Fly Lines

Up into the 1800's most of the line attached to a rod was horse hair that was braided or twisted. By reducing some fibers, a tapered leader could be produced and usually constructed to a 10 feet in length. In the early 1800's, line makers began mixing silk with the horse hair to increase strength and by the mid-1800's, lines were primarily oil-soaked silk woven with a hollow core. These woven silk lines were the mainstay for almost 100 years. Dupont invented nylon in 1938 and by 1950, nylon was the woven material for the flyline with a hollow core so that the line would float. Today, PVC coatings are applied to braided nylon or dacron lines to achieve floatation or sinkability. Either air vacuoles or bits of tungsten are added to the PVC coating to give the line a certain density.

Fly Lines generally fall within three categories: Floating, Sinking, and Sink-tip. The main principals of all flylines and how they work are: Taper, Density, Density Distribution, the Line core, and the Finish formulations. Each of these principals determine how a fly line will respond to the rod action and the caster's performance. These principals are also manipulated by the manufacturers to determine line types for various fishing opportunities. For instance, a longer head length would be designed for extra casting distance in Steelhead lines than a comparatively smaller head length in the Spring Creek lines. In addition, a longer front taper would provide a more delicate presentation on dry flys while a shorter front taper would be required for turning over heavier streamers and nymphs.

Anatomy of a Fly Line

Fly Lines are basically broken into two areas: the Head, which comprises the weighted body as well as the front and rear tapers; and the Running Line, which extends behind the head and allows the line to "shoot" upon casting. Fly lines also have a short tip from 6 inches to a foot in length. A short, thick tip will turn over faster than a longer thinner one. The thinner tips being required for delicate presentations.
The Front Taper plays a critical role in the turnover of the fly. A long taper will create a slow turnover for delicate presentations. The Body, also known as the "Belly" of the fly line head, represents the weight of the line and will store the energy of the cast. The Rear Taper produces the energy transition of the cast. A long Rear Taper will allow the line to cast straighter whereas a shorter Rear Taper will allow you to pick up the line more easily from the water.

Tapers

There are basically four types of tapers: Level, Weight Forward, Double Taper, and Shooting Head. The Level taper was the historic fly line of past, used as a floating line. It had real limitations in casting abilities and is not used very much any more. The level tapers are seen more frequently now within the shooting lines used in conjunction with shooting heads. The level taper offers an ability to flow easily through the guides propelled by the weighted head due to it's smaller diameter. The Weight Forward taper is used in the majority of lines today. They cast farther than Double Tapers since the smaller diameter running line allows much less resistance through the guides. Double Taper lines work well within 15' to 50' casts, particularly with roll casts. A marketing ploy used with Double Tapers is that the line can be reversed at some point to extend the life of the line. However, rarely do you encounter anyone that recognizes the appropriate time to do this. Many of the floating lines available come in either Weight Forward or Double Taper. Within the shorter casting distances touted by the Double Taper, there is no difference in casting performance when using the Weight Forward as they present the same taper design. The Shooting Head is designed for casting long distances. It was originally developed by steelheaders fishing the larger rivers. The heads come in either floating or sinking varieties. Since the heads are short and with a heavy front taper, the lines do not have a delicate presentation.

Density

The density determines the weight of the line. This weight plays an important part in how the line "loads" the rod in casting. The AFTMA (American Fishing Tackle Manufacturers Assoication) has defined lines by determining the weight of the line in it's first 30 feet. Generally the heavier the line, the further it casts. Increasing the density will also determine whether the line floats or sinks.

Density Distribution

The Density Distribution determines how the line will behave in the water. This is particularly noticeable within your sinking lines. The Uniform Sinking lines utilize a density distribution in which the forward portion of the line will sink faster than the body. This distribution allows the line to extend itself straight rather than with a "belly" as a sinking line without density distribution will do.

Line Core and Finish Formulations

Most fly lines use a braided core of nylon or dacron. Some lines utilize monofilament. These cores are surrounded by a coating of polyvinylchloride (PVC) that can contain microscopic air vacuoles for floating lines or flecks of tungsten or lead for sinking lines. If the line core is relatively stiff, as with monofilament, the line will tend to cast well for long casts particularly in windy conditions. The softer cores, dacron or nylon, work well on shorter casts in cooler conditions and where shorter casts are required with delicate presentations. The Finish Formulation applied to the surface of the fly line can increase the casting distances. A harder smooth surface with some lubrication applied will help in getting increased distance to the casts.