Here is the recipe for the Thunderhead that I use found at this site: http://www.uky.edu/~agrdanny/flyfish...r/smpatrns.htm
Hook: Mustad 94840 #12-18
Thread: Grey or black
Wing: White Calf tail, upright and divided
Tail: Brown & grizzly hackle fibres, mixed
Body: Muskrat (or Possum)
Hackle: Brown and grizzly mixed
I use Superfine Adams grey dubbing in place of the muskrat and often don't bother using 2 colors of hackle. This fly has definately caught its share of fish!