Of Rods and Reels
The assorted tapers found today include level (L), weight-forward (WF), and double-taper (DT). There are some specialty lines like the shooting head (SH) line (a short, composite line with a heavy casting section that is attached either to a very thin running line made of monofilament or perhaps to a level fly line), and the triangle taper (TT) line (invented by the late Lee Wulff, it steadily increases in diameter from the tip to the 40-foot mark, where it suddenly tapers back down within eight feet and then runs into the running line). Also, as fly-fishers have become more and more specialized and demanding, tapers designed for fishing certain species have popped up, such as Scientific Anglers' tarpon and bonefishtapers.
The level line is all but useless and should be avoided. They sell because they are inexpensive and people buy them without knowing any better. Weight-forward lines are excellent in that they tend to cast easier because of extra weight in the forward part of the line linked to a running end that is thin. Most fly-fishing situations can be handled with a weight-forward line.
The double-taper line is an excellent line for fishing across stream currents where mending (moving the line upstream in a flipping motion without disturbing the fly in order to get a drag-free drift) is required. Mending is facilitated by a double-taper line's thin ends and thicker middle (belly). And because the ends are equidistantly thin, you can reverse the line on the reel when one end becomes worn.
The line's weight, the next part of the code, is taken from the number of grains in the first 30 feet of line. This ranges from 1 to 15. A 1-weight line would be used for the most delicate and fine trout fishing on tiny streams for dainty trout, while a 15-weight would be used on marlin, big tuna, and other such game fish.
Finally comes the buoyancy of the line. A floating line (F) floats on the surface because of air cells injected into the PVC coating. An intermediate line (I) is meant to have neutral buoyancy; it sinks a little ways and stops. The sinking lines (S) have powdered lead or some other heavy substance added to the coating to make them sink. The sink rates vary, running from one foot every second to about 10 feet every second. Sink-tip lines (F/S) are lines with a floating belly and a tip section (between 10 and 30 feet) that sinks. As far as line lengths go, they all range from about 82 feet to a little more than 100 feet.
All this means that an AFTMA fly line code reading DT-5-F is a double-taper, 5-weight, floating line. A WF-12-F/S is a weight-forward, 12-weight, sink-tip. A L-7-F is a level, 7-weight, floating line. A WF-9-I is a weight-forward, 9-weight, intermediate line. A WF-6-S is a weight-forward, 6-weight, sinking line.
Details mentioned in this article were accurate at the time of publication