The measurements I sent you are in mm, but I think you’d be best served looking for aluminum tubing in imperial sizes, specifically, 1” OD with 1/16” wall thickness.
After some effort searching, I was eventually able to find suitable size tubing on eBay for relatively inexpensive prices, both for low D and low F whistles.
The stopper (with its ears for narrowing the upper bore around the window area) you can just make yourself from delrin rod.
I fear you may be right in my case too. After 50 odd years of playing flute, I’m used to power! My current Treble D whistle has it. It’s a Frankenstein - combination of a Generation Bb head, a Delrin cylindrical barrel, and a Blackwood conical bore tapering downwards and terminating in a flare at the end. It’s loud!
Very positive endorsement! I haven’t yet found an endblown flute I can manage, but I can see this one is different. I have also been looking at the possibilities of bent heads for traditional Irish flutes, but there are challenges to be met in that direction too. My journey may yet take some unexpected twists!
Yes, I spotted the correlation too. Now I sent you a PM seeking a few clarifications. At least I believe I did. Still getting used to the new site!
I don’t see your message yet. I’ll PM you again with my email address and you can just mail me directly.
About bent head flutes, for sure if I played Boehm flute I’d have been playing one of those for the last 20 years. The Boehm flute world has recognised the unergonomicness (!) of transverse flutes decades ago and has addressed it well.
The Irish flute world not so much! Until now.