Picket test

[mike1]

Does anyone have any info on comparative load tests between the different picket styles, i.e. Yates -v- MSR?

[builder206]

Jeebus, what are you going to protect, an elephant? Seems like if you are in a situation where you might load a picket to its limit, you already have more to worry about than the picket.

 

The Yates and MSR websites don't have the info?

[builder206]

If you're going to use pickets to build an anchor, you can use runners to chain them together to back them up and equalize them like a rock anchor. You can stay away from their load liomits that way, if that's the scenario.

[mike1]

I could see loading a picket to failure during a crevasse rescue without the elephant factor... But I'm just curious because they're designs are so different that maybe there is a significant benefit to one over the other. I own both, but haven't really "tested" them.

 

Ya... a picket functioning as a picket... that’s what I mean. I’m not a fan of the picket as a deadman. I think you need to cross the snow layers to get the best results. Laying it on the parallel runs the risk of surfing it along a snow layer to failure. I’m just sayin...

 

The web sites don't have much. C'mon, there has to be some physics major out there that's dying to break this down for me!

Edited May 27, 2008 by Mikester

[builder206]

I've only played around with them in scenarios.

 

Your idea "cross the snow layers to get the best results. Laying it on the parallel runs the risk of surfing it along a snow layer to failure" is interesting. That hadn't occurred to me. When I’ve tested them as deadmen, everything seemed solid like you *could* drop an elephant on the system. I was taught only to keep digging until you are in “consolidated snow,” whatever that really means.

 

There isn’t a lot of cross-section in either design so impact-loading them could be a worry, I’ll give you that.

[nkane]

I found this interesting article a while back (it may have even been posted here!) - PDF

[builder206]

holy moly

 

some of the pictures are sobering

 

maybe someone could start making them out of titanium

[mike1]

Now that's what I'm talking about. Thanks nkane!

[mattp]

Go find yourself an old windscoop sometime and test your pickets. Place them and then you and a buddy or two try to pull them out. In summer snow, at least, I pretty well convinced myself that deadman style is WAY stronger.

 

For what its worth, the only conditions where I've ever really thought pickets placed in their "intended" position were something I actually wanted to depend on were where the snow is bullet hard - approaching neve - such as I've found on Mt Cook in NZ but not often around here.

[korup]

I think skating on snow layers is more likely in the winter, but not too much of an issue on summer glacier snow/ice. I don't have any data to support that, but it fits with the general trends in snow consolidation.

 

Amazing pdf, thanks for the link!

[mattp]

If you tried my test with a Cascade snowpack, Korup, I bet you are right. Once the snow goes isothermal and then sets up, you don't have the same structure alternating low density snow with crust layers or whatever.

[campwire]

Check this report by Art Fortini out. It doesn't directly compare the pickets you are interested in, but could still be enlightening.

 

http://www.mra.org/services/grants/documents/FortiniSNOWANCHORS3B.pdf

[mike1]

Thanks everyone!

 

This is all really good info. Just when you thought you knew how to place a picket... It was interesting to find out that it's recommended to place the V picket pointing towards the load when top clipping, but turning it around for mid clips. It doesn't sound like there is significant difference between the T and the V pickets. At least not for general mountaineering.

 

You’re right about the skating in colder snow. You gotta know the conditions of the snow you’re placing in, for sure.

[korup]

For a full placed vertical picket clipped on the top hole at snow surface, he says "Never assume it will hold more than 500 lb." YIKES!

 

However, the MSR Coyote failed at 7.8 kN (~1800 lbs), and

for comparison, the smaller BD nuts (Size 4 and 5) are rated at 6 kN, which is ~1350 lbs.

 

In light of the "shear wedge" failure mode, the real question is how to build a solid 2-3 point anchor without adding in an American death triangle arrangement? Ice screws in glacial ice would be one option. Really, really long runners to keep the angles small and all pieces in different snow pockets? Other ideas?

 

[mike1]

how about in-line? You set them far enough apart, then rig the back one from a mid clip to the top of the next one in front and so on. Just spit balling... Or how about one in front (load side) and two in the rear (damn). Anyways, you back up the first anchor with others instead of multi point anchors. just some thoughts...

[korup]

The problem with in-line or a main and then backups, is that once the first one fails, you've excavated the whole snow wedge in front, and the rear anchors are now totally worthless, if I understand the pdfs correctly.

[mkporwit]

There's one more NZ article on the matter here

 

Seems to be largely in line with the article posted by nkane...

[pms]

Yates Cable Picket is the shit......

[Gary_Yngve]

In light of the "shear wedge" failure mode, the real question is how to build a solid 2-3 point anchor without adding in an American death triangle arrangement? Ice screws in glacial ice would be one option. Really, really long runners to keep the angles small and all pieces in different snow pockets? Other ideas?

 

Why do you need to build such a burly anchor anyway? It's gonna take a long time, which might expose you to additional objective hazards.

 

In soft snow, I like the hip belay from a sitting braced in a stomped out seat. Good for reducing forces too. Harder snow, carabiner-axe belay. But above all, the rule on steep snow is don't fall.

 

For rescue purposes, we use multiple deadmanned pickets connected via a cordalette or multiple v-threads connected via a cordalette.

[korup]

From the above article,

 

"We often see climbers just sitting in the snow and belaying off their waist, with a snow stake

behind them as a back-up anchor. What they are really doing is acting as a “deadman” themselves,

literally turning into one when things go wrong."

 

I am referring mostly to rescue anchors, as three point deadmen are not exactly fast to put together. However, 500 lb is a joke, and could *easily* be generated under lots of scenarios.

 

Having broken a micro stopper under body weight via an unexplained mechanism, I have a healthy respect for the fact that anchors are often far more complicated than we think, especially with snow and ice.

[catbirdseat]

Yates Cable Picket is the shit......

I've heard of knuckleheads tell people to cut the cables off of the pickets. Dumbest thing I ever heard. I added cables to my MSR Coyote pickets.

 

If the snow is neve, I pound as far as practical and clip hole nearest surface. If the snow is softer than neve, I use the cable. I cut a slot for the cable using the pick of my axe.

 

Also, consider carrying screamers.

[Tom_Sjolseth]

Good info. Thanks for posting.

[Doug_Hutchinson]

The only data that I can provide is empirical - last month I was descending a snow gully coming off the Throne - Little Swizterland AK. It was the first sunny, warm day in weeks and the snow was turning to shit fast - like questionable about holding body weight when it got steeper than 55-degrees. Due to the deteoriating conditions, we down-climbed with a 2-ft MSR picket ever 50 feet even though you could almost push the pickets in by hand the snow was so soft.

 

Shortly after I removed a picket, wet snow slides starting coming down the gully. After digging in for about 30 seconds and getting pummeled, a larger wet slide totally blasted me head over heels for a 100 foot slide down a 50-60 degree gully in a small avy. After I came to stop and climbed up to get the picket it was suprisingly solid. We were using a 7.7mm rope which is probably as good as a screamer and a full single rope. I cringe when I see Mazama/Mountaineer types using an 11mm rope with pickets.

[catbirdseat]

...a larger wet slide totally blasted me head over heels for a 100 foot slide down a 50-60 degree gully in a small avy. After I came to stop and climbed up to get the picket it was suprisingly solid. We were using a 7.7mm rope which is probably as good as a screamer and a full single rope. I cringe when I see Mazama/Mountaineer types using an 11mm rope with pickets.

This is a very good point, not to mention skinny ropes are a lot lighter. People don't always think of skinny being safer, but it's the truth.

[builder206]

We were using a 7.7mm rope which is probably as good as a screamer and a full single rope. I cringe when I see Mazama/Mountaineer types using an 11mm rope with pickets.

 

Finding an insight like this makes putting up with the rest of the bilge on this board worthwhile. In my limited experience placing pickets in the soft snow around here, I've always thought they were worthless. It never occurred to me to think about how a fall's energy deposit would be passed to the picket. Thanks.