/ How strong is a deadman anchor? Answers here

Please Register as a New User in order to reply to this topic.
ENSA - on 13 Oct 2017
The French national guides' school and mountain rescue services tested the strength of various makeshift snow anchors. Results in English in this video link:

https://www.youtube.com/watch?v=yYtYZgeUpek
Andy Nisbet - on 13 Oct 2017
In reply to ENSA:

Interesting. But not the traditional deadman that we know in UK. And not the buried axe which again we use. So only of passing interest to me.
ENSA - on 13 Oct 2017
In reply to Andy Nisbet:

Bonjour Andy, point taken. These tests were mostly carried out on makeshift anchors that Alpine climbers/skiers might use to make an improvised abseil from, or from snowstakes that the rescue service uses when carrying out rescues.

ENSA has also tested buried ice-axe and traditional deadman anchors and got the following results:

Buried ice-axe: 130 to 700daN
Aluminium deadman (standard size): 140 to 360daN

AlanLittle - on 13 Oct 2017
In reply to ENSA:

Is it differences in the consistency of the snow that account for the wide range of results, or how the anchor is positioned?

(Apologies if you already explained that in the video - didn't have time to watch it yet)
ENSA - on 13 Oct 2017
In reply to AlanLittle:

> Is it differences in the consistency of the snow that account for the wide range of results, or how the anchor is positioned?

It depends on both.

The results in the video are only valid for heavy, thawing snow. But one of the objectives of these tests was to measure how the angle of a snowstake affects its holding power. Inserting a snowstake at an angle of 25┬░to the slope increased its strength by 40%.
Dave Perry - on 13 Oct 2017
In reply to ENSA:

Years ago on my winter ML training with one of the leaders/instructors being Andy Nisbet, we made a slot anchor with the rope around a mars bar (rather cold one!!) The mars bar buried a foot into hard neve the whole group of us, 2 instructors and probably five or six students, could not pull it free.... No doubt it was a Glenn More lodge party trick!
Andy Nisbet - on 13 Oct 2017
In reply to Dave Perry:

It was a party trick!
Lion Bakes on 13 Oct 2017
In reply to Andy Nisbet:

> It was a party trick!

A Mars a day helps you work, rest and abseil
Andy Nisbet - on 14 Oct 2017
In reply to ENSA:

> Bonjour Andy, point taken. These tests were mostly carried out on makeshift anchors that Alpine climbers/skiers might use to make an improvised abseil from, or from snowstakes that the rescue service uses when carrying out rescues.

> ENSA has also tested buried ice-axe and traditional deadman anchors and got the following results:

> Buried ice-axe: 130 to 700daN

> Aluminium deadman (standard size): 140 to 360daN

Sorry, I misunderstood the point of the article and didn't realise it was more aimed at ski mountaineers. Surprising that the aluminium deadman (which I don't use) came out basically weaker than the buried ice axe (which I do use).
Big Lee - on 14 Oct 2017
In reply to Andy Nisbet:

Wonder how quickly gradient affects things. I'd expect a deadman (DMM type) to be stronger on a 45 degree snow slope for example compared to a buried axe (certainly more practical).
mattsccm - on 14 Oct 2017
In reply to Big Lee:

In the early 80's on a Bangor Normal College O Ed day we tried all sorts of things. It started with a leather glove that John Brailsford was keen on then got silly. A Mars bar was the starting point but of course other chocolate had to be tried. I seem to remember that a Cadburys Flake wasn't up to much, not having the laminated structure of a Mars. Malt loaf wasn't all that good either. I suppose that in firm snow anything wider than the slot would have some holding power if the rope didn't cut through. I think we tried a sandwich but can't remember what was in it.
Mike Nolan - on 15 Oct 2017
In reply to Big Lee: This is a really good question.

I would be really interested in seeing some tests on buried axes on different slope angles.

Wayne S - on 15 Oct 2017
In reply to ENSA:

Thanks for sharing the outcome of your testing with us.
wbo - on 15 Oct 2017
In reply to Mike Nolan: I might be wrong here but I don't think the slope makes a difference to the strength of the anchor as long as the angle of the rope to the slope stays the same. What it does have a big impact on is the force that an abseiling climber will apply to that anchor

ben b - on 15 Oct 2017
In reply to Andy Nisbet:
My recollection is that the old advice not to disturb the snow immediately beneath the anchor ("to preserve its strength") has been superseded by "compact away guys!" as sublimation effects and rebonding of the disturbed snow results in a much stronger substrate to anchor behind. Distant memories of an article with a picture of dozens of mangled snow stakes, possibly from the US (where stakes are more common than deadmen, much like NZ).

Personally I prefer stakes, as they are more multifunctional and easier to carry (and in NZ shallow depth of snow tends not to be as much as an issue as it can be in the UK); however I don't get out much these days!

Interesting thread - thanks all.

b
Post edited at 21:44
Jonny on 16 Oct 2017
In reply to ben b:

> Distant memories of an article with a picture of dozens of mangled snow stakes, possibly from the US (where stakes are more common than deadmen, much like NZ).

Could it be this one (from guys in NZ)?: http://arc.lib.montana.edu/snow-science/objects/ISSW_O-061.pdf

> Personally I prefer stakes, as they are more multifunctional and easier to carry (and in NZ shallow depth of snow tends not to be as much as an issue as it can be in the UK); however I don't get out much these days!

Multifunctional as in also useful for running belays, you mean, or as half-kilo tent pegs? ;-) Aside from their use as anchors for fixed ropes in rock hard Himalayan neve, I find it hard to imagine taking them along for an alpine-style climb. I've got a couple, but I'd sooner bring a spare lightweight axe, which barely weighs more. Not sure what the style down in NZ is - perhaps that explains their popularity, along with snow conditions.
ben b - on 16 Oct 2017
That's the one - thanks for the link.

I suspect the pain of abandoning a lightweight axe is greater than the pain of abandoning a snow stake, but on the other hand they also make very photogenic tent pegs!

Don't knock the simple joy of erecting your trusty Macpac Minaret off a windward stake buried to the hilt (and preferably tied off mid shaft for full strength as per the paper)!

;-)


b
Kimberley on 16 Oct 2017
In reply to ENSA:

Here's a few other relevant references

SNOW ANCHORS FOR BELAYING AND RESCUE
http://arc.lib.montana.edu/snow-science/objects/ISSW_O-061.pdf

https://www.ukclimbing.com/forums/t.php?t=538482
ENSA - on 17 Oct 2017
In reply to ENSA:

Thanks for the comments everyone, it's made entertaining reading.

We'll make sure we test a range of snack foods next time!
malk - on 17 Oct 2017
In reply to Mike Nolan:

why use an axe when a plastic bottle or bag is (almost) as effective?

Please Register as a New User in order to reply to this topic.