The Chubby Chernobyl is the right anchor fly for a hopper-dropper rig on the South Platte from late July through September — sizes #10–14, foam body, fished with a nymph dropper 12–18 inches off the bend. It floats all day in flat tailwater current, reads subtle takes clearly, and carries enough bulk to suspend a tungsten bead nymph without sinking. It’s the rig I default to on this water once grasshopper populations start moving and water temps settle into summer range.
Why the Chubby Chernobyl Works on Tailwater
Most hopper patterns were designed for freestone rivers — fast riffles, pocket water, banks where a bushy fly lands hard and triggers a reactionary strike. Tailwater is different. Deckers runs cold, clear and slow; Cheesman is pocketwater with glassy pools between the boulders. The fish are pressured. A fly that works on the Madison might get refused here all day.
The Chubby Chernobyl earns its place on this water specifically because of its foam construction. Foam floats indefinitely — it doesn’t waterlog, doesn’t need to be reapplied with floatant every few casts, and holds its profile even after getting chewed. On flat tailwater current where you’re watching a fly drift 20 or 30 feet and reading every micro-movement, that consistent float matters. The fly sits in the film reliably, which means when it twitches, dips, or hesitates, you know something caused it.
It’s also big enough to be visible from a distance while fishing the #10–14 size range that still reads as credible food — not too large to spook fish in clear water, not so small it loses its indicator function with a tungsten nymph hanging below.
Sizes and Colors for the South Platte
The sizes that matter here are #12 and #14, with a #10 reserved for big broken water. A #12 is your starting point when naturals are larger and fish are less pressured — it carries a heavier dropper better and is easier to track. Drop to #14 as pressure builds or water clarity increases later in the season. The #14 is a late-summer option when fish are getting skeptical of the bigger profiles after weeks of seeing them.
Color: tan and yellow-bodied versions read as grasshopper. Royal (red/peacock-style) is a straight attractor that draws strikes without any entomological logic behind it, and it works. On the South Platte specifically, I lean toward tan in bright light because it silhouettes cleanly against the green-blue water. Royal earns its keep on overcast days or when I want a more aggressive presentation.
The foam body is non-negotiable — that’s the whole point of the fly. It’s what separates this pattern from deer-hair or dubbed hopper patterns and what makes it a viable indicator platform rather than just a dry fly.
The Dropper Nymphs: RS2, Barr’s Emerger, Zebra Midge
The Chubby is the platform. The nymph is where you’re catching most of your fish. Through the terrestrial season on this river, the dropper options break down into three patterns that cover the realistic feeding activity below the surface.
RS2 (#20–22): The RS2 was designed in Colorado for Colorado tailwater, and it shows. It sits in the film or just below it, covering both the emerging Baetis nymph and suspended midge stages. Gray is the year-round color — it’s the one to carry if you carry one. It’s a light, minimally-weighted fly, which means you may need to add a small split shot above it to keep it in the strike zone — or let the Chubby suspend it higher in the water column if there’s feeding activity near the surface.
Barr’s Emerger (#18–20): John Barr designed this fly for exactly the kind of fishing Cheesman and Deckers produce — subsurface emerger imitation for fish feeding in the seam between rising and holding. Save this one for the shoulder seasons — Baetis run March–May and again September–November, so it’s a September swap rather than an August staple. The trailing shuck profile reads as a vulnerable, partially-hatched insect, which is the stage fish eat most aggressively.
Zebra Midge (#18–22): These tailwaters are midge factories twelve months a year. Even at the height of hopper and caddis season, trout are still eating Chironomidae pupae subsurface. A Zebra Midge in black or red gives you that ascending pupa profile at depth. It’s my default dropper when I can’t get a read on what’s happening below the surface — it’s almost always in the mix somewhere.
Quick reference — dropper selection by condition:
| Condition | Top Dropper Choice | Size |
|---|---|---|
| Clear water, sunny | RS2 (gray) | #20–22 |
| Overcast, September Baetis | Barr’s Emerger (olive/gray) | #18–20 |
| Any condition, no visible hatch | Zebra Midge (black or red) | #20–24 |
| Stained/higher flows | Zebra Midge (red) or heavier RS2 | #20–22 |
Tippet Length and Diameter Off the Bend
This is where most people set the rig up wrong, and it costs them fish.
Tippet length: 12 to 18 inches from the bend of the Chubby to your dropper fly. I fish 14–16 inches as a default on the flat water at Deckers. Shorter than 12 inches and the nymph rides too high — it’s chasing the surface film instead of sitting in the feeding zone a foot or so down. Longer than 18 inches and you lose the indicator sensitivity that makes the Chubby worth using; the take travels up too much slack before it shows on the fly.
In faster water or deeper runs, you can extend to 24 inches and add a small split shot (#6 or #4) to the tippet above the nymph to drive it down. But in the classic flat tailwater seams at Cheesman and Deckers, 14–16 inches is where I stay.
Tippet diameter: 6X fluorocarbon from the Chubby’s bend to the dropper, dropping to 7X when they get picky or you go below #22. The Rule of 3 puts a size-20 hook at 6–7X and that’s about right here. The foam body carries a heavy dropper without being dragged under, so you don’t need to over-build the connection — you need it thin enough that the fish doesn’t read it.
Why fluorocarbon for the dropper section: Fluoro sinks, which helps the dropper get into the feeding lane rather than riding the surface. It’s also less visible underwater — on pressured Cheesman fish that have seen every nymph configuration in existence, that matters. Save the nylon for the dry-fly section of your leader.
Connection point: Tie directly off the bend of the Chubby with an improved clinch or Davy knot. The Davy knot burns almost no tippet — important when you’re down to the last few inches of a 6X spool. Either knot seats cleanly on a small wire hook.
My take
The 12-to-18-inch dropper is the setting most people skip past because it sounds arbitrary. It’s not. I’ve shortened it when fish were sipping emergers in the film, lengthened it when they were stacked on the bottom in deeper slots. But if I had to pick one measurement and fish it all day without adjusting, 14 inches of 6X fluoro off the Chubby’s bend puts the nymph in the right zone for the majority of the water I fish between the dam and Deckers. Start there. Move from there when the fish tell you to.
Reading the Chubby as a Strike Indicator on Flat Tailwater
This is the part of the rig people undervalue, and it’s genuinely the reason to use the Chubby over a smaller attractor dry. That foam body sits in the film consistently — no gradual sinking, no floatant re-application every few casts, no change in buoyancy as the morning goes on. You get a stable platform that reads current the same way from the first cast to the last.
On flat tailwater, takes are not always violent. A big brown running up to grab a hopper will slam a Chubby and you’ll know it. But the dropper takes — a trout sipping an RS2 two feet down — often show as nothing more than a subtle dip, a slight pause in the drift, or the fly moving upstream against the current flow. Those signals disappear if your indicator is sinking slightly, tilted, or sitting unevenly in chop. A foam Chubby in #12–14 reads those takes cleanly because it holds the same attitude in the water consistently.
What to watch for:
- Dip or hesitation: The Chubby drops slightly but doesn’t pull under — most common take signature on flat water. Set immediately.
- Upstream movement: The fly stops drifting downstream and moves slightly against current. A fish has the nymph and is turning.
- Twitch or dart sideways: The fly moves laterally without wind or current causing it. Fish has the dropper and is moving.
- Full pull-under: A fish ate the Chubby itself. Also happens. Set hard.
The flat, low-gradient sections of tailwater demand a softer, more attentive set than pocket water. Lift, don’t yank — these are light tippets.
Presentation on Flat Tailwater Current
The terrestrial feeding window on the South Platte corridor runs from late July through September, and it’s bank-oriented. Hoppers and beetles enter the water from streamside vegetation — willows, grass, sage. That means your productive water is the bank seam, the foam lane close to the grass line, and the edge of any undercut. Fishing the Chubby dropper rig mid-river over open riffles is mostly wasted effort during that window.
Wind accelerates everything. An afternoon breeze shaking the bank grass blows real hoppers onto the water and gets fish looking up. Concentrate your hopper-dropper time in the afternoon on windy days, working the downwind bank where insects are being pushed. Calm, bright mornings are better served with a euro rig or straight indicator setup for midge work.
Mend aggressively on the first five feet of the drift. Flat tailwater current looks uniform but has micro-seams that pull on the leader. An upstream mend immediately after the cast buys a longer drag-free window. After the mend, hands still, watch the Chubby.
For casting the rig, a 9-foot 5-weight is the standard setup — a medium-fast action that handles the slightly weighted two-fly combo without collapsing on the delivery. A 9’6” 5-weight gives you more reach for mending on longer drifts and is worth considering if you fish a lot of this style.
When the Chubby Dropper Outperforms Euro Nymphing
Euro nymphing is about half my fishing — it and a standard line split my season roughly evenly. But the Chubby dropper rig earns its place in two specific situations where euro becomes the wrong tool.
First: when fish are actively looking up. If you can see fish rising or watching the surface, or if you’re seeing real hoppers blowing onto the bank seams, a dry fly in the equation changes the game. Euro keeps you subsurface. The Chubby dropper covers both lanes at once.
Second: distance. Euro nymphing is a close-range game — effective inside 30 feet, excellent inside 20. When fish are rising or feeding in flat water beyond that distance, or when you want to cover a long glide from a single position without wading into the fish’s feeding lane, the Chubby dropper on a standard 9-foot rod and floating line gets you there.
The two approaches complement each other. I’ll typically euro the morning when fish are deep and eating midges, and switch to the Chubby rig when afternoon wind starts and fish start looking toward the surface.
Frequently Asked Questions
Q: What size Chubby Chernobyl is best for the South Platte in late summer? Size #12–14 is the standard starting point on the South Platte at Deckers and Cheesman Canyon — bigger than that and you’ll draw refusals on pressured tailwater fish. A #10 floats a heavier dropper better early in the season; drop to #12 or #14 as water clarity increases or fish become more selective toward late summer.
Q: How long should the tippet be between a Chubby Chernobyl and the dropper nymph? 12 to 18 inches is the functional range, and the shorter end is the default for flat tailwater. Shorter robs the nymph of depth; longer reduces your ability to read subtle takes on the foam body. Use 6X fluorocarbon for most conditions, 7X when they refuse, 7X when the water is low and clear or the dropper hook is #22 or smaller.
Q: What nymphs work best as a dropper under a Chubby Chernobyl on the South Platte? RS2 (#20–22) in gray or olive, Barr’s Emerger (#18–20) in BWO colors, and Zebra Midge (#18–22) in black or red are the three most productive options. The Zebra Midge covers midge-pupa feeding that happens year-round regardless of the surface hatch. RS2 covers Baetis activity. Barr’s Emerger is the pick when fish are keyed on emerging mayflies just below the film.
Q: Can you fish a Chubby Chernobyl dry-dropper rig with a euro nymphing setup? Not effectively — the Chubby rig requires a floating line to manage the dry fly and mend on long drifts. It’s a standard 9-foot 5-weight setup. Euro nymphing uses a specialized leader without a floating fly line and is optimized for close-range, high-stick subsurface presentation. They’re complementary methods, not interchangeable ones.
Early August is exactly when this river has fully changed character — the midge-only mindset of winter and spring gives way to opportunistic fish that will move for a big profile and a well-placed nymph hanging below it. Get the dropper length right, keep the tippet honest, and focus your presentations on bank seams when the afternoon wind picks up. The Chubby is doing two jobs at once. Let it.
Next: when the fish stop looking up, euro nymphing the same water is the other half of this river.