Thursday, October 27, 2011

bow-making and the anatomy of wood

I have been wanting to make my own bow and arrows for a few years now, but time seems to be lapsing at a much faster pace than I can keep up, so I have been doing no more than a bit of research now and again on this subject. A book called, "The Traditional Bower's Bible" that I own has just a plethora of info on anything you'd want to know about the components of what goes into making a sound bow and arrows, but I am first interested in finding the right wood and am still not exactly sure of how to pick it out and where on the tree exactly to take it from.

Anyhoosenheimer, I thought I would just share a bit of the info on the anatomy of wood that the author's describe in this book. I learned that there is so much more to the intricacies of a tree than I had ever imagined, and it is these intricacies that make or "break" a bow.

All trees can be used for successful bows, but it is important to know where in the tree to retrieve the wood. Interesting, it is, and overwhelming at the same time.

Here you go with a much condensed version of what I read.

First of all there are many factors about wood that are used to decide which part will work for a bow. Looking at the anatomy of the wood, the annual rings, the grain, the age and density,the reaction, tension and compression wood, branch wood, decay, etc. one can pick out a wood suitable for a nice strong bow.

Wood is formed only by a thin layer of living cells between bark and wood, called the cambium. The cell wall is long-chain molecules of cellulose that provides tension strength, lignin compression strength. As the tree grows, the inner portions of the trunk are no longer needed to bring water and nutrients to the leaves and this inner portion is transformed into heartwood. Sapwood becomes heartwood as the tree creates and deposits chemical and mineral extractives in the cells. This is interesting: sapwood is not resistant to fungi, but heartwood is toxic to fungi.

Sapwood can be compression-weak compared to the heartwood, yet one year later when extractives have been infused into the inner sapwood ring, that sapwood, now heartwood is a different creature. Every heartwood serves well in both tension and compression meaning it is good for bows.

Heartwood as well as sapwood is dead wood, and unless discolored by decay or compromised by insects, weathering or physical trauma it's as sound as if new. So in theory any old wood can be fine for bow-making, whether from the inside of a tree, basement storage pile or old doors or flooring. Good to know.

And here's something interesting that I didn't know - Hardwood is called porous wood. Who would've thunk. It's called this because conduction and support are performed by large-diameter, thin-walled cells called pores. Softwood is called non-porous wood. When the pores are concentrated in the early wood like oak, pecan, elm, Osage and ash they are said to be ring-porous woods. If they have evenly distributed pores like cherry, maple, and birch they are called diffuse-porous woods. Semi ring-porous woods like black walnut and persimmon have pores that are larger in the early wood, and become smaller toward the latewood with no distance transition. I know, I know-TOO MUCH INFORMATION, but you have to admit it is interesting and you didn't know it already. OH, maybe you all did, and I am just way too slow for you guys.

Here's something about the annual rings. If ring-porous hardwood rings are thin (many rings per inch) it will be light and weak and not usable for normal-weight bows. Unnaturally wide rings may also be less dense and weaker. But unlike hardwoods, the more rings per inch in conifers the denser the wood. It states in the book that if unhappy with a tree's surface ring structure one should explore deeper, where the wood may be thicker-ringed and denser.

Okay now a word about reaction wood- tension wood, compressions wood. For trunks to straighten themselves once moved from vertical, or to prevent branches bending down from their own weight, hardwood trees lay down tension-strong, cellulose-rich tension wood on the top side of trunks and branches. Conifers lay down denser and thick-ringed, higher lignin content compression wood on the bottom side. Wood with high lignin content is especially strong in compression. Most conifer species produce inadequate bow wood, but the bottom, compression side of horizontal branches can be sinew-backed, yielding first-class results. Compression wood shrinks or expands with moisture content (MC) changes 10 times or more than normal wood. Tension wood contains more cellulose than normal wood, so is especially strong in tension. The tension-wood side of a split stave will often dry into reflex. Hardwood reaction wood rings are not always eccentric as in conifers, so it's important to make the upper side before felling. If the top of such staves are not centered at bow back much twisting and warping will occur.

Anyhoosenheimer, that's a bit about the anatomy of trees from "bow-making eyes", but honestly, I am still confused. If anyone knows of an expert on bow-making let me know. I'd love to actually see all these things that are written, so it makes more sense. From the sounds of it I should be able to make a bow from the old back-porch door I've been storing for a million years. If that works I'll move onto some fabulous arrows with obsidian tips.

1 comment:

Shannon Wright said...

Hi Jen.
I thought I posted some of this sort of info on the readings. If not, I'll lend you the excellent book, Understanding Wood. This is very interesting, but I'm no good at trying to teach that kind of scientific detail about the different kinds of pores. I tend not to use that info in real life! Now, maybe if I were a bowmaker I would.
Okay, interesting research!