Double Dun

Shucks. The nymphal exoskeleton, or exuvia, being vacated by the emerging mayfly dun. Are they important for emerger patterns? One may argue that without a shuck, the pattern is no longer an emerger. So where does the distinction lie?

It is well known that this vulnerable emerging stage is keyed into by the trout. Yet a glance through emerger patterns only sees a representation of a shuck in roughly half, suggesting the jury is still out.

While I have had success using patterns both with and without shucks, I usually add them in when tying. They add a realistic tweak and I like something hanging below the surface to make it easier for the trout to notice. Particularly in rougher water.

The idea of the Double Dun began way back in FlyLife #13 when the late Peter Leuver showcased Scott’s Double Decker — a nymph with a partly hatched dun sitting above. While Scott’s pattern was tied for a tying competition rather than practical fishing purposes, the idea of a double pattern stuck.

Many iterations passed before Fred Steynberg’s shuck emerger was written up in The Feather Mechanic. His use of a trimmed hackle feather for a body provided the perfect representation without the bulk. Using the same technique with a more flexible CDC feather produces the translucent, limp appearance of a trailing shuck. As frail as they look, the trimmed bodies are surprisingly robust.

To tie the Double Dun start by creating the shucks and bodies. For the shuck select a CDC feather and stroke the barbs downward so they stand out from the shaft. Trim out the tip, then carefully trim all the barbs off close to the shaft except for the top one or two either side. Aim to leave the remaining barbs about 2 mm long at the base of the shaft then tapering in to 1 mm near the tip. Then repeat this process with a cock hackle feather to form the body.

Select a light, grub style hook — the curved shank helps angle the shuck downwards like the natural — and lay a base of thread down the shank. Add a pinch of dubbing to form a small ball, then tie in a few of the CDC barbs trimmed off earlier, either side. They do not need to be even and neat.

Tie the CDC shuck in so it hangs out at the back of the hook approximately 10–12 mm. Crushing the shaft of the feather with tweezers or your fingernail will make it easier to tie in if it wants to roll around the hook shank.

Add another small amount of dubbing then tie in the trimmed cock feather for the body, a similar length to the shuck. This time laying straight out from the back of the hook. If the feather has a natural curve, tie it in with the feather curving upwards.

The front of the pattern is much like Barry Lodge’s Emerger. Select a matchstick thickness of EP Fibers and tie them in so they lie back over the body. Pinch tightly for the first few wraps to keep them on top of the hook shank and not slipping around the back of the shank. A wrap or two of thread under the fibres just behind the tie-in point will help kick them up at a slight angle. Adding a brighter colour on top can help with visibility if you have trouble spotting your fly on the water.

Next select the hackle, a size bigger than you would normally use for the hook size. Strip the first few barbs off and tie it in securely just in front of the wing. Dub evenly up to just behind the hook eye, forming a nice plump front to the body. Then wrap the hackle forward over the dubbing in open turns — four or five turns is about right for a size 12 pattern. Tie the hackle down, trim any excess and whip finish to secure. Lastly trim the EP Fibers at an angle — roughly the length of the hackle is a good starting point.

I prefer to leave the finished flies fully hackled. They float well in rougher water and I can trim the underside when I’m out fishing if I need it to sit lower in the surface film in calm conditions. Or if the fish start taking fully hatched duns, I can trim the shuck off and grease the fly up to sit a little higher. An advantage of tying your own flies is you’re more likely to take to your flies with the scissors if things aren’t quite right at the time. Shucks, hackles, tails, all get the snip at times.

With the weather warming it’s time to start looking out for duns. Swallows can be the first hint as they swoop low over the water, seemingly in the know that something is about to happen. A shore with a steady off-shore breeze will carry a trickle of duns out and bring the trout in as they feed upwind.

You can target individual fish by casting upwind of sighted rises —- a metre or two for slower cruising browns while 3 or 4 metres may be needed for quicker rainbows. If the fish are regularly working an area you can also cast upwind and let your fly drift through.

Resist your gaze wandering when you hear other rises. You won’t be the last to look back and find your fly is gone and you’ve missed the take.