String

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. 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

care


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 to 'tame' the yumi.

A well cared-for yumi can last many generations, while the usable life of a mistreated yumi can be very short


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bow lenghs


Height
of archerArrow length
Suggested
bow length< 150 cm< 85 cm
Sansun-zume (212 cm)150–165 cm85–90 cm
Namisun (221 cm)165–180 cm90–100 cm
Nisun-nobi (227 cm)180–195 cm100–105 cm
Yonsun-nobi (233 cm)195–205 cm105–110 cm
Rokusun-nobi (239 cm)> 205 cm> 110 cm
Hassun-nobi (245 cm)



Yumi history

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
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