Magical CDC

Tom Jarman explores the benefits of CDC dries and how to fish them

In fly fishing and fly tying, CDC refers to feathers sourced from the lower back of water birds. CDC is an abbreviation for cul de canard, a French term that literally translates to ‘duck bottom’. They are very delicate and soft feathers and their unique properties make them a valuable fly-tying material for dry flies and nymphs.
I first encountered CDC flies when I began competition fly fishing. At the time, anglers from the Czech Republic and France were the best in the world, incorporating CDC into many of their flies. Over a decade later, the flies that I discovered then, such as the F-Fly, CDC Caddis and Pink Tag Jig are still go-to flies in my box today. So, what is it about CDC that creates such effective flies?
CDC feathers are naturally buoyant because they are located near the preen gland on a water bird that secretes oils to help the feathers repel water. The physical structure of the feather also aids floatation. Each strand or fibre on the feather has lots of tiny soft barbs that increase the surface area and trap air pockets. The feathers are incredibly soft, generating natural movement in the water when tied sparsely, or creating a buoyant wing or body that looks natural when feathers are tied in multiples.
CDC is used for tying both dries and nymphs. Many popular nymph patterns use CDC feathers for collars or hackles to help give the flies extra movement, bulk and a buggy look. The advantages of dry flies tied with CDC are on another level, though, and behave in ways that no other dry flies can.
CDC feathers can be applied in tying a wide range of dry fly patterns. Caddis and mayfly patterns are the most common. CDC Caddis, tied naturally or with coloured ‘tag’ hot spots, and the F-Fly are popular caddis patterns you will come across. And mayfly patterns such as Split Wing CDC Mayfly, Quill Body Mayfly, Plume Tips and Blue Winged Olives are also increasing in popularity. CDC is also effective for tying midges, beetles, ants and stoneflies.
Many of my favourite patterns are CDC based, and the majority use CDC as the wing material. It forms the perfect profile of a wing on the water and can be tied to sit at any angle. The amount of wing material tied in can be increased to improve the fly’s float-ability and, depending on the colour, can also form a slightly translucent wing.
Flies with CDC wings lend themselves to having highly visible coloured ‘sighters’ tied in on top of the wing (Superman cape style). It dramatically improves the visibility of the dry to the angler without compromising or changing how the fly fishes or the trout’s POV of the natural material below. With other non-CDC styles of flies, increasing the amount of sighter and visibility comes at the cost of the natural presentation of the fly.
CDC can be used effectively in other ways, such as dubbing on dry flies — an excellent alternative to hare’s ear because of its buoyancy. Spinning CDC into a dubbing loop creates beautiful hackles on the front of flies, both dries and nymphs. Some patterns consist of just spun CDC, such as ‘Rockerka’, a popular European dry fly. Small CDC beetles can also be created from spun or dubbed CDC. The fine tips of the feathers move naturally on the water and generate excellent floatation and life.
Most CDC dry flies don’t have a traditional cock hackle, or if they do, it tends to be a very sparse one with just a few turns at the front of the fly. The absence of a hackle makes the fly incredibly easy to cast and very accurate. Sometimes stiff hackles on a dry can almost act as a parachute and catch the wind, making casts less accurate or spinning your tippet and leader.
As popular as patterns like the Royal Wulff and Stimulators are, the key features that make these flies so buoyant can also come with a compromise in accuracy and poor hook sets. The extra hackle and bulk that often covers the hook point can interfere with hookups when a fish takes the fly. It is common to miss fish when fishing a Stimulator or similar fly, a phenomenon which often gets misdiagnosed as a poor eat by the fish itself. A simple CDC Caddis or Mayfly avoids this problem by having no hackle. Anglers who start to fish with CDC flies usually find their conversion rate improves significantly.
There are CDC alternatives for most of your favourite ‘traditional’ dry flies. For example, where you would typically fish an Elk Hair Caddis or a Goddard’s Caddis, you can fish a CDC Caddis. Parachute mayflies in smaller sizes, such as the Parachute Adams, can be substituted for the more natural Plume Tip or Upwing CDC Mayfly. Attractor style patterns with hot spots such as Stimulators or Wulffs can be switched out for a Red or Orange Tag CDC Sedge.
Selecting a CDC dry fly, or any dry for that matter, is all about choosing one that will fish well and suit the type of water being fished. If you are approaching a long flat pool and see fish sipping and rising to small insects, then selecting a fly that is similar in size to the naturals is logical. Small dries that sit low in the water are essential in enticing more consistent eats by trout. It is also important to fish a visible fly so that you can see that you are achieving a nice drag-free drift. On slower, calm water, such as a pool or glide, a fly such as a Plume Tip, CDC Upwing or F-Fly is invaluable.
These flies represent a range of tiny insects such as midges, caenids and blue-winged olives. The bodies of the flies are small and slim and sit low in the water, passing muster on close inspection by trout in slow water more often. However, the CDC wing sits up beautifully, making the fly surprisingly easy to see on the water, even in size 18.
On a medium to fast-paced riffle or run, you could still fish a small dry fly and it will get eaten; however, it will be much harder to see and fish comfortably. In faster water, the fish are generally more confident and willing to eat a larger dry. This is also the type of water where you see fewer fish rising but catch more by prospecting and fishing blind with
a dry.
This water is perfectly suited to fishing a CDC Caddis or larger mayfly pattern. These flies have more CDC in their wings and as a result they ride higher in the water, making them easy to see. They are highly effective because they have little or no material that obscures or covers the hook’s point. As I mentioned before, this can create resistance and interfere with hookups when a fish takes the fly.
Managing your drifts in fast water will also improve presentation. Fish shorter where possible, eliminating or minimising the currents your leader is fighting with. High-sticking is also a valuable technique, especially in the tails of pools where you would otherwise lay your leader across vastly different water speeds, creating instant drag.
CDC dry flies also come into their own when used as an indicator dry when fishing a nymph below a dry (dry/dropper). They are extremely buoyant and will hold up a deceptive amount of weight. A size 14 CDC Caddis can hold up a 2.8mm tungsten beaded nymph. But the main reason I find them effective as an indicator is their responsiveness. The wing material is so soft that the slightest touch or take on the nymph will cause the dry to twitch or shoot under and disappear in a flash. The early take detection they offer is valuable because of how quickly a fish can take and then spit out a nymph that doesn’t feel right.
The way I rig a CDC dry fly as an indicator is the same as with any dry dropper rig. I like to have my dry fishing off a short dropper (about 5cm) tied off the main line with a triple surgeon’s knot. Fishing the dry off a short dropper, rather than off the bend of the hook, helps the dry and the nymph to fish more freely, achieving better drifts, and leading to more takes. The distance to the nymph can be from 50cm to 1m depending on the depth and speed of water you are fishing.
Tippet choice for fishing a CDC dry is the same as with any dry fly, but using appropriate diameters will take advantage of the CDC benefits. It is optimal to fish as light as reasonable, as a thinner tippet on the surface of the water will mean a better drift with less drag. A CDC fly drifting downstream is so natural, and we want to encourage this as much as possible by freeing the fly up, and the fine tippet does exactly that.
As a general rule, the smaller the fly, the lighter the tippet you need to fish. Heavier tippet creates a hinge and is stiffer coming off the eye of the fly, which takes away from the natural drift of the dry fly. The larger the fly you are fishing, the less noticeable this is, so you can fish heavier tippets. For example, fishing a size 18 fly, I would want to be fishing 7X or lighter tippet. Size 16 and 14 flies, then 6X or 7X would be ideal. Naturally there are times when you must compromise. If you are fishing for large fish with a small fly, you will probably need to fish heavier tippet to help ensure you can land the fish. New Zealand and North America are great examples of where this is applicable.
The natural qualities of CDC feathers mean you don’t need to pre-treat your dry fly before fishing it. The oils in the feather are essentially a natural floatant. But I still like to add the smallest amount of gel floatant to my CDC dries before fishing them. It doesn’t hurt the CDC and I like to apply the floatant to the body of the fly as well. I feel this helps my flies float higher for longer. Just read the label on the floatant to see that it is optimised for use on CDC.
After you have caught a fish, you will notice that the wing sticks together, and the fly looks all ‘gooped up’ and won’t want to float. The solution is quick and easy. All you need to do is give the fly a quick wash in the water to take the fish slime off it, then dry the fly by squeezing the water out with an absorbent material such as a chamois, amadou patch or cotton tee shirt. Then give the fly a quick shake or dust with some powdered desiccant. Your fly will be completely dry and fishing at its best again.
If you find you have accidentally drowned your fly and it is no longer fishing and floating high in the water, you can just repeat this process. Try not to let your fly drag through the water behind you when walking upstream to a new position — this can sometimes drown your dry too. This applies to CDC, deer hair or any material. Any dry fly will float better and for longer if you manage it and keep it off the water when you aren’t fishing.
The ease with which CDC flies float and remain highly visible, the quality of the drifts they achieve and the confidence that fish take them with, are the reasons why they make up the majority of my dry fly box these days. Treating and managing the flies may appear to be daunting at first, but is quite simple and worth the reward. You will quickly learn how to manage them and which patterns suit the type of fishing you like to do. Once you experience the benefits of them on a river, they are likely to become your go-to flies.

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