Fly Lines & Backing
Fly lines come in different lengths, weights, tapers, colors, and more! It can all seem daunting at first, but the mystery of fly lines can be unraveled somewhat by first learning their key aspects. Buying the wrong line can both hurt the performance of your rod and your overall success rate, so you must choose wisely.
Fly Line Coating/Core
Fly lines have a core and an outer coating. Depending on the line's intended usage, the core will be a soft material like braided nylon or a stiffer one like monofilament. Around the core is the coating, which usually is a type of plastic. While the special coating of a floating line contains tiny air bubbles to help it float, a sinking line is thinner and has material like powdered tungsten in the coating to help increase density so it will go below the surface.
​
The temperature has a big impact on line selection. Hot weather can make some lines sticky/gummy, while cold weather can make others overly stiff and challenging to manage. Fly line manufacturers make lines with stiffer cores and harder coatings specifically for hot, humid climates (often referred to as "tropical" lines). However, most fly lines are more supple and work well for the average weather conditions many anglers face.
Line Weights
Unlike the lines used in conventional fishing, fly line is rated by physical weight rather than breaking strength. Lines have the first 30 feet weighed in grains (minus the short level tip section) and are assigned a numbered "weight" rating based on this measurement. This system was first implemented long ago and is maintained by the American Fly Fishing Trade Association (AFFTA) to provide a standard baseline of line weights. For example, this system would classify a floating line weighing 134-146 grains in its first 30 feet as a 5-weight line.
​
With all of this said, the system mentioned above is not always closely followed. Some fly lines actually weigh more than their corresponding weight range indicates. For example, the first 30 feet of a specific 5-weight line may weigh 160 grains, seemingly classifying it as a 6-weight line! These lines are made heavier to make it easier for today's faster, stiffer rods to cast them more easily.
Line Length/Taper
(These images courtesy of RIO Products)
Fly lines typically span 80–100 feet but also come at even greater lengths. Each line has a specific design that gives it the right properties for casting and performance. There are two main tapers of fly lines, as explained below.
​
The weight-forward (WF) taper is the most common. This taper puts the thick, heavy section in the forward portion of the fly line. WF lines are popular because they are great for many fly fishing situations and conditions. However, there are also many specialized weight-forward taper configurations if you want to grab a line that's optimized for the exact type of fishing you do.
​
A double-tapered (DT) line has the taper extending from the center out to both sides. Since these lines are the same on each end, they can be reversed if one end gets worn out. DT lines are good choices for shorter casts and delicate presentations.
Floating Lines
Floating fly lines are very prolific in the sport of fly fishing. They are generally easy to cast and allow for easy line management since the line doesn't sink. However, just because these lines float doesn't mean they are only good with flies that float. If the fish aren't too deep, a floating line and a wet fly may be all you need. Like all lines, the prices vary, but the better offerings are often touted as higher floating than others. An example of line labeling for a 5-weight floating line would appear as "WF5F," which stands for "Weight Forward 5 weight Floating."
Sinking Lines
The two types of sinking lines are full sinking, where the whole line sinks (great for keeping flies very deep), and sink-tip lines, where only a short portion of the line sinks, allowing the angler to fish deeper while still offering excellent control of the floating portion. Every sinking line is made to descend at a certain speed and carries a particular sink rating.
​
Like floating lines, a sinking line's advertised grain and line weight help match it to a particular rod, but its density determines how fast it sinks. There can be a 200-grain sinking line that sinks slow, yet another 200-grain sinking line that sinks fast. Although their grain weights are the same, the lines' different densities affect their sink rates. Manufacturers design lines like this so you can own multiple lines with varying sink rates for just one rod size.
Sinking lines are usually given a name/number rating to show their sink rates. The inches-per-second (IPS) at which these lines sink are also often shown. Starting out, a line labeled "intermediate" sinks very slowly at maybe 1–2 IPS. As you move past the intermediate line rating, lines start sinking faster and will usually be classified by a name like "type" and a number. For example, a type 3 line may sink at around 3 IPS, a type 5 around 5 IPS, and so on. The exact sink rate can vary, however, so it's best to look at the IPS range listed by the manufacturer to be sure.
Backing
Backing is usually a thin, low-stretch braided line that goes onto the reel first, and the fly line is tied to it. Backing serves two purposes. First, it bulks up the spool diameter allowing for a faster retrieve ratio. Second, since fly lines are so short, backing gives you many yards of extra line capacity to work with should a strong fish make a long run that exceeds the length of the actual fly line. Two main varieties are available and are rated by the breaking strength.
​
Dacron: Easy to find, easy to handle, and relatively affordable, dacron is a popular choice for many situations. You'll find this backing widely available in 20 and 30-pound tests.
​
Gel Spun/Spectra: This type of backing is usually pricier but has a very thin diameter compared to the rated poundage. The narrow diameter of gel spun/spectra gives you the option to fit more and stronger backing onto your reel. This makes it popular with anglers who target big, long-running fish and need that advantage.
