Yarn Wing Dun
This is one of my most favorite mayfly dun designs. It sits correctly, the wing has a strong profile, the poly yarn gives the wing a natural sheen, and the fish eat it very well. It’s super easy to tie, and that makes it even more desirable.
Step One: Wrap the shank with thread and form a small bump of thread just onto the hook bend.
Step Two. Tie in a clump of hackle fibers for the tail and wrap back to the thread bump. The fibers will spread out into a fan shape (the "Fan Tail"). Dub on the abdomen.
Step Three: Tie in a hackle, dub on the thorax, and wind the hackle "X" style. First make a couple of turns forward as if palmering the thorax. Art by Jason Borger.
Step Four. Continue applying the "X" hackle by palmering back over the thorax. Then wrap the hackle forward in several "normal" turns, tie it off and clip away the remainder. Art by Jason Borger.
The completed "X" hackle. Note the hackle fibers are slanting forward and rearward as well as sticking out to the sides.
Step Five. Tie in a clump of poly yard at the head of the fly, extending up and back over the top of the fly. Tie off the thread in front of the yarn. Trim the butt end of the yard the same length as the hook eye.
Step Six. Trim the wing with one clip of the scissors. Put a big drop of head cement into the butt of the wing to fuse the fibers permanently into the wing form. Trim the hackle off the bottom of the fly.
The Yarn Wing Dun seen from above. Note the fan tail and hackle fibers. The hackle fibers point to the rear, to the front, and out to the sides like the legs of the natural.