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1 Design types

A basic sleeping bag is simply a square blanket, filled with cotton or other material, and fitted with a zipper on three sides allowing it to be folded in half and secured in this position. A sleeping bag of this type is packed by being folded in thirds, rolled up, and bound with strap s or cords. The basic design works well for most camping needs, but is inadequate under more demanding circumstances.

The second major type of sleeping bag, sometimes called a mummy bag due to its shape, is different in a number of important ways.

• It is tapered, with the foot end narrower than the head end. This reduces both volume and surface area, improving its overall heat retention properties.
• It usually only unzips part of the way, so that the foot end is permanently cylindrical in shape. The zipper is a weak point in any sleeping bag's insulating qualities. Together with the tapered shape, this design feature helps protect the feetThis article is about a foot as a biological structure. For other uses of foot, see foot (disambiguation). The foot is a biological structure found in many animals that is used for locomotion. The plural of foot is feet and this pair is one of seven mutat, which are more vulnerable to heat loss than other parts of the body.
• It usually has a drawstring mechanism at the head end, to help prevent the escape of warm air.
• The most important difference is the insulating material. "Mummy" bags are filled with synthetic, hollow fibers, or down feathersThe down of birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Down is a fine thermal insulator and padding, used in goods such as jackets, pillows and sleeping bags. (see below).
• A mummy bag often cannot be rolled like a rectangular bag. Instead, it is simply stuffed into a special drawstring bag called a stuff sack. A compression sack is a special type of stuff sack with a cloth lid that is attached to the opposite (sealed) end of the sack with adjustable straps. When the straps are forcibly shortened, the sack is reduced in size, for easier stowage in internal-frame backpackThe simplest form of backpack (also rucksack or knapsack is a cloth sack carried on one's back and secured with two straps that go over the shoulders and below the armpits. The shoulder is better suited for bearing heavy weights for long periods of time ts.

2 Fill

Backpackers have debated for years about the relative merits of synthetic and down-filled bags. Synthetic fill does not readily absorb waterDrinking water This article focuses on water as we experience it every day. The water (molecule) article describes water from a scientific and technical perspective. Water is an abundant substance on Earth. It exists in many forms, such as sea, rain, and, dries easily, and provides some warmth even when completely wet. These properties may be a matter of life and death if, for example, the sleeping bag is accidentally dropped into water on a cold day. Also, the synthetic material is firm and resistant to compression. Any insulation is compromised when it is compressed, so this makes the sleeping bag warmer on the bottom.

Other materials, notably cotton and woolThis article is about wool, the fiber. For alternative meanings see Wool (disambiguation). Wool is the fiber derived from the hair of domesticated animals, usually sheep. Material Most of the fiber from domestic sheep has two qualities that distinguish it, have also been used for sleeping bags. Wool is highly water-resistant, due to its natural greasiness, and quite resistant to compression, but also much heavier than any alternative. Cotton suffers from high water retention and significant weight, but persists in applications like stationary camping where these drawbacks are of little consequence and its low cost is attractive.