Yumi (弓) is the Japanese term for a bow. As used in English, yumi refers more specifically to traditional Japanese asymmetrical bows, and includes the longer daikyū (大弓) and the shorter hankyū (半弓) used in the practise of kyūdō and kyūjutsu, or Japanese archery. The yumi was an important weapon of the samurai warrior throughout the feudal period of Japan.
Early Japanese used bows of various sizes but the majority were short with a centre grip. By the third century BC, the bow length had grown to nearly 2 meters. This bow was called the maruki yumi and was constructed from a small sapling or tree limb. It is unknown when the asymmetrical yumi came into use but the first written record is in a Chinese manuscript from the third century AD which describes the people of the Japanese islands using a wooden bow with upper and lower limbs of different lengths, and bamboo arrows with points of bone or iron. The oldest asymmetrical yumi found to date was discovered in Nara and is estimated to be from the fifth century.
During the Heian period (794-1185) the length of the yumi was fixed at a little over two metres and the use of laminated construction was adopted from the Chinese. By the end of the tenth century the Japanese developed a two piece bamboo and wood laminated yumi. Over the next several hundred years the bow's construction evolved and by the sixteenth century the design was considered to be nearly perfect. The modern bamboo yumi is practically identical to the yumi of the sixteenth and seventeenth centuries.
The yumi is exceptionally tall, standing over two meters, and typically surpasses the height of the archer (ite, 射手). They are traditionally made by laminating bamboo, wood and leather, using techniques which haven't changed for centuries, although a few archers (particularly beginners) might use a synthetic yumi.
The upper and lower curves additionally differ. Several hypotheses have been offered for this asymmetric shape. Some believe it was designed for use on a horse, where the yumi can be moved from one side of the horse to the additional with ease, however there's evidence that the asymmetrical shape predates its use on horseback.
Others claim that asymmetry was needed to enable shooting from a kneeling position. Yet another explanation is the characteristics of the wood from a time before laminating techniques. In case the bow is made from a single piece of wood, its modulus of elasticity is different between the part taken from the treetop side and the additional side. A lower grip balances it.
The hand holding the yumi might additionally experience less vibration due to the grip being on a vibration node of the bow. A perfectly uniform pole has nodes at 1/4 and 3/4 of the way from the ends, or 1/2 if held taut at the ends – these positions will change significantly with shape and consistency of the bow material.
The string 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. 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 (hazu) of the arrow (ya) in place while drawing the yumi. But can additionally be made of strands of waxed bamboo.
Care and maintenance
A bamboo yumi requires careful attention. Left unattended, the yumi can become out-of-shape and might 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's relatively flat when unstrung will usually be left unstrung when not in use (a yumi in this state is at times referred to as being 'tired'). A yumi that has excessive curvature when unstrung is typically left strung for a period of time to 'tame' the yumi.
A well cared-for yumi can last a large number of generations, while the usable life of a mistreated yumi can be quite short.
|< 150 cm||< 85 cm||Sansun-zume (212 cm)|
|150–165 cm||85–90 cm||Namisun (221 cm)|
|165–180 cm||90–100 cm||Nisun-nobi (227 cm)|
|180–195 cm||100–105 cm||Yonsun-nobi (233 cm)|
|195–205 cm||105–110 cm||Rokusun-nobi (239 cm)|
|> 205 cm||> 110 cm||Hassun-nobi (245 cm)|
|Time Period||Type of Bow||Bow Formation|
|Prehistoric||Maruki||Single piece of wood|
|c.800-900||Fusetake||Wood with bamboo front|
|c.1100||Sanmaiuchi||Wood with bamboo front and back|
|c.1300–1400||Shihochiku||Wood surrounded with bamboo|
|c.1550||Sanbonhigo (Higoyumi)||Three-piece bamboo laminate core, wooden sides, bamboo front and back|
|c.1600||Yohonhigo (Higoyumi)||Four-piece bamboo laminate core, wooden sides, bamboo front and back|
|c.1650||Gohonhigo (Higoyumi)||Five-piece bamboo (or bamboo and wood) laminate core, wooden sides, bamboo front and back|
|c.1971-Modern times||Glass fiber||Wooden laminate core, FRP front and back|
The Korekawa bow, from the late Jōmon period which ended about 400 BCE, is laminated.