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Andy Kirkpatrick


25 December 2014

MTN Book extract: Snow Walls


I’ve got eight days left on my Indiegogo Denali Winter solo project, and at 45% I need to give it a bit of a boost.  Although a few people think I’m looking for a handout, this project is about working for the support, either buying an extensive kit list (covering clothing, equipment, technology, custom kit), a ticket to a show in Sheffield at the Library theatre, or a copy of my next book MTN - a book tech book on mountaineering (non technical, big mountain stuff). To those ends I thought I share a small chunk of the book, which should be great for anyone doing greater ranges trips (or UK winter camping!).  If you’d like to support my exped, then anything you can give will help, as the costs involved, although small for a big budget expedition, are quite high for me (Well that is if I want to be able to pay my rent when I get home!).

TENT SURVIVABILITY (extract)

In a high mountain or polar environment your tent can be exposed to winds that can easily exceed the ‘safe working load’ of even the most advanced mountain tents, leading first to broken poles, then fabric/seam breakdown, followed by the doomsday scenario of the whole tent being blown away with you in it!

The strongest mountain tents made (a Snowsled Scott tent) will still only survive winds of 90 mph, which is extreme, but it can and does get windier than that, then the Scott is a 30kg monster with virtual scaffolding as poles!  Now how would a 3kg tent with skinny alloy poles thinner than your little finger do in those conditions?  Mountaineering is full of stories of people who put too much trust in technology (Scott for one), and no matter how strong, how space-age, in a hellacious storm you tent will die (and you too) unless you protect it.  I can talk about this with some experience, having both spent many, many nights trapped in such terror storms, as well as having a tent destroyed in one, leading to a potentially life threatening situation,

There are many ways to increase your mountain tents survivability.  These include:

  1. Snow Walls
  2. Choice of tent (fabrics, construction, shape)
  3. Double poling (full or partial)
  4. Staking out the tents (bamboo, skis, deadman)
  5. Positioning
  6. Storm maintenance

If you use all these techniques you can both survive big storms, but more importantly you’ll be able to do this in relative comfort (warmer, safer) and be able to move on or up once the storm has past.  Of off the skills in this book, this is one of the most important for your survival.

Below I will cover each of these topics.

Snow Walls


A single layer of snow blocks set in the correct position, shape and configuration will not only save your tent, but also make it quieter (less flapping), warmer and if set correctly, less likely to becoming drifted it.  Russian climbers in the past have avoided snow walls, preferring to place their tents in more exposed places so as to avoid drifting (tents getting buried), but the designs of their tunnel tents tended to be more heavy duty then western designs (thicker poles).  For Western climbers the use of a wall in any camping spot should be second nature (with or without a good forecast), but you should also take to to understand how to best build and set one, so as not to create secondary problems.

Never dig down, Dig up!

Before we continue onto the wall itself, it’s worth noting that you should never dig down into the snow in order to find protection unless you’re digging a snow trench or snow hole.  Placing your tent lower than ground level will guarantee your tent gets buried in any storm, with or without a wall.  This is worth noting when climbing established routes such as Denali, where you may come across second hand tent spots.  If they’ve been used over a long period they may have become drifted in so that they are basically below ground.  Although tempting, you should start a new site from scratch at ground level (see how more lazy climbers get on in the next storm). 

Snow Blocks

The art of selecting the ‘quarry’ for blocks, cutting, sizing and moving them comes pretty quickly. Here are some basic rules and tips:

  1. Use your snow saw (or avalanche probe) to check the best place for your quarry, looking for a depth of good snow about 6 inches.
  2. The bigger the block the faster the wall is built, but this is offset that a big block of snow is heavy, and it’s actually common for climbers to injure themselves, bending and carrying.  A big block is also more unstable to carry, meaning they can break apart, and their size allows more variety in snow density (different snow layers), which can further create problems.
  3. I prefer blocks a little bigger than the size of breeze block (45x22x10cm), going for something the full length of my snow saw (this way you can make then all the same length), half its length wide, and a third of its length thick (so about 60cmx30cmx20cm).  This size is easy to move and pass around, and makes a wall with dence blocks without any weak layers, plus their smaller size makes it easier to shape the final wall.
  4. Quarry along the edge of the wall to give your wall a slight boost in hight, as well as make bricklaying a little easier.
  5. Be prepared to move blocks from other locations using a pulk or sleeping mat as a drag sledge.
  6. In a big team have one person in charge of digging, one for moving, and one for bricklaying, and keep rotating the team around.
  7. In Storm conditions make sure the shovel and snow saw are always secure in between use, as they can blow away (If conditions are very extreme then work on the leeward side of the wall, but just don’t quarry in such a way as to lower the level of the tent. If you have multiple snow saws and shovels, you can start by having a everyone quarrying and bulding up a stockpile.  Then while this is being used, one or two people can keep cutting while others build.
  8. In this quarry faze it’s important that team mates who are not needed are moved back into the tent (where they can sort out kit, melt snow, or stay warm ready to switch with someone outside).  Very often everyone gets cold, and have no hot drinks available due to someone not wanting to seem lazy.
  9. Digging, rebuilding and tinkering with your snow walls may seem like a pain, but it’s actually a great way to improve your acclimatisation on the mountain, as sitting around is not ideal (plus having a solid wall means you really can relax).

Bad or no Snow

If you’re forced to try and dig a wall in bad snow, either super dense snow full of power or ice layers, then construction can be pretty tricky.  In very soft powdery snow you will need to stamp it all down in larger area, then let it set for an hour in order to get some density. If you can only quarry thin layers, then you’ll need to build more of a mound (like a pile of books), as the block quality will be two poor to hold its weight.  Such a wall will need to be much smaller, the aim to cast its wind shadow on just the tent, as making a much wider traditional snow wall would take all night.  Once you have the bare bones of a wall, smashing up the hard ground and shovelling the debris can help, and if you can get thin layers of dense snow/ice, then these can be laid like scales to protect the snow underneath. In the past I’ve improvised by using bulks (Secure them so they don’t blow away) to add extra bulk to a wall, and in a real life or death situation, in an exposed position (say you can’t even dig a trench), you could fill up rucksacks, bivy bags, large stuff sacks and heavy duty garbage bags to create a sort of low sandbag defence - which although not ideal, could help you survive the night.  In my experience, unless you’re camping on pure ice, you can always make some kind of wall.

Building the Wall

When it comes to building a snow wall you can either just ‘knock one up’ - a big flat wall that blocks the wind, or you can do something a little more scientific.

The Basic construction

When making your wall start by making sure your have solid foundations (pack down the snow if it’s soft) and make sure this first row is set level.  Each subsequent row should have the blocks offset from the ones below (like a brick wall), and you can use a snow saw to fine tune the joins (this can be filled later by using chinks of snow).  The wall itself may not seem super solid at first, but in low to mid wind speeds it will be strong, and will quickly freeze into one solid object capable of withstanding very high winds. 
If you plan on having a fixed camp in very hostile weather over a long period, then consider making the wall double thickness (or even triple!).  This does not have to but full height, but only half height in order to bolster your defences.

Here are a few tips that apply to all walls:

  • Make the wall the same height, or higher than your tent, as this will reduce a drop off of wind speed a little, and so reduce drifting and the burying of your tent.
  • Don’t place the tent bang up against the wall, but leave a wide gap so that you can easily walk around the tent without standing on it (I would leave about 6 feet between the rear porch and the wall), as this will give you room to go out and dig the tent out (you will always get drifting).
  • Always bring everything in within the walls (pulks etc), and always go to bed with the expection that you will get clobbered (so no kit left loose outside). Keep your shovel and snow saw inside the tent.
  • When placing your tent, try and make sure it is not in the drift shadow of another tent, and in ideal conditions you should be 25 times the width of your tent from any other.  If you’re in a multi tent team, then wand the route between both tents so people don’t get lost (the closer the tents the greater the danger of one tent creating a drift over your tent).

Ok so now lets look at the two types of wall you can build.

Basic wall

This is the most common style of wall, and tends to be placed behind the tent in the expected direction of the wind, about six metres long (depends on the tent).  This will tent to be right angles to the tent, and is quick and simple to build.

Advanced Aero Wall

The biggest danger with all snow walls is that although they can save your tent, they can also create eddies, or slow the wind down causing the to be dropped snow, burying your tent (once your tent is ⅔ thirds buried you need to get out and dig it out).  In order to reduce this (you can not eliminate it) you can make a aero wall (basically and aerodynamic wall).

Instead of a flat wall, construct the wall in either a V shape, or a curve as as not reduce the wind speed as much (think of a river running around the legs of a bridge).
Consider adding snow to the windward side so as to further reduce its drag on the wind, as well as strengthen the wall itself. This will take time, but is worth the effort if you’ll be there a long time.

Placing a second smaller wall half the height of the first around 5 metres from your other wall can reduce drifting, as this will create a drop zone for the snow, before it hits you main wall, causing drifting that should only strength the wall beyond.

With all walls it tends not to be necessary to build the wall all the way round the tent, as this will help to trap any falling snow, and by checking the ground (Sastrugi, local knowledge etc) you can usually get away with one wall (but always be ready to throw up a second one!)

MTN book should be finished post Denali trip, which will be late March 2015, and you can back my project by buying a pre-copy here (format is PDF, Ibook and EPUB, not print… but it’s the words you’re paying for, not how they’re passed on).

 

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A Snicker's bar costs 60p. Were these words worth as much?

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