How to Tie the Double Mop Fly
No matter how you feel about mop flies, there’s one thing for sure, they’ve now more than proven themselves to be extremely effective at catching trout. I’ve long believed that their effectiveness comes from how well they resemble crane fly larvae, which can be found in nearly every river and stream throughout the year. They’re large, absolutely loaded with protein and, much of the time, fairly sessile. Watching them move in my fish tanks has made me realize it’s not just the look of the mop flies that imitate them, it’s also the movement of the mop material. There are few fly tying materials that soak up as much water as mop fibers do. So when they’re fully saturated, mop fibers exhibit a tremendous amount of movement, which has to be a trigger for trout. This movement is increased greatly by tying a Double Mop.
A standard Double Mop begins with a size 12 Fulling Mill 5065 Czech Nymph hook. Make sure the hook is well secured in your tying vise, as you’ll be using a fair bit of thread tension throughout the tying process.
Because of the increased thread tension, it’s a good idea to go a little heavier with your tying thread, here, UTC 140 Denier in a gray brown, to closely match the mop fibers I’ll be using. Get your thread well established on the hook shank behind the eye and, after taking 8-10 wraps rearward, snip off the excess tag.
Adding some weight to the fly actually seems to help its movement, here, .02 lead-free round wire. While leaving the wire on the spool, anchor the bitter end to the top of the hook shank with really tight rearward wraps of tying thread. Once the wire’s anchored, start taking rearward wraps with it behind your tying thread. This will help the wire wraps to stay sandwiched together. After 7 or 8 turns, anchor the wire to the top of the hook shank with a few thread wraps, then bring it in line with the shank and work it up and down as you wrap rearward. This will cause the wire to break off, leaving a gentle slope down to the hook shank.
Take tight thread wraps over top of the wire to anchor it further. Although not essential, a drop of super glue, here Fly Tyer’s Z-Ment, applied to your work thus far then covered with wraps of tying thread, will increase the fly’s durability significantly. End with your tying thread at the back edge of the wire wraps.
For this Double Mop, I’m going to use really good-looking gray fibers from a car wash mitt. They’re among my favorite, as they have some darker flecks, just like real crane fly larva. They’re fairly long and slender but most importantly, they’re very supple and readily soak up water. For a single Double Mop fly, I’ll snip 3 full fibers free from the fabric backing. All 3 should be about the same length, but that’s not super critical. Pick up one of the fibers and strip away a small amount of the fluffy stuff to expose the fiber’s string core. Anchor the string core to the top of the hook shank with nice tight wraps of tying thread. You don’t want it to pull free. Pull rearward on the fiber to ensure that it won’t pull out or worse yet, come unraveled. End with your tying thread at the front edge of the wire wraps.
Pick up a second mop fiber and prep it in the same manner as you did the first, but this time hold the fiber so the string core points to the rear of the fly. Once again, anchor the string core to the top of the hook shank with really tight wraps of tying thread, and make sure it’s not going to pull free or unravel. Clean up the area between the two fibers with thread wraps, ending with your tying thread about halfway between the two. The Double Mop should now look something like this. Check to make sure the hook eye is clear of fibers. This will become especially important later.
Here’s the fun part. Pick up the third mop fiber and separate the string core. Pull in opposite directions to unfurl the fiber into a fuzzy, twisted rope that look’s about like this. Get hold of one end of the rope with a small amount of the remaining string core exposed. Lay the core on top of the hook shank and, once again, take nice tight wraps of tying thread to secure it. Make sure it’s bound down really well then end with your tying thread at the back edge of the front fiber.
Get hold of the fuzzy rope and start making touching wraps up the hook shank with it, to fill in the space between the two mop fibers. Don’t try to sneak an extra wrap in. It’s much better to just loosely cover the area before taking tight wraps of tying thread to anchor the material. An extra wrap with the rope will oftentimes end up blocking the hook eye, which can be really problematic on this pattern. With the material well secured, snip the excess off close. Pull the forward-pointing fiber back to expose the hook eye and take a few thread wraps right behind it. Tilt the fly up in your tying vise to make whip finishing easier. Pick up your whip finish tool and use it to do a 5 or 6 turn whip finish behind the eye, then seat the knot well and snip or cut your tying thread free.
Now, go trim the middle section you just tied in so it blends in with the two mop fibers. Make sure the hook gap is nice and clear. Once again, it’s very important to allow clear access to the hook eye so it’s easy to tie on to your tippet.
Incidentally, the same technique used on the Double Mop can also be used to create a really good-looking bead head mop, if you prefer. It doesn’t have as much movement as a Double Mop, but it’s still remarkably lifelike and effective. You can even forgo the bead and just tie onto the weighted hook shank, and go with a single mop fiber that way. This version is easier to cast and looks beautiful on the swing as well as dead drifted.
Whichever version you choose, I would urge you to use barbless hooks as trout oftentimes will inhale mop-based flies.