Wood, that it were so simple
March 3, 2020
Hey Heather. It’s me again.
As you probably know, last year I built an electric guitar. The decision to start the project was made in haste. I needed a distraction. I thought it’d be a small project that would take a weekend or two. It spanned.. oh I don’t know, about 11 months. This was with going to the shop maybe once or twice a week for 2-3 hours at a time and includes one month for curing the lacquer finish and a two months hiatus. I was asked about it and mumbled something about sanding (soo much sandiing!) but there’s more to it than that. I thought I should write about it.
When you’re building your first guitar the first decisions you’ll probably make will be about the body: the material and the style. Since I decided to build one on a whim I took the wood that was available when I went to the workshop. It so happened to be poplar, which specifically I think was yellow poplar, which is different from just poplar. Tree taxonomy is confusing. Had I done research beforehand I’d probably have chosen a lighter wood and would’ve checked how different woods affect the sound. I did learn that it’s good to check the characteristics of wood for a given project. Some can be difficult to work with and it can make every other step more challenging. You want to be aware of this lest you break a screw or crack the wood you’re working on. Since I had someone showing me along the way, I didn’t worry much.
In regards to style, the woodshop had many templates to choose from and really you want to use a template since they already have the markings you’ll need like the center line, neck cavity, etc. Once you have something that closely approximates what you want, you can customize it to your liking. You do a rough cut with the machines first and then you file and sand it. One thing I’ll say about this is that it goes faster once you know how the tools work. I had a bunch of files of different shapes and sizes that I alternated between and it probably took longer than if I’d known how they each worked. Once you know your tools well, the work is easier and faster. After shaping the guitar, it’ll look deceivingly close to being finished. But it’s not. Not if you’re making the neck yourself. In regards to the body though, you’ll still need to drill the holes for hardware and add some type of finish to it.
The neck is so much more complicated to make than I had thought. You’ve got the truss rod, the fret board, the frets, the nut, the inlays, the headstock, you’ve got to radius the dang thing. It’s a lot of stuff, and there are a lot of details in each of the elements too. If you’re working on it full-time, it’s probably less daunting. The fact that you go to the shop for a day or two and then come back a week later probably slows the cadence. You keep forgetting what you were doing and what the next step is so it’s like you’re working into the void. Had I known then what I know now, I probably would’ve just bought a neck online and made some adjustments to it.
I have questions on sound
Here’s the actual interesting part I still have questions about. So I wrote about pickups before and how they’re basically a transducer that converts the vibrations of the string into electrical signals that are amplified. Let’s say we understand that part. Well my question is why is an A, an A? And how is it that if you play the next fret it’s a semitone up to an A#? And then it’s a B, and so on. How does this work? It’s all ratios, right? This is what I think. So in general, it has been decided that the A above middle C, known as A4, has a frequency of 440Hz. For a sound to register as A4 it needs to oscillate 440 cycles per second. If we take our instrument and tighten the strings until a measuring tool tells us that it’s vibrating at 440Hz, then we have our A. But then when you press down on the next fret and you get an A#. Why isn’t it a B or a C? Or between an A and an A#? By pressing down on the fret, we are making the string shorter. It’s not obvious to me how this makes it vibrate more (a B is ~493.883Hz). It’s not the energy with which you pluck the string that matters since that would mean you’d have to play every note with the same energy. Which we don’t. I know most western music and instruments’ intonation is twelve-tone equal temperament which divides the octave into 12 parts on a logarithmic scale. But how does this translate on physical parts? Luthiers use the constant 17.817 to position the fret. The wiki gives details into how a luthier makes the calculation:
If the nth fret is a distance x from the bridge, then the distance from the (n+1)th fret to the bridge is x-(x/17.817).
This somehow makes the guitars strings oscillate at the correct frequency at each half step. But I don’t understand how this changes the sound in the way that it does. I guess what I don’t understand is how physically shortening a string a precise amount makes this happen. It’s late. Questions for another day.