Playable Cardboard Ukulele...

This Instructable will show you how to create a playable soprano ukulele from cardboard and items found at your local hardware store (plus some tuners and strings).

A video of the cardboard uke in action can be found on YouTube.

Step 1: Materials...

Items you need for this project:

Several large shipping boxes made from corrugated cardboard.  The tighter the corrugation the better.
Several sheets of non-corrugated composite cardboard like cereal boxes or the back of notepads
2 fully threaded bolts or a threaded rod
4 geared guitar or ukulele tuners with flanged bushings
1 set of soprano ukulele strings
12 1.5" long cotter pins
2 small hinges
1 bottle of wood glue
2 wood screws (1.5 - 2 inches)

Tools:
Sharp hobby blade
Pencil
Measuring tape/Scale
Drill
Screwdriver

Step 2: Templates...

Attached are word files (now also in PDF!) with templates for the body and neck.  Print and cut out each template.  Glue these templates onto some thin cardboard or cardstock (I used a file folder) because you will be using them a lot.  In the files, the templates are labeled as follows:

Body A: Top (aka Soundboard)
Body B:  Middle
Body C:  Back

Neck A:  Edge
Neck B: Middle

Step 3: Trace Templates...

Trace the templates on to the corrugated cardboard.  You will need the following number of pieces (save some extra pieces of cardboard in case you need more later):

Body A: 1
Body B: 9
Body C: 1

Neck A: 6
Neck B: 7

Tips: 
1)  The majority of the body pieces should be cut with the lines of the cardboard running along the length of the piece.
2) Mix in a few pieces of "Body B" cut in other directions to provide strength in all directions.
3) For the neck, cut the pieces in a variety of orientations, but avoid any with the lines running along the neck.
4) Avoid any areas of the cardboard that has dents or wrinkles. 

Step 4: A Couple More...

Trace Body A and Body B onto non-corrugated composite carboard sheet (the back of a legal pad or thick cereal box should work).  Do not cut the notch out of the Body B piece.

Step 5: Cut Out Pieces...

Using a very sharp blade, cut out all of the cardboard pieces.

Step 6: Stack the Body...

Stack the cardboard in the following order:  Corrugated Body C, composite Body B, corrugated Body B.  The corrugated Body B pieces can be stacked in any order (because I am an engineer, I like to stack it in a symmetric pattern).  Check the height of the stack, it should be just over 2 inches.  Add or remove Body B pieces to get the height to approximately this height. 

Step 7: Glue Body...

Using a thin coating of wood glue, glue the stack together.  Place a book on top of the stack.  Check back after a few minutes to ensure that nothing has shifted.

Glue the corrugated Body A piece to the composite cardboard Body A piece.  At this point DO NOT glue these to the rest of the body.

Step 8: Soundboard Bracing...

Cut 2 strips of composite cardboard 1" x 8".  Cut 3 score lines running along the length of the strips 1/4 inches apart.  Bend along the score lines to create 2 triangular brace pieces.

Step 9: Cut Bracing...

Cut the triangular bracing pieces to cross the body as shown in the picture.  You'll have to cut a notch in one of the pieces to be able to cross them.  Reinforce the brace where it has been cut.  Notch the body where the braces will touch in order to get a good bond when it is all glued together. 

Step 10: Glue Bracing to Soundboard....

Glue the bracing to the soundboard with wood glue. 

Step 11: Trim Neck...

Check fit the neck pieces in the body cutout.  The notch in the neck pieces should be flush with the top of the cutout in the body.  Trim the bottom notch of each neck piece to make it flush.  You will also need to trim the heel to make it flush with the back of the uke.

Step 12: Glue Neck...

Glue the neck so that you have the following stackup:
3x Neck A
7x Neck B
3x Neck A

I like to glue these pieces together in increments in order to ensure they're all lined up.

Step 13: Create Bridge....

While you are waiting for some glue to dry, you can work on the bridge.  Cut a rectangle of composite cardboard that is the width of 2 hinges (about 2.25 inches) by 4.5 inches.  Score a line at 2.75 inches from one end and crease the cardboard.  This will hold the saddle and also wrap around the bottom of the ukulele in order to hold the hinges.

Step 14: Saddle...

Using some leftover bracing, create a triangular stop for the saddle.  Cut a bolt or threaded rod to a length of approximately 2.0 inches.  While you are cutting the saddle, you can also cut the nut (this can be confusing terminology, but its the thing like the bridge that goes out at the end of the neck).  The nut should be cut to a length of 1.5 inches. 

Step 15: Saddle...

The saddle height should be approximately 3/8 inches above the soundboard.  Shim under the bolt to get a height near 3/8 inches.

Note:  This will result in high action, which is not typical for a ukulele, but with the imperfection of the fingerboard and frets, the higher action will result in a cleaner, less buzzy sound. 

Once you get your height set, glue the stackup together including the bolt.  Make sure the bolt is pressed up against the stop.

Step 16: Finish Head...

Once the neck pieces are set, cut 4-6 strips for either side of the head.  They should maintain the thickness of the head and could be used to get a little creative with the shape of the head.  Glue these pieces onto the neck.

Step 17: Cover Head and Neck...

Using composite cardboard, cover the top surface of the head and the fingerboard, scoring where the angle of the neck changes.  Also, cover the lower surface with composite cardboard.

Step 18: Drill Holes for Tuners...

Once the neck is completely dry, drill the holes for the tuners.  I find that 1.5 inches back from the bend in the neck is a good spot for the first pair of tuners, then draw a 1 inch by 1.5 inch rectangle centered in the head to locate the other tuners.  Drill a hole large enough so that the bushings for the tuners press in with some resistance.  Clean up the holes and glue the bushings in the upper surface.

Step 19: Install Tuners...

Once the glue has set, install the tuners on the back of the neck.  Using wood glue on the screws will make them hold better.

Step 20: Test Fit Neck...

Test fit the neck in the body notch.  If it is too large, trim even amounts of cardboard off either side.  If it is too narrow, create shims to fill the gap on either side from composite cardboard.

With the neck in place, drill a hole from the back of the ukulele through the neck.  This will be used to install a  wood screw through the whole stack-up.

Step 21: Glue Neck...

Glue the neck into the notch in the body.  While glue is still drying, install the screw through the back.  The screw should go through most of the neck, but not poke out of the top.  This joint is very critical, so check alignment often during the gluing and use tape to hole in the proper position.

Step 22: Glue on the Soundboard...

Glue the soundboard with braces to the top of the body and weigh it down with a textbook or two.

Step 23: Make the Fingerboard....

Cut a strip of corrugated cardboard as wide as the fingerboard and long enough to go from the bend in the neck to just past where the neck goes into the body.  Glue this piece on, you may need to shim where the fingerboard overlaps the body.

Step 24: Glue Nut and Bridge...

Glue the nut onto the head, just above the fingerboard.  You will need to shim under the nut in order to achieve a string height of about 1/8th of an inch. 

Glue the bridge onto the ukulele body.  Ensure that it is centered.

Step 25: Attach Hinges...

Attach the two small hinges to the portion of the bridge that wraps around the bottom of the uke.  Use the screws provided, coated with wood glue, to attach only the bottom portion of each hinge to the bridge.  The other portion of the hinge should be free to move.  

Step 26: Add Strap Button...

If you plan on using a strap, at this point, you can add a strap button (aka screw) to the bottom of the ukulele.  You will want to drill a pilot hole in the cardboard to install your screw.  Be sure to not screw it in all the way. 

Wait for the glue to dry.

Step 27: Add the Strings!

Once the glue is completely dry....

Tie the strings to the hinges.  If you purchased commercially available ukulele strings, they will be numbered.  The 1st string would be closest to the ground if you were holding the ukulele to play it. 

Note:  Ukulele strings do not generally go from smallest to largest, like most stringed instruments. 

Once tied to the hinges, run the strings through the tuners and start to tighten the strings to hold them in place.

Step 28: Install Frets...

Measure the distance between the nut and the saddle (scale length).  At this point, you can research how to calculate fret spacing (if you are a nerd.  actually, the math is really easy, but its already out on the web in a million places), or you can enter this distance into a fret calculator.  I use buildyourguitar.com/resources/fretcalc/fretcalc.htm.  You'll have 12 frets... the program will ask you for that.

Mark the locations given by the calculator on both sides of the neck. 

Install the cotter pins at each of these locations.  The cotter pin will poke through each of the layers of corrugation in the fingerboard, so it will take some light pressure and some patience.  If the pins do not lay flat, you may need to use some wood glue to hold them against the finger board.  If you are going to use glue, be sure to double check your fret locations, you won't get another chance.

Step 29: Space the Strings and Tune It Up....

Once you have some tension on each string, space them out on the nut and saddle.  The strings should get slightly wider as they run down the neck. 

The standard tuning for a ukulele these days is gCEA.  The small "g" means that it is higher pitched than the C. 

Once tuned, you are ready to play!  Click HERE  to see a video of the ukulele being played