I’ve have some 1 1/4 inch aluminum tube sitting around since my telescope project (remind me to tell you about that some day). I wanted to make flutes out of it, but couldn’t get my mouth the correct shape to blow over the holes.While tinkering with it, it occurred to me that I could make a wood block to cover the end of the tube and aim the air over the hole, like a fipple flute or recorder.
I started with a few pieces of 1 1/4 O.D. aluminum tube. I drilled a 5/16 inch hole about 1 inch from one end. This hole is the embouchure.
I built a block of wood with 1/2 inch walnut, 3/4 inch cherry and another 1/2 inch walnut. I also build one out of two pieces of 3/4 inch cherry. My early prototypes were made from 2×4 pine. I drilled a 1 1/4 inch hole, but not all the way through. This will act as the endcap.
Now I turned the block on it’s side and drilled a 1/2 hole, but not all the way. I only drilled as far as in the photo. Note that the drill bit cuts into 1 1/4 hole by about a 3/16 inch and forms the top slot seen in the other photos. Drill deep enough so that if the tube were inserted into the large hole, the embouchure would not be covered. The embouchure would point to between 8 o’clock and 9 o’clock in this photo.
Now drill a 5/16 inch hole the rest of the way through. Drill so that the edge of the drill bit would scrape the tube, if it were in the 1 1/4 hole. This is the actual hole that you will blow into.
I used the band saw to take a bit off the block, to open up the 1/2 hole. It made it easier to work and was how the finished piece was to look. I also used a sharp knife to widen sides of the hole a bit. I cut a 3/8 inch piece of 5/16 inch dowel and shaved off a bit. The dowel will was inserted and glued into the 5/16 hole we drilled and be aligned so that the cut off piece faces the right in this photo. The air will go under the dowel and over the embouchure. If you do it right, when you sight through the 5/16 hole from where you put your mouth, you will only see the inside of the embouchure hole. If you slice off too much from the the dowel, then you will hear alot of air moving, but not have much noise. You will have to try different angles by twisting the tube. I made three prototypes out of pine to get the angles and alignment right. There are two in the photo below. If you have trouble, take the tube, cover the end by the embouchure with duct tape and blow over the embouchure with a straw. When you find a place that makes noise, make a picture in your mind and then drill the 5/16 hole to replace the straw in that image.
Now you can shape the block with the band saw and sander. I wanted to make something comfortable for the mouth. Don’t pay any attention to the tuning holes in this photo. I didn’t know what I was doing when I cut them. I tried yet another formula, and it didn’t work.
Forget all those formula for getting the holes in the right spot. To tune the flute, you will need a chromatic tuner. I bought mine for about $12 when I bought my guitar. You will also need a good set of drill bits.
If you look at the holes and ignore the electrical tape, you may notice a pattern. Before I drilled the holes, I kept cutting the tube shorter until I got an A on my tuner. It was about 30cm or just over 12 inches. I wanted the notes A C D E G but I kept getting a B in the first hole, not a C, no matter how far I moved the hole. I decided to keep the B and move on. The trick seems to be to just drill holes and tune the holes from the low pitch to the high. I started with 1/8 inch holes and worked my way up in drill bit sizes until the note was correct. Larger holes sharpen up a note. You can’t flatten a note, so don’t over do it! When you sharpen a note, you sharpen all the notes with higher pitch also, so only work from low pitch up. Make sure the note is right and then move on. If you try to fool with the tuning later, you can throw the whole instrument off.
To get the holes in approximately the right location. Start with the lowest pitch hole at 2/3 the distance from embouchure to the end. The short flute has holes at 1/3, 1/2 and 2/3 the embouchure-to-end distance. The longer flute was at 2/7, 3/8, 3/7, 1/2, 5/8, 2/3. It is interesting to note that 2/7 is almost 2/6, which is 1/3. This means that both flutes have holes between 1/3 and 2/3 the distance from the embouchure to the end.