A few months back a bought a Clarke Sweetone in C while I was at the music shop having my flute looked at. I’ve practiced here and there, but nothing extensive, so I’m still fairly inexperienced. Recently my band director suggested that I try a piccolo solo I’d been playing on the tinwhistle. My problem is that I’m having a lot of trouble with b flat. When I first played it, it was so sharp that I thought I had the wrong fingering. I can’t figure out a way to play it in tune without making it sound airy.
I know this probably sounds stupid, but some advice would be helpful. 
Hi Chareth, welcome.
It’s not stupid at all. And I assume you’re referring to the pitch concert B-flat, which is the equivalent of fingering C-natural on a standard D whistle.
There’s no one right fingering for that note on a whistle, and several possibilities. If you are using only the 0xx000 fingering, you need to try a few of the others, including:
- 0xxx0x
- 0xxxx0
- half-hole the top hole (T1/L1)
One of those will give you a flatter note which you can blow a bit harder.
On my Sweetone C, #2 works best. On my Sweetone D, #1 works best. #3 works on either. You need to experiment. Or use a different whistle with a better-tuned 0xx000 fingering (i.e. closer to Equal Temperament, which is probably what you’re used to).
Good luck!
Welcome to the neighborhood.
I’ll just add a couple things to what MTGuru has shared - he’s always right, you know.
Half-holing works on any whistle though it may be a bit weak on some.
Some whistles require different cross fingerings for the flatted seventh. As far as I can recall, the Clarke fingering chart suggests using a OXX OOO fingering on their C whistles. I agree with MTGuru with the fingering on the Sweetone C. It needs another finger (or two). If the above fingerings do not work out there are six you can choose from, at least from this chart, for the first octave Bb.
And watch your breath pressure. These whistle don’t need a lot of air pressure. It is easy to blow them sharp.
Feadoggie