Wubei Zhi (Vol. 34)

Instructions for Constructing the Crossbow Stave from Bamboo

The wood of the Three-lobed Cudrania original: Zhe (柘); a hardwood traditionally prized for bow-making or the Mulberry original: Sang (桑) is unsuitable for making the stave because it cannot withstand being kept under tension for long periods. Therefore, bamboo is used instead. The quality of bamboo varies depending on where it is grown: some possess a strong recoil while others lack it; some are rigid and do not break, while others are brittle and snap easily; some are prone to boring insects, while others are resistant.

For current purposes, select Sprout Bamboo original: Mengzhu (萌竹); likely referring to a species of large timber bamboo like Phyllostachys edulis that is over three years old. The skin should be covered in a white, powdery frost, similar in color to the powder found on the skin of a winter melon original: Donggua (東瓜); the wax gourd, known for its protective white powdery coating when ripe.

The bamboo should be one foot and two inches in circumference. The nodes must be long, straight, and level—aligned as straight as the character for "one" (一)—and must not be crooked or slanted. Carefully inspect the piece from top to bottom to ensure there are no insect holes or physical damage. The thickness should be consistent throughout, without being overly large at the head or narrow in the middle.

When split open, bamboo with thick walls is of the highest quality. One should discard the three or four dense nodes near the root end. Split the remaining length into four longitudinal pieces. Based on the size of the socket hole in the crossbow stock, calculate the required width and thickness. Finally, determine the specific measurements for the string-notches original: guakou (挂口); the points where the bowstring is secured and the total length required for the stave.