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How to Tie Flies With CDC

By Hans Weilenmann
Source: Fly Fisherman Magazine

From midges to bonefish flies, cul de canard (CDC) is equally at home in drys, wets, nymphs, and saltwater patterns.

The description “Cul de Canard” was reputedly coined in the late 1950s by French tier Henry Bresson for one of his patterns. The description has contributed to some confusion, especially when it was literally translated into English as “duck’s butt” or “duck’s arse” feathers. In fact, the preen gland is located on the back of the bird, a short distance up from where the tail feathers sprout from the skin.

Many birds preen, recondition, and waterproof their feathers with oil secreted from their preen (uropygial) glands. CDC feathers sit on top of the gland and the area close around it. While CDC is normally harvested from members of the duck family (“canard” is the French word for duck), other waterfowl such as geese offer feathers similar in quality. As the size of the bird increases, so does the size of the feathers.

A CDC Type 1 Feather CDC Feather Structure CDC Feather Traps Bubbles
Overall (Type 1) CDC feather.

Francis Friesen Illustrations

Zooming in on the CDC feather structure, the stem shows, besides the barbs, jagged protrusions. The barbs in turn sport ribbon like twisted barbules. Flattened barbules maximize the surface area. In the surface film, a larger and water-repellent surface area assists floatation of the dry CDC pattern. Zooming in even more, this illustration shows a submerged CDC feather. The ribbon like and twisted barbules retain tiny bubbles of air that add buoyancy to the CDC.

Understanding CDC

While the natural oils in the feather assist in repelling water, the hydrophobic properties and the structure of the CDC feather are fundamental to its buoyancy. If the oil in the feather was solely responsible for making it float, dyeing CDC would prevent the feather from floating, but this is not the case–provided the dyeing process keeps the feather’s structure intact.

Furthermore, CDC feathers don’t float well when they are matted with water or fish slime. If the oil was the primary contributor to the feather’s buoyancy, the collapse of the structure wouldn’t matter, but it does.

If you can maintain the feather’s structure, the surface area of the barbules in the film works to keep the fly afloat and the tiny air bubbles retained in the ribbon like, kinked structure of the hydrophobic barbules hold up those barbs that have broken through the surface film.

A closer look at the makeup of a CDC feather shows why applying a liquid or paste floatant collapses the feather structure and ruins the characteristics that help it float.

For me, the primary quality of CDC is the mobility of the barbs, whether moving in the air currents above the water’s surface or in the water currents in the film or subsurface. CDC wings positioned above the surface film do not contribute to buoyancy, but do offer a full silhouette without bulk and respond to the slightest breeze to suggest life. Submerged, the mobile CDC barbs respond to every shift in current, again suggesting life.

Natural and dyed CDC impart a built-in life to flies. This is where CDC shines and what makes it an excellent choice to feature in a broad range of patterns. CDC also blends in well with other materials, where the combinations of their respective properties complement one another for a more effective result.

With correct use of the material and treatment on the stream, CDC flies are among the most durable of patterns as well as some of the simplest to tie.

CDC Types

While CDC feathers are generally lumped together under the single umbrella called CDC, close examination shows distinct differences in their appearance, depending on where they are found in relation to the gland. Certain types of feathers are more suitable for specific purposes.

I designed and use a simple classification system to explain to other tiers the types of CDC most desirable for different patterns or functions. I categorize CDC into four distinct types:

CDC Feather Type 1 Type 1: This feather resembles a partridge body feather. The feather has a rounded tip and a fairly short, tapered stem with barbs set at approximately 60 degrees from the stem. I wrap this feather around the shank to produce body and trailing filaments for the CDC & Elk.
CDC Feather Type 2 Type 2: This feather has a thin stem with the barbs running mostly parallel to it, ending in a square, brush like tip. These feathers are good for wings, including wing posts and loop wings in patterns such as the Snowflake Dun (Roman Moser), the CDC Micro Caddis (Ronald Leyzen), the CDC No-hackle, and the CDC Loop Wing Emerger.
CDC Feather Type 3 Type 3: This one is called the nipple plume and is sometimes referred to as oiler puff. This short feather lacks a discernible stem but looks similar to a Type 2 feather. This feather is ideal for tails, trailing shucks, and emerging wings for such patterns as the Snowflake Dun, the Balloon Emerger (Roman Moser), and various RS2-type flies.
CDC Feather Type 4 Type 4: This feather has a long stem with relatively short barbs. Shop-bought bulk packages mostly hold Type 4 feathers. I use these to tie IOBO Humpy patterns and to wrap the body on large-hook-size versions of the CDC & Elk, such as in the CDC & Elk Streamer or the Bonefish CDC & Elk (Paul Slaney). René Harrop uses Type 4 feathers for down wing flies such as his CDC Transitional Caddis.

Harvesting CDC

The best quality CDC comes straight off the bird. The harvesting process is simple and swift and the average mature bird provides between 70 and 100 usable feathers.

Harvesting CDC Feathers

CDC feathers surround the birds preen gland. Oiler puffs (shaded in the above illustration) distribute CDC oils to nearby feathers.

Once you lift the cover feathers, you can easily locate the preen gland by feel as well as sight. The visible part of the gland shows up like a shiny pebble protruding from the surrounding skin and is capped by a clump of feather puffs (Type 3 feathers, or oiler puffs) saturated with oil. On the illustration, these feathers are darker and are just below the thumbnail. The larger feathers surround the gland and increase in size as they get farther away from the center. On a mature mallard the stem on the longest feathers that still retain the CDC structure may be close to 2 inches long. On a goose they may exceed 3 inches.

Store the saturated oiler puffs with the rest of the feathers and in a few days the oil will disperse evenly throughout the feathers, leaving the oiler puffs fluffy. Fresh CDC feathers are mostly free from vermin, but to be safe put the container with feathers in the freezer for at least two days to kill any mature bugs. Some eggs may remain intact, so remove the container from the freezer for a day or two to allow any surviving eggs to hatch, then put it back in the freezer for two more days to finish the process.

Tips and Tricks With CDC

Bleaching: Bleaching natural dun-colored CDC feathers in a mixture of equal amounts of 3 percent hydrogen peroxide and household ammonia results in a wonderful, warm, light-amber color. The timing is not critical and may range from several hours to an overnight soak. Rinse the feathers in fresh water and let them air dry. The resultant feather stem remains pliant and the bleaching process appears to leave the feather structure mostly intact. The hydrogen peroxide and ammonia mixture gives off unpleasant and unhealthy fumes, so do this in a well-ventilated area.

Dubbing: Barbs broken away from the stem make nice dubbing material. Use them alone or mix in other natural fur or synthetic dubbing.

Bodies: Roll a Type 2 feather on a sheet of firm foam. Press the feather down with your fingertips and roll perpendicular to the stem. Start from the butt and work up toward the tip. Once you form the “rope,” you can tie it in by the tip and wrap it around the shank for a buoyant and naturally tapered body. Many of Marc Petitjean’s patterns feature this style of body. Including the stem makes these bodies virtually bulletproof, without the need of a reinforcing rib.

Trimming: When you cut CDC with scissors, you get an unnatural-looking square edge. “Tear away” the excess length of the barbs for ends that resemble the natural tips.

Drying: I prefer to dry my CDC patterns using amadou. I have experimented with other drying agents such as Shimazaki Dry Shake and Frog’s Fanny, but it appears that once you use either of the two on a pattern, the buoyancy only lasts one fish before the drying agents need to be reapplied. Flies dried with amadou can be fluffed up by blowing air on them or with several false casts.

History:

CDC’s history in fly tying and fly fishing begins in central Western Europe in the 1920s with the dry flies used by fishermen living in the Jura Mountains between France and Switzerland. These patterns, generally referred to as Moustique patterns, remained unchanged until well into the late 1970s. A generic Moustique pattern features a cock-hackle tail, a slender body of wrapped raffia or thread (later the patterns were tied with silk floss) ribbed with silk thread of a contrasting color, and a CDC collar.

In the 1980s similar flies continued to be tied and fished across Western Europe. Sometimes tiers would omit the tail, but they retained the CDC collar and at times combined it with a second material such as cock hackle.

In 1980 Marjan Fratnik, a tier from Slovenia, designed the F Fly. This simple, elegant, and deadly fly was a radical departure from how CDC was used. For this caddis imitation, Fratnik stacked two or three CDC feathers and tied them in at the eye of a thread-covered hook shank with the feather tips facing over the bend. He then trimmed the feather stems short at the eye of the hook and the wing length to the proportions and angle he desired. The F Fly triggered renewed interest for other uses for CDC in a growing number of European tiers.

Between 1985 and 1988, Gerhard Laible wrote a series of articles covering a range of techniques and patterns using CDC for the German fly-fishing publication Der Fliegenfischer. Laible complemented his articles with the first book focusing solely on this material, CDC Flies, published in Germany in 1993.

Dutch tier Hans van Klinken (originator of the Klinkhamer Special) turned CDC upright with his Once & Away pattern in 1988. The Once & Away has since spawned a host of patterns, generally referred to as Shuttlecock flies, which continue to be popular in Western Europe, especially with stillwater anglers. Shuttlecock designs are excellent ascending midge patterns for lakes and tailwaters.

While many European tiers contributed to the development of CDC techniques, Fratnik, Laible, and van Klinken rank as among the first. Another European tier I place in this small group is Switzerland’s Marc Petitjean, who is perhaps the best-known proponent of CDC techniques and patterns today. Some of the techniques he either originated or made known to a wider audience are the use of a full CDC feather rolled into a noodle, tied in by the tip, twisted, and wrapped as a naturally tapered body (1985), his elegant and innovative use of CDC to make split wings, and in 1992 the mental leap to incorporate CDC in subsurface patterns. Since then the range of Petitjean’s patterns has expanded to cover terrestrials, leeches, crustaceans, salmon and steelhead flies, and saltwater patterns.

By the late 1980s the first signs of CDC in North American contemporary fly tying became visible. In 1994 the English version of a French book by Jean-Paul Pequegnot, French Fishing Flies, appeared as the first book on the American market with references to CDC and CDC flies. It was followed by Darrel Martin’s Fly-Tying Methods (1987), which devotes a half page to CDC, and Micropatterns (1994), in which a section on CDC provides the first in-depth description of its properties. The book lists over a dozen patterns incorporating CDC, an indication of its growing popularity among tiers.

René Harrop’s landmark article in the July 1991 issue of Fly Fisherman put him at the forefront of North American CDC proponents and helped popularize CDC in the States. A second prominent North American tier who has been developing techniques and patterns using CDC is Colorado tier Shane Stalcup. Between them, they have come up with a number of imaginative and effective patterns.

[Note: Marc Petitjean, a CDC aficionado and one of the key people in modern development of CDC flies, conducted much of the research into the early use of CDC. His research and that of other angling historians and tiers, as well as over 100 CDC patterns from several continents, has been published in Tying Flies with CDC: The Fisherman’s Miracle Feather by Leon Links (Stackpole Books, 2002).]

 

Hans Weilenmann lives in the Netherlands, but visits the U.S. often for fly-tying demonstrations and shows.