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Hook: TMC 200R #4-12
Bead: (Optional) Brass or Tungsten, sized to hook
Weight: Lead wire, sized to hook, sunk into back of bead
Thread: 70 Denier, Black
Tails: Dark Brown Goose Biots
Rib: Two Strands Tan Rayon Floss
Underbody: Any Dark Colored Dubbing
Abdomen: Peacock Herl
Wingcase: Turkey Tail Quill Slip
Legs: Hungarian Partridge
Thorax: Natural Hare’s Mask Dubbing
The 20 Incher Stone is a product of Colorado’s Roaring Fork Valley. Its’ originator I’m not sure of, but I am sure of the effectiveness of his fly.
A simple combination of common materials put together in an ingenious way to imitate the ubiquitous stonefly, (Thank God for the thesaurus!) this fly is a proven killer on Colorado’s freestone streams.
This fly is really a pretty simple tie. The biot tails are perhaps the most challenging part, and the partridge legs can be a bit tricky but even intermediate tying skills will conquer this pattern. I use a small amount of dubbing to form a tapered underbody on larger sizes. This helps the taper to show in the peacock overbody and keeps you from having to use fifty pounds of peacock to form the abdomen. Follow the directions closely for details on preparing and tying in the partridge legs. Keep an eye on the proportions and don’t fall into the trap of making the thorax too short. The thorax and bead should be equal to half of the shank length. Don’t be scared. Like I said, it’s an easy fly, just pay close attention to the details. I guess that’s the key to all flies…
Place bead on the hook and slide it up to the hook eye. Wrap ten to twenty turns of lead wire around the shank, break the ends off and shove the lead wraps into the back of the bead.
Start the thread behind the lead and build a thread base covering the lead and tapering down to the shank. Continue the thread base back to the bend of the hook.
Clip, oppose and tie in two brown goose biots at the bend. For further details on tying in the biots, see the Copper John. Move the thread forward over the butt ends of the biots to the midpoint on the shank. Clip the butt ends.
Tie in two strands of tan floss at the midpoint and wrap back over them to the bend of the hook.
Apply some dark colored dubbing to the thread (Olive Superfine is used here, although, literally, anything will work). Dub an underbody tapering from the just in front of the bend up to the seventy-five percent point.
Wrap the tying thread back over the dubbing to the base of the tail.
Tie in a large bunch (eight or ten) of bushy peacock herls at the bend.
Return the thread to the seventy-five percent point and then wrap the herls forward forming a robust abdomen. Tie off the peacock and clip it at the seventy-five percent point.
Twist the two strands of floss ribbing together by rolling them in your fingers. Spiral wrap the two strands of floss forward through the body and tie it off at the front of the peacock.
Cut a turkey tail quill slip from the feather that is just a little narrower than the hook gap. Clip the tip end of the slip off square and tie it in by the tip at the front edge of the abdomen with the inside (dull side) of the feather up. Wrap over the turkey to the fifty percent point on the hook (counting the bead).
Select a partridge feather that has barbs equal to about half the shank length. Prepare the feather by stripping the base of the fluff and preening the fibers toward the base. Leave the tip of the feather exposed to tie it in by in the next step.
Tie the partridge feather in by the tip at the point where the fibers change direction with the inside of the feather up. Wrap over the remaining tip and clip any excess.
Dub the thorax area (from the fifty percent point to the back edge of the bead) with hares mask dubbing. The thorax should be about half again thicker than the front of the abdomen.
Pull the partridge feather over the top of the hare’s mask thorax and tie it down at the back of the bead. The outside of the feather should now be facing up.
Pull the turkey slip forward over the top of both the partridge feather and the hare’s mask thorax.
Tie the turkey quill off just behind the bead and clip off the remaining stubs of the turkey and partridge.
Dub a short length of thread with the hare’s mask dubbing and wrap it around the shank at the back edge of the bead to cover the butt ends of the wingcase.
Whip finish by letting the upright thread from the whip finisher roll off the back edge of the bead and slide into the tiny gap between it and the dubbing. Clip the thread.
Finished fly, top view.
Finished fly, side view.