Difference between revisions of "Snow shelters"

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(Igloos)
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Igloos are the mediterranean villas of snow shelters.  They are roomy, confortable, and let in a remarkable amount of light.  They are also notoriously difficult to construct compared to other snow shelters, and require you to have a snow saw in addition to the usual equipment.
 
Igloos are the mediterranean villas of snow shelters.  They are roomy, confortable, and let in a remarkable amount of light.  They are also notoriously difficult to construct compared to other snow shelters, and require you to have a snow saw in addition to the usual equipment.
  
To start, a quarry must be packed out.  The colder the snow, the more difficult this will be.  The quarry needs to be vigourously ski packed (jumping preferred) and then boot packed (again, jumping preffered at the end) and the left to freeze up solid for a few hours.  Blocks must be cut from the quarry with a saw in order to get them uniform.  All blocks must be nearly exactly the same size.  6"x12"x18" is about right.  They can be thicker at the base of the igloo, and thinner near the top, but all block should be square, no tapered.
+
===The Quarry===
  
The idea igloos is a perfect hemispherical dome.  To keep on target throughout construction, use a ski pole or a stick or something to measure from the centre of the iglooStart the igloo by drawing a circle in the snow using the measuring deviceMake it big enough for everyone to fit that needs to fit.  A 4 person igloo is a good size, and not too hard to buildThe first few blocks must be cut off at an angle to make a ramp.  If you want to get fancy, the entire first row can be a continuous ramp.  The first row of blocks should lean in to the centre only very slightly.
+
To start, a quarry must be packed outThe colder the snow, the more difficult this will beThe quarry needs to be vigourously ski packed (jumping preferred) and then boot packed (again, jumping preffered at the end) and the left to freeze up solid for about an hourOnce the quarry has been packed down, do not walk on it any more because doing so may crack the hardened snow.  If there is hard wind slab somewhere in the snowpack, blocks can be cut directly from the slab instead and a quarry is not necesary.
  
Build the igloo in a continuous spiral, keeping one person on the inside.  Each new block in the spiral is supported by the previous one.  This gets very tedious towards the top of the igloo.  Each block must be held in place and allowed to sinter (stick) to adjacent blocks.  Block corners can be trimmed with a saw to maximize contact with adjacent blocks.  Finally, cut a cap to match the size of the remaining hole.  The middle person is critical for lowering the cap into place.
+
===Cutting Blocks===
  
Note that at this point, the middle person will be built into the igloo.  Now is the time to cut out the door.  Just cut a nice arch shaped hole into the igloo wall.
+
Blocks must be cut from the quarry with a saw in order to get them uniform.  All blocks must be nearly exactly the same size, usually 6"x18"x24".  The blocks must be rectangular if they are going to balance properly.  They can be thicker at the base of the igloo, and thinner near the top, but all blocks should be square, not tapered.  Boot packing the snow will usually pack down a hard slab about 10-14 inches thick, meaning the blocks must be cut out horizontally.  Use a ski to help slide the blocks out of the quarry without breaking them.  Save any pieces of broken blocks for later.
 +
 
 +
===Placing Blocks===
 +
 
 +
The ideal igloo is a perfect hemispherical dome.  To keep on target throughout construction, use a ski pole or a stick or something to measure from the centre of the igloo.  Start the igloo by drawing a circle in the snow using the measuring device.  Make it big enough for everyone to fit that needs to fit.  2, 3 or 4 person igloos are a good size, and not too hard to build.  The first few blocks must be cut off at an angle to make a ramp for the next row of blocks.  To make life easier later on, the entire first row can be a continuous ramp.  The first row of blocks should lean in to the centre only very slightly.
 +
 
 +
Build the igloo in a continuous spiral, keeping one person on the inside.  Each new block in the spiral is supported from 3 corners that touch the row below and the adjacent block in the current row.  Each block must be held in place and allowed to sinter (stick) to adjacent blocks.  Breathing on the joint (warm moist air) will speed the sintering process.  Block corners can be trimmed with a saw to maximize contact with adjacent blocks, making the sintered joint stronger, but make sure not to change the overall shape of the block.  Note that there will be triangular spaces between the blocks, as the square blocks lean in on eachother.  The spaces will get bigger towards the top of the igloo.  Don't worry about filling the spaces until the end.
 +
 
 +
It is very important to measure the position of each block with the ski pole to make sure it conforms to the desired shape.  If there are any deviations (especially in the first couple rows) the igloo wall will not be as strong.
 +
 
 +
Finally, cut a cap to match the size of the remaining hole.  The middle person is critical for lowering the cap into place.  Depending on the height of the roof, the middle person may want to stand on some snow blocks inside the igloo.
 +
 
 +
===The Door===
 +
 
 +
Note that once the dome is complete, the middle person will be built into the igloo.  Now is the time to cut out the door.  Just cut a nice arch shaped hole into the igloo wall.  Dig out the snow below the door on the inside and outside of the igloo to make getting in and out easier.  If it's windy, you can make a tunnel over the entrance way using leftover blocks, but this is not always necesary.
 +
 
 +
===Chinking===
 +
 
 +
When the dome is complete, there will still be lots of triangular holes between the blocks.  Now is the time to fill the holes with pieces of broken blocks, or using any leftover blocks.  After chinking the gaps, shovel snow onto the igloo from the outside and tap it down with a shovel to seal any remaining cracks.

Revision as of 15:32, 1 March 2006

Snow shelter are a great way to avoid carrying a tent in the winter. When built properly, they can be very comfortable, especially when the temperature is well below freezing. There are 3 basic kinds of snow shelters: snow caves, quinzhees and igloos. Also, hybrid snow shelters can be built that incorporate other equipment. The simplest of these is building a snow wall around your camp to keep out the wind. There are many configuartions possible that use tarps as the roof and snow as the side walls.

Snow Caves

Snow caves are the easiest and fastest to build snow shelter, but a healthy snow pack is required. 2m of snow is a good starting point, the more the better. A couple good shovels and probe are the only tools needed. Make sure to probe your potential snowcave site before digging to discover any rocks, stumps, ice layers, or crevasses that might be hidden under the snow.

Snow caves are easiest to dig if you start on gentle slope. You can dig into the slope, instead of down, which make getting in and out easier. The slope makes it easier to clear the excavated snow away from the entrance. Don't pick a slope that's too steep, or else you will have to put a 90 degree turn in the cave. Digging into a slope also make it easier to construct a heat trap - read more on this later.

A good sized snowcave fits 2-4 people. Any larger and construction becomes a difficult and long process. There absolutely must be enough headroom to sit up inside without touching the ceiling, or you will be in for an uncomfortable morning. It's best to dig the ceiling into a high arch. This keeps the cave from sagging too much overnight. Don't go oveboard though - keep the thinnest part at least 30cm thick,. Wide, low caves are the worst, and you will wake up with the ceiling 2 inches from your face.

A good tactic for cold weather is to construct a heat trap. To do this, the floor of the sleeping area should be higher than the ceiling of the entrance, thus preventing cold air from flowing into the sleeping area from outside. A heat trap is easiest to build if your snowcave is dug into a slope, as it is very natural to dig somewhat upwards when excavating the entranceway.

Quinzhees

Quinzhees are a Snowcave-igloo hybrid for shallower snowpacks. Snow is piled up to a suitable height, packed, and then dug out from the inside like a snowcave. Quinzhees are much easier to build than igloos, but take a lot more time than a snowcave because of the time required to make the mound. One trick to speed up the mounding process is to pile up all your gear, and then pile snow onto the gear. The gear can then be retrieved during the excavation. Be careful what you use for this, especially if the snow is wet.

Igloos

Igloos are the mediterranean villas of snow shelters. They are roomy, confortable, and let in a remarkable amount of light. They are also notoriously difficult to construct compared to other snow shelters, and require you to have a snow saw in addition to the usual equipment.

The Quarry

To start, a quarry must be packed out. The colder the snow, the more difficult this will be. The quarry needs to be vigourously ski packed (jumping preferred) and then boot packed (again, jumping preffered at the end) and the left to freeze up solid for about an hour. Once the quarry has been packed down, do not walk on it any more because doing so may crack the hardened snow. If there is hard wind slab somewhere in the snowpack, blocks can be cut directly from the slab instead and a quarry is not necesary.

Cutting Blocks

Blocks must be cut from the quarry with a saw in order to get them uniform. All blocks must be nearly exactly the same size, usually 6"x18"x24". The blocks must be rectangular if they are going to balance properly. They can be thicker at the base of the igloo, and thinner near the top, but all blocks should be square, not tapered. Boot packing the snow will usually pack down a hard slab about 10-14 inches thick, meaning the blocks must be cut out horizontally. Use a ski to help slide the blocks out of the quarry without breaking them. Save any pieces of broken blocks for later.

Placing Blocks

The ideal igloo is a perfect hemispherical dome. To keep on target throughout construction, use a ski pole or a stick or something to measure from the centre of the igloo. Start the igloo by drawing a circle in the snow using the measuring device. Make it big enough for everyone to fit that needs to fit. 2, 3 or 4 person igloos are a good size, and not too hard to build. The first few blocks must be cut off at an angle to make a ramp for the next row of blocks. To make life easier later on, the entire first row can be a continuous ramp. The first row of blocks should lean in to the centre only very slightly.

Build the igloo in a continuous spiral, keeping one person on the inside. Each new block in the spiral is supported from 3 corners that touch the row below and the adjacent block in the current row. Each block must be held in place and allowed to sinter (stick) to adjacent blocks. Breathing on the joint (warm moist air) will speed the sintering process. Block corners can be trimmed with a saw to maximize contact with adjacent blocks, making the sintered joint stronger, but make sure not to change the overall shape of the block. Note that there will be triangular spaces between the blocks, as the square blocks lean in on eachother. The spaces will get bigger towards the top of the igloo. Don't worry about filling the spaces until the end.

It is very important to measure the position of each block with the ski pole to make sure it conforms to the desired shape. If there are any deviations (especially in the first couple rows) the igloo wall will not be as strong.

Finally, cut a cap to match the size of the remaining hole. The middle person is critical for lowering the cap into place. Depending on the height of the roof, the middle person may want to stand on some snow blocks inside the igloo.

The Door

Note that once the dome is complete, the middle person will be built into the igloo. Now is the time to cut out the door. Just cut a nice arch shaped hole into the igloo wall. Dig out the snow below the door on the inside and outside of the igloo to make getting in and out easier. If it's windy, you can make a tunnel over the entrance way using leftover blocks, but this is not always necesary.

Chinking

When the dome is complete, there will still be lots of triangular holes between the blocks. Now is the time to fill the holes with pieces of broken blocks, or using any leftover blocks. After chinking the gaps, shovel snow onto the igloo from the outside and tap it down with a shovel to seal any remaining cracks.