CDC & Elk/Deer Hair Caddis
I can somewhat remember when the material CDC first came out - I think it was in the late 80's - either way I know when I first tried it out, it took a bit of getting used to. But since that time, there have been so many different patterns that have been developed through the use of this feather and it's natural ability to float well. Some time ago, I came across a pattern that Hans Weilenmann developed - kind of a Elk Hair Caddis that moves and by using CDC it kind of offers the "trigger" effect on the fly. Mr. Weilenmann tried to improve a bit on the proven Elk Hair Caddis by using different ways to tie in the CDC. After some trial and error he came up with this method and it does quite well as the straggling barbs of the CDC suggest a trailing shuck, crippled wings, or possibly legs on the fly. Simple to tie - only using two materials.
To start off with - for those who have not tied much with CDC...... there are basically three different types of these feathers......
Type 1 This feather is the longest of them all with a tapered stem and rounded tip with the barbs flaring out from the stem. Mostly used for wrapping around the body and/or creating trailing fibers away from the head.
Type 2 This feather has a thin stem and somewhat of a squared off tip. Is shorter in length and the barbs generally run parallel to the stem. Mostly used to create wings, posts, and loop wings on emergers.
Type 3 These are usually called "puffs" and they are very short with very little stem. Used for tailing, trailing shucks, and once again for wings.
You can also get corded CDC which makes for great body material or whatever your imagination sees fit with the barbs flaring our the entire length..... 
Here they are all pictured together: 
So for this fly, use the Type 1 - the longer type feather....
Materials: 
1. Start the thread about half of the way back from the eye and wrap to the bend. 
2. Hold the feather in your left hand and with your right - draw the barbs to the tip and bunch them together. Then tie this clump in at the tip as shown. 
3. Wrap forward to just behind the eye, leaving enough room there to tie in the elk/deer hair. Do not trim off the tips of the cdc - just cover them with thread wraps. 4. Attach hackle pliers to the stem and wrap the feather forward creating the body. Make sure you wrap enough body to allow for the flared barbs to make the final three turns where your thread is hanging. When you get to this point, take the feather and with your finger tips - pull the barbs back away from the stem as shown to prep it for taking the final three turns. 
5. Take three turns of the CDC around the hook shank and with each wrap "train" the barbs to the rear with your fingertips. Tie the CDC feather off and trim. 
6. Cut a small clump of either elk or deer hair (personally I like to use deer but to each his own) - comb out the underfur, stack it, and tie this in tight with the tips extending just beyond the hook bend. 
7. Bring the thread in front of the clump of hair you just tied in, take a few wraps, trim the thread off. 
8. Cut off the butt ends of the hair close to the eye.... and there you have it. 