SOME MONTHS AGO A FRIEND RECRUITED ME to teach her how to fly fish, and the first time I put a fly rod in her hands, she cast it more than 100 feet. Impossible? That all depends on the line. In this case, my friend was throwing a 15-foot two-handed rod with a 75-foot level shooting head. All she really had to do was get it all moving and then let go. And yet, despite achieving world-class distances, she would never have been able to catch a fish, because the line—constructed from scraps and lacking a proper taper—would not completely unroll. Though enjoyable to cast, this unconventional setup amounted to little more than a backyard plaything. If nothing else, however, it illustrates the importance of tapering to fly-line performance.

Heavy duty lines “have a very short, abrupt front taper,” says Bruce Richards, product development engineer for 3M/Scientific Anglers. “All the energy rolling down the line is forced into the smaller tip very quickly,” he says, “and that energy has to go somewhere, like into flipping over the bug.” Thus, the shorter a line’s front taper, “the more energy ultimately gets transferred to the fly.” And the more energy the fly receives, the bigger the bug a particular cast can turn over. Other heavy-duty lines, such as Rio’s Nymph and Clouser models, use the same technique in what’s called a “bullet taper” (because it looks like the necking down of a rifle cartridge into the bullet). Depending on where—and over how much distance—the manufacturer places this rapid decrease in line diameter, the strength of the turnover can be controlled.

A generalist fly line splits the difference to avoid being either too hard or too soft when it flips over a fly. Where a precision front taper might spread itself over 8 to 10 feet, and a bass-bug front taper over only 4, your generalist line will taper to a point in 6 to 8 feet—the sweet spot for the widest range of conditions. Lines such as Cortland’s Precision Platinum Trout, Airflo’s Freshwater Tactical, Scientific Anglers’ Mastery Trout, and Orvis’s Wonderline Trout are all generalist tapers.

How much tapering is really going on here? Not much. “To tell the truth, most anglers couldn’t even perceive the actual taper as it happens,” says Rio’s marketing manager and noted Spey-casting authority Simon Gawesworth, “because in some cases the differences in thickness over an inch of line might only amount to the diameter of, say, 8X tippet. Nevertheless, those small changes do affect the physics of the cast, and they definitely add up to make one line very different from another.”

Improving Your Cast

Every angler wants a line to improve his cast, and manufacturers have the same goal. They tweak a line’s casting qualities mostly by altering the length and rear taper of the line’s head. “Belly lengths are a big deal when it comes to casting,” says Cortland’s Dablock. Shorter belly lengths mean shorter overall head lengths (which are easier to cast because you have to carry less in the air). Some beginner lines, such as Scientific Anglers’ Mastery Headstart, have heads only 35 feet long. Shorter head lengths also allow for quick casts when a rapid presentation is desirable. Monic’s GSP Tarpon Fly Line, for example, has a belly only 17 feet long to quickly aerialize enough weight to load the rod.

On the other hand, longer heads are better for distance casting. Rio’s Gawesworth explains that the more line you can false cast in the air, the longer the overall cast will be. “If you start with seventy feet of line in the air and then begin the shoot, that cast is going to go farther than one which starts with only thirty feet in the air.” Some distance-taper lines, like SA’s Mastery Expert Distance or Snowbee’s Extreme Distance, have heads over 70 feet long! Because it can be challenging to carry that long a head with the running line already out of the tip-top, distance lines have very lengthy rear tapers, as well. Transferring energy from a thin running line into a fat weight-forward head is notoriously difficult even for the best casters.

The rear taper has another important role to play besides helping anglers cast farther: “Controlling the line on the water,” says Orvis’s Steve Hemkens. “The thicker that rear taper is, the farther away you can mend line, and the better you’ll roll cast. That’s why many anglers who nymph a lot still use double-taper lines—they always have the tip of their rod on the head, because there’s no running line.”

Of course, most of us fall in between the need for a super-long head and the casting aid of a super-short head. And, while we need some rear taper to work our mends, we’d also like to be able to shoot line—the whole point of using a weight-forward line in the first place. Thus, most lines have total head lengths in the 40- to 50-foot range—a typical fishing distance. “Unfortunately,” says Orvis’s Tim Daughton, a product development specialist, “most anglers pick their lines on the basis of parking- lot casting, and a lot of times, that leads them to a line that casts well with a lot of head out the tip, but that doesn’t fish as well in more reasonable distances.”

The Name Game

The problem Daughton alludes to is far from new. In the 1960s, the American Fishing Tackle Manufacturer’s Association (AFTMA) came up with a system for naming fly lines based on the amount of grains in their first 30 feet, measured from the tip.

(For those keeping score at home, a “grain” weighs 1/7,000th of a pound.) Five-weight lines have around 140 grains in their first 30 feet. Eight-weight lines have about 210 grains, give or take about 10 grains in either direction. Fly-rod manufacturers quickly came out with 5-weight rods, or those meant to cast a 5-weight line.

Much has changed since the 1960s. As new-fangled graphite fly rods grew stiffer and faster, the norms of fly fishing shifted. Very few modern rods bend like their 1960s counterparts with just 30 feet of line out. Of course, most anglers don’t want such slow, flexible rods; fast action is far more desirable these days. However, the moving target that is “fast action” has created an arms race between fly-rod and fly-line manufacturers. “Ultimately,” says Rio’s Gawesworth, “the (weight-based) naming system has become almost completely arbitrary, especially when it comes to fly rods.”

Enter the half-weight-heavy fly line. Because many anglers have difficulty controlling the fastest rods with their rated lines, manufacturers began offering lines which exceeded their grain window by a half line size. The extra weight helps bend faster rods and slows them down, making them more manageable. Rio’s Grand and SA’s Mastery GPX are examples of this half- weight-heavy profile.

Off with Their Heads

Of course, nothing says you have to use a rod with its rated line. Many anglers experiment outside official grain ratings. Shooting-head lines are the best example. A traditional shooting head is a 30 foot section of heavy fly line looped to a very thin monofilament running line. When the angler releases the head, the running line is drawn rapidly out behind it, like a weight- forward line on steroids. To further pump up the action, many anglers use heads that are rated two to three line sizes too heavy. (Thus, on an 8-weight, you throw a 10- or 11-weight shooting head because you get only 30 feet of line weight to load your rod.) The deeper the bend, the farther the head goes, meaning anglers can make 100-foot casts with little backcast room. Basically, these are fly fishing’s version of casting a heavy plug.

The disadvantage of traditional shooting heads is the abrupt transition between running line and head, which causes a nasty hinging effect that is difficult to handle. Manufacturers, seeing an opportunity, came up with “integrated shooting lines,” which have short rear tapers behind a head that blends seamlessly into a running line instead of monofilament, avoiding the loop-to-loop connection and thus aiding control. Further, the skinny running lines of integrated shooting lines are less prone to tangling.

Rio’s Outbound series—popular with saltwater anglers who need to reach breaking fish in a blitz situation–and almost all Jim Teeny lines are examples of integrated shooting tapers.

The Balancing Act

Just as with line chemistry, manufacturers must balance competing factors to make a line that will meet the widest possible range of needs. The biggest factor is angler skill. With a wide variety of people using these lines, manufacturers have to be careful not to fudge by making a line with, for example, too short a head (good for beginners, bad for distance); or not enough rear taper (great for shooting, poor for on-the-water handling). The biggest change in the last few years has come from species-specific naming. In some cases, tapers may be practically identical for, say, pike and bass, but the new naming system helps anglers know precisely what a particular line is calibrated to do—in many ways an improvement over the old line-rating system, which gave anglers minimum guidance.

Though little more than long plastic noodles at their most basic level, modern fly lines are among the most complex pieces of tackle we use. Without them, no matter how impressive our rods, most of us would have little to show for our long hours on the water.

This article originally ran in the May/June 2008 issue of American Angler magazine. To download a PDF copy of the original article (with magazine layout), click here.