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Winter Camping & Backpacking Camping & Backpacking Presentation.pdf And Backpacking Winter Camping › Hypothermia - is a condition in which core temperature drops below the required

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Text of Winter Camping & Backpacking Camping & Backpacking Presentation.pdf And Backpacking Winter...

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    And Backpacking Winter Camping

    › Hypothermia - is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as 95.0 °F.

    › Frostbite - is the medical condition where localized damage is caused to skin and other tissues due to extreme cold.

    Cold Weather Dangers

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    › Check the local weather forecast for the time period you will be in the backcountry – wet, dry, wind, temperature extremes.

    › Consider where you will be going in the backcountry – water front, mountains, alpine. In dry weather, the temperature drops about 5.5F per 1000 feet in elevation gain (3.2F for moist weather).

    › Consider how long you will be in the backcountry.

    › Consider your own sensitivity to low temperatures.

    › Consider the extent of your physical exertion at the end of the day.

    Deciding What to Bring

    › Conduction

    › Convection

    › Radiation

    › Evaporation

    › Respiration – Combination of

    convection and evaporation

    Mechanisms of Heat Loss

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    › Thermal conductivity, k, is the property of a material's ability to conduct heat.

    › Heat transfer across materials of high thermal conductivity occurs at a higher rate than across materials of low thermal conductivity.

    › Materials of low thermal conductivity are used as thermal insulation.

    Insulation Thermal conductivity

    [W/(m·K)] Vacuum 0

    Water (vapor) 0.016 Air (sea level) 0.025 Silica Aerogel 0.026

    Polyurethane Foam 0.02 - 0.03 Feathers 0.034 Fiberglas 0.035

    Wool 0.03 - 0.04 Polystyrene Foam 0.03 - 0.05

    Cotton 0.04 Hollow Fill Fiber Insulation 0.042

    Paper 0.04 - 0.09 Polyester 0.05

    Straw 0.05 Felt 0.06

    Wood 0.09 - 0.14 Mineral oil 0.138

    Particle Board 0.15 Neoprene 0.15 - 0.45 Rubber 0.16 Snow 0.16

    Polypropylene 0.25 Teflon 0.25 Sand 0.27

    Cement, Portland 0.29 Water (liquid) 0.561

    Thermal grease 0.7 - 3 Glass 1.1 Soil 1.5

    Concrete, stone 1.7 Water (ice) 2.2 Sandstone 2.4 Mercury 8.3

    Stainless steel 14 Titanium 21.9

    Lead 35.3 Steel 45 - 65 Iron 80.2

    Aluminum 237 Gold 318

    Copper 401 Silver 429

    Diamond 895

    Material

    › Thermal resistivity, R, is the product of the material thickness and reciprocal of the thermal conductivity.

    › Good thermal insulators have large R values.

    › An insulating material will have a large R value when the thermal conductivity of that material is small and the thickness is wide.

    › In layered materials, R-values can be added.

    Insulation

    1 tR t k k      

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    › The thermal insulation of clothing is proportional to the thickness of the dead air space enclosed.

    › Dead air is defined as any enclosed unit of air that is small enough that natural convection currents would not arise in it.

    › The dead air next to the skin is heated up by the body and provides a layer of warmth around the body.

    › The clothing is not what is keeping you warm it is the dead air.

    Insulation

    › The key to providing this dead air space is through having a number of layers of clothing.

    › If you have too much clothing on, you will overheat and start to sweat. You need to find the proper heat balance between the number and types of layers and your activity level.

    › Heat loss from a wet surface can be up to 25 times greater than a dry surface (due to the higher density of water).

    › If you sweat and get soaked, you will lose heat much more quickly through evaporation of the water.

    › So you want to control your layers so as to be warm at the activity level you are in but not sweating profusely.

    › Convection may account for the greatest amount of heat loss under most conditions. In order to properly insulate, you need to have an outer layer that is windproof.

    The Layering Principle

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    › The Base Layer - wick moisture away from the body allowing you to remain dry and warm.

    › The Middle Layer - provide thermal protection from the wind and the cold.

    › The Outer Layer - protect against rain and wind, but allowing you to breath.

    › Extremities - heads, hands and feet. Up to 40% of the bodies heat can be lost through the extremities.

    The 3 Layer System

    › Cotton is basically useless in winter time.

    › Problems with cotton occur when the cotton gets wet.

    › Cotton absorbs this moisture and the water occupies the space previously occupied by dead air.

    › When water occupies the space previously occupied by dead air, cotton loses all insulating properties.

    › Because cotton holds so much moisture, it can hold that moisture against your body and sap body heat from you by high evaporative cooling and conduction. This can quickly lead to hypothermia.

    › A cotton garment is almost impossible to dry out.

    › Cotton becomes abrasive when wet.

    No Cotton - Cotton Kills!

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    › Silk loses its insulating properties when it gets wet and does not wick like modern hydrophobic fabrics.

    › Wool insulates relatively well when wet. But while some weaves do shed water for a period of time, it will eventually absorb a great deal more moisture than comparably weighted synthetic garments and become very heavy.

    › All of these natural fiber fabrics take much longer to dry once wet than comparably weighted synthetic fabrics.

    Natural Fibers

    › Light Weight – Capilene 2

    › Medium Weight – Capilene 3

    › Expedition Weight – Capilene 4

    Base Layer

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    › Fleece, made from polyethylene or other synthetics has many of the features of wool, but is lighter. It provides good insulation even when wet, absorbs very little moisture, and dries quickly.

    – 100 Weight – 200 Weight – 300 Weight

    Mid (Insulating) Layer

    › Down Fill has very good warmth to weight ratio, and can be packed down (squeezed) to take very little room. It is expensive, makes a thick garment, dries slowly, loses its insulating properties when wet or compressed, and stops lofting properly after being washed several times.

    Mid (Insulating) Layer

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    › Fill power is a measure of the loft or "fluffiness" of a down product that is loosely related to the insulating value of the down.

    › The higher the fill power the more insulating air pockets the down has and the better insulating ability.

    › Fill power is expressed as cubic inches per ounce (in³/oz).

    › Fill power ranges from about 300 in³/oz for feathers to around 900 in³/oz for the highest quality down.

    › A lofting power of 400-450 is considered medium quality, 500-550 is considered good, 550-750 is considered very good, and 750+ is considered excellent.

    Mid (Insulating) Layer

    Technically speaking fill power is a measurement of the amount of space one  (1) ounce of down (as shown on the right) will occupy in cubic inches when  allowed to reach its maximum loft.

    For example, one (1) ounce of 800 fill power goose down will loft to 800 cubic  inches. The higher the fill power the larger the down cluster. Larger down  clusters will loft higher, last longer and sleep warmer. 

    › Synthetic Fill is polyester fiber (such as Polarguard, Hollofil, Quallofil) used similarly to down, but does not have as good a warmth to weight ratio.

    › It is less expensive, provides good insulation (fairly efficient at providing dead air space though not nearly as efficient as down) even when wet, dries quickly, and absorbs very little moisture.

    › Over time with repeated compressions, the fibers become damaged and become less effective as an insulator.

    › Primaloft - the principal behind super thin fibers is that by making the fiber thinner you can increase the amount of dead air space in a given volume of material. Other super thin fibers include Microloft and Thinsulate.

    Mid (Insulating) Layer

    Primaloft One

    Down

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    › Hard Shell – these materials are waterproof and somewhat breathable. Their essential element is a thin, porous membrane that blocks liquid water, but lets through water vapor (evaporated sweat). The more expensive materials are typically more breathable. The best-known brand is Gore-Tex.

    › All rainwear exteriors (also known as face fabrics) are treated with a durable water repellent (DWR) finish. Even rainwear classified as water-resistant (which includes soft shells) carries a DWR finish.

    Shell Layer

    › Soft Shell – these are water resistant materials only partially block water. On the other hand they are usually more breathable and comfortable than hard shells.

    › Soft Shells use sophisticated stretch woven fabrics (Schoeller, for example) with tight layered weaves and durable water repellent (DWR) treatments to guard against wind, rain, and snow in all but the most severe weather conditions.

    Shell Layer

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