Wood is one of the classic bows materials. Although there are many, many species that are more than suitable for making bows, all share certain common characteristics. It is these characteristics which are discussed in this article.
For more details about wood from the bowmaking perspective, look at the "Cutting and seasoning wood" article in TBB1 (Hardcastle 2000: 19-42).
Wood fibers Edit
All wood is composed of longitunal fibers which are very strong, but the "glue" holding the fibers together is fairly weak. This means that while a long piece of wood is very strong when being bent lengthvise, it's also very easy to split along the fibers.
The above has one very important implication when making a bow out of wood: cutting through the fibers, especially at bow's back, is a very bad idea, because it makes the bow weaker. To determine how much weaker we need to look at the angle of violation. Tim Baker (2000e: 34-36) has estimated that a bow that can pull 100 pounds if the wood fibers are perfectly parallel to the back can only pull 5 pounds if they're perpendicular. Obviously such a bad piece of bow wood is hard to get, but still, even a fairly small angle of violation reduces the amount of energy that the bow can store safely.
Small, localized violations in the fiber angle are especially dangerous, as they're easy to overlook. This includes things such as knots or tool marks left in the wood.
Growth rings Edit
Growth rings are often confused with wood fibers by traditional bowyers. Staying within one growth ring is a good rule of thumb, if you're working with staves cut from a large diameter trunk. If not, you may have to cut through the growth ring, which is perfectly fine, as long as the wood fibers are fairly parallel to the back.
Growth rings consist of alternating layers of earlywood and latewood. The former is created after winter to allow transfer of nutrients and water upwards. The latter forms in the summer and autumn, until the growth period ends. The visibility of growth rings depends on the type of wood:
The most important thing to remember is this mantra: "Latewood good, earlywood bad".
Tillering as a generic, theoretical concept is described here.
Different bow woods Edit
Some woods are more suited for making wooden bows and crossbow prods. In general, the specific gravity (=weight of the wood) is a good indicator of how heavy draw weights the bow can handle safely with any given dimensions. Lighter woods can be used to make bows, but they have to be made thinner and/or longer than bows made from stronger and heavier woods.
A relatively comprehensive list of suitability of different woods species for bow making has been published on this Paleoplanet thread. Further details are available in the Traditional Bowyer's Bible book series.