FIPPLE DESIGN HINTS
Windway: Long and smooth is great except that a long windway is subject to clogging. You want the height of the windway to delivery a sharp focused delivery of air to the opening approaching the blade. Too high of a windway will sound airy, too low of a windway will choke or not even sound.
Floor: Tooling marks on the windway floor can cause disruptions in the approach of the air towards the blade.
Roof: A little turbulence in the roof at the right place can yield a sweet tone. Some instruments like Recorder actually hollow out the roof to cause this turbulence. It can also be created by rough cut surfaces. I have wondered about using some sort of tiny screens in the windway to laminate the flow of air.
Block Wall: Usually flat, it can be also be rounded on low pitched whistles. The geometry of this can affect the cutoff frequency. Some have experimented with a protruding spike which modifies the pitch in the upper register.
If you are building Recorders, most recorder players want a cedar block to absorb moisture. If you're building Tin Whistles, consider putting some clear epoxy on the surface to make it smooth. Many TinWhistle builders make moisture traps rather than let the block soak it up
Lower Chamfer: This important edge is forgotten by many in homebuilt instruments. Actually a radius here is better than a chamfer. A proper cut here will make a more powerful tone.
Upper Chamfer. This Chamfer must be present when the air column within the bore is in its exhaust phase, the depressurization of the bore will push the airstream coming through the windway upward.
Blade or Labium: If you look through the windway at the blade, you will find that one most instruments it is either in the center, half-way between the floor level and the center or right on the floor. You'll also find it above center on cheaper instruments. Slightly below Center or lower is the way to go though. In other words, you should see more of
the top and less of the bottom. Don't oversharpen the blade!
Blade-Overcut: Because this is on the outside, too many people give this too much attention. As long as it isn't too step, you're ok. It, like the windway floor should be smooth. If you are building plastic instruments, you can observe the approach to the Blade-Overcut by running water through the Windway, it's very educational.
Blade-Undercut: This, like the Lower Chamfer is neglected in many designs. A proper Undercut can enhance tone production and remove "airy-ness" in the sound. Lack of Under-cut usually cause the symptoms of a weak upper register. If you play the second octave and it dies out half-way up, it may be due to a poor undercut.
Testing the fipple for dead spots:
Find a toothpick or use a sharpened pencil. Place the point into the middle of the fipple opening and play a note on your instrument. If the point in the Windway affects the sound by a small amount, that's good. If the point does not, you've hit a dead spot. Adjust this spot until performs like rest of the fipple. Note, the affect will not be uniform across the fipple - the side walls will cause some interference. (Note: Ralph Cook Whistles for example have a walls around the fipple to improve voicing, this is one of many ways to improve voicing).
When building fipple flutes, consider that the air must take three different paths:
1. From the windway across the Over-cut.
2. From the windway across the Under-cut into the bore.
3. From the Bore through the opening. When the tone column is in the depressurization phase, some of the air pushes out of the bore through this opening, it also causes the windway to be deflected upward momentarily.
Now, remember - if you are play an "A" at 440 Hz, the air in the windway is blowing in all these directions at this rate.
Jubilee Music Instrument Co.