My friend Bill Sweetland once told me "The most demanding thing you can ask of a piece of wood is for it to become an arrow shaft. You reduce it to the smallest of dimension yet ask it to remain it's strongest, straightest and most durable. Therefore you must understand and pay attention to the smallest of details during it's manufacture so as not to lose any of these attributes mother nature has given it".
Wooden arrow shafts come from trees. Whatever qualities or shortcomings a wooden arrow shaft possesses can be traceable to the tree from which it came. Wood exists as a functional tissue of plants rather than as a material designed to satisfy the needs of archers. Thus knowing wood as it grows in nature is basic to working successfully with it.
The cell is the basic structural unit of plant materials. Each cell consists of an outer cell wall surrounding an inner cell cavity. Wood cells typically are elongated. The proportion of length to diameter varies widely among cell types, however, the majority of wood is composed of longitudinal cells, whose axes are oriented vertically in the tree. The largest cells in some species are visible to the unaided eye, but most are too small to be seen without magnification.
Scattered through the wood are "groups" of cells whose axes are HORIZONTAL These groups extend radially outward from the pith or center of the tree and are therefore called RAYS. Rays are like flattened ribbons of cells stretched horizontally in the tree, with the plane of the ribbon vertical. The size of rays varies according to the number of cells contained or making up the group. Although individual ray cells and even the smaller rays are not visible to the naked eye, the largest rays of some species, such as oak can be seen easily. These ray cells pass nutrients horizontally back and forth to each other in the living portion of the tree known as the cambium layer or sap wood. Sweetland always referred to this structure as the nutrient path, so bear with me here and in the future if I refer to nutrient path it is one and the same as "Rays" or "Ray cell structure" as it is known to the botanical world. As the tree grows and adds mass on its radius these cells cease to function at the inner most active layer and give way to the younger cells just under the bark. But they remain as dead tissue for support of the trees mass, same as the longitudinal cells. It's how the tree grows and adds mass at the cellular level. I emphasize these things at this point because it is the most difficult to perceive, yet it is of the most importance to archers because this is where the quality of their arrow shaft lies. This ray cell structure or nutrient path, if you will, always runs perpendicular to the annual growth rings which everyone refers to as "grain". Annual growth rings are visible, ray cells are not, but both are of equal importance when making an arrow shaft. One MUST keep the axes of both these "grain" or "cell structures" down the length of the arrow shaft if we expect our shafts to remain straight when subject to differences in relative humidity or moisture contents. If we expect our shafts to remain the most durable and rupture resistant due to impacts. Would you shoot and expect an arrow shaft to have the best of these properties if you could see the growth rings run off from one side of the shaft to the other? No! So why shoot an arrow shaft if the ray cell structure runs off the shaft every couple inches? It's just as important, it's just not as visible. You may ask,.. How do we make sure that BOTH annual growth ring and ray cell structure stay the closest to the longitudinal axes of our arrow shaft as possible?? Simple, split your raw product perpendicular to the annual growth rings!! Your wood will split on the ray cell structure and thus identify it without using the microscope. Then and only then start your sawing processes either into squares or flitches. If you cannot keep your saw cut parallel with your "split" (within reason) and your annual growth rings you've got fire wood not arrow wood. Saxton Pope, in his book "Hunting with the bow and Arrow" referenced this "grain run off" to a minimum of 12 inches for a bow stave. I would not go less than this for an arrow shaft either. As grain runs off of wood per a given length it's rupture strength lessens exponentially. For example, lets take annual growth rings, since everybody knows what they are and can be seen by the naked eye. Say the grain runs off the shaft from one side clear off the other side at a measured length of 12". We apply a force perpendicular to the longitudinal axis until it breaks say at 50 lbs force. We compare this with an equal specimen that the annual growth rings run off side to side at 6". The arrow shaft would not rupture at ½ or 25 lbs force but at the square root of 50 lbs which is 7.07 lbs!! Wow!....This could be important stuff huh?? And if it were Ray cell structure which can't be seen vs. growth rings which can, maybe we got something we should be concerned about here.
TWIST...Seldom does the ray cell structure run from the root of the tree to the crown of the tree without twisting. Twist is designed to allow trees to continue to supply nutrients around limbs or other defects such as scars from a big ‘Ol buck scraping the bark off down to the cambium as he rubs off his velvet. Fire scars to the cambium are another reason for trees to possess a means of providing nutrients around defects. The ray cell structure in most tree species maintains the flow of nutrients around these defects, and most likely a lot of other scenarios to keep the individual tree alive. However this twist is one of the largest contributors ruling out it's ability to live on as an arrow shaft. I once had a discussion with a horticulturist from OSU (Oregon State University) about twist. I wish I'd had a recorder so I could quote rather than paraphrase but I will give you what I can of the conversation here for the benefit of knowledge. He said the Cedars were less complex than other species of trees. They have not been designed to perform the function of twisting. If you took an axe and chopped a scar at the base of a cedar tree (Port Orford I'm assuming he is referring to, which is actually in the Cypress family) the tree would die from the point of the axe mark near the ground, clear to the crown of the tree above the scar, because it lacked the capability of twisting and feeding nutrients around defects. I don't know if this is true or not but if so it could be a reason P.O.C. has a history for straightness.
The lumber industry cuts trees into dimensional lumber for maximum volume, period. They pay no attention as to whether a tree has twist. In my 20 years experience of cutting trees into arrow shafts and experimenting with dimensional lumber I would estimate only 10%-15% of dimensional lumber will have ray cell run-off within reason to make an adequate arrow shaft. I find only 15%-20% of trees that have already past all other inspections such as annual growth ring count, straightness of cambium layer, center of pith, knots etc. will split straight enough for Surewood Shafts. Lumber is sawn to provide the population with a product for building structures, houses, commercial buildings, even structural support beams for the above. Engineering values that calculate size and strength of wood products to support given loads have been de-rated to offset the loss of strength due to this twist of the tree, ray cell structure, nutrient path, what ever you want to call it. In the arrow shaft industry we cannot afford to have a de-rate value because, as Bill said, "The most demanding thing you can ask of a piece of wood is for it to become an arrow shaft. You reduce it to the smallest of dimension yet ask it to remain it's strongest, straightest and most durable."
Read and re-read this part until you understand it. It is imperative that as traditional archers if we are going to shoot wooden arrow shafts we be educated about it. Show the world that we are dedicated to our sport. We are educated and make the best and the safest arrows that can be made. If we buy from someone whom manufactures them, ask questions. It will vastly improve the quality of our arrow shafts and thus the image of those within the sport we love so much.