Yumi
Yumi (弓, ゆみ) is the Japanese term for bows (which includes the longbow, Daikyu and the shortbow, hankyu) used in the practice of Kyudo (弓道, Japanese archery).
The yumi is exceptionally tall (standing over two meters), surpassing the height of the archer (kyudoka). They are traditionally made of bamboo, wood and leather, using techniques which have not changed for centuries, although some archers (particularly beginners) may use a synthetic yumi. The yumi is asymmetric; the upper and lower curves differ and the grip is positioned at about one-third the distance from the lower tip. It is believed the asymmetric shape was designed for use on a horse, where the yumi could be moved from one side of the horse to the other with ease.
The string (tsuru) of a yumi is traditionally made of hemp, although most modern archers will use strings made of synthetic materials such as Kevlar, which will last longer (around one thousand shots). Strings are usually not replaced until they break; this results in the yumi flexing in the direction opposite to the way it is drawn, and is considered beneficial to the health of the yumi. The nocking point on the string is built up through the application of hemp and glue to protect the string and to provide a thickness which helps hold the nock of the arrow in place while drawing the yumi.
Serious kyudo archers treat the yumi with reverence, as pieces of great power, and as teachers with much to impart to the student (a yumi is said to hold within it part of the spirit of the person who made the yumi). A kyudo student will never step over a yumi which lies on the ground (that would be considered disrespectful), and will typically treat a yumi as they themselves would wish to be treated (e.g. kept away from excessive heat or cold, kept dry, kept away from excesses of humidity or dryness, carried upright). It is also considered disrespectful to so much as touch another person's yumi without his permission; yumishi (yumi-maker) Kanjuro Shibata, Sensei has said this is like touching someone's spouse.
A bamboo yumi requires careful attention. Left unattended, the yumi can become out-of-shape and may eventually become unusable. The shape of a yumi will change through normal use and can be re-formed when needed through manual application of pressure, through shaping blocks, or by leaving it strung or unstrung when not in use.
The shape of the curves of a yumi is greatly affected by whether it is left strung or unstrung when not in use. The decision to leave a yumi strung or unstrung depends upon the current shape of the yumi. A yumi that is relatively flat when unstrung will usually be left unstrung when not in use (a yumi in this state is sometimes referred to as being 'tired'). A yumi that has excessive curvature when unstrung is typically left strung for a period of time in order to 'tame' the yumi.
A well cared-for yumi can last many generations, while a mistreated yumi's usable life can be very short.