with the hope the following article will help clear out a few ideas on fly line selection and since there’s been some recent comments regarding the use of level lines…, here’s an introductory excerpt on the hows and whys of fly lines tapers from Bruce Richards‘ seminal book Modern Fly Lines via Virtual Fly Casting.
as a reminder, Bruce was head line designer at Scientific Anglers for over 30 years. we can consider him to be the ‘father of modern fly lines’, “What Bruce doesn’t know about flylines, probably isn’t worth knowing. In fact some of what Bruce *does* know about flylines you probably wouldn’t want to know either.”
“Obviously, heavy and wind resistant flies offer more resistance to the fly line than light, small flies. Lines with long front tapers have less mass in the front section of the line than lines with shorter front tapers. Less mass means earlier acceleration, earlier dissipation of energy, and a more gentle, less powerful delivery which will effectively deliver small, light flies, like most trout flies. Lines with short front tapers dissipate energy less efficiently, resulting in a more powerful “turnover”, suitable for the heavier, wind resistant flies usually used for bass or saltwater fishing.
Casting into the wind increases the wind resistance the line encounters, and more energy is dissipated from the line than in calm-air or downwind casts. Lines with shorter front tapers, which dissipate energy less efficiently, work better for most anglers casting into the wind. When all else is equal, lines with longer tapers deliver less powerfully than lines with shorter tapers. It is the actual line weight that determines the range of fly sizes that can be cast effectively. A light line (2 to 5- weights) with a short, powerful taper is not going to throw big bass bugs well, because the line is just to light to carry the energy necessary to overcome the resistance offered by a large bug.
The primary purpose of the front of the fly line is to allow proper delivery of the fly and leader. The taper from the belly of the line to the tip acts to reduce the mass of the line. As the loop of any fly line travels through the air, the mass of the moving part of the line decreases because that part becomes shorter. In lines it decreases even more because the line becomes smaller towards the tip. This increases acceleration, resulting in greater Drag, wind resistance and greater Dissipation, and therefore a more delicate delivery.
It should be mentioned that the tapered leaders tied to the end of fly lines continue the dissipation of casting energy. If you have ever cast a line without a leader, you probably noticed it did not cast well. Lines are designed to be cast with leaders. A properly designed line will have just the right amount of energy left at the end of the cast to turn over the leader and deliver the fly. If a line is cast without a leader, it will ‘kick’ and be most difficult to cast. Lines are designed to be cast with a particular leader commonly used with that size type of line. A light fly line will be overpowered by a heavy saltwater leader; the line will not have enough energy to turn it over properly. By the same token, a light trout leader won’t be able to handle the large amount of energy a heavy saltwater line passes to it, and the line will ‘kick.’ Casting a level line with no front taper demonstrates very clearly how tapering effects the way a line casts. Even with the correct tapered leader, level lines ‘kick’ when casting because thy have so much undissipated energy left when the line straightens. To avoid the kick the caster must modify his or her casting stroke to reduce the amount of casting energy by slowing the line and by casting with a larger, more wind-resistant loop.
Level lines turn over very abruptly and land on the water forcefully because the energy dissipates poorly because the tip is just plain heavy without the line taper. Sinking lines are said to ‘hinge’ when cast; there is a significant change in the density where the floating and sinking parts of the line join. If cast correctly, a properly designed sinking-tip line does not ‘hinge’ but rather ‘kicks’ just as the level line does. The tip of a sinking line is very heavy and dissipates energy poorly. To compound the problem, lines with very high density tips are very small in diameter and offer less wind resistance even when the do finally accelerate. The key to casting these lines effectively is the same for level lines, namely to open the casting loop and slow the line down as much as possible.
The ability of the caster is important to consider. Lines with longer, more delicate tapers require good loop control and may be difficult for an inexperienced caster to use. There are lines on the market specifically geared toward beginning casters, lines with shorter tapers that dissipate energy less quickly during the cast. Most novices cast with relatively wide, open loops that are quite wind-resistant. If a line with a long, delicate taper is cast with this kind of loop, too much energy is dissipated and the line and leader will not straighten. With a shorter, more powerful taper, effective deliveries can be made even with less than perfect technique.
Instructors may often overlook the fly line a student is casting with. Ask the student what line it is they are using. This may be especially important when dealing with advanced or intermediate casters.
For example, many intermediate casters attempting to cast a line to 75 or 85 feet are simply unaware that in the case of a Weight Forward line, they must learn to control and understand what “overhang” is, and how it will affect their ability to control the line for longer casts. Overhang is simply the position of the rod tip in relation to the distance between the running line and the end of the rear taper. While experienced casters can control lots of overhang the intermediate caster should not attempt to cast with more than 2 or 3 feet of overhang outside of the rod tip. It is highly recommended that an approximate overhang point be marked with a permanent magic marker allowing the student/ caster a consistent “pick up” point that will promote greater efficiency when learning to cast a longer line. Again we turn to “Modern Fly lines” for a detailed description of why understanding “overhang” is critical.
A fly line is controlled by the tip of the fly rod, the angler’s last point of contact. The rod tip moves the part of the line that is in the rod tip, and that part of the line moves the rest of the line. For the rod-tip part of the line to move and control the rest of the line effectively, it should have enough mass to move the line connected to it.
A good caster can cast effectively with running line in the tip, however, if the line is kept very straight during the cast. Energy can be transmitted through the straight, small- diameter running line to the head of the line. But it usually desirable to choose a line with a belly that will insure the belly is at least very close to the rod tip during overhead casting, roll casting, or mending. In closing it is important to note that it is the fly line that delivers the fly to the target. Understanding how fly lines transmit energy to deliver the fly to the target is predicated on a firm understanding of taper design.”
EDIT– since publication of this article the Virtual Fy Casting site has been deleted/removed which also deleted the images previously added to this post.