I recently lost my most favorite Fèadog whistle, and as a kind gesture a good pal of mine gave me a black Clarke D with wooden mouthpiece. Now this takes ALOT more air then my previous whistle, I really like the tone and all, but is there any way to make it so i dont have to fold a lung after a nice paced reel?
The standard tweak here is to mush the windway, that is to press down the tin arch above the wooden fipple block to make the airway smaller. May take a bit of adjustment, because you don’t want too much of a dent in the middle (that’s not a problem as such though). It will improve the breath requirements, but you’ll still be putting more air out than on a feadog…
Jerry Hadrubal Freeman does a very successul tweak on Shaws, which are similar to Clarkes in this respect, and I daresay that whether you want to hear them or not, he’ll have a view on this… 
OK, here goes.
I agree with Bloo on this. The mash tweak is the standard for this kind of whistle. I also laminate some aluminum to the top of the windway to additionally narrow (from floor to ceiling) the windway to the point that I have exactly the result I want. If you’re going to do this, you want the mashing to result in the top of the windway being pretty evenly flat, not domed or indented.
For this, I use aluminum foil ductape, which is pure metal with an agressive adhesive backing. I cut strips to the correct width and add layers to the top of the windway until I have the result I want, trimming off the overhang of each layer with an exacto knife as I go along. You need something flat and stiff to get into the windway with and press the aluminum foil tape firmly to the ceiling of the windway each time you add a layer. I use the non-business end of a portable jigsaw blade. It’s important to press each layer firmly and thoroughly all over.
I’ve also found that adjusting the position of the windcutter blade edge so it’s just a tiny bit above the windway floor significantly helps focus the voice and reduce breathiness. The more closely you can get the blade to match the windway floor all the way across, the better the result. You may also find that the whistle becomes louder, which would be a benefit with most Clarkes.
Best wishes,
Jerry
mush? mash? Oy, what a stupid language. 
Mish mash.
What a drunk Catholic does if he’s still drunk Sunday morning.
I would suggest not tweaking the Clarke to take less air, unless you really are in need of medical assistance after a hard reel. 
You will get used to the higher breath requirements, and after you will be happy for it while you will play the Clarke normally, most other whistles will be much easer on the lungs.
There are other issues besides just the amount of air required.
A whistle that takes less (meaning a moderate amount) air and offers even just a little back pressure is often amenable to more nuanced and expressive playing because it gives you more direct control of the subtleties of the airstream.
The sense is that the linkage between your blowing and the notes is tighter; whereas with a whistle that takes too much air, the linkage between your breath and the music tends to feel looser, less precise.
You might want to take a look at this string for some confirmation of this:
http://chiffboard.mati.ca/viewtopic.php?t=11712
Best wishes,
Jerry
I usually pop the block out, then I’ve got a dowel that’s roughly the inner diameter where the blade edge is, it’s sanded flat on the top so it looks like a D in cross section, I put it in under the blade and then use a brass rod on top to make the blade flat, and then I do the same with the windway with a different chunk of wood. then I put the block back and use a 2 part epoxy to seal it, then a couple of very small nails on each side for good measure. they end up sounding pretty good. now if I can just make one tunable…