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Let’s Get Technical on Tenkara

8 Mins read

By Karin Miller

Tenkara fishing is a Japanese reel-less fly-fishing method, in which the line is tied directly to the flexible tip of the rod, leaving the battle to the skill of the angler and the character of the rod. Not to mention, the tenacity, size and smarts of the fish. – Ed

Several requests have recently been made in various Facebook groups for more technical write-ups on the aspects of designing and making a tenkara rod. The requests have been for manufacturers to respond. The questions pertain to design and how design impacts rod performance. Three years ago, I wrote an article on this very subject but, as the tenkara community continues to grow and new people become interested in this fly-fishing method, it seems like a good time to revisit the subject.

A Bit About Blanks

Both fly and tenkara rods are only as good as their blanks (that’s a term used to refer to the actual rod, minus component parts such as the handle and finishes). The blank is what determines rod character, flex profile, accuracy, power, strength, and overall performance. Components minimally impact weight, balance and very slightly, the rod’s recovery time – or how quickly it “dampens” (stops wobbling). When you choose a tenkara rod, the most critical part of the rod is the blank. That’s really where your money should be going. Not the paint, not the handle, not the packaging, but the rod blank itself. This alone determines how the rod performs.

While we’re on the subject, let’s talk about performance; “the action or process of carrying out or accomplishing an action, task or function.” All tenkara rods will “perform.” How each rod performs, on various fish and various water, varies greatly from brand to brand and model to model. This is the result of different designs and the use of different materials. But, because one rod is “soft” and another rod is “stiff” doesn’t necessarily make the rod better or worse. It simply means the rod has a different character and a different flex profile. What appeals to YOU, the individual angler, is a personal choice. However, certain rod characteristics lend themselves better to certain scenarios. So, let’s dive a little deeper into tenkara rod blanks.

Beyond the obvious measurements of length (standardized) and flex (somewhat subjective and non-standardized), a plethora of variables exist that impacts how a rod blank behaves. These include blank taper, diameter, girth, wall thickness, number of sections (which also impacts flex, strength, durability and collapsed length), carbon fiber quality, carbon fiber modulus, the number of wraps used to form the rod blank, wrap directionality and, whether any resins or composite materials have been added or used in conjunction with the carbon fiber to make the blank.

All these factors give a rod blank its character. These variables determine how strong the rod will be, how much “backbone” the rod will have, whether it will be brittle and break under stress, the rod’s dampening rate, how deeply it flexes, how slow or fast it loads and how sensitive it is (how quickly and accurately it transfers information to the angler through tactile feedback).

Combine these dimensions, specs, material, and the components of the rod handle, along with the finishes used to complete the rod, and you produce a finished product that will perform in a certain manner. These variables also determine whether the rod feels well balanced in the hand or front heavy. They determine how accurately the rod will cast and, how much and what type of line it can move. So, when comparing tenkara rods, touch and feel is important and, giving consideration as to how you will most likely use it, should guide your purchase.

Ask yourself where you’ll be using the rod. What species will you be targeting? On average, will you be fishing very small creeks or wider rivers? Are you using it for fresh or saltwater? Will you be using the rod mostly to wet wade or from a boat? How you respond to all these questions impact the type of tenkara rod you might prefer, and which characteristics might be most beneficial and effective to get your particular job done, with the most success from the least effort.

The Lowdown of CF

The moment you pick up a tenkara rod and give it a wiggle you get feedback or a “sense” of the rod. What talks to you the loudest is the material; what the rod is made of. Today, most tenkara rods are made from carbon fiber, but not necessarily the same quality or grade of carbon fiber. Not all carbon fiber is created equally. There are also other options or composite materials like E- Glass or S-Glass that can be used to roll the rod blank. These have their own characteristics. Fiberglass is strong and flexible but much heavier than carbon fiber, especially the higher modulus carbon fibers. For the purpose of this article, we’ll keep to CF.

Carbon fiber is a material made up of extremely fine fibers consisting mostly of carbon atoms that are bonded together in crystals that align parallel to the long axis of the fiber. These fibers are then bundled together in quantities ranging on average from 1K to 24K (K= thousands) to make up “tows” or “yarns.” These different sized tows or yarns can then be woven into different patterns such as unidirectional, tweed, braids, and several others to make various carbon fiber “fabrics.”

Different patterns have different characteristics and qualities based on the pattern itself and the tow size used to create it. The same pattern can be made using different tow sizes which change the character and performance of the woven fabrics. Variables are almost unlimited.

Strength to Elasticity Ratios

Carbon fiber is defined by grades. Grades are based primarily on two factors: tensile strength and tensile modulus. Tensile Strength (ksi) is a measurement of the maximum stress a material can withstand while being stretched or pulled apart before it breaks or fails under pressure.

Tensile Modulus (msi) is a measurement of elasticity or flexibility – how much the material deforms (and returns to its original state) under pressure…or bends before breaking. Tensile modulus is a ratio of stress to strain. While tensile strength (ksi) and tensile modulus (msi) are correlated, they are different, so don’t confuse stiffness or “elasticity” (tensile modulus) with strength (how much pressure is takes to break it or be pulled apart). I know, a bit confusing, but hang in there and keep following me.

Carbon fiber grades are broken out into four categories based on a range of tensile strength and tensile modulus:

  • Standard Modulus
  • Intermediate Modulus
  • High Modulus
  • Ultra-High Modulus

The higher the modulus, the smaller and denser the fiber strands used to create it. This results in needing less of a higher modulus carbon fiber material, to obtain the same strength and stiffness as a lower modulus carbon fiber material. Since you require less material, the weight is reduced. The manufacturing process to create these higher purity strands is more time consuming and complex, so higher modulus carbon fibers are more expensive. High and Ultra-High Modulus carbon fiber is extremely expensive and primarily used in aerospace applications.

The sports industry, think golf clubs, bicycles and fishing rods, use Standard and Intermediate Modulus carbon fiber. Intermediate Modulus (IM) carbon fibers range from a low IM5 to a high IM12. When you review the differences between tensile strength and tensile modulus within the IM range, there is only a small difference between the tensile modulus’ (elasticity) – roughly from 40 to 45 msi within the range.

There is, however, a considerable difference in the tensile strength (what it takes to break it or cause failure) between IM5 and IM12 – from 770 ksi to over 1010 ksi. Remember, the higher the carbon fiber grade and IM, the lighter the material will be….and the stronger. These factors create the price discrepancy between different Intermediate Modulus – or any of the modulus carbon fibers and as such, the products manufactured from them. How else, besides price, does this lesson in carbon fiber transfer to rod blank performance?

It’s How you Combine It

Rod blanks made from a lower IM carbon fiber material will be heavier, they will be less sensitive, and much less accurate than those made from a high IM carbon fiber. They may also be more “elastic” and wobblier. A rod blank made from a high IM carbon fiber will be lighter, stronger, and more efficient since it will also be more accurate. It will dampen quicker and may also be less “elastic.” Thus, it is the combination of carbon fiber material used, along with the blank’s specific dimensions and other variables described above (like wall thickness, number of wraps, taper, girth, etc.) that determine how a rod blank behaves.

So, it’s not just the material alone, but what you do with it. Remember, regardless of the grade or IM of the carbon fiber used to make a blank, a rod can still be designed to have a specific “flex profile” (that ratio used to describe a rod’s action such as 5:5, 6:4, 7:3 or 8:2 which represents the percentage of the rod blank that is stiff verses soft), by adjusting its other specs.

A tenkara rod may have great flex but have very little backbone (for steering large fish). While it may not break, it also may not be effective in managing or turning a load or casting very accurately. Another rod may be called “stiff” and appear to have backbone but will snap and break under pressure.

Variables, variables. How a manufacturer combines these variables; girth, taper, number of sections, wall thickness, wrap directionality, etc., in conjunction with the grade of carbon fiber (and its rating within that grade,) determines what I refer to as “overall performance” – the end-result of balancing all these things to create the rod’s character and of course, the end-product.

Your rod blank determines it all. Don’t get caught up in the frills and packaging. Will your rod only cast delicate super light lines? Do you want it only for tiny flies? If you hook into something big, will you be able to steer it efficiently and land it quickly? Will the rod break under pressure? How solid are your hooksets? Does it take a lot of effort to set a hook? Do you miss many of them? How sensitive is your rod? Does it cast extremely accurately? What size tippet can it handle? How much does it weight? How balanced is it in your hand? How does your rod cast in wind? All these questions have answers that are determined by the rod blank, not by the finish.

While you may or may not know the IM of your tenkara rod, (and some manufacturers don’t or at least didn’t, prior to my writing on it), know there is a difference. Whenever possible, do rod-in-hand comparisons. Ask the hard questions and then consider how you personally, will be using the rod. Different rods will undoubtedly perform differently in different situations. One tenkara rod may excel in one scenario but fail in another.

Decide what you want or what you need. Then, as a consumer, you can make your own educated choice on the characteristics and qualities that will be most effective for your angling requirement. What one angler loves may not fit your bill. Do your homework and talk directly to manufacturers. Look to them to provide you with the information needed to choose a rod that’s right for you.

Zen Tenkara grew organically from owner Karin Miller’s passion for the sport. When she relocated to Colorado from South Florida, her need to be on the water led her to fly fishing. Tenkara was the perfect tool for the small streams near her home. She was captivated with tenkara’s efficiency, simplicity, and fun. In 2012 Zen Tenkara was born. Karin’s curiosity and hunger for adventure fueled her desire to target bigger fish and test the limits of this method. This is the driving force that has led Zen Tenkara to be the pioneer of American Tenkara.

Today, Zen Tenkara/Zen Fly Fishing Gear is a Colorado company that designs, manufactures, and sells a broad range of tenkara rods, lines, and accessories. Zen has revolutionized this fixed-line fly fishing method and is known for creating a “fusion” of traditional fly fishing and tenkara to target not only small traditional tenkara species, but also large, powerful fish not typically associated with this ancient Japanese method.

Karin Miller, who remains at the helm of Zen, has established a reputation for being innovative, cutting edge and for pushing boundaries with her high-performance tenkara rods. Zen Tenkara is the first and only 100% women-owned rod company in the world. It is also the oldest independently owned American tenkara company continuously operated by its founder.

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