Flute Bore Diameter vs. Sounding Length

Here are some flutes just completed. From the top, one of my Folk Flutes in D. Then one of my E/Eb Combo Flutes. And then a pair of F flutes.

The F flutes are of two different types. The top one is a newly prototyped model I am calling my “Irish Style” F flute and features a head joint bore of 18.1mm, tapering down to 12.75mm at the foot. This flute supports the first two octaves well for a rich tone. The 3rd octave is totally missing!

The bottom flute is one of my Requintas intended for Galician music, playing usually an octave above the Bb Gaita. This flute has a head joint bore of 16.25mm and tapers down to 10.75mm at the foot. The first octave is present but not very impressive. Where this flute lives musically is from A in the 2nd octave to C in the 3rd octave. French simple system military flutes of the Napoleonic era (the Requintas were derived from these) are very similar. American flutes by Firth et al have a slightly larger bore in the head joint (above 17mm) and do not respond as well in the 3rd octave. The middle joint of this flute was reamed out using a Napoleonic-era Belgian made bayonet!

Note that its sounding length of the Requinta is slightly longer than the larger bored “Irish Style” flute. The smaller bore generally “speeds up” the vibrations raising the pitch thus the flute has to be longer to play at the same pitch! I thought that some would find this interesting. It also points out the problems of going by sounding length alone when assessing an online flute purchase!

Casey

Thanks for posting these observations Casey. Certainly food for thought.

I’ve started making cylindrical bore wood Renaissance flutes (some C, D and G flutes so far). I was surprised at the differences in expected/calculated SL between 18mm bore flute and 15mm. However, I know that cylindrical flutes are much more predictable acoustically and my maths is pretty bad! :slight_smile:

Vaughan

Double post

Triple post!

I tried the mathematical approach years ago and it really wasn’t much use to me. Better to make a tube, make an embouchure, then drill a number of test holes and iteratively arrive at what works. Or measure something by a past or current maker (nothing is sacred). On conical bored flutes the bore taper does much for tone quality and understanding what works and what doesn’t intuitively is something that one develops over one’s flute making career. 34 years into this and I am still experimenting.

Casey

Yes, my approach (I’m slowly finding) is similar.

First thing I did was imitate my favourite (cylindrical) flute. A beautiful Rafi copy I have in A=392. Then I made many rough prototypes and then tried different pitches - all in different materials. Finally I’m working now in wood. Jarrah, Gidgee and Rock Maple.
The bore reduction was the least ‘easy’ part to marry with my undrrstanding of toneholes and soulnding length. Test, test, test… but I’m quite happy so far with my smaller bore G flutes.

Conical bore is a whole other story!

V