Intro: Laser Cut Tenor Ukulele
I have been wanting to make a classical guitar from scratch, but I decided to start first with a tenor ukulele to be able to work on a slightly smaller scale. I have been playing around with the laser cutters at my school and am sold on the speed that it allows for one to take a project from idea to finished product. Cutting pieces out by hand on a scroll saw is rewarding in some ways, but the precision and speed (and ability to mess up and start over) of the laser cutter works much better for me. I was partially inspired for this project by a laser cut ukulele shown on Thingiverse (http://www.thingiverse.com/thing:30986), but this model was a little less traditional than I wanted.
The dimensions for my project came from a variety of images, etc. available on the internet. I just finished the project and haven't had a chance to get feedback from a real ukulele player, but I think I need to make the neck/fret board a little wider and also add the position of the bridge to the Inkscape file to make it easier to put in place. The headstock is a little too thick for the tuning pegs I got. For a nylon string instrument, I chose not to add a truss rod, but I may remount the neck in the future to get it to sit a little more "flat" relative to the body of the ukulele.
The *.svg file included here was created using Inkscape which is available for free and works well for designing files for laser cutting. You may need to save this file before opening it with Inkscape depending on your computer/software. Google Chrome worked for me for this.
I have found tuning pegs that will fit the headstock thickness that are meant for a cigar box guitar so I am going to get them and leave the dimensions unchanged for that. I found a fret board for ~$7 that I am going to use to resize my fretboard.
I have been working on a second ukulele to fine tune the design files.
For this project you will need:
Materials: (You can do this with ~$40+ of materials depending on what you choose and have laying around)
3 sheets 12" x 18" x 1/8" Baltic birch plywood (~$2.50 per sheet - found on Amazon)
3 sheets 24" x 24" x 1/2" Baltic birch plywood (I tried cheaper pine BC plywood for my second attempt which didn't work very well on the laser cutter) (~$7.00 per sheet - from Lowes)
1 set nylon ukulele strings (~$4.50 per set - found on Amazon)
1 set of 4 tuning pegs (get the worm gear variety versus friction fit)(~$10.00 per set - found on Amazon - also found a set for $6.50 that are a little shorter)
1 hardwood 1/2" dowel - need a few inches of this -(had this laying around)
a few wood screws ~1" long - (already had these)
optional - 1 fret board for tenor ukulele (~$7.50 from Amazon)
wire or fret wire - ( I haven't added this yet, but I will probably use the a same aluminum wire I used to make my electric guitar since it works pretty well.)
a couple of small zip ties
Pieces to cut:
6 inner form layers from 1/2" plywood
2 outer form parts from 1/2" plywood
2 side panels for body from 1/8" plywood
1 front panel for body from 1/8" plywood (add a logo in the laser cut file if you want)
1 back panel for body from 1/8" plywood
3 wider supports for inside of body from 1/2" plywood
10 narrow supports for inside of body from 1/2" plywood
5 or 6 neck pieces - "silhouette"- from 1/2" plywood
1 fret board from 1/8" plywood
laser cutter (used Full Spectrum free standing model)
lots of clamps
drill and various bits
Step 1: Create Inside Form and Outside Form
So the first thing to do is to create a form to shape the side panels around. I used 6 layers of 1/2" plywood here. I put in holes in positions to make it easier to clamp the panels to the form. The layers were glued together and allowed to sit overnight.
I modified the outside form to follow the shape of side panels to make it easier to clamp versus the random shape used the first time through. Originally I wasn't planning on having the outer form at all, but it works much better for getting the final shape and allows for the addition of the inner supports while still keeping the panels in the form. It may be possible to get away with just the outside form, but it helps to use the inside form to get the shape started before placing the panels in the other form.
Step 2: Put Side Panels on Form
I used a string on the form to get the dimensions to go halfway around the form and then added a little bit. Side panels (2.9" x 17.8") were cut out of 1/8" birch plywood using the laser cutter (dimensions are included in the Inkscape file that is attached). The panels were placed in warm water and allowed to soak for a couple of hours. Soaking them longer didn't seem to improve the flexibility. One site I looked at recommended putting them in boiling water, but I didn't have that available in the "Idea Lab" I was working in. I also considered building a steamer, but my goal is to keep the project as simple as possible.
Once the panels have soaked, I used clamps to push them into the right shape. Be careful here since there isn't too big a difference in the amount of bending between bending to shape and breaking the wood. There will be a slight gap at the bottom if you start at the top with each panel, but this won't be a problem in the next step.
I added a lot of pictures here to hopefully help follow the process. I clamped the first side at the top and pushed it into place with my hand partially and then used the clamps to pull it in the rest of the way. I found it helpful to clamp a section and then go back the previous clamp and reposition it to get a tighter fit. It is important to put clamps on both the top and bottom to hold the piece flat against the form. I used half of a 1" dowel (left over from a failed attempt at making a Native American flute using the laser cutter) on each side to help pull the panel into the narrow part of the form. Without this I couldn't get the panel all the way into the form. You should left this try overnight before moving on, but I took it off after an hour+ and moved onto the next step and got it to work.
Step 3: Put Side Panels Inside Form
Once the sides have dried (be patient here). Take them off the form and place them inside two pieces left over from cutting out the original form. I modified the Inkscape file slightly after making this to make the clamping process more straight forward. Clamp the side panels into the form starting at the top with the two pieces flush to each other. Be careful in clamping into the indent since this seems like the spot that it is most likely to crack. When you get around to the bottom you should have a slight overlap that can be cut out with a hand saw to get the pieces to sit flush against each other on the bottom.
Now glue the larger top and bottom supports inside the body. I used two on the top to give a place to anchor the neck later. Also put in smaller supports to anchor the front and back panel to. Some designs use a kerfed piece that goes all the way around which seems like a nice idea in the future but looks more complicated.
This process is much easier if you have a bunch of good clamps. I needed to use clamps to pull the wood into position when it wasn't sitting up again the form. Let all of the glue dry (or not if you aren't patient - I didn't wait for them to fully dry, and it worked out okay.)
I used the new version of the outside form here, and it worked much better for getting the panels to the right shape. I added a lot of pictures to hopefully help if you are trying to follow the process here. It is helpful to put on clamps and then reposition them after you have put on the next clamp in line. This makes it possible to get the panels tighter to the form. Don't take the panels out of the form until after you have attached the supports, especially the wider ones at the top and bottom since they help hold the panels in their shape.
Step 4: Add Top and Back Faces
Once the supports for the face are "dry" you can attach the panels. I didn't add any extra support to the front and back panel like most guitars have. I may try this in the future, but it didn't seem necessary for this instrument with nylon strings. I clamped on the panels after placing glue all around the edge and on the supports. You will need to use clamps to pull the side panels "under" the front and back panels. I was left with a slight overhang in places, but that can easily be sanded off at the end. If you want to personalize your instrument, add a little graphic in the Inkscape file and engrave it into the front panel before you attach it to the ukulele.
Step 5: Create Neck and Fret Board
I cut the neck pieces out of 1/2" plywood (4 of them - I will probably use 5 in the future) and glued them together. There is a slight groove for the nut (the part that holds the strings up away from the fret board) at the top. Next time I will thin the headstock part of the neck a little so my tuning pegs fit better. Right now the wood is too thick for them to fully extend through the wood. Invest in good tuning pegs if you want the instrument to stay in tune. The pegs with worm gears will work better than the friction fit pegs.
I cut the fret board out of 1/8" birch plywood. It is a little too narrow compared to some designs I looked at so I may widen it in the future. I attached the fret board onto the rest of the neck making sure it sits up flush the slot for the nut. I then used a scroll saw to cut the 1/2" plywood part of the neck down to fit up against the fret board. The headstock was left a little larger to give space for the tuning pegs.
Step 6: Attach Neck and Clean Neck and Headstock
I drilled small holes through the butt end of the neck and then put a larger hole part way through to allow the screws to sit below the wood in case I want to fill them in with wood putty in the future. I put glue under this and then screwed it into place. Make sure the fret board sits flat against the body (put glue here too and clamp) of the ukulele and that the neck is centered properly. The neck sits at a slight angle on my ukulele so I probably should have spent a little more time sanding it down to make sure it was seated completely flat.
I used a palm sander to clean the burned wood off the headstock and neck and to round off the neck a little.
Step 7: Add Bridge, Nut, and Tuning Pegs
The bridge was made from 1/2" oak dowel which was flattened off on one side. Make sure you get the height right so that the strings will sit at the right height over the fret board to not hit it. The strings pass over the dowel and then in through holes on the back. They then pass through a second hole to come back, and finally the string is placed through the loop created on the neck side of the bridge. The string is then pulled tight. The string will slip a little here until you pull it tight enough to get it to bind up against the wood. The position of the bridge is ~432 mm from the nut (top of neck).
Holes were drilled for the tuning pegs in the neck. The middle string tuning pegs were pushed a little towards the center to keep the strings from hitting each other, but the headstock is not quite large enough so the pegs had to be offset from each other.
The nut was also created from 1/2" dowel. This was cut down to give a nice thin piece that fit in the groove on the neck. It was ~1/4" high. I didn't add slots for the strings since I was trying to avoid damping the vibrations in the string, but it may need the grooves to hold the string at the right spacing at the top.
Step 8: String Ukulele and Test
The strings were now added (see description in previous step), and the instrument was tuned. Overall it sounds pretty good. It isn't staying in tune perfectly yet so some fine tuning will be needed to figure out where the string is slipping. The neck is at a slight angle, but the tension in the strings doesn't seem to be the cause of this. I will keep an eye on this to see if the neck needs to be reinforced in the future.
Step 9: Up Next...
I used the ideas from this project to start creating the forms for the body of a classical full size guitar. I ordered some larger clamps since having clamps that run the whole length of the body came in very handy with the ukulele.