Experimental Data on Bow Wood
The question—what constitutes the best material for bows?—has been answered in an empirical way by the usage of thousands of years. Of all known woods, yew is most resilient and elastic. Many other woods, such as hickory, bamboo, and palma brava, will stand a great deal of bending without breaking, but their recoil from the bent position is sluggish and weak. Compared with yew wood, spring steel is slow and dead. Experiments have long ago shown that metal is not fit for hand bows, and even on the crossbow it is poor material.
In the use of yew we take advantage of two qualities inherent in its structure. The red or heart wood is resilient and has a great capacity for standing compression strain. This gives the desired recoil from the bent position. The white sapwood has the quality of being tough, resistant to fracture, and of great ductile strength. Its position on the back of the bow serves as a buffer against which the red wood can pull, and prevents fracture, much as a sinew backing would do. The backing of bows with the fascia, tendons, or hide of animals seems to have been an almost universal custom among people using coniferous wood of the temperate or arctic zones.
The famous English longbow, from all the evidence we have at hand, was not backed but was made long for the very purpose of avoiding backing. Having discovered the superior shooting qualities of the unbacked yew, the English attained a higher proficiency in archery than their predecessors. That the early Saxons and Celts did use short backed bows is suggested by a drawing by A. Dürer in which an Irish archer is shown with a bow not over 4 feet long, having recurved ends. The arrows in the picture are about 26 inches long. It is practically impossible to draw any strong unbacked bow to such an arc without fracture. The inference, therefore, is that this bow is backed.
Archers in the past have ascribed the resiliency of their bows to the white or sapwood of the yew. The universal custom has been to place this sapwood at the back of the bow and have it constitute about one-quarter of the thickness. The grain of the white wood as well as the red is never cut in the process of bow making but is followed with great fidelity. This of course adds to its strength. To test whether the white wood or red wood of yew has the more spring the following experiment was conducted:
Three sticks of well seasoned yew (four years) were cut the following dimensions: ⅜ by ¾ by 14 inches:
No. 2, coarse grained yellow yew, 16 lines to the inch.
No. 3, fine grained red yew, 35 lines to the inch.