February 24, 2022

Rotational Moment of Tenkara Rods 4 meters and Longer

When it comes to fishing big water for big trout, tenkara has traditionally been the odd man out. We've all heard the argument, "tenkara was never meant for large fish. In Japan, a large ______ (insert Iwana, Yamame, Amago) is 40 cm (15.8 inches)". Pursuing these "large" salmonids is the realm of the Shaku hunter. In order to successfully be considered a Shaku Hunter, one must catch one of these fish that measures over 30.3 cm, a task that to some may never be accomplished. (Ref. 1)

Brent Auger and one of his typically huge trout. (Used with permission)


But soon after tenkara arrived in America, folks started trying to catch the largest trout that they could using tenkara rods and gear. Rods were breaking right and left, and tenkara was getting laughed at by traditional fly fishers as a tool meant for children chasing small trout. 

Karin Miller, with one of her tenkara rods, and a large salmonid. (Used with permission)


Then along came some pioneers. You know them, Brent Auger, Karin Miller, Rob Worthing, Eric Ostrander, and others. These tenkara anglers refused to stick with small trout; they went for much larger fish than tenkara was intended. But early on, the tools to tackle large trout didn't readily exist. Tenkara USA came out with the Amago, and Chris Stewart imported the Daiwa Enshou LT44S-F and some keiryu rods (most of which had light tippet ratings), but these few 4+ meter rods didn't always answer the needs of these "American Shaku Hunters". 

Rob Worthing with one of his big browns. (Used with permission)


Nowadays, the tenkara angler who wants to fish large water for large trout has many choices. What a world we live in! But many people have questions regarding these long sticks, such as can they be cast one handed and how heavy do they feel? Well, even though I'm not a Shaku hunter, and prefer catching trout smaller than 16 inches, I thought I'd put together some data for the tenkara community regarding the rotational moment (or torque) of these large tenkara rods. 

Just as a reminder, rotational moment is a mathematical tool used to estimate the tip heaviness of a rod. This measurement has been validated and used by Gamakatsu, a premium quality Japanese rod maker. I've written about Moment of Inertia and Swing Weight in the past, but these are harder to calculate, and since Gamakatsu has already accepted rotational moment as a measurement for their rods, I decided just to stick with it. 

A portion of a chart from the Gamakatsu MultiFlex Suimu rod page showing the moment of some tenkara rods. Translated from Japanese. 


The rotational moment of a rod is calculated by measuring its weight in kilograms and multiplying that by its center of gravity distance in centimeters from the butt of the rod, when the rod is fully extended. Any number over 6 and the rod begins to feel tip heavy, over 7 and you'll definitely notice. Simply put, the larger the number, the more tip heavy the rod will feel. Likewise, the larger the number, the more stress on your forearm and more chance of micro-tears being induced in the extensor tendons with repeated use (think tennis elbow, ouch!). Moment of inertia is likely a better mathematical model, but it's also more complicated, so rotational moment (RM) makes sense to be the mathematical tool of choice.

Moment of Inertia is way to complicated. It makes my brain hurt!


I put together a spreadsheet of the currently available tenkara rods advertised to be four meters (13' 1.5") or longer that I've used (or know of) and some of their measurements, including their RM. I might have missed one or two rods, but I think I got most of them (I'm sure I'll hear about any I missed). Now before you say, "what about the Suntech _____, or the Daiwa ______, or the Keiryu Rod Co. ______, let me remind you that this chart is about 4+ meter tenkara rods, not keiryu or seiryu rods. I did include one keiryu rod, the Diawa Kiyose 43M-F, because it's commonly thought of as a "big fish" rod and so many people have one. Besides, it's my chart, and I wanted to include it. I also chose to include the Nissin Zerosum Oni Honryu 395, although it's advertised as a 395 cm rod. It measures nearly 4 meters in length, and so it bears inclusion. Of the rods in the chart with missing data, if you have one of them and would like to contribute data, please contact me (use the contact me form at the top right of this page)!

So, here's the data. I pass no judgment or opinion on any of these rods; I only present the data. I include the Oni Type-I and Tanuki XL-1 for reference, but they are not considered "big fish" rods. BTW, I placed a new tab called Rotational Moment Chart on the Tab Bar of the Teton Tenkara homepage and will update the chart as needed. 



For the updated chart, click HERE to ask for the link. Here are some screenshots of the current chart (RFI is the Rod Flex Index):

Advertised 4+ meter tenkara rods in order of rotational moment, least to greatest. *Oni Type-II measures shorter than other rods, although it's advertised as a 4 meter tenkara rod. This may skew its rotational moment value. The measured rod is from the first production runs by Nissin. (Information provided by John Vetterli)



Advertised 4+ meter tenkara rods from shortest to longest



Conclusion: So, what to do with this data? I don't know. I'll let you decide if it helps you when you're researching 4 meter and longer tenkara rods for larger fish. Maybe you'll find it helpful, maybe not. But at least the data's now out there for the tenkara community to peruse. Use it (or ignore it) as you will! And remember, not all 4+ meter rods are designed to be equal. An Oni Type-II may have the lowest rotational moment, but it won't take down a salmon like the Zen Taka will! So, it goes without saying, when targeting large fish, don't bring a knife to a gun fight! (Ref. 2) 


Acknowledgments: I'd like to thank a few people for their help in getting data for rods I didn't have on hand. In alphabetical order: Amanda Hoffner = TUSA Ito, August Gresens = TUSA Ito, Chris Cameron = Anglo & Co. Wasabi 40, David Noll = Shimano BG Tenkara 48NV, John Vetterli = Oni Type-II, Karin Miller = Zen Tenkara Taka, Kris Franqui = Daiwa Expert LT H44, Nick Feller = TRC Rocky, Paul Vertrees = Zen Tenkara Sagi, Tom Bayly = TAO Wisco 2 (he actually sent me one to measure. Thanks, Tom!). I'd also like to thank Karin Miller who reminded me that just because you have a long and powerful tenkara rod, you still have to use correct technique to properly play and land large fish. It takes finely honed skills, not just a rod with some numbers. 

Disclaimer: All rods and production runs have slight variations in weight and length. These data may vary slightly from rods from different production runs. 





5 comments:

  1. Question: what are these "honed skills"? What is "correct technique"? Since we are talking about long powerful tenkara rods, this is most likely fishing in the mainstream. Fishing in the mainstream of the river is considered difficult as it is difficult to find fishing spots. In fact, it would be more accurate to say that it is difficult to choose points for fishing. Inside the main course of the river there are streams in which fish feed. But ... if the river is wide enough, there are too many such flows in the water column. I know fishermen who have been unable to catch grayling for almost years due to the fact that they cannot “read” these internal currents in the water column. In this sense, indeed, the rod itself without the skill of reading the river does not matter.

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    1. Here's a start: https://youtu.be/br_nRWo5TDM

      https://castingaround.anthonynaples.com/2014/11/guest-post-fixed-line-fly-fishing-for-big-fish-by-rob-worthing

      http://www.tenkaratimes.com/tenkara-blog/archive/bigfishtenkara

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  2. Thanks for your work on that Tom. As a self-proclaimed nerd, I enjoy it!

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    1. Thanks, Kris. I thought you might find the results interesting.

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  3. Great videos for beginners! BUT ... pay attention, they have everything - casting, playing fish, classification of mountain river flows, etc. , - and there are absolutely no detailed recommendations for finding parking lots on a full-flowing river (main stream). This is what I'm talking about: in my fifteen years of experience fishing tenkara, keiryu and fly fishing, this is the main issue, not the length of the rod

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