Fly Line Basics


Been using the fly line that came with the packaged starter kit you either purchased or were given? Thinking about upgrading? While everyone has an opinion on whether the fly line or the fly rod is the most critical piece of gear to improve on-stream performance, I agree with the fly liners. I believe a high-quality fly line neutralizes the limitations of most entry-level rods since a line with a slick, frictionless surface helps overcome even the most stumbling cast on a midgrade rod. Before you pick your preferred line construction technology, you must understand the basics of type and taper.

At the most fundamental level, fly lines range between 80 and 105 feet long with the typical line being approximately 90 feet – more than you could ever cast. Add the backing to the length, and you should never run out of line given the typical size fish most of us are lucky enough to catch. Obviously, if you go to heaven where every trout is at least 15 pounds (or deal with steelhead or saltwater fishing), you may need more, but it will come from additional backing, not fly line. 

All fly line has a “weight” standardized by the American Fishing Tackle Manufacturers Association. Without getting into the intricate details, it’s simpler to say that there are fifteen weights (wt) with one being the lightest and fifteen being the heaviest. Each has a stock weight, usually in the middle of the defined, acceptable weight range associated with the rating. Therefore, when you buy a four weight line, no matter what its type or configuration, the overall weight is predictable.

The key differences between the types trace to line diameter and how the manufacturer distributes the allowable weight. Line weights one through four are great for small flies. Midrange weights of five to seven are the utility lines good for most situations while anything at eight or above are for large flies, windy conditions or distance casting. What should you use on your rod? Without getting into when to over or under line (using a line different from the recommended weight for the rod), just match the line to the rod. A 4wt rod should use 4wt line. On rods with multiple ratings (3/4, 5/6, etc.), use the higher rating to select the line. Hence, a 5/6 rod should use a 6wt line. Once you know the size line you need, you have two additional choices – floating or sinking.

Most fly lines float. If you consider your last visit to the stream, you know it would be hard to get a drag free drift on a dry fly with a line that consistently pulled the fly underwater. Additionally, you are already familiar with adding a few split shot to the end of your tippet to push streamers or nymphs down the water column to obtain the sinking characteristic required to fish those flies. However, the fly line itself floats on top, ready for the flicks necessary to mend and protect the drift. The variation in floating lines lies in the distribution of the weight along the length with four general choices – weight forward, double taper, shooting head, and level line.

Weight forward describes a line with most of the weight in the first 30 feet followed by a gradual taper to the longer running line section. It is the type of line that should have been included in your entry-level package. By pushing the weight closer to the business end, the line is easier to cast since the heavier weight exercises the rod to store and release of energy during the cast. Remember this formula from high school physics? Force = Mass times Acceleration (f=ma). A weight forward line has more mass (matter) at the front. Higher mass with the acceleration provided by the combination of the rod flex and the “hurry up and stop” push of your forearm produces the force to move the line. 

With more mass at the end, it’s easier to get the cast moving. Beyond getting your cast in the air, being front-loaded is important for windy conditions. The weight makes it easier to punch the appropriately sized fly through a moderate breeze. The disadvantage of weight forward is it is harder to achieve a decent roll cast, but you can overcome that problem through practice and experience. Weight forward lines come in various tapers tailored to either fish or conditions. You can buy bass, trout, saltwater, redfish and other specialty tapers. All the word “specialty” means is the manufacturer rebalanced the weight at the front end with custom tapers to the running line to account for the typical condition associated with the fish or situation. Remember, the manufacturer is dealing with a fixed amount of weight according to the standards, and all they can do is move the weight to stay within the specification. Of course, this is where the manufacturing technology (coating, construction, material) comes into play to achieve additional advantages independent of the weight of the line.

Unlike weight forward, a double taper line places the bulk of the weight in the long middle of the line with an identical short taper to the running line on each end. Its advantage is the smaller business end is lighter and produces less of a splash/disturbance upon landing; critical when dealing with heavily pressured or easily spooked fish. However, since the weight is in the middle, it is harder to cast since more line needs to get into the air than with the weight forward configuration. Novices will have a challenge achieving distance using this type of line. 

A double taper is easier to roll cast and better for nymph fishing. With the weight in the middle, when you bring the rod back for a roll cast, the line is balanced and better positioned for the flick that shoots the fly out. Having a thinner diameter line at the end is better for dry flies and nymphs since you can mend the line easier. A final, minor advantage is it either end works equally well. Once you wear out one end, reverse the line on your reel. Given the quality of today’s fly lines, you will probably never do this since you will find cracks or nicks in the belly of the line mandating retirement to the trash heap before the business end becomes unserviceable.

A shooting head line is a specialty taper that pushes the bulk of the weight into a compressed area at the front of the line. Instead of a gradual transition from taper to running line, a shooting head abruptly changes from thick to thin. The heavy front end improves your ability to cast long distances although you are guaranteed the line will create a greater splash upon landing. Shooting heads are good for heavier flies or windy conditions.

The level line, as its name implies, is a line that does not have any variations in thickness with the same diameter throughout its length. Level lines have fallen out of favor because they are hard to cast. In fact, I did a brief search of Orvis, Cabela’s and Bass Pro shops using the keyword “level line” and did not find any. It has no “must buy” advantages over weight forward or double taper. Granted, the thinner diameter reduces line slap for a stealthier presentation, and it is easier to roll cast than weight forward since you do not have to overcome the heavy business end, but the overall difficulty in casting overwhelms those two positives.

Sinking lines are the other major category, and they do precisely what the name implies. Instead of floating, they begin to sink at different rates depending on the rating associated with the line. Since weight standards remain in effect for sinking lines (a 4wt is still a 4wt), the manufacturers achieve the sinking characteristic by reducing the diameter of the line and coating it with heavy metal particles. You can purchase sinking lines with sink rates ranging from a 1/2 inch per second all the way up to 10 1/2 inches per second. There are two types of sinking lines, sink tip or full sinking (lumping intermediate sinking with full sinking). 

A sink tip line transitions to floating between five and fifteen feet from the end and does not achieve as much penetration of the water column as a full sinking line. Since you can tie on a sink tip as part of your leader, you really do not need to invest the money for a single purpose sink tip line unless you consistently need the full performance a dedicated line offers.

After reading this, you can understand why reels come with spare spools! Unless one line, one weight meets all your needs, you need spools to give yourself quick change options. Need a gentler presentation? Drop a line weight or pop on that double taper. Need to deal with wind? Change to a higher weight, a specialty line or a shooting head. In an area where every cast is a roll cast? Double taper. Fish deep in the water column? Sinking line.

For more information on tackle selection, I recommend either (or both) of these references used for most of the expert background supporting this article:

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