb" from Joe Josephson.

Generally one should back the v-thread up while the first person raps, ie. a bomber screw with a draw clipped to it with the other end through the rope. The last person can disassemble the backup.

I've only read about one fatality involving v-threads, and I recall it had to do with someone's confusion about an existing v-thread they came upon where the rope was not threaded through the loop itself, but through the tails somehow (the ends of which were half-buried in the ice I guess).

As I see it, if there is any confusion about an existing v-thread, back it up or make a new one (preferred).

rhyang wrote:I've only read about one fatality involving v-threads, and I recall it had to do with someone's confusion about an existing v-thread they came upon where the rope was not threaded through the loop itself, but through the tails somehow (the ends of which were half-buried in the ice I guess).

It was at Selenium Falls, Banff National Park, Alberta - 12/12/2000.
alpineclub-edm.org/accident…

..."The cord had iced over since its original installation and the climbers mistook the long tail end of the cord for the main, knotted part of the loop. When the first climber, began to rappel, the loose tail pulled out of the ice and he fell 140 metres to the base of the climb, sustaining fatal injuries"....

On alpine routes in particular, I like to use a v-thread much more than a slung block. You can't tell anything about how stable a block is. It's sort of like a piton. It might look good on the outside, but who knows how bomber it is underneath. I, too, did the chip away at a v-thread test. We used 4 big guys bouncing on the rope. The v-thread was down to about the size of an ice cube before it failed. This was in fairly solid, though warm, glacier ice in Washington.

Anyone have any particular experience or knowledge when it comes to rapping off an *existing* v-thread? Always makes me a little nervous, but I had a partner who sweared by solid-looking ones when climbing up in Cody.

In theory, I'd think they'd only get better with a few more days to freeze/thaw (so long as not in direct sun), but would be interested to hear some input.

Avery Nelson wrote:Anyone have any particular experience or knowledge when it comes to rapping off an *existing* v-thread?

Back 'em up, then do a little bounce test.

I've not used other folks' v-threads for a myriad of reasons, though. Cord too skinny, ice funky and cracked through, poorly drilled/executed holes...

Seems like folks never leave a rapide/link for rapping off. So, if I can move the burned spot, I'll pull the cord (if its not frozen in) to orient a fresh piece of cord for the next rappel. Usually not a deal, though, but, I try to inspect where the rope pulled through prior to committing my rope.

Usually, though, other person's v-threads are bomber...

Last man at risk!

Brian -- agreed on the 'fresh spot' and yet another reason to not use someone elses thread.

This brings to light another issue that many climbers do not consider. By it's nature, ice melts. That means that cord, webbing, etc tied into ice ends up in the watersystems or on the ground as garbage.

I believe that folks up in the S. Fork of Cody have taken notice to this in recent years and that it has been raised as an issue.

So, please keep this impact in mind when setting or rappeling by an existing v-thread that should be considered for removal!