Shurtleff FOM Winged CDC Biot Dun

J. Stockard Pro Tyer: Paul Shurtleff, Springville, UT

I first came up with the idea for this pattern after a long afternoon of being humbled by the trout during an epic BWO hatch on my local tailwater a few years ago. The fish in that particular tailwater are fairly pressured as well, which typically makes them harder to catch anyway, but that day the fish were being extra picky and would only look at and eat the naturals… I had a close matching fly in my box but the trout still give refusal after refusal to where all I could do is watch boil after boil and rise after rise seeing trout noses coming out of the water. Cast after cast and still nothing… I couldn’t buy a rise to my fly, even by accident, let alone hook one by mistake! Anyone that has ever experienced this knows exactly the frustrations I met with that day… Anyway, after I got home that night, still feeling the sting of being skunked and reflecting upon the refusals made by the trout… I watched a few YouTube videos for some inspiration in an attempt to come up with a mayfly dun pattern that would more closely match the naturals in hopes of fooling the fish for my next outing. The following pattern is the result… Upon my next outing armed with a few of my new creations, my very first cast to an active rising fish ended with a fat 18″ brown trout in my net… What surprised me most about that fish, is that the wind caught and picked up my cast, which fell a bit short and I missed the ideal presentation but the fish moved out of its feeding lane at least 3 feet to sip down my fly despite my bad cast! 2 casts later and I had another brown trout to net, not as big as the first, but just as spunky. Moving up river hitting the pockets and other fishy spots with risers yielded a few more fish to net… The new fly was proving itself worthy of seducing the super selective and pressured trout of my local tailwater… I can’t remember how many fish came to net that day falling victim to my new fly, but I do know I went home that night very satisfied and tied at least a dozen more flies just like it!

This fly is really just a combination of a couple of different mayfly dun patterns, and my own variant of the 2 different patterns adapted into 1… This pattern has the upright and split wings of Medallion Sheeting made popular by one of my favorite fly tyers of all time, Shane Stalcup (RIP), and the thorax of CDC tied in with a split thread tying technique made famous by Marc Petitjean and the adaption of his Magic Tool set. The tails are Coq De Leon splayed out with one of my favorite body materials, goose biots. Although it looks like a fairly complex pattern, it’s actually a simple and easy fly to tie. And because there isn’t any expensive dry fly hackle involved, it’s easier in the wallet when buying the materials to tie it. Using only 4 materials (minus the hook and thread), the combination makes a nice semi realistic mayfly adult that’s more than proven itself worthy.

Since I first came up with it and started field testing it, this pattern has quickly become one of my “go to” fly patterns for picky mayfly sipping trout. It’s a very versatile pattern too, in that by simply changing size and color it can be tied to match just about any mayfly hatch one would encounter pretty much anywhere in the world. I personally tie these from size 10 and 12 for the bigger mayfly drakes (green drakes and brown drakes) all the way down into the 20’s for the little guys (BWO’s and Tricos). One of my favorites is a size 16 in a yellow/gray dun, which makes a really nice PMD dun.

How do I fish it? Straight from the fly box to the leader to the water… CDC is highly buoyant, so I typically don’t use any floatant at all until either I catch a fish or the fly starts to sink. After which, I blot the fly dry using my shirt, cloth, bandana or a peice of chamois cloth and then I’ll use a dry shake or desiccant floatant… Sometimes, I’ll use a standard floatant like Gink, but I only use it on the tippet about 3″ above the fly and not on the fly itself. I also use a floating weight forward fly line and a custom made floating furled leader (From Moonlit Fly Fishing/Nirvana On The Fly) with a piece of mono tippet from the leader to the fly. I usually only use one fly at a time, but a larger sighter fly as a dropper could be added on if visability becomes an issue.

Materials List:

Hook: Moonlit ML052 competition barbless
Thread: 18/0 Semperfli Nano Silk
Tails: Coq De Leon
Body: Semperfli Inferno Goose Biots
Thorax: CDC
Wings: Medallion Sheeting


1. Start thread towards or at the 3/4 point on the hook, remove the tag end and work your way towards the bend of the hook.

2. Tie in a few fibers of CDL for the tails (more than 3, less than a dozen) and splay the tails with a thread turn under the tails and a securing thread wrap so save the work.

3. Tie in a single goose biot at the tail. (notch forward for a raised ridged body, or notch backwards for a smooth body… Both biot tie in methods give nice segmentation and are equally effective)

4. Wrap the biot forward to the start of the thread (at the 3/4 point) and tie off.

5. Using the Marc Petitjean Magic Tool, select 2 CDC feathers (color(s) of choice) and prepare the CDC feathers in the clips.

6. Tie in a strip of Medallion Sheeting in at the 3/4 mark (1/4 behind the hook eye) using x-wraps. The Medallion Sheeting strip should be at least as wide as the hooks gape.

7. Stand up and prop up the Medallion Sheeting strip for the wings.

8. Flatten and split the thread for the split thread tying technique.

9. Introduce the CDC feathers from the Magic Tool clip into the split thread.

10. Close the split thread and ready it for tie in.

11. Wrap the CDC dubbing loop in X-style fashion, in front of and behind the wing.

12. Pull the CDC up and back to expose the hook eye.

13. Whip finish and remove the thread at the hook eye.

To finish the Fly:

1. While pinching the wings together, pinch and pull the CDC Fibers out and to the sides (for legs) on each side of the fly.

2. Clip the CDC thorax flat on the bottom.

3. Remove or trim down any long or unruly CDC Fibers from the sides of the fly.

4. While pinching the wings together, trim the wings with a straight cut for wing length.

5. Make a shallow angled cut on the wings in front.

6. Make a deeper cut to the back of the wing and then shape the wings as desired.

7. Add a drop of desired head cement to the thread wraps and it’s a completed fly.


  1. I am , to say the least, very happy for my sons tying success. We are outdoor people and appreciate the pleasures we have. Paul has worked very hard to get where he is today. I am very proud of his success. I and his older brother may have helped lite the fire, but he has surpassed our ability by far! Just so you all know, Paul is also a great hunter and marksman with several mounts on the wall.

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