Lesson 4: Reading a taper chart

Bamboo School · Lesson 4 of 12 · about 6 minutes

Builds on: Short Course Lesson 2 (what a taper is, and the three action families)

In the Short Course you learned that a taper is the rod's blueprint: its thickness at every five inches, mostly in thousandths of an inch. This lesson is about reading one. Not memorizing numbers, but looking at a chart and seeing how the rod will bend before you ever cast it.

You won't need to do any math. You'll need a pencil, maybe a sheet of graph paper, and some patience.

What's on the sheet

A taper chart is a list of stations and measurements. The stations are the points along the rod, every five inches, usually counted from the tip down to the butt. Next to each station is a number: how thick the rod is at that point.

That number is measured across the flats, from one flat of the hexagon straight across to the opposite flat. It isn't a round diameter, because the rod isn't round. Each strip is planed to half that number, measured from its point to its outer flat. Put six of those triangles together and you get the full dimension.

A chart usually also tells you the rod's length, the line it was designed for, how many pieces, and where the ferrules sit. Some charts show only the finished dimensions. Some show the strip dimensions instead. Know which one you're reading before you compare.

What the numbers mean

The single number at one station tells you very little. What matters is how the numbers change from one station to the next.

Where the numbers climb slowly, the rod stays slim over a longer stretch, and that stretch bends more. Where they climb fast, the rod thickens quickly and stiffens. So the rod's character lives in the steps between stations, not in any one measurement.

Here's the part that surprises people. A small change makes a big difference. A rod's stiffness grows much faster than its thickness. Make a section a little thicker and it gets a lot stiffer. That's basic beam behavior, and it applies to cane as much as steel.

It also means a thousandth matters more in some places than others. At the tip, where the rod is very slim, one thousandth is a large share of the total. Down at the butt, the same thousandth is a small share. That's why makers fuss over the tip, and why the planing tolerance you heard about in the Short Course is so tight.

See the shape: plot it

Numbers in a column are hard to read. A line on a graph is easy.

Put the stations along the bottom, tip on the left, butt on the right. Put the thickness up the side. Mark each point and connect them. Now you can see the rod.

Look for these patterns.

A steady, even climb. The line rises at about the same angle all the way. The rod bends more deeply as you add load, without a single hinge point. That's the general picture of a progressive taper.

A fine tip that climbs fast. The line starts low and rises steeply through the middle, then stays high. The tip does most of the bending and the rest stays firm. That's the fast family, what we mark Medium Fast.

A climb that eases lower down. The line rises, then flattens out through part of the lower rod. That softer zone lets the bend travel down toward the cork. That's the direction a parabolic taper goes.

Look also for small dips, flat spots and bumps. A flat stretch is a place where the rod will bend more than its neighbors. Some of those are deliberate. Others are hinges you'll feel in the cast. Near the ferrules and the grip you'll often see the line change, because the metal and cork stiffen the rod there anyway, and makers account for it.

Comparing two tapers

Plot two tapers on the same sheet, in two colors, and the comparison almost makes itself.

Start with rods of the same length and line weight. Then ask three things. Which one is slimmer at the tip? Where does each one start to thicken? And where do the two lines cross?

The crossing point is often the most telling. A rod that's slimmer at the tip but thicker through the middle will feel quick and light at the top, with a firmer core. A rod that's thicker at the tip but softer lower down will feel slower and bend deeper.

Then check yourself against what you know. Plot a progressive taper and a parabolic one together and look for the parabolic rod's softer lower section. Predicting how a rod will feel from the chart, then checking it with a cast, is how you learn to read tapers.

Garrison's stress curve

Everett Garrison came at tapers from a different direction. He was an engineer, and he wasn't satisfied with only building, fishing and adjusting.

He worked out how much stress each station of the rod carries during a cast, taking into account the weight of the line and the weight of the rod itself. Then he plotted that stress along the length of the rod. The stress curve showed where the rod was working hard and where it was loafing.

That turned taper design into something you could reason about on paper. A maker could choose the stress curve they wanted and work back to the dimensions. Or take an existing taper, plot its stress curve, and see why it fished the way it did. His method is laid out in A Master's Guide to Building a Bamboo Fly Rod, completed with Hoagy B. Carmichael.

Garrison's approach didn't replace fishing a rod. It gave makers a second way to see the same thing.

Why makers adapt tapers

Tapers get changed all the time. A maker might lengthen one, move it to a different line weight, or split a two-piece rod into three pieces. Every one of those changes shifts the numbers. Adding a ferrule adds weight and a stiff spot partway up the rod, so the dimensions around it often get adjusted.

That's why you'll find several versions of the same famous taper floating around. Some are careful adaptations. Some are copying errors. And charts measured off old rods can be thrown off a little by the varnish, which adds its own thickness on top of the cane.

Our rods are built to the original measurements, and every one is marked with its taper name. When you read a chart for one of them, you're reading the numbers the maker settled on.

One last thing a chart can't show you. Two rods built to the same numbers can still feel a little different. The cane, the heat treatment and the node work from Lesson 2 all change how the strips behave. The chart is the blueprint. The cane decides how well the blueprint gets built.

Next: Lesson 5 is about the other half of the system: the line. Weight versus rating, over-lining, double taper versus weight forward, and silk versus synthetic.