A Short Scale Hollow Body Bass Guitar

I just completed my 34th guitar, this one being a bass. I used the same body shape as my recent Corona style, which was convenient in several ways: I had the mold for it, and it reminded me of the Hofner Club Bass. I own a Jazz Bass solid body which is heavy and has a 34″ scale. I wanted a short scale instrument that would be easier to play and also lighter, so I decided to use the Hofner look for inspiration. I ordered a Chinese made copy of the tailpiece and bridge, and set to work designing the instrument. If you set out to build a guitar, or any instrument, you better have an accurate plan, unless you have built whatever you plan to make many times. I can build a guitar almost from memory now, but the bass has significant differences. So I designed it with my old CAD program (Vectorworks 10) which although now an antique of software, still does what I need it to do. I have designed all sorts of buildings and other things with this, and I am very comfortable with how it works.

Since the bass has long strings, which are also very thick, the forces involved are much greater than on a typical six string. I did some research and figured out what the best strings weights would be (50-105) for a short scale bass. The shorter scale also requires heavier strings for the same frequencies, or else the strings will flop around more than they should. Think of down tuning a guitar and how sloppy the strings feel. To use regular strings made for 34″ necks on a 30″ neck would be like detuning a regular bass. I tried this, and it was bad! Using information published by D’Addario I was able to build a table of string weights, unit mass, frequency, scale length and break angle. This gave me the string tensions and the pressure on the bridge. From this I basically guessed how heavy to make the braces, hoping that my intuitive feel for the strength of wood would suffice. To be safe I erred on the side of overbuilding, so the whole thing would not collapse. Since it was to be an acoustic bass however, I didn’t go too far in that direction, or it would have been acoustically dead.

In any case I built it as per plan and of course when it was done I discovered that my instrument was not exactly what I had planned for. Tiny angular rotations, like the neck angle, make large differences at the bridge. I had planned for a bridge of a certain height, which would mean a certain break angle of the strings. That determines the down force on the top, and the higher the bridge is, the greater the angle and down force.

My bridge height was higher than expected, meaning my bridge was now too short! I had to add a spacer underneath it to bring it to the correct height. This was not a problem except that I realized that this was going to increase the force on the top by about 10 lbs. I thought about using regular strings to reduce this, but decided that was not going to work, so I went ahead and strung it with the proper strings and hoped that my extra heavy braces would hold up. After 24 hours they seem to be fine. My sense is that the bracing was the right size after all, and like most well engineered things, had a decent margin of safety. Time will tell however, but so far it sounds great and is performing as well as hoped for.

In keeping with my desire to make my instruments as unique as I can, I made my own pickup using my home made pickup winding machine – an old sewing machine. I built the pickup from a maple core and walnut plates, with 4 neodymium magnets and many thousands of winds of 42 gauge magnet wire. The DC resistance is 10K, for those who know about this. That’s a lot of wire, but it makes for a strong signal and in this case it does not hum at all, unless I get close to a fluorescent light that is, like the one on my workbench. That induces a loud 60 cycle hum, but otherwise the single coil is fine.

I used Gotoh bass tuning heads rather than the silly little bass tuners Hofners have. For a Hofner you must buy special short scale strings with reduced end wraps in order to fit into the tiny tuners. This looks good and is lighter weight, but it restricts the sort of strings you can usually find in the music stores. These tuners allow me to use all off the shelf strings. I put Ernie Ball Slinkys on it, which are very good and as cheap a string as you will find. Maybe one day I’ll try flat wounds, but they don’t offer much except for lower noise from the friction of your fingers. I have tried them on my guitars and I always go back to round wounds, because I like that friction under my fingers. It all depends on preferences of course.

So far I resisted getting a bass amp, because in the house all I need is a low power amp and my Roland Cube Monitor can handle bass very well at low volume. For some reason bass amps are much cheaper than comparable guitar amps, but I have no idea why that is. A bass amp will work just fine with a guitar, but most guitar amps are not suitable for bass. So why do they cost more? Something about this tells me we are getting hosed!

2 Comments

Filed under Guitars, Uncategorized

2 responses to “A Short Scale Hollow Body Bass Guitar

  1. Wow, thanks for taking us along for the ride in a way that even those of us who don’t build instruments can understand. I actually think that the particular Gotoh tuners you ended up choosing nicely compliment the shape of your headstock design.

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