In the late summer of 2016, after a very long layoff from music, I decided to purchase an inexpensive bass guitar. I found someone selling an Ibanez GIO on Craigslist for around $50. I thought that was a reasonable point of entry, so I bought the guitar and also picked up a small Fender amp from Guitar Center.
I got the bass-bug, and ended up purchasing two more cheap bass guitars off eBay, with the intention of modifying them at some point. What I initially envisioned was a setup like Mark Sandman‘s bass: Two strings, custom tuned, and played with a slide. I may still end up doing that at some point, however, what I ended up doing first was converting one bass to fretless.
As an aside: If you’re unfamiliar with the band Morphine, I highly recommend looking into them. They are one of my favorite bands of the 1990s due to their unique noir sound.
I had made a couple tweaks to this particular bass already. I changed out both the potentiometers from the original 500K Ohm to 250K Ohm ones. Additionally, when I added the tone capacitor, I opted to install a socket so I could experiment with different capacitors. I’ve played with the capacitor values, but haven’t found one that makes a significant difference in treble cutoff.
I read up on fretless conversions, scouring the bass player forums for posts by people who had done it. Mostly what I learned was people can’t agree to anything online. So I took the ideas that made the most sense to me and ran with them. In particular, once the frets are removed the fingerboard, there’s a significant loss in structural integrity. (In addition to being rough surface.) So what do you fill the slots with? Putty? Epoxy? Sawdust and carpenter’s glue? Maybe even superglue? Eventually I found the idea I liked best: use slips of polystyrene and superglue them into the fret slots. With this plan in mind I set to work.
I called the local hobby store to make sure they had 0.020″ polystyrene sheets available (they did) and picked those up. I’d already pried the frets out, so, all that i needed to do was glue the styrene in place, sand and finish the neck, then bolt her back together.
I used a Japanese style pull saw to clean out the fret grooves before gluing the styrene in.
The process I used to the styrene inserts was to cut strips that were slightly wider than the neck, and about 1/4″ thick. I had WAY more styrene than needed, so conservation of materials didn’t come into play.
Once the glue had set, it was a matter of trimming the styrene down and fairing the fingerboard.
To maintain the curvature of the fingerboard, I used a radiused sanding block which matches the fingerboard’s convex shape. After knocking down the rough bits and ensuring the entire length of the board was being sanded, I moved through several grits of sandpaper. Starting with 80 grit, and working my way up to 220.
Once the fingerboard was sufficiently smoothed out, I applied three or four coats of wipe-on polyurethane, letting each coat thoroughly cure before sanding with 220 grit paper, and applying another coat. After making a huge dusty mess in my office, I was finally ready to bolt the neck back on, and try it out!