Ever found yourself wondering just how big a 20 incher really is? Whether you’re shopping for a monitor, a bike, or a pizza, knowing what “20 incher” means can help you make smarter choices and avoid surprises.
Understanding this measurement is key to meeting your needs and expectations. In this article, we’ll break down exactly what a 20 incher refers to, where it matters, and how to ensure it’s the right fit for you.
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Understanding the “20 Incher”: What Is It and Why Is It Popular?
When fly fishers talk about the “20 Incher,” they’re referring to a highly effective stonefly nymph pattern. Despite its name, it’s designed to catch big fish—not to be 20 inches long! The name has become synonymous with a robust, heavily weighted nymph that imitates various stonefly and large mayfly nymphs.
If you’re looking to upgrade your nymph box with something proven to catch trout in fast, deep water, the 20 Incher deserves a top spot. This article explains exactly what the 20 Incher is, how to tie it, how to fish it, and tips to make the most of this classic pattern.
What Is the 20 Incher Stonefly Nymph Pattern?
The 20 Incher is a fly tied to look and behave like a large nymph, mostly imitating stoneflies and some bigger mayflies. It stands out because of its:
- Realistic profile and movement in the water
- Durability (it can handle many fish before it needs replacing)
- Heavy weight, which helps it sink quickly into deep runs
It gets the job done whether you’re targeting trout in Western tailwaters, Rocky Mountain freestones, or even steelhead in bigger rivers.
Why the 20 Incher Works
- Size and Weight: Most aquatic insects trout feed on are larger than many people realize. The 20 Incher represents this big meal.
- General Appearance: Its “buggy” look and peacock herl body appeal to trout, even if it isn’t a perfect match for anything specific.
- Versatility: By tweaking color and size, the 20 Incher can mimic several large nymphs.
Anatomy of the 20 Incher
Before tying or fishing it, it helps to know what goes into this fly:
- Hook: Usually a #8–14 heavy-wire nymph hook for strength
- Bead Head: Often brass or tungsten to add weight
- Lead Wire: Wrapped around the hook shank for additional weight
- Tail: Brown goose biots, creating lifelike split tails
- Body: Peacock herl, offering a natural sheen and bugginess
- Ribbing: Fine copper wire for durability and segmentation
- Wing Case: Dark turkey, goose, or synthetic material, giving a true nymph look
- Thorax: Peacock herl, denser and heavier than the body
- Legs: More goose biots or rubber/synthetic legs for lifelike movement
How to Tie the 20 Incher: Step-by-Step
Tying the 20 Incher is straightforward, even for newcomers with basic fly tying experience. Here’s a simple step-by-step process:
1. Prepare the Hook and Weight
- Slide a bead onto the hook.
- Secure the hook in the vise.
- Wrap lead wire around the shank (about 10-20 wraps) behind the bead.
2. Attach Thread and Tail
- Start your thread behind the bead.
- Attach two goose biots on either side to form the tail. Split them using your thread to create a natural-looking forked appearance.
3. Form the Body
- Tie in copper wire at the tail—this will be your rib.
- Tie in several peacock herls.
- Wrap the peacock herl up the body to about two-thirds of the way up the shank.
- Secure with thread.
4. Rib the Body
- Wrap your copper wire through the peacock herl in open spirals to reinforce the body.
- Tie off and trim excess wire.
5. Create Wing Case and Thorax
- Lay down a strip of turkey or alternative wing case material over the top of the body.
- Tie in additional goose biots or synthetic legs on each side.
- Build a thorax with more peacock herl.
- Pull the wing case over the top and tie it down.
6. Finish
- Add a few whip finishes behind the bead.
- Apply head cement for extra durability.
Tips for Success:
- Keep proportions balanced: Don’t skimp on the thorax or the number of biots for tails/legs—these make the fly look alive.
- Use quality materials: Strong wire and robust herl pay off after fighting tough fish.
Techniques for Fishing the 20 Incher
The 20 Incher shines when fished deep and slow. Here’s how to maximize your catch rate:
1. Dead Drift Under an Indicator
- Rig it under a strike indicator and let it drift naturally with the current.
- Add split shot if the fly isn’t ticking the bottom.
2. As the Top Fly in a Nymph Rig
- The 20 Incher works well as an anchor—its weight gets other, smaller flies into the fish zone.
- Use a lighter, more imitative nymph as a dropper behind it.
3. High-Stick Nymphing
- Use a short line and keep the rod tip high for maximum control.
4. Steelhead Fishing
- The beefy profile of the 20 Incher attracts steelhead in addition to big trout.
Where and When to Use the 20 Incher
The beauty of the 20 Incher is its versatility.
Ideal Waters
- Rocky mountain freestone rivers
- Tailwaters with healthy stonefly or mayfly communities
- Fast, deep runs where getting down quickly is essential
Best Times
- Spring and early summer, during stonefly and large mayfly hatches
- Anytime bugs are moving and fish are feeding deep
- As a searching pattern when you’re not sure what the fish want
Benefits of Adding the 20 Incher to Your Fly Box
- Catches Big Fish: Its size and weight are like ringing a dinner bell for trout.
- Easy to Tie: Once you learn, you can churn out a dozen in an hour.
- Durable: Survives multiple hookups, rocks, and snags.
- Customizable: Change bead color, body material, or use lead-free wire for regulations.
- Proven Track Record: Anglers across North America swear by this pattern.
Challenges and How to Overcome Them
1. Getting the Sink Rate Right
- If your 20 Incher isn’t ticking bottom, add split shot or use a heavier bead/tungsten version.
2. Durability of Peacock Herl
- Counterwrap with wire carefully to reinforce.
- Consider using synthetic substitutes for even more durability.
3. Tying with Biots
- Goose biots can be tricky to split and keep aligned. Use a dubbing needle to hold them in place while tying.
4. Hooking Losses
- Big patterns need sharp hooks; always keep your hooks honed.
Practical Tips for Tying and Fishing
- Practice With Cheaper Materials First: Don’t waste your best herl or biots while you’re perfecting technique.
- Vary Sizes: Tie some #8 for big stonefly hatches, and #14 for picky fish or shallower water.
- Try Different Colors: Brown, black, and olive can all be effective.
- Store Properly: Keep your finished flies in a waterproof, compartmentalized box to prevent damage and rust.
- Sharpen Your Hooks: Check your hook points before each outing. The heavy fly can dull hooks faster than light ones.
Cost Tips: Saving Money on Tying and Buying
- Buy Materials in Bulk: Goose biots, peacock herl, and beads are cheaper when bought in packs.
- Watch For Sales: Fly shops often put fly tying materials on clearance in the off-season.
- DIY Kits: Some shops sell 20 Incher tying kits for beginners.
- Shipping Considerations: If ordering online, combine items to minimize shipping costs—beads, hooks, and herl are light and inexpensive to ship in bulk.
- Pre-Tied Flies: Buying ready-to-fish 20 Inchers is cost-effective if you don’t tie flies, especially when ordering a dozen or more for discount rates.
Inspiration: The 20 Incher in Action
Anglers report that the 20 Incher shines whenever fish are feeding on big bugs. Whether you’re plugging deep pools or fishing the pockets behind boulders, this pattern can mean the difference between an average day and an epic one. Many successful guides and experts consider it a “confidence fly”—one they always have tied on or in the box.
Frequently Asked Questions (FAQs)
What size hook is best for tying the 20 Incher?
Most anglers tie the 20 Incher on a size 8 to 12 hook, depending on the imitated insect and water conditions. For larger stonefly nymphs, go with size 8; for general prospecting, size 10 or 12 works well.
Can the 20 Incher imitate mayfly nymphs as well as stoneflies?
Yes! While it’s primarily a stonefly imitation, the general profile and “buggy” look fool trout during large mayfly nymph activity as well.
How do I keep the peacock herl body from unraveling?
Reinforce the peacock herl with fine copper wire ribbing. Wrap the wire over the herl in open, even turns to lock it in place. Some tiers also use a drop of head cement for added strength.
Is tungsten necessary for the 20 Incher bead head?
Tungsten beads help the fly sink faster, which is ideal in deep or fast water. However, brass beads work well in shallower streams or when you want a slower sink rate.
What’s the best way to fish the 20 Incher in heavy currents?
Use the 20 Incher as your point/anchor fly in a tandem nymph rig under an indicator. Add split shot if needed. Be sure the fly is drifting just above the bottom, bouncing occasionally to stay in the fish zone.
In Summary
The 20 Incher Stonefly Nymph isn’t just a fly—it’s a proven solution for anglers who want to target big trout and steelhead in demanding conditions. With its heavy weight, lifelike movement, and durable construction, it belongs in every fly box. Learn to tie it, learn to fish it, and you’ll quickly understand why the 20 Incher enjoys legendary status on rivers across North America.
Whether you’re a seasoned tyer or just starting out, bringing the 20 Incher into your arsenal will open up new opportunities and make your time on the water more successful and enjoyable. Happy fishing!