I am of the opinion that if we trace the guitar back to its earliest origins, we would find its DNA firmly rooted in the longbow.
It stands to reason that at some point in our evolution while sitting around a campfire, a bow rested against some hollow form, like a gourd, and the plucked string was amplified. Ever since we have been experimenting with how to couple that hollow form and the taut string. One only has to look to the history of these instruments to see a clear evolutionary path of how we got here today.
Regardless of the lineage, the bow and the guitar are quite different in what we ask of them and as one might imagine our approach to their construction should differ as well. As a side note, for anyone aspiring to build guitars, I would highly recommend building bows first, if for no other reason than to truly understand how wood works, and more importantly, how it fails.
If we look at the cross section of a longbow, you’ll notice that the back of the bow is taken down to one outer growth ring, often sapwood, or sometimes even backed with a material like sinew to aid in handling the tension when the bow is drawn. The rest of the limb material follows suit with grain orientation, leaving the heartwood to handle the compression seen along the belly of the bow.
This grain alignment is perfectly suited for a piece of wood that is repeatedly bent and released, like a spring. It is that inner stasis, the shear strength in that neutral zone that keeps everything from exploding. Over time with force applied, this matrix will creep and wood cut like this will eventually take a set. Early bowyers hedged this bet by building reflex into their limbs, hoping things would settle in to an acceptable compromise.
In the modern world of woodworking, we commonly refer to this as flat sawn material.
The vast majority of what comes off of a sawmill today is flat sawn, or rift sawn at best. Very little is truly quartersawn. It is a rarity today to find anyone that takes the time to roll the log to achieve the choice cuts, even rarer to find material that has been radially split for perfectly quartersawn stock.
Does any of this grain alignment really matter?
The difference comes down to stability. Quartersawn stock is by far more stable along its axis.
Wood swells and contracts across its grain, happening mainly in the summer growth.
The material is somewhat like a compressed bundle of straws. The ends of those straws suck in moisture any chance they get. Anytime you cut through, leaving end grain exposed, it's simply a way for moisture to get in ,..or out, more so than the adjacent material.
As one could imagine, with the grain being aligned perpendicular to the face of a board, something we commonly refer to as quartersawn, as that material changes with its environment, its structural changes are evenly distributed because of the grain alignment, showing itself as nominal differences in width but usually remaining fairly flat in plane.
By comparison, flat sawn and to a lesser degree rift sawn material, simply has an uneven distribution of summer to winter growth as seen from the face of the board. As this material goes through asymmetrical structural changes, it shows itself in a board that cups off of plane.
If we look at the breadth of guitar necks throughout the last hundred years or so, by far the bulk of these will be made of flat sawn material. The reason being is that when trees are rendered into lumber, the driving factors are more about efficiency and yield and not so much about grain alignment.
In the case of the guitar neck, we’re not shooting for maximum flexibility. Yes, we want the neck to bend a little, but only enough to allow for the strings above to oscillate without buzzing against our frets. Stiffness and stability is what we’re shooting for here. Any relief required will be the result of string tension kept in check by a truss rod or such.
Guitar necks that are made out of quartersawn stock, will usually be noticeably stiffer, more stable and result in a guitar that better stays in tune and intonated. Quartersawn stock also allows for uninterrupted grain through transitions, like headstocks and such, providing a much stronger core.
Not being much of a gambler, with the rarity of these choice cuts being available, I have found the best way to side step fickle Mother Nature is to simply employ laminating billets for my neck construction. It takes considerably more time to prepare and render a neck this way, but the outcome is so much more reliable in its flexibility and uninterrupted grain through transitions, all based on a law of averages, excluding less material and making the most of this resource.
By having a billet made up of opposed grain, those internal stressors find equilibrium quickly during the reduction process of becoming a guitar neck and result in a more stable core during the life of the instrument.
As testament to this, I have a number of guitars that actually went through the flood waters of Katrina, though looking pretty rough, all are still playable to this day. And with all of the accidental bumps and bruises in the shop during their making or in the hands of negligent traveling musicians after the fact, I can honestly say that as of this writing I have never had a broken headstock, knock on wood.
Not to suggest that it can't happen, it just hasn't happened yet.
All of this is not to say that a great guitar can't be found with a flat sawn neck. I am pretty certain that much of our favorite music has been played on less than stellar gear. There are too many variables here to jump to any definitive statements, and there are so may other contributing factors at play. No, this writing is not intended to vilify any historically proven approaches to guitar construction. This is simply here to inform those with maybe a less intimate knowledge, about how wood responds to its environment.
As a guitar player, at my core I am admittedly lazy. I turn to the guitar as a daily escape from the grind, simply a way to unplug. As a player, I don't want to turn any wrenches, I just want to get on it and ride.
Yes, strings stretch and everything goes sharp a half step on rainy days, but for the most part, I just want a guitar that pretty much stays in tune, and seemingly stays on track with intonation, stable in its relief, ready to go at a moment's notice. I don't want to think about it. I don't want to tweak it. I just want to play it and know that it has held its spot for me.
All of those things rely on the stability of the guitar neck.
food for thought.