Thanks for your interest in the tongue drums -
I apologize but I did not keep precise dimensions for my tongue drums. I made about six in total, mostly as experiments to discover how the various materials and sizes worked. I made some with red oak sound boards and pine sides, one with a mahogany board and oak sides, one with a hard maple and etc. I gave all but this one of away so no longer have them around to measure, but the sound boards on all of them were of a similar size.
I have taken some pictures which may help you on relative sizes and dimensions. The background is a grid with 1” squares, and I have laid my rule directly on the drum to help in some pictures. There is some information online you can find as well which will be of help. I remember I printed out some schematics I found online which I glued onto my stock to guide the cutting. I was pleased with the results in any case.
The best sound seemed to be with the one made from the traditional padauk material from Africa, and which is pictured here. The hard maple and mahogany also produced pleasant sounds, and the oak not quite as nice, but still OK. My recommendation would be to use maple or mahogany (not Philippine) since you don’t need much, and it is easier to find than the padauk. I also made various inside depths, from 4” to about 8” inside under the sound board. All the ones I built have 6mm high quality ply bottoms and fairly small sound holes cut in the ends. The bottoms were screwed in place onto thin fillister cleats glued to inside of the sides and ends, and recessed enough so the bottoms are slightly recessed so they do not contact the surface the drum rests on. All the other joints were glued. I found it was good to glue on small felt furniture pads for the box to stand on to isolate it from solid contact with whatever it is placed on. I cut the linear parts of the tongues with with a very thin kerf battery-powered panel saw and finished the curved parts with a 24” scroll saw. Sanding the sides of the tongues was a challenge and was done mostly with power sander belts cut into narrow strips and used by hand before the soundboards were glued in place.
The outside dimensions of this particular drum are 18” long by 9-1/2” wide by 8” inside depth. Keep in mind the soundboard itself fits inside the sides – maple in this case, so its width is reduced by their combined thicknesses and it winds up approximately 8” wide. The soundboard goes over the end pieces, and I found it makes a difference how far the slits are from the ends. The soundboard is 3/4” thick at the ends, but some of the individual tongues are tapered somewhat in my efforts to ‘tune’ the drums to particular tones – a haphazard and difficult process for me since I am ‘musically challenged’, i.e., I don’t know very much about music. I think with a little research though you could come close to whatever notes/tones you seek. This particular one sounds very nice to my ear, and the ones I made for children seem to be pretty popular with them – then again children just like to make noise sometimes don’t they?
EDIT JAN. 5, 2017:
It is difficult to TUNE each key. The pitch of the note produced is related to, and controlled by many factors:
Of the keys themselves: Length, Width, Thickness, Mass (density of the material), and for the lack of a better word, its ‘sympathetic’ interaction with its neighboring keys. (There is probably a more proper term, I just don’t know what it is);
Of the sound box: The shape, size, depth, volume, material used and size of openings to the air. Also whether or not it has an enclosed bottom (all mine do, but I plan to experiment with one without a bottom sometime). I am told each component of the wood used should be held lightly near one end close to one’s ear and tapped lightly with a fingernail to see if it has a ‘ring’ to it. Anything which ‘thuds’ should be rejected. The same goes for the keys, obviously!
Generally speaking and as you would expect, the larger a key is by any factor, the deeper in pitch its note will be. Therefore, by reducing a given dimension its pitch is raised and vice versa. The problem lies in reaching a defined pitch on a specific key without the adjacent keys interfering too much, as they will all vibrate ‘in sympathy’ more or less, and some are prone to ‘buzz’ if everything isn’t in harmony. Any buzzing is an unpleasant and unwanted sound.
I think the solution is to deaden all keys except the one being tuned in some way, much in the way a capo is used in a guitar. In other words, ‘ground’ them in some way as you tune a specific key. This will require some ingenuity on your part to find a way to do this for each key. Obviously removing material, or reducing its size raises the pitch and vice versa. You can also glue wood on the bottom of a key if needed. I use a tuner app on my iPad to tune, but any tuner should work. Now the problem is, how does the key sound when the other keys are freed to work in sympathy? I try to first tune all the keys individually, and they try them all after they are un-grounded. Seems to work OK, but there’s some back and forth too sometimes. Patience is required!
There is some very timely information from ‘Texcaster’ in the comments below on suggestions for tuning. Texcaster appears to be a much more musically literate person than me, and I’m sure he is right. Next time I build one of these I will follow his advice.
I hope you make a drum – at least one – they are a little addictive! I would be very interested in seeing your completed project.
-- "Never let your dogma get run over by your karma!"