Plywood Mini Cajon (Hand Drum With Guitar String)

This instructable describes the process to build a small cajon similar to commercially available ones. I will call it mini cajon, but the instructions can be easily applied to build a full size cajon.

At the time of writing I could find 3 instructables on how to build full size cajones:
https://www.instructables.com/id/How-to-build-a-cajon/
https://www.instructables.com/id/built-your-own-Cajon-for-less-than-25-Euro/
https://www.instructables.com/id/How-To-Build-Your-Own-Cajon-Box-Drum/


So why bother with another instructables? The reason is simple: instead of using snare wires to obtain the snare sound I have used a guitar string. Many cajones are built in this way and I thought someone out there might find this interesting.

Unlike full size cajones, you cannot sit on a mini cajon but you rather hold it between your legs at knees height when playing it. It is a very compact and portable solution when you need a good percussion instrument on the go.

If you like this instructable please vote for it in the musical instruments contest and the weekend project contest.Thanks heaps!

Step 1: Tools and Supplies

Here is a list of tools and supplies that I have used for this project

Tools:
- Drill
- Sander
- Jigsaw
- Circular saw
- Grinding machine (optional)

Supplies:

Multiplex plywood for the resonating box and sizzle effect (snare sound)

- 290x130x10 mm (2 pieces)
- 200x130x10 mm (2 pieces)
- 290x180x10 mm (1 piece)
- 290x30x10 mm (1 piece)
- 100x21x10 mm (1 piece)
- 310x200x4 mm (this will be the slap surface)

Pine wood for the inner frame:

- 140x20x20 mm (2 pieces)
- 290x20x20 mm (2 pieces)


- Glue for wood
- 10 wood screws
- 1 classic guitar string (A)
- 2 t-nuts (size 6mm)
- 2 hex socket head screws (at least 6 cm long)
- Wood finish

- 4 rubber feet
- 4 washers
- 4 bolts
- 4 nuts

Step 2: Cut Parts

I had most of my ply cut at the local DIY store. I only had to cut  2 pieces of plywood with a circular saw and the the 2-by-2 pine wood for the inner  frame

Step 3: Cut the Hole

I used the compass to draw a 40mm radius circle centered at the intersection of the diagonals of one of the 290x130x10mm boards. I then drilled a hole within the circle and used a jigsaw to cut out the resonating hole.

Step 4: Glue Resonating Box and Inner Frame

I assembled the box using glue and clamps during drying. When gluing the inner frame made out of the 4 sticks of pine it is IMPORTANT to make sure that it is NOT flush with the top of the sides of the box (see picture), in order to 1) allow enough space for the guitar string 2) allow the slap face to vibrate more when played.

Step 5: Built in Sizzle Effect System

OK this is the interesting bit and I hope the images are clear enough for everyone to understand how it works. Basically, I have drilled 2 holes on one of the short sides of the resonating box all the way through the pine frame and the small plywood slider clamped inside the box. The hex cap screws will have to pass through these holes, whereas the holes on the small plywood part will be enlarged to accommodate the t-nuts (i have used a clamp to push the t-nut in the wood).

I have then assembled  all the parts and placed the slap face on the resonating box to check whether there was enough room between the plywood slider and slap face for the string to run through. There was not, so I had to sand down the slider a bit and use the grinder on the t-nut as well. With better planning and measuring you can probably avoid this, but be careful as you don't want too much of a gap or your string will not be touching the slap face. 

Step 6: Set the String and Close the Box

I have drilled tiny holes for the guitar string on the pine frame just opposite of where I had installed the slider. Run the string through one hole and made a not under the frame, then passed the string on top of the slider and underneath the screws. Then back on top of the slider and in the other tiny hole. The image probably provide a better explanation than words do. I would suggest to tie the string as tight as possible and to have the slider in a central position on the scews (as shown in the pictures) so that it has some leeway to move in both directions.

The tension of the guitar string is therefore adjustable from the outside of the cajon using the hex cap screws: by tightening them the slider will move towards your hand increasing the tension of the string. It allows you to find the sound that you like the most and to change easily sound (perhaps removing completely the snare effect) simply using an allen key. 

IMPORTANT: if you are using this guide to build a full size cajon I'd recommend to use more than one string (I generally use three. The slider will be at the bottom of your cajon and you should separate the tiny holes where the strings are blocked a couple of cm one from the other. This is obviously a guideline: feel free to experiment!

Being a drummer, I have screwed the slap face on the box following the scheme that I would use on a drum head. To be honest I don't think it makes much of a difference using plywood.

I have rounded the edges with an orbital sander.

Step 7: Finishing: Rubber Feet and Paint

I have applied different colors to the slap face and resonating box, screwed the rubber feet to the box and then re-assembled the snare mechanism.

In order to improve the snare sound it might help to apply some masking tape inside the box to keep the string against the slap face. I use this common little trick also on the full size cajon. I am not expert enough to say whether it sounds better with guitar strings than it would with snare wires: I have only built one with snare wires (full size) and I am not fully satisfied with its sound whereas I have built a few more with guitar strings... anyway, i suppose there are pros and cons with the different solutions. 

Unfortunately I don't have any video to show how it plays: I have completed this project months ago and did not take it with me when I have moved to a different continent! Personally I still very much prefer the richness of tone of a full size cajon. Obviously a mini cajon will not have the same bass tone, but it still makes a nice percussive option when you are travelling and you have limited space! 

I hope you enjoyed this instructable.
If you did, please vote for it in the musical instruments contest. ​Thanks heaps!