2019 Breakout Flies: Smethurst’s Stone Bomb and Twenty Bomb

2019 Breakout Flies: Smethurst’s Stone Bomb and Twenty Bomb

One of the moves everybody who guides for PFS except Richard is making is towards heavyweight flies that can be fished without additional weight. Most of these flies are tied jig-style, rather they’re derived from previous Euro-nymph designs or adaptations of standard patterns. We like these flies whether we’re fishing them as droppers beneath big dries, Euro-nymphing, or fishing with indicators. Regardless of technique, the advantages of flies that plummet to the bottom yet don’t hang up too bad are clear: a fast sink rate gets the flies to the fish, leaving off additional weight is more efficient (both in casting and in rigging) and also puts you in direct contact with your flies (or direct between indicator/hopper and fly, if not Euronymphing), so strike detection and drift control are easier than with lighter flies aided by shot.

It’s consistently difficult to find good large (#6 through #10) stonefly nymphs that fit this bill. Sure, there’s always a Girdle Bug (Pat’s Rubber Legs), but in large sizes these typically ride hook down. I tie some Girdle Bugs upside-down, but it’s hard to find jig nymph hooks in the sizes we need, which are generally big and at least 2x long shank. Another problem is that Girdle Bugs are also the most popular nymphs around these days, probably, so the fish are seeing too many of them. So a stonefly that both looks a bit different, a bit snazzier, than the Pat’s, but doesn’t hang up as much and still checks the same boxes has been a sort of Holy Grail the past couple years.

That’s where the Stone Bomb and Twenty Bomb come in. We started fishing these patterns back in 2018, but fished them a lot harder in 2019, in a lot more places. Simply put, they knocked it out of the park on guided trips on the Madison, Yellowstone, Stillwater, and especially the Gardner and the Boulder. On the latter two rivers, these flies were godsends because of the tendency for normal-orientation flies to hang up, the abundant stonefly populations, and the need for flies to get down quick in small pieces of deep, turbulent holding water.

The Stone Bomb is a brown nymph that fills the same niche as the classic brown Girdle Bug, but has quite a bit more going on. Here’s a side view. The top view is comparable to that of the Twenty Bomb below. We found the Stone Bomb to be most effective before the Salmonfly hatch and again in the fall, when chasing fall-run browns.

illustration of stone bomb stonefly nymph

The Twenty Bomb looks somewhat like the Nocturnal or Midnight Stone, and is also an excellent attractor in the same vein as the Mega Prince or Twenty Incher. The latter pattern is obviously the source for the Twenty Bomb, hence the name. My clients and I caught fish on this one through most of the season, on many sizes. In June we ran #8s under indicators on high water Boulder River floats (the Boulder has the shortest runoff season of any of our freestone rivers, FYI). In July, it was #6-8 early on on walk trips on the Yellowstone and Gardner, suggesting big stoneflies, while later in July #10s under giant hoppers worked well on the Yellowstone. In October, it was back to the #6-8 flies on the Gardner for fall-run browns. Believe it or not, I went three trips using Euro-nymphing techniques without losing or tearing up one of the flies too badly to fish it, which on the Gardner with its abundant boulders is miraculous.

pic of twenty bomb fly

We’re looking forward to fishing these even harder next year, and will be stocking them in a wider size range at least in our guide boxes.

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