A client brought in a Cordoba C1M with the intention of making it fretless. The decision to use this particular model was selected because it has an adjustable trussrod.
Although generally nice to have, trussrods aren’t always necessary in classical guitars, due to the relatively low amount of tension exerted by the nylon strings.
The reason a trussrod is important for this particular job, is because without frets, there is a high probability that the neck will have too much relief without anything counteracting the string tension.
For a good example of this concept look no further than vintage Martins. For decades they were built without adjustable rods, and instead relied on the pressure of the slightly oversized fret tangs (relative to the fret slots) to exert enough back-bow pressure on the fretboard so that the neck has correct relief when tuned to pitch.
When compared to the modern adjustable trussrod, compression-fretting seems like a bad idea. But I have yet to encounter one of those old Martins with less than perfect relief. So as long as luthiery suppliers keep stocking fretwire with varying oversized tangs, it’s a pretty cool design.
Anyway my point is that the pressure exerted from fret tangs is crucial to the structural integrity of a guitar neck – especially one without the reinforcement of a trussrod.
The Process:
Step one is to remove the frets. The easiest way to do this is to use a soldering iron so that the oils in the rosewood are released from the heat, and the amount of tearout from the barbs on the fret tangs, is minimized.
Now that the frets are out, you can see the oils released during the fret removal process is gathered around the slots. I’ll get rid of it with a file, since it’ll tend to gum up sandpaper.
Next, the trussrod is adjusted so that the neck is as straight as possible, and the fingerboard is levelled with 120-grit sandpaper on a straight levelling block.
The fingerboard is marked in pencil so that once the pencil marks are gone, the board is sufficiently level.
Rosewood dust collects in the fret slots during the levelling process, which is perfect, as we’ll see in the next step.
After the board is levelled, I adjusted the neck into a slight back-bow, and then wicked super-thin CA glue (super glue) into the rosewood dust-filled fret slots.
It took about 3 iterations of sanding, gluing, sanding some more, gluing some more, etc. until the slots were sufficiently filled, without any voids, loose dust, or air bubbles.
The next issue is the side dots, which need to be relocated from the center between the frets, to on their respective frets.
After the side dots are drilled out, the holes are filled with rosewood dust and superglue.
Then they are scraped and sanded flush with the side of the fingerboard. By now, they are pretty well hidden.
Now the face of the fingerboard is sanded out to 220-grit, then rubbed with 0000 steel wool, and finished off with some lemon oil.
The corners were too sharp so I broke the edges with some 220-grit, for comfort.
The new plastic side markers are drilled, glued, and scraped level.
The nut and saddle were both cheap plastic – the stuff that melts when you try to sand it – so I made a bone nut, and corian saddle. Time to string it up.
Now the side dots are exactly lined up with their respective fret slots, and quite helpful.
This was surprisingly a lot of fun to play. The sound is similar to an Oud, and is more resonant than I originally thought it would be. I had to take it for an extended play-test. Very cool, and I highly recommend!
