Choosing a floating fly line may seem like a simple task. Pick your favorite brand or color and be on your way, right? Not so easy. There are a few key factors to consider when choosing a fly line including taper profiles, taper lengths, and applications. While there are countless fly lines on the market, we’ll focus on floating fly lines for a variety of single-handed applications.
Tapers
To start, we’ll break floating fly lines into two broad categories, Double Taper and Weight Forward taper profiles. We’ll consider them from a fundamental standpoint and make a few generalizations along the way due to the number of offerings on the market.
Double Taper (DT) Profiles
Double Taper (DT) fly lines are built symmetrically, with a taper on each end and an even diameter line between the tapers. Double taper profiles are often preferred by dry fly anglers for a variety of reasons. When roll casting a DT line, the weighted “belly” helps transfer the energy of a cast through the line to your leader with ease. The weighted belly that makes DT profiles better for long-distance roll casting will also enhance mending ability. When you mend your line, the force applied through your rod tip is more easily transferred through the entirety of the line due to its constant diameter.
As you’ll see below, Weight Forward lines have less mass in the running line which makes it harder to transfer the energy of a roll cast through a longer length of line to the head. Lastly, the even mass distribution will help maintain large loops throughout the cast. Large loops make it the perfect presentation choice for dry flies.
An added benefit that this profile provides is that you essentially get two lines in one! You can simply flip the line around and fish the end that was previously attached to your backing. This is a great choice for anglers looking to get a little more out of their lines and money.
Weight Forward (WF) Taper Profiles
Weight Forward (WF) floating fly lines are defined by compact, weighted, shooting heads. Behind the shooting head that contains a majority of the line’s mass is a length of thinner running line. Once the shooting head is beyond your rod tip, the thinner running line will experience less friction as it passes through your guides as compared to a double taper line that has a constant, thicker diameter throughout the entirety of the line. Less friction means that the line’s shooting head will travel further resulting in longer casts than a double taper of the same weight.
When casting at short ranges, a WF fly line will act much like a DT. This is due to the shooting head diameter being similar to the belly of a DT line. Once you have cast the entire shooting head past your rod tip, the true benefits of casting a WF line become apparent as the running line effortlessly passes through your guides. Many anglers prefer WF fly lines for larger bodies of water for this reason. An added benefit is that the compact, weighted shooting head can help punch a cast through the stiffest winds.
Taper Length
Once you have decided upon your taper profile, Double or Weight Forward, the next factor to consider is taper length.  The length of the front taper on either type of line will have an effect on how your flies are presented. A longer, thinner front taper will help delicately present a dry fly while a short front taper will cast more aggressively and help turn over larger patterns.
Long Front Tapers
The Scientific Anglers Amplitude Trout WF Line is a great example of an elongated front taper. This line is designed to help deliver small dries delicately and handle a variety of other common trout fishing scenarios.
Short Front Tapers
The Scientific Angler Amplitude MPX WF Line pictured below is a great example of a shorter front taper. This line has a slightly more aggressive front taper that helps turn over larger nymph rigs, streamers, and poppers while still maintaining the ability to deliver a dry when a hatch starts to pop off.
Rear Tapers
Weight Forward lines also have rear tapers that come into play (or two in the case of compound tapers, a conversation for another day). Rear taper profile and taper length each have an effect on casting and mending. An elongated rear taper helps maintain stability while casting since the mass of the head is more evenly distributed. The same goes for mending. Having the mass of the head spread out over a longer length reduces the typical amount of running line that you would have to mend.
As you can see in the two diagrams above, the SA Amplitude Trout line has a head length of nearly 60′, with a majority of that profile being the rear tape where the SA Amplitude MPX has a head length of about 40’. This means when you mend the SA Amplitude Trout Line with 60’ beyond your rod tip, you will still be mending the heavier head of the line which transfers energy more efficiently. In the same scenario with 60’ of line beyond your rod tip with the SA Amplitude MPX line, you would be mending 20’ of the lighter running line first which lacks the ability to adequately move the heavier head.
You might be wondering, why even bother with short, aggressive WF tapers then? Great question! These lines are great for turning over larger patterns think streamers and poppers and when you need to punch one out there through a stiff breeze. These lines can be picked up and cast quickly. Â For these reasons, nearly all warm water fly lines are made in aggressively tapered weight forward profiles. The Scientific Anglers Amplitude Grand Slam designed for bonefish, permit, and tarpon is a great all-around tropical line.
There will always be some sort of compromise when it comes to choosing a line. Casting distance, shooting ability, accuracy, presentation, and ease of mending are all characteristics to account for. There is no one correct way to catch a fish so try a few different profiles and taper combinations to see what works best for you. Considering your fishing style and application is the final key to choosing the proper fly line. Understanding how to apply the different taper profiles and lengths to different rods and scenarios will open a new world of angling opportunities.
Application
Now that we have covered the technical side of fly lines, we’ll look at another aspect that is equally important, application. This includes the type of rod you will be fishing (in terms of flex and composition), the water you will be covering, and your most common fishing scenarios (i.e. dry fly, nymphs, streamers, & poppers).
Fiberglass Rods
If you are fishing a slower action fiberglass rod, having a fly line that matches your rod weight is crucial. Over-lining a fiberglass rod creates a clunky setup that can be difficult to cast. An over-lined glass rod makes properly presenting your flies a chore, defeating the purpose of fishing it! Your best bet is to choose a line that is built to the exact weights specified by AFTM standards. Watch out, as many modern floating fly lines are designed to be a half or a full size heavy. Additionally, when fishing with a glass rod, considering a double taper would be an excellent choice. The mass of the belly on double taper lines help enhance the pleasure of casting slow action rods.