Traditional Japanese Asymmetrical “Yumi Bow
Yumi 83.5′′- 96.5”
Yumi 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 and the shorter hankyū used in the practice of kyūdō and kyūjutsu or Japanese archery. The yumi was an important weapon of the samurai warrior during the feudal period of Japan. It shoots Japanese arrows called ya.
The Yumi is exceptionally tall, standing over two meters, and typically surpasses the height of the archer. They are traditionally made by laminating bamboo wood and leather, using techniques that have not changed for centuries, although some archers (particularly beginners) may use a synthetic yumi.
The Yumi is asymmetric According to the All Nippon Kyudo Federation, the grip (nigiri) has to be positioned at about two-thirds of the distance from the upper tip.
Scale representation of a drawn yumi
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 yumi 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 yumi 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 the shape and consistency of the bow material.