Chapter 3: The Sawn Back—How to Select a Board Stave
With this method, all you have to do is pick the right board and your back will be established for you. Choose a straight grained board, with little runoff, and fibers that go all the way across the back—from end to end with little to no interruption. In other words the fibers on the back need to be unviolated.
With a natural back, you can use a character stave loaded with bends and wiggles, since the fibers across the back will share those same wiggles. But if you try to make a board out of characterful wood and you cut across the wiggles indiscriminately, you’ll violate the fibers and introduce runoff. With board bows, you’re limited to wood with near perfect straight grain. Since the board is sawn straight, you need fibers that are also straight.
In other words, for a board bow: the growth rings along the back can be violated, but the board has to be sawn in a way that is parallel to the fibers on the back—that way at least the fibers are relatively unviolated, and can retain their strength in the back of the bow.
By the way, if you’re looking for a practical guide to wood selection for board bows, check out chapter 1 of my board bow tutorial.
Before we get back to it let me clear up what bowyer’s mean when they talk about violation. There’s plenty of confusion surrounding this term because some bowyers talk about violation in the context of growth rings, and others in the context of the fibers or the back in general. Violating a growth ring means you’ve cut all the way through that growth ring. On the other hand, violating the back, or the fibers, just means there’s a little nick or cut in the back, or a spot where the fibers don’t go from end to end across the back.
When you make a board, you will almost always have to violate the growth rings. You’re sawing a flat shape, and the growth rings aren’t perfectly flat—so there’s almost no chance of not violating them. However, if you have a board with perfectly straight fibers you can cut your board parallel to them leading to a back with unviolated fibers. In this way, you will have a back with violated growth rings that still manages to be sound in tension.
This is why it’s possible for a board bow to have a strong back without having a backing. The debate surrounding this issue is a fairly tired and cliche argument. If you’re a veteran bowyer you’re probably sick of hearing it hashed and rehashed. I’m just going to scratch the surface here—for in depth arguments check out the Bowyers Bibles series of books, in particular Tim Baker’s chapters on Bow Design.
Despite what you might have heard about wood selection, know that you can use flatsawn, or quartersawn wood, or anything in between. Growth ring orientation doesn’t really matter unless you plan to chase a growth ring. Arguably there are minor performance differences between flat and standing rings that I wont get into today, but the choice is not a make or break aspect of bow design. If your bow breaks or has issues, it wasn’t the growth ring orientation: much more likely the wood selection, design, or tiller.
Part of the reason this is such an annoying argument to participate in is that it’s not a level playing field on both sides of the discussion. One failure isn’t equivalent to one success. One failure doesn’t prove that it can’t be done, and neither would a thousand. But one success is enough. And there are thousands. They’re all over the internet and forums. But this discussion will drag on for decades more and confuse many new bowyers for for generations.
Just to be clear: many excellent bowyers prefer to back board bows, or have a favorite growth ring orientation. There’s absolutely nothing wrong with that. But it’s nonsense to say you must back a board bow, or that you need to use only certain growth ring orientations. As long as you choose a straight grained board with little enough runoff and little enough violation, you can absolutely make an unbacked bow. And you can do it with any growth ring orientation too.
Please feel more than free to challenge me on this or any point, and strike up the discussion again in the comments. Certain bowyers do have practical reasons for choosing one orientation over another, particularly when it comes to imperfect boards, but in principle if you have a board with an unviolated back it matters little what the growth ring orientation is. The big advantage of flat sawn boards is the possibility of chasing a growth ring, but this doesn’t mean you need a board stave to have flat rings like natural staves do.