Folding Travel Electric Guitar

DIY Design and Fabrication: Final Project, Spring 2019

As a student attending college on the opposite coast from home, I travel back and forth a few times a year and wanted to be able to take a guitar with me. I’m still a very novice guitar player, so building up and maintaining callouses has been one of the largest hurdles for me to practicing. I designed this guitar to be compact while still offering a similar experience to playing a normal electric guitar.

This was a super fun project for me, and I really enjoyed the entire process of ideation, design, and fabrication. I think this is one of the most multidisciplinary projects I’ve undertaken so far, and I particularly liked how it relies on a combination of machining, woodworking, and basic electronics. But, if I were to do it over, I would definitely have CNC’d as much as possible- doing everything manually is incredibly time-intensive and didn’t always produce the best results (with my skill level, anyway).

Maybe it’s not the most technically challenging project in terms of calculations and engineering principles, but I learned a lot about fabrication and system design. There were a lot of components and parts that had to work together, and the thought process that went into considering how they all interact and affect the design is the most valuable lesson that I learned here.

Features:

• Magnetic hinges

• Under the bridge piezo pickup

• Three way switch for piezo, single coil, and blended outputs

• Individual volume knobs for each pickup

• Standard truss rod

• Rosewood fingerboard

• Maple through-neck and body

Final product photos first:

Process

The first thing I did was look at existing designs for inspiration. There’s actually quite a lot of travel sized guitars out there already, so I had plenty to look at. I was particularly inspired by the Traveler Guitar Pro Series as well as the Yamaha Silent Guitar. As you can see, I took the cut out design idea from the Yamaha Silent Guitar, and the electronic feature set (single coil + piezo pickups with volume knobs) and headstock/tuning peg design from the Traveler Guitar Pro. I also did a lot of background research (I’d estimate at least 15-20 hours), reading through forums and just generally Google searching things in order to get familiar with the DIY guitar process.

Then, with a rough plan in mind of the necessary supplies, I put in orders at StewMac and Amazon and headed off to Home Depot. As with most projects, I did have to make multiple trips and some last-minute orders as I figured things out along the way.

Tools (all available from CMU’s Makerspace):

• Band saw

• Jig saw

• Lathe

• Mill

• Hand file

• Dremel

• Drill

• Belt sander

• Soldering iron

• Orbital sander

• Laser cutter

Fingerboard

Since I received the supplies from StewMac first, I started with the fingerboard. I calculated how much I wanted the fingerboard to taper, cut it with a band saw, and then used a mallet to hammer in the fret wire. The spacing calculations and radius curvature can get a bit tricky, so I went with a pre-slotted fingerboard. I trimmed the fret wire to the approximate length with wire cutters and put in a thin strip of super glue into each slot before putting the fret wire in.

I started with the first fret at the top, but in hindsight I should’ve started at the bottom to practice this process before I get to the upper, more commonly played frets. I had a noticeable improvement in seating the frets by the time I finished.

The next step was to file down the ends of the fret wire so that it won’t cut or catch on the player’s fingers. The fret wire is actually pretty sharp, so although this was very tedious, it is also very necessary. This took a long time since I was using a hand file at first- I wanted to avoid damaging the wood, but I eventually switched to a dremel for efficiency/time and used a hand file for finishing touches. The center photo is unfiled fret wire and the right is filed.

Neck and Body

With the 4 foot plank of maple from Home Depot, I started sketching out designs on 1:1 paper templates. I had originally started modelling it in Solidworks, but with all the curves of the design, I found it way faster to just sketch it out on 1:1 paper templates and check the fitting directly on the wood plank.

The most challenging part was designing the cavity for the electronics that:

1. Is large enough to fit all the electronic components

2. The switch/knobs/input jack protruding through the top of the body wouldn’t interfere with the player when strumming

3. The cover on the back of the guitar is in a position that allows the guitar to fold flat

It was also challenging to find the right proportions that made the guitar still look like a regular electric guitar, particularly the curvature and dimensions of the body. Those are surprisingly hard to find online!

Once I settled on a design that I liked, I cut it out using both a jig saw and a band saw, depending on the curves of the part. Since the pieces are so curved, it was pretty difficult and I may or may not have snapped the band saw blade a few times (shout out to the machinists and Makerspace staff for being so patient). The cuts were pretty rough and I did make a few mistakes but I figured that I’d sand it out later. I used a mill to make the electronics cavity, the indent for the truss rod, and the slots for the tuning pegs and pickup. Again, a huge thank you to the Makerspace staff and machinists- I received a lot of help along the way in selecting the right approach and tools to achieve what I wanted in my design.

I used a laser cutter for the pieces that bordered the pickup and the bridge.

Next, I turned to sanding. I started off with a belt sander for initial sanding, although I couldn’t use it on that many sections since most of the pieces were too curvy to sand or too long to evenly sand the entire section. I used an orbital sander with 60, 80, 120, 240 grit pads and eventually hand finished with 400 and 800 grit sand paper. This was one of the most time consuming parts of the project and it sometimes took some creative clamp positions, but the results were worth it.

Machined Parts

My design relied on two custom parts, based off of the Traveler Guitar Pro Series design. The first is a cylinder peg type thing that allows the strings to wrap around to the “headstock” on the back of the guitar, and the second is the plate at the top that holds the strings at the top.

Luckily, I was able to use scrap aluminum lying around in the machine shop. After calculating the dimensions for the even spacing of the strings, I used a lathe for the wraparound piece and a mill for the plate. I messed up my first attempt at the plate, which is why there are two sets of holes on it. After I finished the pieces, I did a few coats of spray paint black to fit with my desired color scheme.

Electronics

The circuitry isn’t super complex, and there was plenty of documentation about how to wire up volume pots, switches, and pickups. The specific combination of a single coil pickup and piezo rod pickup is a bit unique because it’s a mix of traditionally electric and traditionally acoustic pickups, but overall this was probably the easiest and least time consuming part of the project. I used heat shrink tubing and electrical tape to reinforce the soldered joints (pictures taken before I used the heat gun for the tubing).

Assembly and finishing

Now all that’s left is to assemble everything together…!

I glued in the truss rod with steel reinforced epoxy, drilled in the holes for the switch/knobs/jack, and stained everything except the fingerboard. I used a mix of the dark walnut and black cherry stains for a warmer but still very deep brown. After one coat of the wood stains, I applied the polyurethane coating. After the stains and finishes dried, I used wood glue to glue the fingerboard to the neck and steel reinforced epoxy to glue the machined aluminum pieces in place.

Unfortunately I did have to go back and make some adjustments- for one, the slot for the tuning pegs were a bit too tight to comfortably turn them, and I just had to generally fine tune how all the pieces fit together. I also decided, last minute, to add in magnets on the hinged portions. It was a good idea in concept, but in practice I don’t think it was worth the trouble. For some of the magnets, I didn’t drill the holes deep enough, so they had to be sanded down in order for the folding piece to lay flat. That was a pain, but at least I got a fun GIF with sparks flying out of it?

And that’s all, folks!

Here’s the supplies list in case you’re interested in giving it a shot yourself:

• 4 ft, 0.75” thick Maple plank

• StewMac pre-cut medium fretwire set, 16” radius

• Slotted fingerboard for Martin Guitar, Indian Rosewood

• CTS Control Pots, 500k Ohm (x2)

• Multi-contact 1/4” output jack

• Fretboard marker inlay stickers

• StewMac Hot Rod low profile 2-way truss rod, 4mm allen nut, 18”

• Rod piezo pickup

• Acoustic guitar bone bridge saddle and nut

• D’Addario EJ15 extra light acoustic guitar strings

• Musiclily 3 way pickup selector

• Alnico sngle coil bridge pickup

• Acoustic guitar tuning pegs set

• Refrigerator magnets

• Varathane black cherry interior wood stain

• Minwax dark walnut interior wood stain

• Varathane gloss triple thick water based polyurethane

• Everbilt 1” utility hinges

• Black spray paint, matte

• Foam brushes

• Steel reinforced epoxy

• Wood glue