Taper Design
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Taper design affects a number of important aspects of a cast. By modifying the different components of a fly line you can change:
• How it turns over the fly
• How large or air resistant of a fly it will cast
• How far it will shoot
• How quickly it will load a rod
• How far it will roll cast
• How smoothly it will cast
Let’s look at the different components of fly lines. The upper line is a Double Taper and the lower line is a Weight Forward.
At the front of the line you will have a Tip section. The tip is usually from 6 to 12 inches in length. The purpose of the tip is to allow transition to the leader by adding some kind of "butt section" to which you connect the leader. On sinking lines this butt section is usually a braided loop or a loop that was built into the line, while on floating lines it is usually a section of monofilament line. The tip also allows kinetic energy to transition from the front taper throught the "butt section" or loop to the leader.
The second element is the Front Taper. This determines how quickly and how forcefully the line turns over. A shorter head will turn over quicker and more forcefully than a longer front taper. Tapers can be straight tapers like those shown in the illustration or they can be compound tapers in a convex or concave shape.
Next is the (usually) level Belly section of the fly line. This is the power conserving part of the line. It maintains much of the kinetic energy in the line until the loop turns over into the taper. It is the portion of the line that enables the line to cut into the wind. The belly of the line can be of varied length. Longer bellied lines will usually allow more line to be carried out of the tip of the rod. This in turn allows the caster to shoot more line (Having said that there will be a point of diminishing returns based upon the weight of the line being shot). A double taper line will usually not shoot as great an additional amount of line as a weight forward line because the WF has a thinner (lighter) running line to pull behind it.
After the belly is the Rear Taper. The rear taper is the transition from the head to the running line (on weight forward lines) or rear tip (on double taper lines). Most lines have shorter rear tapers from 4-9 feet in length depending on their weight. This length is sufficient to allow for a smooth transition of energy to the head on shorter headed lines. Some specialty lines have longer rear tapers up to 25 feet in length to allow for improved mending abilities and longer line carry. These long rear tapers also smooth out the energy transition when carrying greater lengths of line out of the rod tip.
The last element is the Running Line (not on a double taper which only has an additional tip). The running line is of a smaller diameter and lighter weight than the head. This allows the head to cast farther because it does not have to drag along as much weight as the double taper would. The running line allows the caster to still have control of the line when stripping the fly in with less chance of it slipping from the fingers thanif it were a thin monofilament material.
Front Tapers:
Illustrations of tapers and line specs used used on this page are with permission from:
3M Scientific Anglers
There are 2 types of tapers: Straight and Compound.
There are 2 basic forms of the compound taper: Concave and Convex.
These can be mixed and matched to accomodate the desired characteristics of the line. Please note that none of the illustrations below are to scale. They are all exagerrated to easier illustrate the concepts and characteristics being discussed.
Straight tapers are those that taper at an even rate along their length. Energy is dissipated smoothly through the entire length of the taper. To understand how a taper affects line turnover visualize the taper as a road you are travelling on. A striaght taper would be like a gradual downhill slope on a road. Your car would begin to pick up speed as it moved along the slope and would accelerate at a fairly constant rate along the slope. In other words it would accelerate smoothly down the hill. So does the straight tapered line.
A good example of a gradual straight taper would be a Scientific Anglers Mastery SeriesTM GPX taper. It should be noted that the GPX line is 1/2 line weight heavy in each line weight class.
If the slope was steeper the car would accelerate faster than when on a gradual slope. Of course, once the slope leveled off the car would begin to decelerate. A shorter straight taper will also dissipate energy smoothly, it will just be more abrupt and may not feel smooth if the leader and fly are not matched to the line. A shorter straight taper would be used to turn over larger flys and to increase the amount of belly length in the line.
The Scientific Anglers Air CellTM Bass Bug taper fits the description here. You might think that the taper length between the Bass Bug and the GPX lines is negligible. But you need to also note that the diameter of the Bass Bug belly is greater than the GPX due to the short head length. This increases the slope of the taper. When you combine this with the shorter taper then the effect is considerably more pronounced and creates a forcefull tunover.
A concave taper starts by dissipating energy quickly then drops off to gradual dissipation allowing for a light turnover of the fly. Consider the car initially starting down a fairly steep slope, then part of the way down coming to a more gradually sloped section. The car will accelerate at a fast pace to begin with then at the slope change the rate of acceleration will slack off. This type of taper is often used in situatons where a line with delicate turnover is required.
An example being the Scientific Anglers Air Cell Trout Taper which has a "Concave compound front taper for positive turnover and delicate delivery with typical trout flies."
A convex taper dissipates energy less in the rear most portions of the taper, then it increases dissipation rapidly as it nears the tip. This is valuable for turning over large flys. In this case the car would first encounter a very slight downhill slope then a considerable steeper slope increasing the acceleration rate considerably.
Bellys
In general, shorter bellys will load the rod more fully and quicker than a longer bellied line. These lines are made to cast heavier or air resistant flys a short distance. A good example of this kind of line is a Bass taper and some saltwater tapers. Though some of these lines may have heads shorter than 30 feet in length they will still comply with the AFTMA line weight standards. For the most part shorter heads are less than 35 feet in length.