CityCaster-005

April 2025

As I'm progressing on CityCaster-004, sanding and applying coats of oils on the guitar, I am also starting working on the next project, continuing on the CityCaster guitars theme, adding experience each time.
I had the opportunity to help a musician friend with his (beautiful) anniversary LesPaul; he has vision problems and was staring to have a hard time seeing his neck side dots when it's getting too dark during gigs. So I crafted him a small, 4mm wide strip of LEDs to set along the guitar neck - Absolutely no modification done to the guitar -  using my own LesPaul as a 'template' to build this simple but effective garland of sorts, as can be seen below with the early test on a single LED.

Of course, soldering 10 or 12 LEDs to these wires is a valid solution when one cannot touch a guitar or bring any modifications to it, but there are better ways, such as the one proposed by a guitar amateur, removing the fretboard and installing LEDs behind dot inlays, a quite invasive method (https://www.youtube.com/watch?v=-ox3dZSufxk), or  probably the best one (patented?) by FretFX (https://www.fretfx.com/) is to use a single (flat?) optical fiber that runs on the side of the neck and exposes light dots where needed. Unfortunately they don't seem to offer these anymore... A great solution nevertheless, maybe the best.

Finally the approach proposed at https://www.projectguitar.com/forums/topic/19909-fiber-optic-sidemarkers-tutorial/ or by King Blossom Guitars (https://www.facebook.com/watch/?v=602214747285921) is the most appealing one to me, as I have the right equipment to perform the needed operations.
So I went on with ordering some Ø1mm fiber optics, and designing a prototype, with channels for sending light to several side-like dots as shown below. 

This validates the principle! Time to work on a real fretboard... I modified my Aspire fretboard files to accommodate for the needed changes, nothing too hard indeed but there are places where there's not a lot of wood left! :-) Each side dot is fitted with a fiber that runs down to the neck heel, where the neck meets the guitar body. Lighting will come from the guitar body, the neck being purely 'passive'. The carved channels are typically radius ~20mm, 1.2mm deep channels, except where the channel meets the side dots and needs to get to the dot center, this calls for a 2.75mm deep channel.

My CNC is a 'simple' 3-axis CNS, so I had to be creative to drill the side dots, with creating a specific fence/jig for the fretboard, after being shaped and cut, would receive said dots holes (Ø2.5mm/ 4mm deep) for small beads of aluminum to fit and center the fiber. For the fretboard to itself, nothing special, I used pre-filled Ø8mm aluminum inlays I had from a previous build, ran the top shape on them once the Cyano glue cured with an Ø8mm round bit, and sanded the resulting 16" radius board with 100, 150, 220, 320, 400 and finally 600 grit.

The result is a rather 'classy' fingerboard/fretboard, with perfectly aligned side dots (thanks to that CNC and jig), ready to receive frets and with incorporated lights! I'll get to choose the color of LEDs later on... By the way, this is iroko wood. It creates nice fretboards, but make sure you wear a mask while sanding as iroko dust is known to cause health issues.

Time for a Neck

I went through my stock of walnut and chestnut woods and selected three pieces I glued together, barely wide enough for the neck headstock so I added two small pieces of walnut to cover this.
And off to glueing and cure a full night before heading to the CNC for neck carving. The "usual" process and I used files I already have and provide a good neck. There are always things to adjust, such as length or wideness of the truss rod, whether or not to drill all tuner screw holes, etc.
My CNC did a good job and soon enough, I had a neck ready for sanding... yes... sanding again.

Sanding, Fretboard assembly

 Time for 80 grit sanding (no more at this stage) and providing a better neck to headstock transition, which I prefer to finalize by hand. I keep the neck heel for later as it will likely need adjustment with its receiving body. Once happy with the neck shape result, I have about 15.5mm thickness at 1st fret and about 19mm at heel junction, with a 22mm heel and a 15mm headstock.
Th place two tiny reference holes through the fretboard and neck prior to applying glue (truss rod is protected) and reposition the fretboard for lots of clamping. This will sit for a few days, ensuring the glue fully cures.

Fret installation time!

On this neck/fretboard, frets must be shortened to fit in the slot on the fretboard (so-called blind fret slots). This is done with a special tool (fret tang nipper). Once all 21 frets are prepared and set to correct length, I rounded the fret ends with a diamond coated sand disk that process to a concave, round shape (the smallest I found was 3mm). T used a plastic hammer and a hand-press to fit th frets in their respective slot, applied a little bit of glue to secure them in place and sanded them (slightly) to ensure they presented a straight surface.
Once this was complete, A crowning file enabled reshaping fret tops. I also cleaned/(600 grit resanding) the top of the fretboard, and protected it before sanding the fret surfaces to 600 grip, and then 0000 steel wool. 

And then all went wrong...

With the neck finished (or close to finished) I thought I'd have a great neck and side dots. Well... No. It tuned out I made several mistakes in using the fibers... 1st one was to have them aligned flat, something that's quite hard to light in an even way without advanced plastic devices I don't have. 2nd one is the fact the line of fibers were cut just at the edge of the fretboard and basically will come over the body of the guitar, This will not be something not visible on the instrument and with the guitar PU just rigt to the neck, it will not be easy to install a lighting device for the line of fibers. 3rd one is the fact my fibers are Ø1mm and my side tots openings are Ø1.5mm, which leaves room for the fibers to come at some random angle within the side dot... and when I cut them, they do not provide a consistent 90° angle cut, and as a result, an inconsistent light coming out of the fiber.

All things I had to modify in several prototypes/attempts (3 total!!!), but I now have something correct I believe. Below some of the steps and changes that took place in the fretboard and (new too) neck that I carved. I am waiting for new truss rods to arrive for glueing fretboard and neck together, and will keep the neck above for another build (ans the neck is quite nice indeed, and despites all the tests it went through.

The new neck I built/carved is a thinner than previous ones and results in a 20mm→24mm thick neck (including fretboard, 1st and 15th frets measurements). This neck should be quite nice to play.

Assembling the new neck...

Finally time to put the truss rod inside (just received 6 of them this morning!), put some glue on both the neck and the fretboard and use all available clamps to glue the neck!

Nice neck!

I did a little sanding on the neck, to 320, and shaped the fretboard hanging part at the headstock/nut junction. And a little cleaning, sanding (to 600) and oiling on the fretboard. A fin looking neck! I think I'll like this one, I made a quick video about it: https://youtu.be/mRp99qmwA_0

The frets have been installed with my fret-press, ensuring the fretted fretboard was flat and consistent all along the length. frets aere crowned and polished, some more sanding on the neck and several coats of Osmo Poly-X oil have been applied to it. It is then time to set the neck in place with a body, and I used my own Lyon CityCaster for this, exchanging the existing neck with the new one.
I drilles a pass through for the fiber optics in the body, so a single LED could fit at one side of the drilled channel while fibers would join from the other side when the neck is set in place. The LED itself is driven with a PWM device (see above) to enable progressive lighting of the side dots; This is accomplished using a small PWM module for motors that runs from a single CR2032 battery cell, and a constant current device for LED lighting. A new pot with ON/OFF in the control cavity of the guitar body manages this, as shown here.