Making a simple bamboo flute
I can't think of too many instruments as simple as a plain piece of bamboo with 7 holes in it and one closed end. If you know what you are doing, you can build one in an hour or so and you can make a lot of music with one of these little whistles. I am still experimenting but i have made several of these in different keys and here is what i stumbled onto in the process. These are all blown from the side in true flute style, like the big boys do. This is all discovered, not learned information and may not be accurate, but it works great and that is all that counts. The flutes sound very nice and with a little practice, will produce a full two octave range. I you would like to hear what this particular flute sounds like, then click this link: Hard Times
The first thing you want to do is get some good cured (ripe and dried) bamboo from which to build your flute. The diameter is not as critical as the length for determining the key, or pitch of the fundamental note. (the lowest note the flute will produce) The ratio most flute makers aim for is around 25 to 1 for a ratio of length to inside diameter. here are a few suggestions based on the fundamental tone for a "C" flute, as shown in the photo above. I used a piece of bamboo with a 5/8" (15.8mm) inside diameter, and 12 1/2" (32 cm) for the over all length. Make it longer by a half inch (13mm) so that you will have some material to take off when you do the fine tuning later on. You will need a few simple tools as well. Something to drill or burn the holes in the bamboo, a file, some sand paper, an exacto knife with a #10 blade (or similar) would be helpful, and a pot of paraffin wax. You can use 1/4" dia drill for all the holes. Or if you do not have a drill, then anything made of steel that is 1/4" dia or less will do. You can heat it up to burn the holes into the bamboo.
Because bamboo is so porous the nodes (the little walls between the bamboo sections) are not air tight and prone to absorb moisture. Not only that but they are not very strong at all and need to be sealed and strengthened to produce a good closed end for the flute. I use hot paraffin for this but first we must dress up the closed end and make it look good
The closed end
This is what the raw end of the bamboo looks like b/4 sanding smooth and finishing it off. Notice the extra stuff on this side of the node compared to the shot on the right, with the end trimmed. After cutting close to the node, as shown at the left picture, use a file, and sand paper to remove the excess bamboo, and round over the closed end, as shown above
( If you have a belt sander you are in good shape. That is what i use to do this operation. )
The blow hole
The part that makes the noise is the blow hole located at the closed end of the flute. I am currently experimenting on how far to put this hole from the end of the flute. The diameter of the hole may effect the tone too but i have not experimented enough on this to pass on anything useful on this. It would be better for you to experiment yourself and try out various lengths. The one we are building here was drilled 3/8" (9.5mm) diameter and located with the center of the hole about (3/4") from the end. I suspect making this distance longer or shorter will effect the optimum playing pitch. The notes that are the easiest to achieve is what i am speaking of. Some times the higher octave is easier to play in and some time the lower one is easier to play. I suspect the placement of this hole from the end will effect this. My guess is the longer the easier to play in the low octave, and the shorter the distance the easier to play the high notes in the second octave.
Above left you see that the blow hole is drilled in the closed end of the flute. I used a razor knife to shave the blowing edge of the hole later on, so the angle came in almost tangent to the inside diameter. See the shot above right and you can see how the knife edge of the blow hole blends with the inside diameter of the flute. I am not sure if this is the way it is supposed to be but it gives a lot more control of the tones you can produce. However i think it could make it a little more difficult to actually make the note resonate properly as it is possible to hit the third octave and several harmonics with this sharp and steep blowing lip. Everything is a swap off that i have discovered so far.
Sealing the porous end and the inside diameter.
After putting the blow hole in the tube you must seal the porous node end and the edges of the blow hole, as well as the inside of the tube itself. Get some paraffin and a melting pot, like the one at left. Notice the pouring lip? This is a very handy feature. Heat the wax until is starts to steam and you can see the steam coming off of the hot surface. immerse the end of the flute in the hot wax, making sure than it covers the blow hole. Pour the excess wax out of the flute and wipe it clean. Next put a piece of duct tape (or green tape) over the blow hole and pour a half inch of hot wax into the tube. Rotating the tube, slowly start tipping it towards the paraffin pot so as to eventually pour it all back into the pan, leaving a coat of wax completely covering the inside of the flute. After sealing the blow hole and inner surface of the flute, you must "Tune" it to the fundamental pitch. In this case the flute will be a "C" flute and the fundamental pitch is the "C" above the middle "C" on the piano. Blow across the blow hole and make a tone. Using an electronic tuner, check that tone for pitch to see how much lower it is than normal. Keep taking martial off the end of the flute, making it shorter, to bring the pitch up to the proper frequency. Do not exceed this pitch or you will have to make the flute into a C# or a D instead of a C instrument. When you have the pitch registering on the electronic tuner as perfect, then you have tuned the "Fundamental" Pitch for the flute and also determined the "musical length" of the instrument. Measure the distance from the far side of the blow hole to the fat end of the flute and this figure is your "Musical Length"
Musical length and hole ratios
Looking down at the flute you see that the holes are of different sizes. Generally speaking the larger the hole the louder the note produced and more wind to blow it. The distance from the bottom edge of the blow hole to the end of the flute is the musical length. The layout of the holes is a function of this distance. This flute has a musical length of 11.45". The only part of the hole that counts is the top edge. The edge nearest the blow hole as this determines the pitch of the note. The distance from the top of the 6 holes to the lower edge of the blow hole have these ratios, for a 5/8 bore.
1 = .765, 2 = .651, 3 = .590, 4 = .515, 5 = .428, 6 = .358
You probably noticed the holes are not in straight line. I made them to suit my fingers and everybody is different. Make them as comfy as you can when in the playing position.
Key M-Length 1st hole 2nd hole 3rd hole 4th hole 5th hole 6th hole G 15.250 .800 .679 .612 .515 .428 .354 C 11.450 .765 .651 .590 .515 .428 .348 D 9.450 .797 .690 .623 .524 .437 .358
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