Fly Line

The Science of Aerodynamics

When the torch was lit at the 2012 Olympic Games in London, the United States began the track and field events with what Team U.S.A. sponsor Nike claimed was a technological advantage, and some critics called "technological doping."

The Nike Pro Turbospeed track suits offered to every member of Team U.S.A. were skin-tight body suits oddly reminiscent of a superhero costume. The suits—made from recycled water bottles—are not only lightweight, they use "zoned aerodynamics," which means Nike prints raised, 3-dimensional bumps on the legs and arms of the suits to cut wind resistance, and help track athletes (sprinters essentially) run faster.

How much faster? Before the games, Nike said 1,000 hours of wind tunnel testing showed that athletes wearing the suits were up to 0.023 second faster over 100 meters than athletes wearing smooth uniforms without bumps.

Like the dimples on a golf ball, the tiny bumps are meant to reduce drag caused by air by creating "turbulent flow" around an object. The principle only reveals itself at high speeds, which is why the effect is so pronounced in golf balls, why marathoners don't bother with the suits, and why sprinters only have the bumps on their arms and legs, which are moving much more quickly than the runner's actual land speed.

If you haven't already figured out what this has to do with fly fishing, you may not realize that U.S. fly line manufacturing is divided into two broad camps:

RIO Products of Idaho Falls manufactures smooth fly lines, and for the existence of the company has constantly sought a chemical composition and manufacturing process that produces fly lines that are slicker, smoother, and more hydrophobic than ever before. On the other side of this great divide is the manufacturing giant 3M, and its subsidiary Scientific Anglers.

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Scientific Anglers produces Sharkskin and Mastery Series Textured lines. Sharkskin has sharp-edged microscopic diamond patterns on the line surface, and Textured lines have rounded raised bumps more like the Nike Turbospeed suit. Or should we say Turbo-speed is more like the Scientific Anglers lines, since 3M was making its lines years before Nike unveiled the suits.

"For fly lines, wind resistance is probably the single biggest external factor that limits how we cast," says Tim Pommer, product development engineer at Scientific Anglers. "Obviously, a windy day on the flats is frustrating, but even on the calmest days, wind/air resistance is playing a huge role in our casting. In fact, the resistance of a fly line cutting through the air accounts for why our lines unfold in the air like they do.

"Theoretically, adding a structure to a fly line will do the exact same thing as it does to a golf ball. However, a golf ball is big enough in diameter, and its corresponding structure is big enough on the surface to make the effect very noticeable. The structure on our lines is probably small enough that the effect in the air is not noticeable to average casters. What the average fly fisher will notice, however, is how easily the line goes through the guides, which is a guide/line surface interaction instead of line/air interaction."

The advantage therefore, according to Pommer, is not how the line cuts through the air, but how the line "shoots" through the guides.

So which side of the fence should you fall on when purchasing a fly line? First, consider a typical trout-fishing situation where a rainbow is feeding on mayflies 40 feet away. You don't "shoot" line. In fact, in any short- to medium-range situation where accuracy is at a premium, you'll use a fixed length of line to get the fly right where you need it.

Shooting line is mostly for distance casting, and for blind-casting with searching patterns. When you do cast for distance, and you want to shoot line, both RIO and Scientific Anglers say in-house laboratory testing showsFlu  their lines produce less friction in the guides and are therefore farther shooting than the other.

In the end, it's mostly your talent and practice that will produce 99% of the results, and not the surface of the fly line. After all, Usain Bolt did fairly well wearing and "old-fashioned" track suit!