The Funneldun is a dry fly style rather than a specific mayfly imitation – tie it in sizes and colors to match the hatch, or tie it as an attractor pattern. The Funneldun was originated by Neil Patterson as an easy way to tie upside-down duns. As an added bonus, it makes use of those large hackles on the sides of that rooster neck that you usually can’t utilize for reasonably sized mayflies. I don’t know about you but my dry fly necks all look a little used-up in the middle. Tie it with or without wings. When using wings feather fiber wings such as duck flank are recommended. I used mallard flank dyed wood duck in the Hendrickson Funneldun (above top left).
The unique hackling style differentiates the Funneldun from most other dry fly patterns. An over-sized hackle is used, and it is “funneled” forward at an angle of approximately 45 degrees from the hook shank. According to the originator this was done in an effort to get more of the hackle’s surface on the water – as opposed to just the hackle tips.
The over-sized hackle is tied in at about the one-third mark on the hook shank, then a thorax of dubbing is installed on the front third of the hook. Wrap the hackle and then use thread wraps to “funnel” the hackle forward over the thorax (which will support it). Wrap in a hackle-fiber tail – this needs to be wrapped a bit around the bend of the hook, so that the fly sits on the hackle and tail properly (as in the picture). The body is then dubbed from front to back and the fly is whip-finished at the tail end. The hackle can be clipped in a “V” on top (as it sits in the vice), this will of course be the bottom of the fly when it turns upside-down. I didn’t clip the hackle on these flies pictured, as they seemed to land and rest just fine without the hackle trimming. Due to the elongated hackle profile – you may want to tie these flies on one hook size smaller than usual.
As an aside, for all you tenkara fly fishers, if you get tired of fishing it dry, tug it under and call it a tenkara reverse-hackle fly.
Reference: I found this pattern in the book, Collins Illustrated Dictionary of Trout Flies, by John Roberts. This is a fairly thorough compendium of fly patterns, that makes a nice addition to a fly tyer’s library. It is not a fly tying instructional book however, and it assumes that the reader is already a proficient fly tyer.