Fads come and go in fly fishing. When I was a kid the use of a "cast" of two or three wet flies was in fashion. My dad and older brothers taught me how to tie and fish downwing wets. We caught most of our trout on the Captain and Rio Grande King. Since flies cost two-bits apiece, tying our own seemed an economic necessity. My dad and brothers were more skilled than I in avoiding the inevitable tangles of fishing more than one fly, but we all spent too much time sitting on the bank unraveling leaders and flies. Nevertheless, the traditional dropper set-up was (and is) a very productive method of exploring the water.
Usually fished on an across and down swing, the unweighted wet flies can also be fished dead drift, skittered and dapped.
As I grew up, and nymphs began replacing traditional wets, I gradually abandoned the use of the multiple fly casts in favor of the single fly. I read somewhere that it was more sporting (?). Experience taught me that it was certainly less troublesome and I seemed to catch my share of trout using only one fly. Casual observation confirmed that few fly anglers were fishing multi-fly set-ups.
Along the way I read a thought provoking article by A.J. McClane, one of my favorite fishing writers, about commercial trout fishers in Europe. They used a rig of 8 to 12 small wet flies fished on a spinning rod with a quarter ounce dipsey sinker on the end of the line for weight. Their secret to avoiding tangles was very short droppers or tying the flies directly into the leader itself.
Fast forward to the present. I recently discovered that it has once again become popular to fish two flies at a time. I was initially skeptical because of my earlier frustrating experiences with tangles. However, some creative thinkers have solved most of the tangle problems of regular droppers.
There are at least four ways to attach more than one fly to a leader. I use these tangle-free set-ups for nymphing, with a little weight in the flies or on the leader:
(1) The first method is modified conventional leader dropper. Tie a fly on the end of the tippet. Tie a second fly on the tag end (dropper) coming from the side or bottom of the leader/tippet knot, only keep the dropper very short. After the fly is attached the dropper should only be an inch or two long.
(2) The second approach is dropperless and is popular in England. The point fly is tied on the end of the tippet. The second fly is threaded onto the leader through the eye of the fly. The leader is tied to the tippet with the second fly above the knot. The second fly is loose on the leader, but will seat against the tippet knot. Trout are not spooked by the fly on the leader and there is no dropper to tangle.
(3) A third way is to tie the point fly on the end of the tippet, then tie the other end of the tippet into the eye of a second fly; also tie the leader end into the eye of the second fly. Thus the fly at the junction of the leader and tippet will have two knots tied into its eye. This dropperless method is favored by many drift boat guides who don't have time for tangles.
(4) Another method is to tie a fly on the end of the leader, then tie an extension leader to the bend of the fly hook and tie a second fly to the end of the extension. This set-up can be used for trolling two streamers, or fishing a pair of deeply sunk nymphs from a float tube, as well as stream nymphing.
I'm not sure I catch more fish using a brace of flies, but it is fun to compare the success rates of various flies fished together. The increasingly popular serendipity fly is definitely more effective when fished in tandem. It is possible to catch two trout on one cast, but I've only done it a couple of times. Usually one or both hooked fish will break off.
There remains one negative aspect to multi-fly rigs, even after the tangles problem has been removed. There is a higher percentage of fish foul-hooked than on the single fly. Apparently the fish makes a pass at the dropper fly, misses and then gets snagged as the tippet drags across its body and the point fly is pulled into its belly or side. I consider it only a minor annoyance. If I encounter numerous short-striking fish I remove the dropper to avoid foul-hookups.