What’s Behind the Unique McInturff Guitar Neck Design?
Everyone knows that the history of fretted instrument necks is one which includes tales of warping, twisting, back-bowing, instability, tuning problems, and let’s be honest—frustration! One only has to look at the number of truss rod designs, wood combinations, etc. to see the multitude of efforts that have been made to defeat the common problems that all traditional neck designs can experience. Yet we continue to see the same problems.
I try at all times to be a bit humble, and so to keep my mind open and to continue to learn. In the subject of neck design however, I have arrived at what seems to be the ideal recipe for me. There are over 3,700 TCM guitars out there and there has not been a single report of any neck-related problem. The TCM neck design is not only extremely stable, it also acts as the sort of predictably great sounding “tone filter” that is another hallmark of any outstanding neck. It took me 25 years to arrive at the final version back in 2006.
The way that a neck reacts under load (i.e. string tension) is incredibly important because the shape the neck assumes under load has everything to do with how the neck “feels” and how well the guitar can be set up for ideal playability. My prerequisites for a neck under load are as follows:
- The neck must be able to be adjusted straight along its length +/- .001″
- The fretboard radius must match blueprint specifications to no more than +/- .005″
- There must always be tension on the truss rod, no matter what amount of neck relief the artist requires
- There must be forward-bow built into the neck so as to assure there will always be tension on the rod, and no chance of back-bow
- Under load, any and all relief tapers to zero at the 9th-10th fret area; from there on up to the highest fret (22 on a TCM) the neck remains straight +/- .001″
- The only truss rod to use is a modified version of the circa 1924 Gibson curved single-action rod
- There will be no chance of any bowing 9th fret-22nd fret
- The neck should not be overbuilt to the point where it begins to contribute the wrong sort of tonal filtering
There are over 3,700 TCM guitars out there and there has not been a single report of any neck-related problem. The TCM neck design is not only extremely stable, it also acts as the sort of predictably great sounding “tone filter” that is another hallmark of any outstanding neck.
That’s quite a list of marching orders! The way to achieve these specs involves a recipe, a series of construction steps which, if followed to the letter results in a great neck every single time. EVERY TIME! While I am reluctant to give-away my secrets, there’s plenty that I can say which will satisfy many of the questions I’ve gotten so many times.
The guitar neck is a cantilever, i.e. a beam supported at one end.
If we consult with a structural engineer, a designer of road bridges for example, and ask him what a neck is, he will say, “It’s a cantilever.” If we then ask him how a cantilever will respond to the sort of longitudinal stress that the strings apply, the engineer will then describe exactly what we see a guitar does under load. He would predict exactly what some of the problems will be. This is something that remarkably few guitar builders are aware of. Take the matter of “stress concentration” for example. The engineer will tell us that the cantilever (neck) will tend to bow forward near the body joint; where the stiffness abruptly increases. This is why many necks tend to bend up there, in an area in which no truss rod of any design has any effect whatsoever.
A neck with relief above the 10th fret will not be able to be set up low and fast. When fretted in the “trough” of this bow, the strings will see the frets upstream as being high and the notes will buzz, rattle, or even refuse to speak at all. This stress concentration bow has been the bane of guitar necks since day-one, and I have defeated this problem by a certain means without ruining the sound of the neck.
Overall, the TCM neck recipe is a series of steps that are followed in strict order. Each step advances the build, whilst eliminating any wood motion that is the result of the preceding step. In this way, the wood relieves all of its internal stress to the point at which it is free of these internal stresses. Then, at a pivotal point in the build, a type of intentional stress is introduced, and from that point forward the neck does exactly what it is told. The builder is in complete control. All too often with traditional neck designs, the opposite is the case.
Another big advantage that the TCM neck design brings to me is the very predictable tonal nature of the completed neck. I can design sounds knowing exactly what the neck is going to sound like. Because I build for a pre-determined acoustical response, this is a huge advantage or me as a designer.
But the biggest advantage of all is for the guitarist, who can now tour the world without having to adjust the truss rod constantly, all the while enjoying the sound of a guitar that is in part due to the woody flavoring that a really great neck brings to the party!