A longbow is a type of bow that is tall (roughly equal to the height of a person who uses it), is not significantly recurved and has relatively narrow limbs, that are circular or D-shaped in cross section. It will normally allow its user a fairly long draw, at least to the jaw; the average length of the Mary Rose arrowshafts is 75 cm (30 inches). Organizations which run archery competitions have set out formal definitions for the various classes; many definitions of the longbow (see links section) would exclude some medieval examples, materials, and techniques of use. According to the British Longbow Society, the English longbow is made so that its thickness is at least ⅝ (62.5%) of its width, as in Victorian longbows, and is widest at the handle. This differs from the Medieval longbow, which had a thickness between 33% and 40% of the width. Also, the Victorian longbow does not bend throughout the entire length, as does the medieval longbow. Longbows have been used for hunting and warfare, by many cultures around the world, a famous example being the English longbow, during the Middle Ages.
In ancient Japan, very distinctive long bamboo and wood laminated bows, known as yumi, became important to mounted samurai warfare. Modern Japanese archery (called kyūdō or kyujutsu) still uses this style of bow. Modern yumi can be made of fibreglass or carbon-fibre, as well as of the traditional wood/bamboo laminate. Yumi are recurved bows, and have the unusual characteristic of being off-center. That is, the lower arm of the bow is shorter than the upper arm; this is useful when the bow is used from horseback, so that the archer can turn without the bottom of the bow hitting the horse.
In the Middle Ages the Welsh and the English were famous for their very heavy, long-ranged English longbows, used to great effect in the civil wars of the period and against the French in the Hundred Years' War (with notable success at the battles of Crécy (1346), Poitiers (1356) and Agincourt (1415)).
Although firearms supplanted bows in warfare, wooden or fibreglass laminated longbows continue to be used by traditional archers and some tribal societies, for recreation and hunting. A longbow has practical advantages compared to a modern recurve or compound bow; it is usually lighter, quicker to prepare for shooting, and shoots more quietly. However, other things being equal, the modern bow will shoot a faster arrow more accurately than the longbow.
One of the simpler longbow designs is known as the self bow. By definition, a self bow is made from a single piece of wood. Truly traditional English longbows are self bows, made from yew wood. The bowstave is cut from the radius of the tree so that the sapwood (on the outside of the tree) becomes the back two thirds and the belly, the remaining one third, is heartwood. Yew sapwood is good only in tension, while the heartwood is good in compression. However, one must make compromises when making a yew longbow, as it is difficult to find perfect unblemished yew. The demand for yew bowstaves was such that by the late 1500s, mature yew trees were almost extinct in northern Europe. In other desirable woods such as Osage orange and Mulberry the sapwood is almost useless and is normally removed entirely.
Longbows, because of their narrow limbs and rounded cross-section (which does not spread out stress within the wood as evenly as a flatbow’s rectangular cross section), need to be either less powerful, longer or of more elastic wood than an equivalent flatbow. In Europe the latter approach was used, with yew being the wood of choice, because of its high compressive strength, light weight and elasticity. Yew is the only widespread European timber that will make good self longbows, and has been the main wood used in European bows since Neolithic times. More common and cheaper hard woods, like elm, oak, ash, hazel or maple are good for flatbows. A narrow longbow with high draw-weight can be made from these woods, but it is likely to take a permanent bend (known as "set" or "following the string") and would likely be outshot by an equivalent made of yew.
Wooden laminated longbows can be made by gluing together two or more different pieces of wood. Usually this is done to take advantage of the inherent properties of different woods: some woods can better withstand compression while others are better at withstanding tension. Examples include hickory and lemonwood or bamboo and yew longbows: hickory or bamboo is used on the back of the bow (the part facing away from the archer when shooting) and so is in tension, while the belly (the part facing the archer when shooting) is made of lemonwood or yew and undergoes compression (see bending for a further explanation of stresses in a bending beam). Traditionally made Japanese yumi are also laminated long bows, made from strips of wood: the core of the bow is bamboo, the back and belly are bamboo or hardwood and hardwood strips are laminated to the bows sides to prevent twisting.
Today, good laminated longbows may be made of wood or can be purchased commercially. Any wooden bow must have gentle treatment and be protected from excessive damp or dryness. Wooden bows may shoot as well as fiberglass, but they are more easily dented or broken by abuse. Bows made of modern materials can be left strung for longer amounts of time than wood bows. Wooden bows should be unstrung immediately after use to avoid large amounts of set.