Tent
A tent is a shelter consisting of sheets of fabric or other material draped over or attached to a frame of poles or attached to a supporting rope. While smaller tents may be free-standing or attached to the ground, large tents are usually anchored using guy ropes tied to stakes or pegs. First used as portable homes by nomadic peoples, tents are now more often used for recreational camping and temporary shelters.Tents range in size from one-person "bivouac" structures for a hiker to sleep in to huge (circus) tents capable of seating thousands of people. The bulk of this article is concerned with tents used for recreational camping which have sleeping space for one to ten people. Larger tents are discussed in a separate section below.Tents for recreational camping fall into two categories. Tents intended to be carried by backpackers are the smallest, lightest, and most expensive type.
Smaller tents may be sufficiently light that they can be carried for long distances on a touring bicycle, a boat, or even a person's back. Some very specialised tents have spring-loaded poles and can be 'pitched' in seconds, but take somewhat longer to strike.The second type are larger, heavier tents which are usually carried in a car or other vehicle. Depending on tent size and the experience of the person or people involved, such tents can usually be assembled (pitched) in between 5 and 25 minutes; disassembly (striking) takes a similar length of time. The military organisations of most nations use tents to temporarily house troops living and working under field type conditions.At times, however, these temporary shelters become a permanent or semi-permanent home, especially for displaced people living in refugee camps or shanty towns who can't return to their former home and for whom no replacement homes are made available.
General considerations
Tent fabric may be made of many materials including cotton (canvas), nylon, felt and polyester. Cotton absorbs water, so it can become very heavy when wet, but the associated swelling tends to block any minute holes so that wet cotton is more waterproof than dry cotton. Nylon and polyester are much lighter than cotton and do not absorb much water; with suitable coatings they can be very waterproof, but they tend to deteriorate over time due to a slow chemical breakdown caused by ultraviolet light. The most common treatments to make fabric waterproof are silicon impregnation or polyurethane coating. Since stitching makes tiny holes in a fabric, it is important that any seams are sealed or taped to block up these holes to retain waterproofness.Rain resistance is measured as a hydrostatic head in millimetres (mm). This indicates the pressure of water needed to penetrate a fabric.
Heavy or wind-driven rain has a higher pressure than light rain. Standing on a groundsheet increases the pressure on any water underneath. Fabric with a hydrostatic head of 1000 mm or less is best regarded as shower resistant, with 1500 mm being usually suitable for summer camping. Tents for year-round use generally have at least 2000 mm; expedition tents intended for extreme conditions are often rated at 3000 mm. Where quoted, groundsheets may be 5000 mm or more.Many tent manufacturers indicate capacity by such phrases as "3 berth" or "2 person". These numbers indicate how many people the manufacturer thinks can be fit snugly into a tent with just sleeping bags. These numbers do not allow for any personal belongings such as luggage, inflatable mattresses, camp beds, cots, etc. nor do they allow for people who are of above average height.
Parts of a modern tent
There are three basic configurations of tents, each of which may appear with many variations:
Single skin (USA: single wall): Only one waterproof layer of fabric is used, comprising at least roof and walls. To minimize condensation on the inside of the tent, some expedition tents use waterproof/breathable fabrics.Single skin with flysheet: A waterproof flysheet or rain fly is suspended over and clear of the roof of the tent; it often overlaps the tent roof slightly, but does not extend down the sides or ends of the tent.Double skin (USA: double wall): The outer tent is a waterproof layer which extends down to the ground all round. One or more 'inner tents' provide sleeping areas. The outer tent may be just a little larger than the inner tent, or it may be a lot larger and provide a covered living area separate from the sleeping area(s). An inner tent need not be waterproof. The double layer may provide some insulation.
Components: A flysheet or rain fly (found only in double skin tents) is used to protect the inside of the tent from water. It is waterproof on the outside and also provides a surface to collect condensation on the inside. Condensation then runs down the walls to the ground. When a flysheet is used, it is important that there be no contact with the inner tent it is protecting; this keeps the inner dry. 'Expedition' tents often have extra poles to help ensure that wind does not blow the two layers into contact. The inner tent comprises the main body of the tent. For double skin tents, the inner tent (often mesh) is not waterproof since it is protected by the rain fly. For single skin tents, the inner tent is often made of waterproof-breathable material that prevents liquid water from penetrating the inside of the tent, but still allows water vapour to be transported out.
Design factors
Many factors affect tent design, including: Financial cost, Intended use, Backpacking/tramping, lengthy duration for carrying the tent. Weight and size are the most crucial factors.Touring, high freqency of pitching and striking the tent. Ease of pitching/striking the tent is important. Static, staying at one campsite for a week or two at a time. A comfortable camping experience is the target. Camping season A tent required only for summer use may be very different from one to be used in the depths of winter. Manufacturers label tents as one-season, two/three-season, three/four season, four season, etc. A one-season tent is generally for summer use only, and may only be capable of coping with light showers. A three-season tent is for spring/summer/autumn and should be capable of withstanding fairly heavy rain, or very light snow. A four-season tent should be suitable for winter camping in all but the most extreme conditions.
An expedition tent (for mountain conditions) should be strong enough to cope with heavy snow, strong winds, as well as heavy rain. Some tents are sold, quite cheaply, as festival tents; these may be suitable only for camping in dry weather, and may not even be showerproof. Size of tent
The number and age of people who will be camping determines how big and what features the sleeping area(s) must have. To allow for inclement weather, some covered living space separate from the sleeping area(s) may be desirable. Alternatively, cyclists on a camping trip may wish for enough covered space to keep their bicycles out of the weather. To allow for sunshine, an awning to provide shade may not go amiss. Some tents have additional poles so that the fabric doorways can be used as awnings. Ridge tents have a steeply sloping roof so the whole height is rarely usable.
Shelters
Shelters are not normally used for sleeping. Instead they may act as a store or provide shelter from sun, rain, or dew. A flysheet consists of a single rectangular sheet of material. Two opposite sides are held up in the middle by poles, or sometimes just a rope between conveniently placed trees. The tops of the poles are attached via guy ropes to pegs, in order to keep the poles upright. Additional guy ropes are attached to the lower edges to pull them outwards away from the poles.
A Gazebo uses a framework of metal poles to support a roof. This structure provides a lot more usable space than does a flysheet, since the gently sloping roof allows for a reasonable amount of headroom even at the edges. Because a gazebo is free-standing, it is often used as a shelter for a temporary shop at a fair or street market. Beach tents are often a simplified form of dome tent and provide a useful place to temporarily store beach equipment, but are at most showerproof.
Some beach tents use specially treated fabric which is opaque to ultra-violet light, and so provide some protection against sunburn. Maximum height is typically about 120 cm (4 ft), and they are usually not large enough for an adult to lie down in. Fishermen's tents are also modified dome tents, often with a projecting awning high enough to sit under, but sometimes with no closable doorway.Frame tents are double-skin tents. They have a living area and one or more cotton/nylon/polyester inner tents. The outer tent is draped over a free-standing steel frame, and may be made of canvas or polyester (the latter often has a hydrostatic head of 3000mm, i.e. three season camping). The living area is generally at least as large as the sleeping area, and there may be a specific section with window and extra air vents for use as a kitchen. The walls are nearly vertical and are typically about 150 to 180 cm high (5 ft to 6 ft).
Flexible poles
Flexible poles used for tents in this section are typically between 3 and 6 metres long (10 and 20 feet). Cheap poles are made of tubes of fibreglass with an external diameter less than 1 cm (1/3 inch), whereas more expensive aluminium alloys are the material of choice for added strength and durability. For ease of transportation, these poles are made in sections some 30 cm to 60 cm long (1 to 2 ft), with one end of each section having a socket into which the next section can fit. For ease of assembly, the sections for each pole are often connected by an internal elastic cord running the entire length of the pole. Dome tents have a very simple structure and are available in a wide variety of sizes ranging from lightweight 2-person tents with limited headroom up to 6 or 9-person tents with headroom exceeding 180 cm (6 ft). These may be single wall, or single-wall with partial flysheet, or double wall.
Depending on the pole arrangement, some models pitch outer-tent first, while others pitch inner-tent first. The former helps keep the inner tent dry, but the latter is easier to pitch.The basic dome has a rectangular floor and two poles which cross at the peak; each pole runs in a smooth curve from one bottom corner, up to the peak, and then down to the diagonally opposite bottom corner. There are usually special fittings at each corner which fit into sockets at the ends of each pole - pole tension keeps everything in shape. The poles can run on either the inside or outside of the tent fabric. When located on the interior, poles are held in place by a variety of means including hook and loop style straps, clips, and other fastening hardware. Poles that are located on the outside of the tent fabric are attached via fabric pole sleeves or plastic clips. Dome tents do not require guy ropes and pegs for structural integrity as they are considered free-standing.
Inflatable airbeams
Inflatable pole supports, also known as airbeams, serve as rigid structural supports when inflated but are soft and pliable when deflated. Much like a bicycle tube and tire, airbeams are often composed of a highly dimensionally stable (i.e. no stretch) fabric sleeve and an air-holding inner bladder. However, other airbeam constructions consist of coated fabrics that are cut and manufactured to its intended shape by a method such as thermal welding. Depending on the desired tent size, airbeams can be anywhere from 2-40 inches in diameter, inflated to different pressures. High pressure airbeams (40-80 psi) that are filled by compressors are most often used in larger shelters, whereas low pressure beams (5-7 psi) are preferred for recreational use. The relatively low pressure enables the use of a manual pump to inflate the airbeam to the desired level. Airbeams have the unique quality of bending, rather than breaking, when overloaded.
Tents that use inflatable airbeams are structured almost identical to those that use flexible poles.
Dome tents that use inflatable airbeam support are available in a variety of sizes ranging from lightweight 2-person to larger 6+ person shelters, and are virtually identical to the arrangement of flexible-pole supported dome tents. Beams are usually integrated into the tent shell such that they do not have to be reinserted every time setup occurs. Airbeams can be located on either the inside or outside of the tent shell. Similar to the pole-supported construction, airbeam supported dome tents are free standing but should be staked out with pegs and guyout lines to increase stability and strength.Tunnel tents are a common form of airbeam supported tents because their size can be easily modified by adding additional hoops. Military applications use this style of tent for a range of purposes including medical shelters, helicopter enclosures, and airplane hangars.