Greetings earthlings,
What did the scarf say to the head?
To even attempt to understand this joke of mine, which I am quite proud of and am excited to share the punchline to, you must know what the scarf joint is.
The scarf joint is named for the famous 18th-century Dutch woodworker Franklyn Scarfe, who, in his authoritative Treatise on the Methodologies of Working Woode, describes how he stumbled upon this method of joinery while trying to construct the world’s first Dutch Oven.
That may or may not be true. You chose.
Regardless, it is the method of constructing a guitar neck I have been playing with lately.
Many of the guitar necks out there, especially those made by Gibson, are fatally flawed. (Yes, I have reached the level of self-delusional pomposity required to make such a bold claim.) It all has to do with the point at which an angled headstock departs from the plane of the neck.
Wood cells are typically long and their walls contain cellulose and a mysterious substance called lignin. Both are polymers, but less is known about lignin because, apparently, isolating it from the cell wall alters it chemically. Molecularly bonded, lignin and cellulose create very strong fibres in wood. This is why trees can grow so large and why large branches that shoot out horizontally from a tree do not break from the trunk due to their sheer weight.
In a guitar neck, these fibres run along the length of the neck and, like in a tree, provide strength and stiffness. But in a guitar neck cut from the same board, the fibres become very short in an angled headstock, and given the more than one hundred pounds of string tension pulling on the headstock, make the wood very vulnerable to break here–especially if the guitar is dropped while the strings are tensioned.
Fender necks do not have this problem as their headstocks are straight, thus the wood fibres run straight through their length. String trees are required, though, to pull the strings down behind the nut so that they stay seated in their nut slots. I don’t like this method, though, as the string trees introduce friction on the strings, which can result in tuning issues. When a string is bent or a vibrato unit is used, the friction can prevent the string from returning to its precise original tension (tuning).
In the past, I have constructed necks with headstocks that have a much gentler angle than is traditionally used. Tradition will tell you that a headstock angle must be 13 degrees or 15 degrees or whatever in order to keep the strings from popping out of their nut slots when played. I don’t buy this. I’ve constructed necks with headstock angles of 8 degrees and have had zero issues. The gentler angle means those wood fibres get a little bit of extra length in the headstock, which equates to a little bit more strength and resilience to breaking.
Yet, as always, there is a better way.
Utilizing a scarf joint is a method that keeps the wood fibres running through the length of an angled headstock. It requires a few more steps, but I’m coming to think it is worth it.
The method, in short, is this: saw your board at an angle that matches your desired headstock break angle, then flip the headstock portion and glue it to the surface of the neck you just sawed. The surfaces to be glued will need to be planed flat and square before they are glued, of course.
More than producing a superior guitar neck, constructing a neck using the scarf joint also allows me to use wood much more efficiently. The board of wood being used only needs to be a little thicker than the final neck thickness, about twenty-five millimetres. If more thickness is needed for the heel, a piece of wood can be planed and glued to it. Some builders create decorative effects by laminating contrasting thin pieces of wood and veneers.
Conversely, constructing a neck with an angled headstock from a single board requires that board to be significantly thicker than the final thickness of the neck in order to accommodate the angled headstock. That means a lot of that wood will end up in the scrap-wood bin.
So, to conclude: what did the scarf say to the head?
No boggarting.
Reading
Two books in particular have been very useful in my research into scarf joints and the strength of wood fibres. The first is Building Electric Guitars by Martin Koch. This is the book that got me started in guitar building. I spent months front-loading the information that is in this book before I ever put chisel to wood. It remains my go-to resource for guitar-making processes, including constructing a neck using a scarf joint.
The second book is Understanding Wood by R. Bruce Hoadley. This book is intimidating, and I am mostly too dumb to understand much of the information in it. But the first chapter on the nature of wood and its cellular structure is fascinating and, I think, important: it reminds us that wood is not just some material for us to use, but comes from complex living beings and deserves to be treated with respect. As Hoadley puts it, “Wood evolved as a functional tissue of plants and not as a material designed to satisfy the needs of woodworkers.”
I’ll drink to that.
I hadn't thought about why the structural compromise in Gibson necks existed to such a specific degree. Although I understood a volute adds structural integrity, your drawing illuminated the inherent flaw in the Gibson design (and of course the infamous splayed tuning pegs being no end to tuning instability). One neck break on an SG I had was enough for me to disregard Gibsons in favour of more dependably built guitars.
So, my question for you is when you use a scarf joint, is there any additional strength added by incorporating a volute into the neck? Or is a volute more a preference instead of a necessity for durable headstock designs?
I wonder if there are examples of guitars out there where the blank was steam-bent to create the ideal grain direction without the compromise of a joint?