Engineering:Yumi

Yumi (弓)
from behind, profile
Type	Asymmetrical bow
Place of origin	Japan
Service history
Used by	Samurai, Onna-musha, Kyudo practitioners
Production history
Produced	Since 3rd century (the asymmetrical )
Variants
Specifications
Mass	12–16 kg (26–35 lb)
Length	212–245 cm (83–96 in)
Cartridge	Arrow length: 85–110 cm (33–43 in)

Japanese bows, arrows, and arrow-stand

bow names

Yumi (弓) is the Japanese term for a bow. As used in English, refers more specifically to traditional Japanese asymmetrical bows, and includes the longer daikyū (大弓) and the shorter hankyū (半弓) used in the practice of and , or Japanese archery.

The was an important weapon of the samurai warrior during the feudal period of Japan. It is typically shot with Japanese arrows known as .

The most famous style of is an asymmetrically shaped long bow with a length of more than 2 m (6 ft 7 in), characterized by the archer holding the part of the bow below the center to shoot the arrow.

History

Most of the excavated Jōmon period (c. 14,000–300 BCE) bows are 1.2 to 1.6 metres (3 ft 11 in to 5 ft 3 in) in length, while most of the Yayoi period (c. 3rd century BCE–2nd/3rd century CE) bows are 2 to 2.3 metres (6 ft 7 in to 7 ft 7 in) in length. The bows in these periods were made from a single processed wood, and the bows with this structure were called maruki yumi (丸木弓) and were used until the Nara period (710–794 CE). It is unknown when the asymmetrical came into use, but the first written record is found in the Book of Wei, a Chinese historical manuscript dating to the 3rd century CE, which describes the people of the Japanese islands using "spears, shields, and wooden bows for arms; the wooden bows are made with the lower limbs short and the upper limbs long; and bamboo arrows with points of either iron or bone." The oldest asymmetrical found to date was discovered in Nara Prefecture, and is estimated to be from the 5th century.

Some of the bows found as burial goods in (ancient tombs) during the Kofun period (300–538 CE) were decorated with gold or silver, and it is believed that they were also used in ceremonies. The length of most bows in this period ranged from 70 to 150 cm (28 to 59 in), and it is thought that they were powerful enough to shoot enemies and animals at close range.

In the Nara period, lacquered bows with more weather resistance and decorative features appeared. Euonymus hamiltonianus, Zelkova serrata, and Toxicodendron succedaneum, which are highly elastic wood, came to be used for making , and many became as long as roughly 7 3 (2.21 m (7 ft 3 in)), increasing their power and range. Since then, the structure of the bow has gradually evolved, but its length of roughly 7 3 has been passed down to the present day.

From the mid to late Heian period (794–1185), the Japanese developed the fusedake no yumi (伏竹弓) style of , the first in Japan with a laminated structure. This style of was made by attaching bamboo to a wooden with a flat front side using glue made from a fish float, and the elasticity of the bamboo improved the bow's range, power and durability. Nasu no Yoichi was famous as a master of archery in the late Heian period; his fame was depicted in The Tale of the Heike and , and he was the subject of various Japanese traditional performing arts and fine arts such as Noh, , , kabuki, and ukiyo-e of later generations.

From the end of the Heian period to the beginning of the Kamakura period (1185–1333), the sanmaiuchi no yumi (三枚打弓) was developed, and bamboo was glued not only on the front side but also on the reverse side of the . In the late Kamakura period, the shape of the bow became more asymmetrical, with the upper part bent from the lower part, so that it resembled a modern bow, further increasing the range and power of the .

From the middle of the Heian period, the tōyumi (藤弓) style of , in which wisteria was wrapped around a laminated-structure to improve its elasticity and sturdiness, became popular. The shigetō yumi (重藤) style in particular was the strongest weapon of the Kamakura period, with a maximum range of 400 metres (1,300 ft) and an effective range of 80 metres (260 ft) that could inflict fatal wounds on targets. There are more than 20 varieties of , depending on how and where on the bow the wisteria is wound. In the Muromachi period (1336–1573), the went from its luxurious exterior to a piece of equipment that symbolized the rank of commander.

During the Kamakura period, when the samurai class came to power, (archery) became more and more popular, especially the three types of mounted archery: , , and .

The shihodake no yumi (四方竹弓) was developed during the Muromachi period, and bamboo was used on the side of the bow to increase its range and power.

During the Sengoku period (1467–1615), the higoyumi (弓胎弓) used in modern was developed, completing the original form of the Japanese bow now known around the world. The characteristic of the bow is that it has a greatly changed laminated structure from the conventional bow. The core of the structure is about four pieces of bonded bamboo, with bamboo glued to the front side and the other side and wood glued to the sides. This improved the range and power of the bow and enabled it to shoot through targets 132 metres (433 ft) away in the Sanjusangen-do archery contest, , a famous event still held today. Research on (arrowheads) was actively conducted to enhance their killing ability, and of various shapes were developed. During this period, the was mass-produced by Japanese swordsmiths, and mobilized (foot soldiers) used them to exert tremendous power on the battlefield. However, because took a long time to load, were inconvenient in rainy weather when damp gunpowder would not fire, and were not exactly subtle in terms of noise, the did not go out of fashion and continued to be used as an important military force on the battlefield.

When Japanese society became more peaceful in the Edo period (1603–1867), the spirituality and decorativeness of the became important, and developed as a samurai's way of doing things.

Even today, the is used in and ceremonies, and in Grand sumo tournaments, a ceremony called the yumitori shiki (弓取り式), which is dedicated to Shinto , is held.

Time period	Type of bow	Bow formation
Prehistoric		Single piece of wood
c. 800–900	or	Wood with bamboo front
c. 1100		Wood with bamboo front and back
c. 1300–1400	or	Wood surrounded with bamboo
c. 1550		Three-piece bamboo laminate core, wooden sides, bamboo front and back
c. 1600		Four-piece bamboo laminate core, wooden sides, bamboo front and back
c. 1650		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

Shape

The is exceptionally tall, standing over 2 m (6 ft 7 in) in height, and typically surpasses the height of the archer (射手, ite). They are traditionally made by laminating bamboo, wood and leather, using techniques which have not changed for centuries, although some archers (particularly beginners) may use a synthetic .

The is asymmetrical; according to the All Nippon Kyudo Federation, the grip () has to be positioned at about two thirds of the distance from the upper tip.

Scale representation of a drawn

The upper and lower curves also differ. Several hypotheses have been offered for this asymmetric shape. Some believe it was designed for use on a horse, where the could be moved from one side of the horse to the other with ease; however, there is 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 other side. A lower grip balances it.

The hand holding the may also 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.

String

The string of a , a , 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 flexing in the direction opposite to the way it is drawn, and is considered beneficial to the health of the .

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, a , in place while drawing the . However, it can also be made of strands of waxed bamboo.

Care and maintenance

A bamboo requires careful attention. Left unattended, the can warp out of shape and may eventually become unusable. The shape of a 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 is greatly affected by whether it is left strung or unstrung when not in use. The decision to leave a strung or unstrung depends upon the current shape of the . A that is relatively flat when unstrung will usually be left unstrung when not in use (a in this state is sometimes referred to as being 'tired'). A that has excessive curvature when unstrung is typically left strung for a period of time to 'tame' the .

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

Bow lengths

Height of archer	Arrow length	Suggested bow length
<150 cm (59 in)	<85 cm (33 in)	(212 cm (83 in))
150–165 cm (59–65 in)	85–90 cm (33–35 in)	(221 cm (87 in))
165–180 cm (65–71 in)	90–100 cm (35–39 in)	(227 cm (89 in))
180–195 cm (71–77 in)	100–105 cm (39–41 in)	(233 cm (92 in))
195–205 cm (77–81 in)	105–110 cm (41–43 in)	(239 cm (94 in))
>205 cm (81 in)	>110 cm (43 in)	(245 cm (96 in))

Gallery

• 

  (bottom nock)

• 

  (grip)

• 

  (top nock)

• 

  (string holder) and (string)

• 

  Antique (shortbow)

• 

  Antique (longbow) and (shortbow)

• 

  (cloth cover)

• 

  Ukiyo-e by Tsukioka Yoshitoshi depicting Minamoto no Tsunemoto hunting a sika deer with a .

• 

  A (quiver) decorated with . Edo period, 18th century. Tokyo National Museum.

Popular culture

• are featured in the Teenage Mutant Ninja Turtles franchise, used by Splinter in Teenage Mutant Ninja Turtles II: The Secret of the Ooze and the 2003 episode "Exodus, Part 1". The Foot Clan includes Foot Archers who use . Leonardo, Donatello, Raphael, and Michaelangelo occasionally used in the 2012 version, and were also used by Karai, as shown on the flashbacks of the 2003 episode "City At War, part 3". A bow was used by Murakami Gennosuke, a rhino bounty hunter in the 2003 episode "The Real World, Part 1".
• Power Rangers Samurai features the Blue Ranger Kevin Douglas using the Hydro Bow, which is based on a bow.
• bows were used by samurai in Deadliest Warrior and The Last Samurai.
• The character Hanzo Shimada from Overwatch uses a futuristic yumi as his weapon of choice due to him abandoning the way of the sword after nearly killing his brother Genji.

Further reading

• Herrigel, Eugen (1999). Zen in the Art of Archery. Vintage. ISBN 978-0-375-70509-0. 
• Michael, Henry N. (1958). "The Neolithic Age in Eastern Siberia". Transactions of the American Philosophical Society. New Series (Philadelphia: The American Philosophical Society) 49 (2): 1–108. April 1958. doi:10.2307/1005699.