Another Cardboard Ukulele

Inspired by a combination of eplunkett's Playable Cardboard Ukulele, which then inspired parrster's Make a Ukulele out of cardboard, I built this -- I call it the George Harrison "signature model" cardboard ukulele, featuring a more authentic method of constructing the sides, some headstock shaping tips and a compensated saddle for better intonation. It's also fitted with a pickup!

This is a soprano sized instrument (34cm scale length) but tuned to D4-G3-B3-E4 (baritone re-entrant tuning) just to prove that there are no rules when it comes to this sort of thing. Also it's easier to translate guitar fingerings, as these are (almost) the higher four strings of a guitar.

This is my first attempt at any kind of luthiery, after watching a DVD or two of the pros at work, so I'm amazed this worked at all.

Materials

• 4 Machine Tuners (2 left, 2 right) (eBay: cheapest were a £3.19 set of 6 from China)
• Ukulele strings (I used DADI UK080N .028/.033/.041/.028 Nylon) (eBay: £2.39)
• Double wall corrugated card (6mm thick) (top, back, part of neck)
• Single wall corrugated card (4mm thick) (sides, part of neck)
• White artboard (1mm thick)
• Black/Dark Brown glossy card (< 1mm thick) (fretboard and trim)
• Silvered mylar plastic film (not silver foil, too easy to tear!)
• Silver self adhesive labels/dots
• Wooden Dowel (6-9mm hardwood)
• Plastic tubing (Soft/flexy 2-4mm diameter aerosol/pump action spray bottle tubes)
• Plastic tubing (Hard, 1-2mm diameter plastic tubing (empty Bic/biro pen ink tube is good))
• Cocktail sticks (about 15)
• Wooden skewer (1)

• PVA Wood Glue
• Pritt/UHU glue
• Stick Cyanoacrylate/SuperGlue/Krazyglue
• Scotch Invisible/Magic Tape or other low-tack tape.

Optional - Strap

• Strap material (0.5-1 inch wide)
• Eyelets (2) and eyelet fitting tool
• Two wood screws/chipboard screws/self tapper screws, No 8 x 0.5 inch

Optional - Pickup

• Plain (non cased) piezo disc (27mm)
• 1/4" Jack socket (Mono)
• Short piece of screened wire

Tools

• Small Needle files (triangular, round)
• Xacto scalpel knife (a new sharp one not a blunt one!)
• Xacto (or similar) small razor saw
• Sanding block
• Sewing needle (fine pointed)
• A4 Hole punch
• Steel safety rule
• Dremel/Minicraft and grinding stone wheel
• Kettle (full of water, gas preferably to keep the steam flowing)
• Clips, clamps, clothes pegs (plastic), weights, elastic bands ... to hold stuff together
• Soldering kit (for pickup only)

Other

• PDF templates from eplunkett's instructable https://www.instructables.com/id/Playable-Cardboar...
• My modified neck template (see step 3 JPG), fretboard guides, and artwork (for these, see the final step)

The back and soundboard are cut straight from double wall corrugated card (for rigidity), using eplunkett's template for "top". The pieces you cut the top and bottom out of need to be kept in one solid piece, as these will be needed later as guide jigs.

Select which side is going to be "inside" and "outside" if there are any marks or printing visible. Remember you will be able to see the inside of the back through the soundhole! I chose this particular card because it had a nice "wood" colour, not dingy grey.

Transfer the shape onto the card by Scotch taping the printed template to the card and piercing through it with a sewing needle, about every 1cm along the curves. Then cut directly from hole to hole with the Xacto blade.

The same template will serve for top and bottom, but only the top needs the soundhole marking (unless you are making a stereo ukulele). Use the same needle holes on the second go. If you are using twin wall corrugated, try and cut through just the top layer at first, then go back and push through the second layer, it's easier.

The neck is cut from eplunkett's template for "Neck A" and "Neck B". I created an additional "Neck C" template to make the neck a little thicker and to add more "rounding" to the neck. Print one "A" template, and two "B" templates. The second "B" template is extended into a "C" template as in the picture

Again, tape the template to the card and pierce through the corner of each right angle (join the lines with a steel rule while cutting) and every so often along the curves (join these freehand with the blade).

I made 2 x Neck "A" out of double wall corrugated (visible outside), 4 x Neck "B" out of single wall corrugated, and 7 x Neck "C" (centre) out of single wall corrugated, making a stack of 44mm thick when squeezed together. Some corrugations run along the length of the neck, others at right angles. 44mm will end up being the scale width of the neck. You may need to do a few more, or less, to achieve this width.

Don't glue them together just yet!

I reshaped the headstock using some additional card as follows. There are two wedges (as shown) inserted into the headstock laminated layers. Each is just three pieces of card, almost the length of the headstock, half the length, and one quarter the length, glued together. These are the same width as the headstock is thick, and can be measured off the template directly. When inserted into the laminated card it will widen it out in a pleasing fashion. Hopefully.

Still don't glue them in yet!

Next I added another strip of double wall corrugated around the whole headstock, further widening it, tidying up the ratty ends visible at the top, and protecting it from knocks. Note which way the corrugations go here, it's important for a later step. When the headstock is squeezed in, measure the width at the widest point and CRUSH the inner wall of the additional strip to get the corner folds. Also, thin out the end of the additional strip so that it will blend in better later, by removing some of the INSIDE layer and corrugation for about 1 cm.

Now you can glue the neck together. First I glued all the C parts in one stack, two sets of B parts in another pair of stacks, and left them to dry. Then, I sandwiched the A-BB-CCCCCCC-BB-A pile together, gluing ONLY the main neck (NOT the headstock yet -- no glue beyond the nut!). At this stage the headstock is still uniform thickness, but can be slightly fanned out and adjusted. Let the glue dry.

Finally, I added the additional wedges into the headstock and glued them between the faces of the headstock, and added the outer protection strip. By now the neck is solidly glued, so any squeezing and adjusting of the headstock won't affect the neck.

At each stage above, make sure everything is aligned exactly together at the tail end of the neck, and on the "face" of the fretboard. These are the important edges.

Once all the glue is dry, I injected PVA glue into the protective strip from BOTH sides. This serves two purposes. It will dry HARD and prevent the headstock getting dinged. It also SOFTENS the cardboard so that you can shape it now. I pushed the side of a roll of electrical tape into the top of the headstock, caving in the card, and clamped it there while the glue dried. You can also GENTLY crush down where the protection strip meets the neck "A" pieces to blend in the shape even more.

This is going to be the attachment point for the two sides, somewhere to put a strap button into, and sets the thickness of the ukulele. This piece is 47mm high on mine. I cut this all from double wall for strength. The triangular support is exactly a right angle, and is dead on the centre line of the ukulele. The strap button screw will penetrate the edge of this angled piece, so make it thick. Set the upright square panel slightly back from the edge. This distance will be about 4-5mm, the same as the thickness of your sides. Glue the angled piece on two sides, and the tail block on the bottom.

This is where the neck will slot in, so its internal size needs to be a very close fit to the neck you created. I used the general shape from eplunkett's body template, and cut this from about 7 layers of double wall, with a couple of layers of single wall. It needs to make a stack that will exactly fill between the front and back of the ukulele, and be the same height as the tail block.

A panel of single wall was used to close off all the holes for better looks through the soundhole, and to plug up the gap where air could escape from the body.

When the heel block is dry, glue it onto the base. Again it needs to be set back a little (4-5mm) from the edge so that there is space for the sides to fit round it. It also needs to tightly fit to the neck leaving no gaps. Trim and adjust as needed.

Make sure the slot for the neck is dead centred on the ukulele back, and is dead square (insert the neck temporarily and run a straight edge down the whole neck, body, tail piece. When everything is square and straight, with the neck fully home, and there's still space for the sides, that's where it goes.

Glue it and clamp it down. Don't accidentally glue the neck in.

After the glue is dry, make sure the heel block is still the right depth. Mine wasn't. It shrank (honest) and had some give in it, so you'll see an extra piece of card to shim it up. Make any last minute adjustments now, as you want the top sound board to attach to this point.

I used some white artboard to give a smoother surface to the headstock (front, back) and fretboard. Measure off the fretboard part of the neck to get the size required (about 44mm wide on mine), and cut the fretboard to a uniform width all the way along. Trace round the headstock to exactly copy it.

For the back of the headstock, I cut a half moon shape out to avoid the "C" neck pieces so it would lie flat.

Save the remains of the artboard (with the hole in it) as a template needed for later.

When the fretboard is glued on, ensure that any variation in the width of the neck is squeezed out so that it matches the artboard (44mm) all the way down) -- mine had a slight variation. Put a clamp or elastic band where there is any bulging visible.

Then glue on the headstock top and bottom white veneers. A gap was left at the point where the neck changes angle to attach the nut (later) directly to the neck.

I also created a "heel cap" from a scrap piece of corrugated card, to match the shape of the curved profile of the end of the neck.

This is where you need the pieces of card the top and bottom were cut from. You kept them, right?

Although I like eplunkett's method for laminating the body from layers, I prefer the more conventional look of parrster's sides. However, I didn't want to score the card every few mm without breaking through, or have external cuts to hide.

The way guitar sides are usually made is by steaming, bending, and trapping in a mould under pressure. So why not do that?

Cut two strips of single wall corrugated card, about 47mm wide by just more than long enough to fit around one half of the ukulele (that's not a precise measurement). The corrugations need to run at right angles to the length of the strip, otherwise it won't bend well.

Armed with one of the reverse-cutout body pieces, and a full kettle, I steamed the card until it only JUST begins to bend, pushed it into the mould, held it until it retained the shape, and moved on to the next part. You want a little excess card at each end (neck, tail) so that it can be trimmed later.

Go easy at first, if you over-steam it will go soggy. If you under-steam it and force it, it will just bend nastily. Concentrate on getting one section bent at a time. Then repeat for the second side. Keep your fingers out of the steam, you can't play ukulele if you scald your fingertips off.

The pieces should retain their shape out of the mould, once they are dry. They might expand a little, but should be very easy to push back in the mould, and they should follow the mould with little persuasion.

Once they are the right shape, trim the tail and neck end to their correct length. The tail end should meet at the half way line of the guitar. The neck end needs to be cut so that the heel block and neck can engage -- a small amount of overhanging card is okay, it will get folded in when the neck is pushed home. This is better than it finishing short and leaving a gap.

This is where the side mould jig comes in useful again. Before gluing, make sure everything fits and can be propped into place under pressure. Make sure you have something to clamp it all down (a spare piece of card, then books, weights etc.) and a damp cloth for any glue accidents.

First fit the two trimmed sides into the jig, and using scrap card as a "spring", force the shape into the mould at the widest and narrowest points as shown. The jig is about 1/3rd up the side. A second jig will be added 1/3rd down from the top to keep the sides upright. The sides should stay put on their own when the jig is handled.

Then lower this over the heel and tail blocks. It should slide in and down and go into approximately the right spot, and be easy to adjust to the exact spot. If not, don't even think about adding glue. You need to be able to drop this in, line it up, cover it, weight it, and walk away.

Practice it a few times!

Finally, with the sides in the jig, glue goes INTO the corrugations on the sides (as per the headstock strengthening) and then the whole thing is flipped over and adjusted into place.

The second hole-jig goes on top, a spare piece of card on top of that, to spread the load, a big weight on top of it all. Done. Leave it alone!

There should be very little glue squeeze out, as it runs back down the corrugated channels and bonds them to the back board.

When this is dry, remove the weight and jigs, and run a second bead of PVA glue around the join inside, it can't escape now, and it will properly seal it.

Using GIMP, I created a simple design for the soundhole rosette, printed it out, and cut round the outside circle (only). This was glued on with Pritt stick.

Then, I sliced from the edge of the soundhole to the centre about 16 times to create tabs to fold round and under, trimming off the excess. Pritt stick these in place.

Finally, a thin strip of paper was Pritt sticked around the inside of the hole. This paper is the same width as the soundboard is thick (about 6mm) and the same length as the diameter of the sound hole, plus a small overlap.

Again using GIMP, I created a simple label design to be view through the sound hole. This was Pritt sticked in place to line up right under it.

I didn't need to brace the soundboard on mine, as it was thick/strong enough. A thinner soundboard would give a louder instrument, but less sustain. So I skipped that step and went straight to putting the top on.

You can re-fit the two jigs to make sure the sides don't spread out, although they should be more stable now. Don't put any packing "springs" inside this time, unless you are sure you can get it back out through the sound hole!

This is the last chance to make sure everything lines up right and that the soundboard will contact the heel block, the tail block, and the sides all the way round. If anything needs trimming or shimming, do it now.

Just as for the bottom, the glue was run INTO the corrugations on the sides, and the whole thing placed face down onto the soundboard (also face down), weighted, and left to dry.

The nut for this uke was made from a piece of dowel, 42mm long, sawn down the middle to make a D-shape. I then filed four shallow notches at 10mm spacing to guide the strings.

Do the bare minimum here, you can always make them deeper later.

The nut was glued and clamped into the gap left between the two white "veneer" pieces.

The dark finishing material for the guitar is a glossy black card. For the headstock, I traced round the inside of the leftovers from the white artboard (used to make the white veneers) and cut inside the line to make an undersized piece. These were glued on with Pritt stick.

The fretboard piece is exactly the same width as the white fretboard veneer (about 44mm), except it continues down onto the body of the ukulele. This is also held on with Pritt stick (only glue it to the neck, not the soundboard at this stage! It will overhang, this will be tacked down later)

The saddle is also cut from 9mm dowel, 60mm long. This one doesn't need splitting. The string spacing here is 12mm, wider than the nut. Again I marked in four shallow notches, to just about hold the strings still.

The bridge is constructed from more of the white artboard. I didn't use a template for this, the dimensions aren't actually important, but it needs to place the saddle at 340mm from the nut -- the scale length of the instrument, and needs to be about as wide as the saddle (60mm).

As a guide, the piece shown is 80mm long (on top) and tapers from 60mm wide to 40mm wide, and reaches over the end of the ukulele to the back.

There are two small piles of shaped artboard that hold the saddle in place. These fiddly bits were cut out and glued in, using the saddle as a guide to their position. It should tightly hold the saddle from moving back and forth.

Next, a second piece of artboard was cut as shown, the strings will thread through this.

To make it easier to thread the strings, I used 4 short lengths of tubing, cut to match the angle of the card, and superglued in place. This tube is often used for aerosol dusters/cleaner sprays, and comes in variety of sizes. This will guide the string through and out the other side without it getting lost. Anything large enough to take the fattest string will do.

The top part of the bridge is then glued into place against the saddle backstop, and a cocktail stick covered in PVA was used to strengthen the joints on both acute angles. Cut the spare ends off when the glue dries.

A cover from thin card was made to cover the bridge to close in the sides and neaten up where the tubes come through. The tabs on the sides fold down when it's glued in place. After the glue is dry, trim along the edges to get the bottom edge flush.

If you struggle to wrap Xmas presents, look away now. The whole thing was wrapped over with some mylar film (silvered, plastic sheet) to give it a metallic look. Silver foil is too fragile for this. I started with the three larger faces, using Pritt, and then worked over the two bumps for the saddle, before cutting, folding and sticking the remaining sides under all those corners. Keep the saddle on hand to check that it pushes all the way down and in, don't accidentally create a hammock for it!

Carefully locate and puncture the eight holes for the strings, and trim off the excess mylar underneath, it will get in the way of gluing to the soundboard later.

I decided to use machine heads, bought cheaply on eBay, rather than friction pegs that can work loose.

Work out the positions for the tuners, and drill the centre hole to clear the tuning peg. For mine, I also had to enlarge the top side of the hole to accept the ferrule/bush, which should be a push fit. I glued the ferrule in with a small amount of PVA.

Once the tuning peg fits clear through, mark up the hole for the screws to hold it in, and put a fine drill bit through to start the screws. I put the screws in, loosely, removed them, and then squirted some PVA into the resulting hole before doing them up fully. Don't overtighten, the glue will do the work.

I used a couple of chipboard screws to provide a strap attachment point. The one on the tail should be exactly in the centre of the bridge/ukulele. Here the bridge is not yet glued on, but I've fitted and very loosely tensioned the strings to check bridge position/saddle height. The screw is all that's holding the bridge on. The neck isn't glued yet either, so not much tension allowed!

Having checked that everything lines up where it should, the neck needs to be glued in straight, and flat to the soundboard. Use a steel rule to check. Do not skimp on glue inside the neck/heel cavity, it's important that all five faces of the neck are in contact with glue and cardboard. Use the centre line of the headstock/nut and the centre line of the bridge/tail to make sure it's square. Leave this joint to dry for at least a day to make sure it is SOLID before any tension goes in.

Now the bridge can be hooked over the edge and positioned. It too must be square, and flat to the soundboard. I tied some uke strings onto a piece of wooden skewer, fitted the saddle, and partly tensioned them. The saddle should be 340mm from the nut, and parallel to it. Mark round the bridge so you can replace it back there easily.

The strap button screw should go through the bridge and into the centre of the guitar to hold it on, but it will still wiggle side to side a bit, in an arc.

Apply plenty of glue to the bridge, on both parts of the "bracket" you've created, and place it onto the soundboard, aligning the strap button screw (put it in and partly tighten it), aligning it to the marks you created, and then put some tension in the strings to help hold the bridge down. Additional elastic bands around key areas will help it hold in.

Again leave it to completely dry before removing the bands/strings/screws.

Ukuleles tend to have a degree of "mistuning" about them. I wanted to try and reduce that. Most guitars (electric, acoustic) have a saddle that is angled or stepped, so that fatter (lower) strings have a slightly longer scale length compared to thinner (higher) strings. Ukuleles usually don't, and the intonation suffers. This means that no matter what you do, it will never be in tune across the whole fretboard.

Initial checks with the strings up to tension showed that there was no way the 12th fret would be an exact octave on all the strings at the same time (kind of important). So I set about carving up the saddle as shown here.

I cut four slots into the dowel with a Dremel grinding wheel, to about half the thickness. These were centred on the original 4 shallow slots.

Into each new slot, I placed a short piece of a Bic biro ink refill plastic tube. Each should be cut to be a tight fit, but moveable by gentle persuasion. These started off in a straight line at the half way mark.

With the strings re-fitted and tensioned, I picked the "harmonic" octave on each string. The position of the point where the harmonic was clearest varied between strings. I ended up moving the plastic pieces to the positions shown so that the fattest string was longer, thinnest strings shorter. The pieces can be moved with tension on the strings by bumping them gently with a screwdriver. When they were in the right spot, they were superglued in place. Do that step with the strings removed, otherwise you'll glue the strings on!

I didn't glue the finished saddle into place, it is held by the string tension into its spot on the bridge. Also, two cocktail stick ends (saved from the fret-ends, later) are placed into small blind holes drilled on the underside, and glued in. These act as spikes to connect it into the soundboard. They go through the bridge and into the soundboard - make two small starter holes for them with a pointy thing, once you know where the spikes have ended up!

I used a simple spreadsheet to work out the divisions of 340mm (my scale length) into mm measurements from nut (or bridge). Then I drew a template of the fretboard in GIMP at 300dpi and printed it out. Check that the scale is the size it's supposed to be! Confirm that the nut to 12th fret is half of the distance of nut to bridge on the real instrument.

This allowed me to place the paper fretboard and move it around to check it was correct (scotch taped temporarily). Lucky that I did, as it needed to be placed offset from the theoretically correct place, this is why the first fret looks quite small!

Again, back to those harmonic octaves.

The exact place where the "harmonic" octave is found is marked by the blunt ended cocktail stick. This is half way between nut and saddle. But pressing down at that point noticeably SHARPENS the note, due the extra tension from the fingers.

The pointy cocktail stick is in the correct location to get an octave when fretted. So I offset the whole scale back by that much, and then ran up and down checking each fretted note with a cocktail stick. The scale was now spot on.

As you can see the "NUT" line, which should be at the dowel, is in fact just PAST the dowel, so that first fret needs to be a bit shorter.

I'm glad I check this before sticking anything down!

Now you're sure that you know where the frets go. Mark across from the template onto the fretboard using a biro/ballpoint pen and push HARD to get a furrow into the cardboard. This will provide a positive "click" feel when you get the fret in place.

Then glue the 13 cocktail sticks into these ridges. A small amount of PVA on each one, and wiping away excess quickly (while pressing down, don't wipe the fret off) will lock them in. Leave them to dry before trying to take off the excess ends. Saw them off gently with a fine razor saw, it's easy to split a fret. And keep pressing DOWN on them to counteract the saw acting sideways.

The fret dots were produced using a standard ring binder hole punch, and silver floppy disk write protect labels. If you don't know what they are, ask your dad. And empty the hole punch BEFORE you start, otherwise finding them will be hard. Each one can be peeled and placed using the tip of an X-Acto knife to carry it into place, and then rubbed down with a soft cloth.

I placed them as I'm used to them for guitar, on the 1st, 3rd, 5th, 7th, 9th and (double) 12th fret.

Finally, sand down the edge of the frets at a 45 degree angle with a sanding block, so no splinters stick out over the edge. Sand towards the fretboard only, in a direction that WON'T catch on a fret and rip it up.

I put a small dot of PVA glue on both ends of every fret, just to seal over the cut end and make it smoother still.

I made the strap from some polyester webbing. To prevent fraying and damage, I folded the end over and punched an eyelet through both layers of fabric. The number 8 tail screw passes through the eyelet. I then stitched the folded end down for neatness. A second strap button (another number 8 screw, cut SHORT) was placed on the back of the neck opposite the nut. Make sure you don't screw it in too far and pop the nut off! You'll need to experiment to find a balance point, as the tuners are very heavy compared to the rest of the ukulele.

Fit a set of strings, and gently tune them up to tension. I used the tie-on method, with the spare "end" of the string tucked back into the tube so it's out of the way. When making the knot, pass the end through TWICE (once for a normal knot, and then once again), and adjust the position as you tension it up so it looks neat.

I made the action pretty low, (an eighth of an inch at the 12th fret) and I found that there were a few buzzes from frets. Rather than taking the strings off, adjusting, restringing etc. I adjusted the frets with strings in place, by bending them aside and scraping the fret with a dull X-acto blade. Don't slip! That's scrape, not cut. A dull blade is great for that.

In my case, fretting at fret 3 caused a buzz from fret 4, so fret 4 got scraped down a little at the point where each of the 4 strings cross it. The same happened around fret 12-13. It only takes tiny adjustments to clear this up, so don't do too much at once. Check every note on every string sounds cleanly as a distinct note.

Once you get the strings on and tensioned it will take a while for it to stabilise. I was still waiting, 4 days later, but it came good eventually.

Fortunately all the strings seem to drift at the same rate, so it stays in relative tuning, even if not in absolute tuning. After a while, it will stop.

So if it's like a guitar with two strings missing, and one string an octave higher ... then I can probably play it.

If you want to, you can add a piezo pickup. I added this as an afterthought, you could integrate this step to the main assembly if you wanted. I cut a small hole in the lower wall which would JUST take an entire mono 1/4" jack socket body, and a 27mm Piezo disc (diagonally extend a slit to minimise damage).

Wire the piezo disc to the jack socket before fitting it, with a short length of cable, and then the tricky bit: Place a couple of drops of superglue onto the piezo disc's plain (brass) side and stick it up to the soundboard near the bridge. Don't glue your finger into the hole. When it's stuck (the piezo, not your finger), the jack socket and it's "mounting plate" (a small piece of card with a hole large enough for the socket's neck) can be pushed in and glued in place.

I've attached the fret calculator for a 340mm scale (Open Document Spreadsheet), and a zip file with graphics for the fretboard, label and rosette. These are PNGs, sized for 300dpi = 100% size.

And the mp3s are what it sounds like, when the strings stop drifting!

What to do with the two spare tuners? What is the ukulele duelling with? Another instructable explains all ...