CDC

[Traditionalist]

CDC which is the abbreviation for the French "Cul de Canard" are the feathers found in the vicinity of the preen gland on ducks and similar birds.

One point which I would like to make here, as several people asked me about it recently, and because there is still a lot of confusion ,if one uses these feathers taken directly from a duck, and they are not treated in any way, then they float extremely well for two reasons, the first reason is that the feathers contain, and are coated with natural grease or oil which effectively waterproofs them. This means that the feathers do not get wet, and float very well as a consequence! This property disappears with time and use as the natural oil washes out eventually. The flies still float well however, because of the second reason.

The second reason, and by far the most important one for the fly-dresser is that these feathers have an unusual structure of fine radial barbs which helps them to trap air, and gives them a very large surface area which enables them to float much more readily than other types of feather. Once treated, by dyeing etc, most of the natural grease has been removed, but the feathers will still float very well indeed because of their structural properties. Once thoroughly soaked they will sink however, and as they are no longer waterproof must be thoroughly dried before using them again. I have mentioned this quite a few times in the past on various occasions, and have even had people argue about it. Once again, Hans Weilenmann has provided some excellent info on CDC feathers indeed a complete system of identification and usage! Although he is far too modest in this regard, this has now become the de-facto standard for many fly-dressers.

Consider this, nearly all water-birds possess a natural waterproofing system in the form of a preen gland which exudes oil, and this is then applied to the feathers by the bird using its beak. If this gland ceases to function, or the birds are degreased for some reason (use of detergent after an oil spill for instance,) the birds no longer float because the feathers become waterlogged and the bird sinks and drowns. The structural properties of the feathers are of no use to the bird in this case. Waterlogged flies may be dried out and used over and over again of course, relying entirely on the structural properties to maintain the excellent floating capability independent of the natural oil.

These feathers are best not treated with various paste and similar type floatant at the streamside when used for dry flies, this will have the effect of clogging the fibres usually, and actually make them sink more quickly. There is a fairly new product on the market called "Watershed" this is a waterproofing liquid which is applied to the flies twenty four hours before use, and supposedly renders them completely waterproof, I have tried this recently on quite a number of flies and it seems to work very well, even on treated CDC feathers. I will have more to say on this as soon as I have fished a reasonable number of times with these flies.

If it works as well as the makers say then it is a major breakthrough for fly-fishing in my opinion A couple of false casts sufficing to shake off excess water after drowning and the fly is high and dry again. My tests up to now are very positive. Even hen hackles may be waterproofed effectively, opening up whole new avenues of attack for dry flies and some upstream spider energers and similar.

UPDATE In the meantime I have fished quite a lot with these flies. Although it seems to help a little pre-treating them, it does not make as much difference as I had hoped. The best way to dry these flies is still to use a pad of amadou, and either ground silica gel, or one of the various dry-shake products available, which also contain powdered floatant. Opinions on various floatants are legion, some anglers having decided preferences for one or the other. If it works for you, then that is fine!

CDC feathers may also be used on wet flies very effectively, as the structure described, holds small air bubbles and is extremely useful for imitating emergers and similar flies where a silvery translucent thorax or body is desired. This effect is very marked. I use CDC for the thorax on some wet and "semi-wet" emergers because of this. Patterns for some aquatic beetles and other swimming insects are also a good use for this material. Recent experiments using it for wings have also proved very promising indeed.

This material and its peculiar properties was mainly unknown to the old dressers as far as I can determine, but I am sure they would have used it had they known about it. In some areas it has indeed been used for a very long time, but not in the UK. For an informational article on CDC and its use;

http://globalflyfisher.com/tiebetter/tying-with-cdc/