Fly Fishing Insider Podcast
A fly line taper moves mass along the line's length. Push mass toward the front and the line turns over hard, which suits big flies and wind; push it toward the back and the line lands delicately, which suits small dry flies. Taper is chosen for the fly being cast, not for the fish.
Josh Jenkins is the research and development manager at Scientific Anglers, where he designs fly line tapers and develops the additives that go into line coatings.
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What does a fly line taper actually do?
Fly fishing is the one form of fishing where the line, not the lure, carries the mass that loads the rod, because a fly weighs almost nothing. Tapering the line changes its diameter along its length, which redistributes that mass. Mass pushed toward the front makes the line turn over aggressively, which is what a tarpon line needs to punch a big fly into wind. Mass pushed toward the back gives a long, fine front taper that lays a small fly down softly. A taper is therefore matched to the fly being cast more than to the species being pursued.
Why are so many fly lines half a size heavy?
A fly line's stated weight is determined by cutting and weighing the first 30 feet, which is the trade association standard. That number only helps if you are actually casting 30 feet of line. Fishing a small creek at 20 feet, a true-to-weight line never gets enough mass outside the tip to load the rod, so an overweighted line puts the correct weight in the first 20 feet instead. The second reason is fly size: a 7-weight rod casts an 8- or 9-weight line perfectly well and handles a deer hair diver or a popper far better than a standard 7-weight line will.
How do you tell whether a fly line is overweighted?
Scientific Anglers lists it. Every line that is overweighted carries a bullet point on its catalog page and its web page stating by how much, so a buyer does not have to work backwards from a grain weight table. The Grand Slam saltwater line, for example, is three-quarters of a size heavy. True-to-weight lines are still made for anglers who want them, with the Expert Distance line the most popular of those, aimed at casters working on distance and accuracy rather than at fishing shorter than 30 feet.
What is head length on a fly line and why does it matter?
Head length is the length of everything on the line except the running line. A long head gives better presentation and better distance once it is outside the rod tip. A short head is not as accurate but is much quicker to pick up and shoot, which is what matters when a fish appears at short notice. That is why saltwater and bass lines are built with short heads and trout lines with long ones. A shooting head takes the idea to its limit: about 30 feet of line with no running line attached, which is the category most Skagit and Scandi spey heads fall into.
What makes a sinking fly line sink, and what does a T-rating mean?
Sinking lines get tungsten powder mixed into the plastic coating, and the ratio of tungsten to plastic sets the sink rate, from an intermediate or sink 2 at the light end up to a sink 7 or sink 8. Sink rate is stated in inches per second, so a sink 7 drops about seven inches per second, which is a genuinely useful number. A T-rating is not that. T-12 simply means a foot of that line weighs 12 grains, and it says nothing about density at all. You could build a floating T-18. Manufacturers happen to use their fastest sinking material for T-rated heads, which is why the two have become confused.
How do fly lines actually fail?
Two ways. The first is friction: the coating wears down where it runs in and out of the guides, which is what slickness additives address. AST Plus is a liquid formulation of that additive rather than a solid particle, so it migrates within the coating and pushes back toward the surface as the outside wears, replenishing the line's slickness on its own. The second failure mode Jenkins calls the wire coat hanger effect: a line built too stiff cracks prematurely from being bent back and forth during casting. Build it too soft, though, and it will not shoot, so stiffness is tuned to the environment the line will be fished in.
Should you take fly lines off the reel for winter storage?
No. The coating is plastic, it does not rot, and a line can sit on the reel indefinitely without harm. What does shorten a fly line's life is UV, so store reels out of the sun even though the line obviously sees sun while fishing, and solvents, specifically high-SPF sunscreen and the DEET in many bug sprays. Dirt is the third factor: a line fished in silty tailwaters or in salt picks up grit that raises friction, so it stops shooting well first and then starts losing coating durability if it is left dirty.
Key takeaways
- A fly line's stated weight is measured over its first 30 feet, so if most of your casts are shorter than that, an overweighted line loads the rod properly.
- Sink rates in inches per second are exact; a T-rating only tells you grains per foot and says nothing about how fast the line sinks.
- Leave lines on the reel. UV, DEET and high-SPF sunscreen do far more damage than storage ever will.
- On a textured line, the aggressive diamond texture is confined to roughly the front 3 to 6 feet, where it aids flotation and your hands rarely go.
- Long heads present and cast far; short heads pick up and shoot quickly, which is why saltwater lines are short-headed and trout lines are not.
- Every production run starts with a 30-foot cut and weigh, then five or six more lines are pulled and checked across a run of about 100.
