A fly line is a fundamental piece of specialized equipment for the fly fisher. Modern fly lines are made from special polymer materials which are extruded around a core generally of monofiliment or more recently braid. The key difference of the two core materials to the fly fisherman are the stretch and sensitivity factors with monofilament being the material more prone to stretch and less sensitive to the feel of the two. There are applications for both types of fly lines and by in large I trade the sensitive touch of fly lines manufactured on braid for monofilament based fly lines when I am fishing fast because I like  the comfort of some stretch in my fly lines when a fish hits my fast moving flies. When I fish ‘twitchy twitchy’ (i.e static or very slow retrieve) I opt for a braid based line so that I can feel every little touch of a fish. Fly lines are manufactured with the polymer  material extruded over the core in such a way that it can be applied in different thicknesses along the length of the line. More co polymer is applied to the front 30 feet or so of the fly line according to intricate thickness formulas to create what is called the taper of the line. Tapers of various thickness formulas are designed to suit differt types of fly fishing, different types of flies and different desired presentations and invariably you will have to make a compromise in what style of taper suites your application and technique best.  I have listed in the following the fly lines I use and why I use them.

• Fly lines that I use

Fly lines are generally around 90 to 100 feet long and the balance of the fly line beyond the taper is also covered with thin coating of copolymer to produce what is called the running line. There are of course exceptions to the lenght and how the running line is created but they are just that ‘exceptions’ not the rule.

The  head of fly lines is much heavier than regular nylon fishing line and because of its weight it can be used to ‘load a fly rod to achieve a cast.  The loading is created by the casting process and involves bending the fly rod through what is called a casting a stroke so as to load potential energy into the flexible rod.  That energy is released into the fly line when the direction of the travel of the fly rod is brought to a stop on the casting or presentation stroke releasing the stored up potential energy into the fly line. By making a number of forward and backward strokes, called false casts, with an appropriate arc in the travel of the fly line and  well timed stops at the end of each stroke the fly fisher can load an increasing amount of energy into the fly rod (but only to the maximum amount of energy the blank of the fly rod can hold) which ultimately can be released to the fly line.

• Casting a fly line

The weight of a fly line  is not usually spread evenly over the full length of a fly line but is generally in the first 30 feet of a fly line allowing for three basic configurations:

1. Weight forward fly lines have the majority of their weight dispersed throughout the first 30 feet of fly line but with more at the front of that section than at the back. This is the most common configuration of fly line and because of the taper and the long running line is favoured by those wanting to achieve long casts. Within this category there are heaps of specialized tapers designed for slightly different purposes including presentation, turning over big flies or bead head flies, etc. etc..
2. Double taper fly lines are similar to single taper fly lines except that there is a taper at each end of the fly line and generally only around 30 feet of running line in the middle. The running line is generally thicker than the running line in a single taper weight forward line creating the ability to better roll casts. The other advantage of this category fly line is also river fishing oriented. Presentations in rivers tend not to be as long as presentations in open water and consequently by having a double taper fly line the angler really has two fly lines. When the first taper gets worn the fly line can be reversed on the reel.
3. The third type of fly line is generally a single taper with the majority of weight well forward in the taper and a thinner running  line than normal single taper lines. These lines are designed for when distance rather than presentation are the main criteria.

There are also several types of fly lines running from those that float through  lines that sit in the slick (often referred to as slime lines), intermediate lines that sink at between 1.5 to 2.5 inches per second and there are a range of full sink lines that are often referred to a Type 3 through to Type 7. The number refers to the nominal sink rate per second.

There are also fly lines that a are a combination of the above fly line types and floating lines with sink tips, and intermediate lines with full sink tips have become very popular over recent years.

The last variable is the core construction and traditionally the fly line core was a monofilament. More recently braid has been used as the core for many fly lines with the claim to fame being the lack of stretch which is endemic with monofilament core and of course the increased sensitivity that comes with braid cores. The trade of here of course in the stretch and in many types of fly fishing stretch is considered a benefit of monofilament cores.