Above is the prototype as it was.
I cut a piece of all-thread (I'm not even going to ask what it's called in England) and made some square Delrin nuts to use as stops for the hole template. I put the nuts on the rod in positions matching the holes in the prototype, then played the prototype into Flutini, chewed on the exported data with Polygraph, and got the RTTA plot I expected, inclined from one end to another since the ID of this pipe is different from that which the template was created for.
So I cranked the nuts around on the rod into positions that I thought would be better and drilled a set of holes opposite the exiting holes. Did I mention I engraved "Set 1" on the side with the original holes? Gotta keep track of who's who here. It's easy to get confused when they all look the same.
After de-burring/undercutting the new tone holes I taped over the old set of holes and played the whistle for the computer. Better, but still a way to go.
Above is the hole template and Prototype 1, Body 1 with three sets of holes.
So I make a final adjustment to the hole template and went for the new section of pipe. I could have done another set in the old pipe, but frankly I was running out of time if I wanted to take this whistle to the session that I was about to attend. That, and the "spare" holes, even tho taped over, are perturbations in the air flow so if you get close, one needs to go with a fresh section of pipe.
The last hole arraingement going into the drilling jig.
Locking the template in the jig. The sliding car which holds the whistle body for drilling is see on the right here. It slides in the grooves of the aluminium extrusion under my bench-top drill press (pillar drill.)
Here's the last hole, with the clamping mechanism of the sliding car on the left, and the brass pin (like the knurls?) that locates against those Delrin nuts.
Not perfect, but not too bad either. Good enough for folk music as the saying goes.
People who played the prototype like the sound, but said they needed some time with the whistle to see how they really liked it.
I also would like to make the mouthpiece and markings the same cream color I'm using on the Bb whistle. That may be a challenge given the dims the CPVC is available in. But I'll have a go and see if I can manage it.