Snow Anchors

[TrogdortheBurninator]

Maybe people have seen this before, but I thought it was an excellent and practical study on snow anchors. I stole the link from Crackers' blog. http://www.alpineclub.org.nz/documents/activities/instruction/snow%20anchor%20report.pdf

 

I have had numerous discussions with partners about snow anchors, and it is surprising to learn how little me or they knew. Amongst other takeaways, the report makes a strong argument for wire swaging to the middle hole on your picket.

[BirdDog]

Wow, haven't read the whole thing yet - but defintely interesting. Quite a few years back I ran into some guys on Rainier testing wire swags on pickets. From what I saw they worked well unitl the wire cut into the snow and then levered the picket out. I believe it was SMRC dudes - maybe they could add some insight.

[billbob]

Do you mean like the way Yates does their pickets? I tried out my new brightly-colored picket and it worked great when horizontal but I don't think I understand how to plant it vertically. Should the wire be routed up and out the lowest exposed hole before connecting to a biner?

[G-spotter]

Maybe you need to drill an Abalakov-style hole for the wire to come out of. I mean if the wire runs up then it's just going to pull the Picket up out of the hole isn't it?

 

Ultimately the best snow pro is soloing with two long-shafted ice axes planted to the hilt.

[foraker]

Mind you, they are using the Kiwi V-shaped stakes. Never had a problem with them really but then I didn't tend to have vertical placements and clip them on the top. If you don't dig a slot for the cable/sling, you're pretty much asking for it to get pulled out anyway. I imagine some of the overall results would be different with the T-shaped stakes in common use here. Still, I'm not surprised the V-stakes show a fair bit of failure.

[TrogdortheBurninator]

The make regular mention of msr coyotes throughout their report, so it looks like they used both cross sections.

[TrogdortheBurninator]

Badbill, this is exactly why you should read the report. You need to dig a narrow trench for the wire, or else drag the wire so that it runs plum from the anchor.

 

I actually thought their results were rather reassuring in the sense that properly placed snow pro can be quite strong in a wide range of snow conditions. The practical tests (dry/wet, fingers/pencil/knife) are easily reproducible in the field.

[foraker]

TtheB, yeah, I should too. I just did a quick perusal of it at work while I had a few minutes. I agree, than can be used well if seated properly. If we had adequate snow depth, which we usually did there, we'd also back them up with an ice tool.

[billbob]

OK, I read the report. I have a Yates picket w/ a wire permanently swaged onto the middle hole. Works great horz. but if it is planted vertically then the wire is gonna pull it up unless you do the Abalokov thing per G-spotter's question (above email). Kinda seems the paper is saying to dig a trench for the wire and then fill it back in, but the snow must get stronger with the rework or else the stake will be weaker and you get to slide for a bit. Is that correct or did I just not get it?

 

The wire on the Yates anchor has a loop at the distal end that can be threaded through the top hole, then out to the tie in point or whatever. Their website doesn't say, guess I'll call. http://www.yatesgear.com/climbing/hardware/index.htm#7

 

Note the paper doesn't delve into other ways to prevent picket failure.... some people like to use the Yates Ice Screamer on pickets in addition to ice screws. I pre-rig the pickets and carry for quick and hopefully sound anchoring. I know, it adds weight and complexity. Still, after watching three guys last June 16 on Hood SS tumble down the chute because their picket pulled out, it seems like a good idea to do everything possible to bolster ice & snow anchors.

[TrogdortheBurninator]

I think the report makes frequent mention of the importance of surface area. If you dig your trench narrow enough (ie by dragging the wire, or using an axe pick), you lose very little of the total surface area. If you backfill with slightly weaker snow, I would expect the loss in strength to be almost negligible for a very narrow trench :speculation:.

[catbirdseat]

This sort of picket placement is often much more practical than a typical Tee Deadman when you are on a very steep slope. It's much easier to cut a vertical slot for the cable than it is to cut a horizontal slot for the deadman.

[billbob]

OK, got it. I just have always buried a vertical picket as far as possible and then clipped to the hole just above the snow surface. Never thought to attach to the middle and drag/cut a slot for the wire. Obviously using slings instead of wire would give a wider slot.... Just the excuse I need to go climbing again next weekend :-)