The Shinai (Japanese: 竹刀, lit. "bamboo sword") is a sports device and the weapon used in Kendō combat. In Korean Kumdo, it is called "bamboo sword" or jukdo (Korean: 죽도).
The Shinai is a sport and competition weapon modeled after the Katana. It is made of bamboo or carbon and was invented as an alternative to the Bokken in 1760. Together with the Bōgu (armor), it allowed for strikes to be executed without seriously injuring the partner.
Shinai Structure
Structure of the Shinai The Shinai consists of four bamboo or carbon slats held together at the bottom by a Tsukagawa (柄側, lit. "handle covering" or "handle sheath," usually made of leather). Underneath this covering is the Tsuka (handle, 柄) of the Shinai. At the bottom part of the Tsuka is the Tomegana (iron plate).
Above the Tsukagawa, there are Tsuba and Tsuba-dome (rubber ring). At the upper end, the Shinai is held together by a (leather cap).
Approximately 25 cm below the Sakigawa, there is a Nakayui (leather strip) that ensures the strength of each individual Take (bamboo slat).
The measurements of a Shinai are regulated in competitions. In women's competition, a Shinai must weigh at least 440 g, while in men's competition, it must weigh 510 g. Additionally, the tip must have a diameter of at least 25 mm or 26 mm and the overall length should not exceed 120 cm.
The Tsukagawa above the Tsuka is connected to the Sakigawa with a Tsuru (nylon string). The Tsuru represents the blunt back of the sword, which is why hits with the Tsuru-string side of the Shinai are considered invalid in Kendo.
The tip of the Shinai is also called Kensen (剣尖, 'sword tip').
The valid target area in competitions is the area between Sakigawa and Nakayui.
Variations of Shinai
The most original variation of the Shinai is the Fukuro shinai, in which a bamboo tube is split only in the upper section and then covered with leather.
In addition to the typical round shape of the four bamboo slats, there are also Oval-Grip-Shinai that have a grip shape similar to the Katana, which served as the model for the construction of the Shinai. Many users appreciate this because the Shinai feels more secure in hand and is easier to control, and it also has a greater resemblance to the traditional sword of the Samurai.
The thickness of the grip can also vary. Some Kendoka prefer Shinai with a thinner grip, while others prefer those with a thicker grip, similar to the handle of a real sword.
Users with larger hands can potentially transfer more power to the Shinai and handle it more easily with a firmer grip.
These Shinai also have their center of gravity closer to the grip, making the weapon easier to control. This affects "small" techniques without big swinging movements as well as strikes to the Do and throat thrust (tsuki).
There are also particularly heavy Shinai called Suburi-Shinai, consisting of six to eight bamboo slats. These are not intended for competition but to strengthen the grip and other arm muscles during striking exercises (Suburi).
A variation is the solid wood carved Shinai, which consists of a single piece rather than multiple slats. They are also significantly heavier than bamboo Shinai but not distinguishable from them at first glance. There are also special weights that can be attached to the tip of the Shinai to achieve the same effect.
For women, men, and children, there are different prescribed measurements and weight guidelines for the Shinai. The unit of measurement is the old Japanese length measurement called shaku, where 1 shaku equals 30.3 cm.
In colloquial usage, the decimal point is not pronounced, so a 3.9 shaku long Shinai is called a 39er Shinai. The most common lengths are 37, 38, and 39, with 39er Shinai typically used by adult men.
Additionally, there are very short Shinai that resemble the Wakizashi. They are used when fighting in Kendo nitō (ni 二 = "two", tō 刀 = "sword") style, with two swords. In this case, a 37er Shinai is held in one hand, and a small one in the other.
The position of the bamboo nodes (節, fushi), which are the thickest parts of the bamboo slats, varies slightly for each Shinai. It is advisable to acquire Shinai with bamboo nodes positioned similarly so that the slats can serve as replacements for each other.
Many users appreciate Shinai with the center of gravity located near the grip due to the bamboo nodes because it makes the Shinai feel lighter during striking exercises. This provides similar advantages to the weight distribution of a Shinai with a particularly thick grip.
Maintenance of Shinai
The Shinai is usually subjected to high stress during Kendo practice when striking the allowed target areas or other Shinai. Therefore, if it is made of bamboo, it requires special care by the user to prevent injury during training.
The Shinai must be examined for splinters or fractures before each use. If it is made of hard bamboo, the risk of splintering or splitting lengthwise is higher, while softer bamboo tends to break across. If splinters are found, they should be scraped off towards the Kensen with a sharp knife, and the area should be smoothed with sandpaper.
Furthermore, a bamboo Shinai needs to be regularly oiled before its initial use and thereafter to keep it supple, flexible, and prevent it from drying out, which would increase the risk of splintering. Ordinary plant oil can be used for this purpose. This treatment is especially important for Shinai used in drier areas since bamboo requires high humidity.
A splintered Shinai poses a serious health risk during training, particularly when strikes are directed towards the head or the head protector (Men), as the splinters can penetrate the skin or eye of the person being struck. On December 22, 1977, Kendo instructor Kunihiro Goto died in an accident during training in Germany due to this cause. In commemoration, the Dr. Goto Memorial Tournament is held annually by the Kendo Club Düsseldorf e.V.
Carbon Shinai does not require special maintenance.