A Beginner's Guide to Fly Lines

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Fly line is arguably our most important piece of equipment, as it can dictate the effectiveness of both casting and presentation–two critical elements of catching fish. It can be helpful to think of fly lines like golf clubs–they’re purpose-built to perform specific tasks. Throwing the same line for every fishing application is like playing 18 holes with only a 9-iron. You can certainly do it, but it’s inefficient, uncomfortable, and largely ineffective. The sheer volume of modern fly lines, however, can be intimidating to anglers who don’t quite understand all their characteristics. Developing a fundamental understanding of the main variables associated with line design can help us make informed purchases, maximizing our time on the water as well as our budgets. 

Grain Weight

In fly casting, the rod is loaded by the weight of the line. Thus, the line’s weight, relative to the stiffness of the rod, is a key factor in determining casting performance. Light lines fail to adequately load stiff rods, and heavy lines overburden lighter rods. Peak performance, then, is achieved when our lines and rods are properly paired. To do this, we must understand how line and rod weights are categorized.  

The weight of a fly line is measured in “grains.” Every line is given a grain weight, which indicates the weight of its first 30 feet–which is about the length of line most anglers will carry out of the rod tip while making casts. Rods are given their own weight classifications which indicate stiffness, usually ranging from very light 1-weight rods all the way up to 12- or even 14-weight. The American Fly Fishing Trade Association provides guidance for pairing lines with rods by recommending grain ranges for each size fly rod. Typically, 5-weight rods pair well with 140 grain lines, 6-weight rods with 160 grain lines, 7-weight rods with 185 grain lines, and so on. These guidelines, however, are merely starting points as most rods can effectively handle a range of line weights. Modern lines, as a result, often fall outside the standard ranges in order to elicit specific performance benefits. Scientific Anglers’ Amplitude Bass Bug lines, for example, are built two full weights heavier than the recommended grain range to load rods deeper into the blank, store more energy, and throw heavier or wind-resistant flies. They also allow anglers to make casts with less line out of the tip, minimizing false casts in between retrieves when stripping streamers. 

A line’s weight also determines the size of the flies it can deliver. As flies get bigger, heavier, or more wind-resistant, the mass of the line must increase as well. Lighter lines that adhere more closely to traditional grain windows, like Scientific Anglers’ Amplitude Trout line, will superbly cast small streamers, nymphs, and dry flies, but would struggle mightily with foot-long musky streamers. Thus, we have lines like Cortland’s 10wt Pike Musky Line, which is beefed up to 380 grains (100 grains heavier than a typical 10-weight line) to launch giant flies to apex predators. It’s safe to say that grain weight should be near the top of our list of variables to consider when choosing a fly line to ensure our lines are suited to our rods as well as the size of the flies we plan to cast. 

Head Length

Most lines are designed in a “weight-forward” configuration, with thin running lines that transition into thicker, heavier front ends or “heads.” Most heads, which include the front taper, belly, and rear taper, measure between 30 and 60 feet in length, with both ends of that spectrum providing their own advantages and disadvantages. Long heads provide stability while overhead casting, allowing anglers to carry more line out of the rod tip for longer casts and improved accuracy. Their longer sections of thick diameter line also assist with line control for long-distance mending and improved roll casting. The Anadro Indicator line from Scientific Anglers features a rear taper of nearly 30 feet to extend the head and take advantage of these benefits. 

Shorter heads, on the other hand, exit the rod tip in fewer false casts, lending themselves to quick shots of short or moderate distances–a great feature for banging the bank from a drift boat or sight casting to moving targets like bonefish. Their shorter heads of 30 to 40 feet also punch through wind better than longer heads, a key consideration for many anglers. The Sonar Titan Sink Tip line from Scientific Anglers boasts a short, powerful head to rapidly pitch oversized streamers to a variety of predatory species. 

Taper

Taper describes the head’s shape and how it transitions into the thin running line in both the front and rear. The length of the rear taper largely determines the overall length of the head, and dictates casting distance, line control, and accuracy as previously outlined. The front taper’s length determines both presentation as well as the size of fly a line can carry and effectively turn over. Longer front tapers allow energy to gradually dissipate through the line, to the leader, to the fly, allowing for soft and delicate presentations. Scientific Anglers’ Trout Taper line features a 10-foot compound front taper to slowly unroll and fall lightly to the water. 

Short front tapers, when paired with short or stiff leaders, allow energy to transfer quickly from the line into large or air resistant flies, helping to turn them over. Cortland’s Bass Specialty Series line employs an aggressive head design with a 3-foot front taper to drive bulky bass flies to the target. Heavy heads with short tapers are excellent for casting massive streamers for bass, pike and musky, but they do have a few drawbacks. Specifically, they tend to lack delicacy, landing with a thud–no problem for many warmwater predators, but less than ideal for spooky fish. 

While many lines are built to address specific species or situations, it’s important to note that plenty of “general purpose” lines are also available, like Airflo’s Superflo Ridge 2.0 Universal Taper or Orvis’s $49 Clearwater Fly Line. They are fantastic starter lines for anglers unsure of the exact types of fishing they may encounter, or for those on tighter budgets. These models usually feature middle-of-the-road head lengths, weights, and tapers to handle wide ranges of flies and on-water scenarios, however they are rarely the best choice for any one application.

Density

Fly lines are manufactured to either sink or float depending on their composition. Sinking lines have powdered tungsten blended into their coatings to make them sink. Floating lines do not, as they sit atop the water’s film and work well for a variety of applications. They are necessary for buoyant topwater flies, but they’re also effective for sub-surface presentations with longer leaders and weighted flies in shallower water. Slow-sinking lines are referred to as “intermediate lines,” and they sink at a rate between 1 and 2 inches per second. Intermediate lines are excellent choices for presenting just below the water’s surface or hovering flies mid-water column. 

Faster-sinking lines can present flies in deep or fast-moving water. They can also be used to burn streamers in shallow water with aggressive retrieves to trigger reactive responses. Line manufacturers typically label their lines using a “type” system that indicates how many inches per second the line sinks. For instance, full-sinking type 2, type 3, and type 5 lines sink at 2, 3, and 5 inches per second respectively along their entire length. Many lines, however, are designed with multiple densities to meet the demands of specific situations.

Sink tip lines, for example, combine a floating or intermediate line with a sinking head or tip section. Cortland’s Bass Intermediate Line features a 26-foot intermediate tip in front of a floating running line. This combination is an excellent choice for wading small to medium-sized rivers, as the intermediate tip pulls flies down below the surface, while the floating running line sits on top to avoid tangles. Cheeky Fishing’s All Day Sink Tip line features a 15-foot, type 6 sink tip in front of floating running line, to drive flies down a bit faster. Likewise, Airflo’s Superflo Ridge 2.0 Streamer Max Short has a 22-foot fast-sinking head, a 10-foot intermediate sinking “haul zone,” and floating running line.

There’s also an array of “triple-density” lines on the market that incorporate three different densities at different points on the line. These can help anglers maintain a more direct line of contact with their flies by eliminating big bellies of line in deep water. The Sonar Titan 3D series of lines from Scientific Anglers offers triple-density lines in a variety of combinations to cover every portion of even the deepest water column. 

And all of this is to say nothing of Spey and Skagit lines for two-handed rods, and specialty lines for saltwater and stillwater and beyond. 

Choosing a Line

Fly lines are a significant investment for anglers of all levels of experience. As such, it’s beneficial to learn about their characteristics to better utilize the ones we already have and make informed purchases in the future. Anglers should consider grain weight, head length, taper, and density among other variables when investigating new lines for their arsenal. That said, it’s never a bad idea to chat with the professionals at your local fly shop before purchasing a line. They possess a vast amount of experience on your local waters as well as a working knowledge of the current brands and models that may fit your needs. The right line can significantly improve our time on the water. 

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