Before starting on a tour the ski mountaineer should provide himself with the means of constructing a shelter adequate to protect him against the strongest wind, the worst snowstorm, and the lowest temperature he may encounter. Requirements will obviously vary with terrain and climate. Types of shelter range from the simplest bivouac caves and brush huts to complete igloos, tents, and multi-room caves. The competent ski moun­taineer will not only familiarize himself with each type, but also will construct all of them in order to have the knowledge and experience necessary to meet all condi­tions.

Brush for shelters may not be securable, snow may not be deep enough for caves nor sufficiently compacted for igloos, time may be needed for touring rather than for constructing shelters out of locally available materials. Any or all of these causes warrants the carrying of some sort of a tent.

Tent Requirements

No single type of tent can truly be described as best. Each has distinct advantages. The small, two- to three-man tent with a tapered floor plan and sloping ridge is the most popular model. There are also the tried and proved mountaineering tents, such as the Mead, Logan, and Whymper.

Design of tents.—Whatever model is selected, certain factors are important:

1. Weight should be kept to about two to three pounds per man. This compels the elimination of many poles required by some types. Skis at front and rear, skis or ski poles for pegs, should fully satisfy all require­ments. The tent is dropped if left all day, and its location marked.
   
   
2. Tents that require numerous guy lines to support the various edges and walls have no place in winter mountaineering.
   
   
3. Tents with perpendicular walls will catch the wind and should be avoided wherever possible. Slop­ing walls, on the other hand, spill the wind, particularly if the guy lines which hold up the peak or ridge are supported by rubber bands.
   
   
4. A sewed-in bottom is indispensable. The tent will then be held down in heavy wind by the weight of the occupants even though all stakes and anchorages fail. If it is planned to use a tent primarily in timber, a permeable floor of two-or three-ounce percale is better than a waterproof floor. Laid over fir boughs it is warm (no air mattress is necessary), dry, and at the same time never allows puddles of water to form from melted snow or from condensation of breath, insensible perspiration, or steam from cooking. If the tent is to be used much above timberline, a light waterproof sheet may be laid over the percale floor or a waterproof floor of regular tent fabric substituted. The separate sheet, although heavier, has the advantage of permitting the condensa­tion on the inner walls to run down through the per­meable floor into the snow without wetting the contents of the tent.
   
   
5. Provision should be made, either by the tent design or by zippers on the tent floor, to cook on snow rather than on the floor itself. Water is then available inside the tent, and a toppling pot of soup is not a disaster.

The tent must be made of lightweight fabric in order to come within the rigid weight restrictions re­quired for comfortable ski mountaineering. Fabrics weigh­ing two to four ounces per square yard have tensile strengths of forty to eighty pounds per inch and in a properly designed tent are rugged enough for the most violent storms. Excellent lightweight nylon fabrics weigh­ ing from 11/2 to 21/2 ounces per square yard are now being made. Coated fabrics have not proved acceptable owing to the excessive condensation on tent walls, which cannot be effectively controlled by ventilation, particularly in stormy weather.

It is apparent that tents should be barely large enough to provide room for sleeping. Any additional size increases weight, requires the use of heavier fabric and stronger anchorage to resist winds, and decreases warmth because of the increased volume of air required to be warmed by the cook stove or body heat.

Pitching tents.—An area large enough for the tent is leveled if necessary by using a ski as a scraper. The snow is then compacted by vigorous stamping with skis. The floor of the tent is laid out with the entrance away from the direction of the prevailing wind. At each corner the snow is stamped hard by the boots, then more snow is kicked into the holes and similarly stamped in order to provide a firm anchorage. Skis and ski poles are usually used as pegs, although locally secured poles and sticks may serve. Tent pegs one foot long, made of sheet du­ralumin, bent longitudinally into a right-angle section, are sometimes carried. If the snow is fluffy or sloppy, these short pegs can serve as a dead-man anchor; the guy line is tied around the middle of the peg, which is then buried horizontally at least one foot below the snow surface at right angles to the guy line. The overlying snow is tamped thoroughly.

If fir boughs are used as a floor, they should, if tent design permits, be laid after the tent is pitched, but with an adequate supply along the sides of the tent. This elim­inates the tendency to roll off the edge of a fir-bough mattress.

Other Shelter

Under ordinary circumstances ski mountaineers should use a tent for shelter. But tents may be destroyed by fire or storm, and skiers may be separated from the member of the party carrying the tent. Therefore, every ski moun­taineer should know how to construct certain basic types of shelters from field materials. In addition, snow caves and igloos are more comfortable in heavy winds and un­der conditions of intense cold than are tents, and if time permits will be constructed out of preference. In the spring when the snow is deep and well packed, some ex­perienced snow campers travel without a tent, relying entirely upon bivouacs.

There are infinite variations of the basic types here described. Every man may well indulge his ingenuity.

Open bivouac.—On calm nights or in areas protected from the wind when no storm is threatening, there is no necessity for the construction of any shelter. A fir-bough bed laid on the snow for insulation and to keep the bag dry (or ground sheet and a mattress as a substitute) is all that is necessary. The deep snow hole under a dense drooping fir is an excellent spot for a one- or two-man bivouac. A low snow wall or a line of branches stuck in the snow will reduce snow drifting should a wind arise during the night.

If several persons are bivouacking together the quan­tity of boughs required for a mattress is reduced and con­siderable body heat is conserved. Two feet in width should be allowed for each person. A waterproof sheet may be thrown over all the sleeping bags for increased warmth. This will not condense excessive moisture be­cause ventilation is provided between the sleeping bags.

Brush shelter.—If the snow is not deep enough for a snow bivouac a brush shelter can be constructed, in the heart of the densest thicket available and well out of the wind. The design is unimportant provided the walls are interlaced densely for windproofing, and the entire shel­ter is made no larger than necessary. Covering the brush with bark, snow, or sod will aid windproofing and better retain air warmed by body heat.

Trench and wall bivouacs.—By shoveling a trench or building walls of snow blocks, using skis or field-cut poles for rafters, and a waterproof sheet or fir boughs for a roof, a satisfactory shelter can be produced. There are many designs, each with its vociferous advocates. Some prefer a lean-to, others a flat roof; some prefer a rec­tangular shape, others a hallway with alcoves accom­modating two skiers each; some prefer complete enclo­sure, others insist on an opening with a fire in front. Whatever the design or method of construction, these points should be borne in mind:

1. Provide adequate rafter strength to support a snow load should a snowstorm arise during the night.
   
   
2. If a waterproof sheet is used, be sure it slopes for drainage and is well anchored with snow blocks or other means to prevent the wind's ripping it away.
   
   
3. If a brush roof is used, cover it with snow if the weather is cold to keep in the warm air; but if the air temperature is near or above freezing do not do this as otherwise melting snow will drip, drip, drip.
   
   
4. If an open-front shelter is used be sure an all-night supply of wood has been gathered. And just in case you get tired of stoking the fire, or a storm douses it, have enough brush or snow blocks handy to close the entrance completely.
   
   
5. Trench bivouacs can be constructed in any size. The simplest is the one-man type, 31/2 by 21/2 by 7 feet, which can be stamped or kicked into the snow and lined and covered with fir boughs in about half an hour.

Fig. 4. Snow cave for one man.

One-man snow cave.—The simplest bivouac for a lone skier provided with a sleeping bag and a waterproof outer cover is the one-man cave. In the shelter of an overhanging conifer or beside a rock or log, or best of all, under a bent-over sapling, a cave can be kicked into unconsolidated snow with the boots, or dug out of packed snow with a cup or cooking pot in a few minutes. The cave should be just large enough to squeeze into after the lining of fir boughs or the air mattress has been in­serted. If a slope is not available a pit can be dug 31/2 feet deep and the cave dug as a drift from the pit. For greater warmth the top of the pit should be covered with boughs and snow blocks.

Wall of snow blocks

Fig. 5. Plan for a four-man snow cave.

Snow caves.—Here again there is an opportunity to choose from an infinite number of designs. For simplicity the standard four-man cave only will be described. Its layout is shown in the accompanying illustration. A com­pacted snow slope at least six feet in depth is selected, preferably a steep bank or drift. A tunnel with arched roof, about three feet wide and four feet high is dug directly into the bank. A small shovel, such as the army trench shovel, or a lighter duralumin substitute, is the best tool for the purpose, but a satisfactory job can be done with a long knife, or the heel of the ski (but do not pry hard with it). The face of the tunnel is cut into blocks, the lowest layer chipped out and the successive upper layers pried down. These blocks, remaining in­tact, can be removed by hand and the better ones used for the construction of the wing wall shown in the dia­gram. Broken blocks can be scraped out of the cave with hands or cooking pots.

Side alcoves holding two men each, 31/2 feet wide, 4 feet high, and 61/2 feet long, are constructed at right angles to the entrance hallway. A shelf 18 inches above the floor is cut at the end of the hall and used for cook­ing-

If the snow is too shallow or inadequately compacted, the same design may be constructed in the form of a ditch and roofed with local poles and branches, or with skis and waterproof sheet, the roof covered with snow.

Igloos or snow houses.—There is no mystery about this structure, nor any particular difficulty. Four men, after an afternoon's practice, should be able to build a snow house, large enough to hold them, in from 45 min­utes to an hour. The only thing needed is snow packed firmly enough (not simply crusted over) to support a man without his sinking in more than enough to leave a slight footprint. Probing with the handle end of a ski pole will help decide whether the snow is right all the way through, or only crusted.

A flat-bladed shovel, or the heel-end of a ski may be used for cutting the snowblocks. They should be cut in the shape of a domino, at least 4 inches thick, a foot and a half wide, and 2 or 3 feet long. Undercutting, in ad­dition to cutting around the edges, is necessary to secure well-shaped blocks. If four men work as a team, it will be well to have one cut blocks, another carry them to the building site, a third (standing inside the structure) put them into position, and the fourth caulk the joints with loose snow, or aid the builder. If blocks are cut from in­side the structure, the necessary height of wall to be con­structed is greatly reduced.

The floor plan may be oval or circular, but not rec­tangular. It is well to make an outline first, by standing in the center, grasping a ski at the desired radius, and sketching with the point the course to be followed with the first row of blocks. An inside diameter of eight feet will provide adequate quarters for four men.

Depending upon whether the house is to be high or low, each block of this first row is undercut along the lower edge. So beveled, the block will lean inward at the desired angle. Later rows will be similarly beveled.

When the first row has been completed, the next row may be built on top. But a better system is to provide for a continuous spiral in the following manner. Choos­ing any block in the first row, cut away a diagonal half —from the top of one side to the bottom of the other. Begin the second row of blocks by placing the first in this space. Then build continuously around and around in smaller and smaller diameters until space remains for only one more block at the top. This final block will act as a keystone, and the igloo as it stands will be satis­factory, if caulked with loose snow. But added strength will be provided, and the brushing off of snow at con­tact prevented, if a little time is taken for icing the in­terior. This is done by lighting a stove (or woodfire) inside the igloo, sealing the door, and leaving until the snow becomes sufficiently moist inside to form ice when the fire is extinguished and the cold air from outside let in.

The temperature inside such a house may easily rise to 70° or 80° while the stove is in operation. If this results in undue softening of the roof, it is only necessary to go outside and, with a ski, scrape down the thickness of the structure until the heat can be dispersed. If, on the other hand, hoarfrost begins to form and drop off the roof inside, it means that the structure is not thick enough to give adequate protection from the weather. The remedy here is to pile loose snow on the outside. Cooling may also be secured by increasing the number or size of vent holes.

In thawing weather igloos cannot be used because the blocks will shrink, causing the roof to sag and eventu­ally to collapse.

Even in the coldest weather, once the temperature in­side an igloo has been brought to 60° and kept there a while, mere body heat will ordinarily suffice to keep it comfortable thereafter.

An igloo which has been iced over inside by the method indicated is strong enough to hold the weight of several men standing on its roof, although a sharp blow at one point will puncture it. Igloos are also nearly sound­proof. But a man sleeping on the floor will feel, in a manner akin to hearing, any footsteps or vibrations com­ing from an appreciable distance. If the slope of the snow permits, the entrance can be made below the level of the floor. This prevents the escape of warm air except through the vent hole at the top and results in a much warmer igloo. Brush or a rucksack will serve as a door and permit control of ventilation. Lining the floor with fir boughs will provide additional warmth for sleeping.

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