Fundamentally, a graphite fly rod starts out as a sheet of carbon fiber that is impregnated with various types of glues or resins, depending on the manufacturer and the rod model. These “prepreg” sheets come in huge, glistening rolls, like an extra-jumbo tube of gift wrap. In order to make raw carbon fiber sheets into the tube shape of a fly rod, you need something to form it around—a mandrel. Mandrels are where the design process of a fly rod really gets started.
Cutting carbon fiber into the "flag" which will be rolled into a blank. Courtesy Scott Fly Rods.
Obviously, if you want to create a rod “taper” (the ultimate shape of the rod tube), you have to start with the internal form. “Mandrels are made of stainless steel, and they require very precise machining, with tolerances often tighter than a tenth of a millimeter,” says Scott Fly Rods’ Ian Crabtree. Mandrels are designed on computers, and are typically made by machining companies to a rod manufacturer’s very detailed specs. Since the mandrel must go inside of a graphite rod tube, and since the tubes get very, very small (especially in the tip sections of 1- and 2-weights), there’s no room for error. In their smallest sizes, mandrels essentially resemble long steel needles (and of course they must be handled with extreme care). Gary Loomis (now consulting for Temple Fork Outfitters) confirms that most multi-piece fly rods get a different mandrel for each section, meaning “a four-piece rod will have four different forms.” (Contrary to a popular misconception, almost no multi-piece rod is cut from a single long blank, due to the difficulty of keeping a lengthy blank from twisting when it is pulled from the mandrel.)
Once a manufacturer has a mandrel (typically after a lot of prototyping), it’s time to roll out the blank. A sheet of carbon fiber is pulled from the roll and hand-cut with a sophisticated knife “that kind of resembles a box-cutter,” according to Scott’s Crabtree. Once cut, these sheets are called “flags” or “patterns.” For U.S. manufacturers, they always take the form of a trapezoid of some kind, since the tip will always be somewhat narrower than the butt (this goes for every section of the rod). According to rod designer and casting guru Jason Borger, these trapezoids may still wind up being quite complex, with multiple compound angles to create different actions. (In contrast, some very budget-conscious overseas manufacturers simply cut a rectangular pattern and allow all corners to overlap in a twist when rolled. These rods are typically sold in bubble packs in big-box stores).
“If you bend it, first it will ovalize, then it will crack out at the edges.”
But wait! Here the manufacturers have to deal with a serious design problem. If you make a graphite rod out of nothing more than impregnated carbon fiber, which is almost always aligned to run lengthwise down the blank, then it will snap the first time you bend it. “Think of it like a drinking straw,” says Paul Johnson, formerly of Sage. “If you bend it, first it will ovalize, then it will crack out at the edges.” TFO’s Gary Loomis analogizes an unreinforced rod to an egg: “It’s very strong if you’re pushing from outside, but much weaker when the stress comes from inside. That’s how come a little chick can break out of its egg so easily.” To prevent this, rod makers use something called “scrim.” Scrim is a reinforcing material that is aligned perpendicularly to the carbon fiber of the rod. Once rolled, it gives the rod hoop strength that helps it resist ovalization. “In the old days,” says Johnson, “scrim was always fiberglass, but in recent years we’ve been able to use carbon fiber.” Some manufacturers use a chopped mat of “paper carbon” scrim, like particle board, while others use a unidirectional product that allows all the scrim fibers to be aligned into hoops. And, of course, many rods are still made with fiberglass scrim, to maximize strength and minimize cost.
Depending on how strong the manufacturer needs the rod section to be, the scrim flag might be cut wide, to cover all of the main carbon fiber flag, or narrower, giving less reinforcement. Once rolled, the scrim is sandwiched in between layers of carbon, meaning if you cut a cross-section you’d see scrim, then carbon, then more scrim, etc.
What's on the horizon?
I asked many manufacturers what kind of technology anglers may look forward to in future rods. Several mentioned the development of carbon nanotubes as an exciting up-and-coming development. Steve Rajeff explains: “Carbon nanotube fiber has great promise. Nanotube graphite fibers are all hollow. Currently, they can be ‘grown’ in short lengths, a couple millimeters long.” Because carbon nanotubes are even lighter than their solid brethren, they may have a very bright future in fly rods. “Right now,” Rajeff says, “nano fibers added to golf shafts and some rods have shown modest improvements, but they’re still too short to be optimal. If a continuous-length carbon nanotube can be developed, we stand to see some significant performance jumps.” —Z.M.
Once the main carbon flag and the accompanying scrim are cut, they are laid on a work surface together, scrim on top. Then the rod maker—at this point a skilled worker with years of experience building various parts of the rod—very carefully lays the mandrel on one edge of the overlapping trapezoidal flags, and makes one complete turn or roll. “We spray a release agent on the mandrel to help it come out once the blank is baked and cured,” explains Johnson, “and that agent also is somewhat sticky when it’s wet.” The sticky release agent helps, but this is a tense point in the rod’s construction.
“It is very important that the first turn be perfect,” says Scott’s Crabtree, “so we do them by hand. If you have a void or gap at this early stage, the blank will twist and will have to be discarded.” Once the first turn is made, the rod is ready to be rolled into that “blank,” or tube. If you’ve ever made pasta, you can imagine roughly what the next step looks like. Manufacturers use expensive industrial rolling machinery resembling two giant pneumatic drums, with a small slot in between. With a worker carefully tending the machinery, the flag and mandrel are fed through the drums and tightly rolled into the familiar shape of a flyrod blank. Depending on the weight of the rod, the position on the blank and the materials used, the blank section may require dozens of turns, or as few as 10. The number of turns determines the thickness of the blank wall (which can affect a rod’s action significantly).
Once a blank is rolled, it must be tightly bound in a heat-resistant polypropylene tape, to hold it in its rolled form. This tape is wrapped around and around the rod in a spiral pattern, and ultimately gives “natural finish” rods their ridged shape, which I’ve heard compared to a snake belly. Once taped, the blank sections hang vertically in a giant walk-in oven to cure. All the resins are heated and harden, in a process akin to firing pottery. Interestingly, the tape wraps must stay in place during this process, both to hold the form and also “to keep all the resin from liquefying and dripping off the blank onto the floor,” according to Crabtree.
Final marking of the almost-finished rod. Courtesy Scott Fly Rods.
In recent years the resin a manufacturer chooses has become one of the most important elements in rod design. G. Loomis’ Steve Rajeff explains that fundamentally “resin is the glue that holds all of the fibers in a rod together.” Most of these resins are “trade secrets,” according to Orvis’ Tom Rosenbauer (including Orvis’ thermoplastic resin used in its top rods). Basically, though, “the stronger the glue, the stronger the rod,” says Loomis’s Rajeff. “Epoxy has been the preferred resin for over 25 years. Over time, it’s gotten a lot stronger, which allows us to reduce blank wall thickness and thus weight. We can also use higher-modulus graphite. All things being equal, lighter-weight, higher-modulus rods take less effort to cast and perform better.
When the resin in all the blank sections is done curing, the blanks are ready to be turned into castable fly rods. First, the mandrels have to come out of the blank. “We use a pneumatic pull press and a specially-sized die that exactly fits the butt of each different blank section,” explains Johnson. Next, the tape is removed from the outside. For natural-finish rods, like Scott’s current G2 series or Orvis’ older Clearwater, the ridged blanks go straight through to production. Most rods, however, are sanded at this point. Orvis’ Rosenbauer explains that there’s no performance difference one way or another, but most customers now prefer “shiny rods,” so the manufacturers usually oblige. However, sanding is a delicate process that requires a lot of skill (take too much off and you’ll weaken the blank). Throughout, the blanks are also carefully inspected: Those with cosmetic blemishes are typically discarded, even if the blemish would not affect the performance of the rod, “because it isn’t worth the expense of the hardware componentry to build out an imperfect rod,” says Crabtree.
Many manufacturers paint the blanks after sanding, though different rod makers use a different order from this point on. Most use automotive-style paints, which require breathing apparatus and clean rooms. Other manufacturers use a UV-curing paint based on pine resin, which can be “set” by being bathed in powerful UV light, like some new knot glues (“Those lights will burn you,” says Crabtree). In addition to being painted, the rods get ferrules now. For the most common sleeve-over ferrules, this process involves installation of glue caps or moisture plugs in the male ends of the blank; if designers do their jobs, the fit should be tight right out of the oven. The few remaining companies using internal ferrules have a multi-step process requiring fitting, insertion and gluing of the male ferrule section, which must then be carefully sanded to fit the female side.
With ferrules in place and the blank sections painted, the rods are ready to be dipped in a permanent protective coating of epoxy. This uses a variable orifice die that Crabtree says is “kind of like a round squeegee” to push a smooth bead of epoxy all the way from one end of the blank to the other. The rods are then left to cure for several hours in a clean room, so no dust or blemish mars the finish.
Where does carbon fiber come from?
Carbon fiber production is its own incredibly complex story. Generally speaking, carbon fiber can be spun from carbon dust, like cotton candy, or created in a lab by charring a precursor fiber similar to rayon. According to Orvis’ Tom Rosenbauer, only the charred type (called PAN carbon fiber) would be appropriate for most flyrod applications. Brad Loomis, owner of X-Stream Composites (and son of Gary), who makes all kinds of products out of carbon fiber, explains that it is manufactured by lots of different chemical and industrial companies, but also by some textile companies, some of which also make the fabrics in your waders and fleeces. This fiber, which initially comes in thread form, can then be mixed with resins to make the prepreg rolls that eventually become rods. Interestingly, many terms you would be familiar with from fly rods (such as IM6 graphite) are actually trade names used by the carbon fiber companies (in the case of IM6, a supplier called Hexcel). —Z.M.
Once dry, the blanks are ready to be wrapped up and have hardware affixed (this is the point at which custom rod builders would be able to buy a “completed” blank). The first thing to go on is most of the reel seat, using two-part epoxy. Next comes the cork grip, which must be carefully fitted with tape bumpers so that no voids under the grip cause creaking or breakage. Some manufacturers used to affix the cork rings directly to the blank and then form the handle on a lathe with the blank in place. Unfortunately, with declining quality of cork stock worldwide, this has become risky: The danger that a lathe technician may uncover an unacceptable void or cosmetic blemish hidden in the cork is very high. Consequently, just about all rod makers are now pre-turning their cork grips to confirm that the quality is adequate before they install the grip.
With the grips in place, the rods are ready for guides. After carefully aligning the blank, the builder tapes the guides in place, then wraps thread to hold them on permanently. As the builder completes each wrap, they remove the tape holding the guide feet, until ultimately the guides are ready to be epoxied (the final, shiny coating).
But first come decals. Some companies use stickers, while others continue to hire trained calligraphers (who must all have close to the same handwriting) to write on blanks. Any alignment dots (witness marks), decorative wraps, inlays or other “jewelry” would also be placed at this time.
All epoxy must be very carefully applied while the rods rotate to prevent unsightly bubbles and sags. If anything goes wrong here, the rod must be stripped and re-wrapped, or even discarded. When the epoxy has cured, the butt-end of the reel seat is affixed—the last piece of the hardware to go on—and the rod is ready for inspection.
Final inspection for many manufacturers is simply the last step in a long process of ongoing quality control. Throughout a rod’s construction, workers are trained to check for blank twist, unsightly blemishes, paint runs or misaligned guides. R.L. Winston’s Leslie Clark confirms that each worker who touches a rod “is empowered to discard any blemished rod they see.” With this many moving parts and this much hand labor, it’s easy to see how fly rods have come to cost as much as they do. Today’s rods are lighter, more responsive and less likely to break than ever before, all while being made with the same hand craftsmanship that is the hallmark of a quality fishing tool.
This article originally ran in the Spring 2011 issue of Fly Rod & Reel magazine.