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Rod Breakage due to 'material fatigue'?

by Pete

I've just got back in from a reasonable few hours fishing on one of my local urban streams — 15 wild brownies up to 12". That's the good news... the bad is that I broke my beloved Shimotsuke 240 rod. Actually that's not quite true, a fish broke my beloved Shimotsuke 240 rod!

I've had the Shimo 240 for a couple of years and it has been my go-to rod for urban streams where the trout can range from 3" to 15" and the overhanging trees and bushes, plus submerged detritus, cause multiple foul-ups. When I know I'm not going to get anything bigger than 10" and the vegetation is less dense, I'll use my beautiful Nissin Air Stage Hukabai 240, but I generally feel much safer using my cheap and cheerful Shimo in most situations.

As soon I hooked fish number 16 today I knew that it was considerably bigger than anything I'd previously caught on this river (and I've caught hundreds of fish there). The Shimotsuke bent double, as it often does with larger fish and I caught a brief glimpse of the big guy as it headed downstream taking advantage of the strong current.

The next thing I knew there was a loud "crack" and I was left holding the butt-end of the rod, which had somehow broken just above the second lowest section. Once I got over the shock I wet-waded downriver until I spied the rest of the rod caught up among rocks. I picked it up carefully, making sure to get hold of the line at the same time in case the fish was still on. It was, but only briefly... a big tug and the 6x tippet snapped between fly and level line.

I have no complaints about the Shimotsuke 240; it's an inexpensive rod and I've probably caught more fish on it than all my other rods combined (although that's obviously a reflection of the type of rivers I fish). However, I'd always assumed that, providing the recommended tippet strength is used, a Tenkara/Keiryu/Seiryu rod should not break under normal conditions, especially not where mine broke. User error is another matter... I should know, I've broken two tip sections on other rods through clumsiness.

So the only thing I can attribute my Shimotsuke's demise to 'material fatigue'.

Has anyone had a similar experience?

Comments for Rod Breakage due to 'material fatigue'?

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Aug 01, 2019

by: Chris Stewart

I don't know if material fatigue is an issue in tenkara/keiryu/seiryu rods.

I do know the big fish in strong current break rods, whether the rods are new, old or in between.

It is a myth that the tippet will always break before the rod does when using the recommended tippet (and I am probably at fault as much as anyone in helping to get that myth started - when tenkara was young in the US, I didn't know either).

I am now of the belief that the recommended tippet strengths (and by the way, Shimotsuke does not publish recommended tippet strengths) are basically guidelines for beginners, along the lines of "these are the tippet strengths that most anglers use", and have little to do with a rod's strength.

Tenkara anglers in Japan catch 9-10" fish. Fish that size do not break rods, so rod breakage because of big fish is probably close to unheard of in Japan. The Shimotsuke 240 in Japan would be used to catch 4" fish in 4 foot wide irrigation ditches. Those fish don't break rods either.

Where your rod broke is exactly where rods break when the fish (or the combination of the fish plus the current) is too strong for the rod. No surprise there.

I'm glad the rod has served you well, accounting for many, many fish. With this fish, though, the rod met its match. Therein lies the dilemma. A rod that would have landed the biggest fish you ever hooked, in strong current, would not be nearly as much fun with the fish you normally catch.

The good news (or the least bad news) is that you can replace the broken section and now you know the limits of the rod. Next time you hook a huge fish in strong current, salute the fish by lowering your rod and pointing it directly at the fish. Then the tippet will indeed break before the rod does.

Aug 01, 2019
Thanks Chris
by: Pete

Hi Chris,
Thanks for your comments and wise words. To tell you the truth it all happened so quickly the fish was dictating events and I had little time to react.

It's occurred to me that by placing my non-casting (left) hand slightly higher up the 'handle' to relieve the stress on my right arm (as I often do with bigger fish) I might have taken some of the flex out of the rod.

Whatever...I've just ordered another Shimotsuke 240 rather than trying to get the broken section alone... at least I'll have a few spare parts should another big fish surprise me!


Aug 01, 2019
Second hand on rod
by: Chris Stewart

If you have your "upper" hand on the grip section, it may take only minimal flex out of the rod. The grip section doesn't flex much. However, if the fish is so strong that you need two hands to hold a 2.4m rod, that is a pretty good indication that it is too strong for the rod.

If the upper hand is on one of the sections above the grip, it will greatly increase the likelihood that the rod will break. That is true with any rod, not just with the Shimotsuke 240.

Aug 01, 2019
Fatigue/Rod Quality/and "Think-So's"
by: John Evans

For what it's worth, my wife and I have managed to break 5 tenkara/keiryu rods in 5 years, including one Shimotsuke 240. Of the five rods, three were cheaper "brand-X" rods that should not have broken. In other words, we weren't doing anything dumb, the tippet strength was sufficiently light, the fish weren't too big--the rod just gave way. I could only conclude that the cheaper rod blanks in the cheaper rods played a role. The other two rods were high-quality Japanese poles, and the breaks were definitely our fault. We hooked "tree fish" and decided to whip the line to free the hook. Big mistake! Again, no excuses . . . we did it to ourselves.
So, fatigue might play a role, but I'm fairly confident that, if you fish correctly, and don't repeat our mistakes, the better-quality rods will give better service. That's my "think-so" for the day.

Aug 01, 2019
Sorry to hear about the break!
by: Les Albjerg

I've only had one Keiryu rod break and that was on the other end of the spectrum. It was my 6 meter Suntech Keiryu Sawanobori. I was using a Keeper Kebari with 6.5x tippet. Indeed within the tippet guidelines. The nice sized rainbow took the fly from underneath, went airborne wrapping the tippet around himself, and when he hit the water and torpedoed off, he broke my number 2 section! I was surprised. He paid for it by being my dinner up in the mountains that night! He was only a 16 incher, but he had leverage! Chris had my replacement to me before my next fishing trip, so I was a happy fisherman. I consider it a part of the game, and if we want these ultra-light rods with amazing sensitivity, there is a price to pay. I have landed several 26 inch rainbows with the Sawanobori with no issues with even a hint of breakage. I have followed Chris' technique with a few cutthroats on the Kurenai 30 that were 12 - 14 inches when I was fishing for small brook trout, not knowing there were cutts lurking in the tiny stream. It does pucker the cheeks when you feel your rod maxing out! It is just part of our game! I doubt it was material fatigue, these rods are high quality graphite, even the less expensive ones from Chris.

Aug 01, 2019
High sticking
by: Randy Knapp

I have broken rods in the same place. It was always "high sticking" meaning that due to distraction I lifted the rod angle such that the handle was vertical or past toward the rear whether straight up or to the side. I have done this with regular fly rods, spinning rods, and tenkara style rods. In the heat of battle it is easy to lose focus on rod position. When I have my wits about me, I focus on keeping the base of the rod at about a 45 deg. angle. I use much heavier tippets(4x to 2x) than most anglers and the rods don't break if the base of the rod angle is less than vertical. Sorry I haven't maintained contact, Chris, but I'm still kicking and am pleased with your success.

Aug 02, 2019
by: Pete

Thanks for all the comments folks. Seems like what happened to me is not that uncommon an occurrence.

I suppose I could buy a stronger 240 rod (e.g. Daiwa Keiryu X) but as Chris said earlier, that would take all the fun out of catching the 4"- 10" fish, which make up the majority of my take on these little rivers. In any case, even the Shimo 240 is pretty stiff for fish at the smaller end of the scale and I loose plenty after hook-up.

Until the replacement Shimotsuke 240 arrives I'll have to use my Nissin Fine Mode 270 for these situations. Let's see how that goes...

Aug 02, 2019
High Sticking
by: Pete

Randy, you may well have a point there.

With full flex rods of 3.6m and above I don't think raising the rod vertically should be a big issue (I understand that some people even point the butt-end of the rod at the fish in certain situations) but with a short, stiff rod like the Shimotsuke 240 it's probably a good idea to keep the tip lower until the fish is partially subdued and/or out of the current.

Aug 11, 2019
Rod breaking
by: Jim

Hi guys,
I have broken the lower sections of both my Suntech kieyru stiff and extra stiff rods. I am convinced that it is because I didn’t set the sections together tightly. If the sections aren’t tight enough there is a tiny gap on the very end of the sections, this created a stress riser that causes the section to crack right at the end. I now extend the rods out and give each section another pull and twist to ensure that each section is tightly seated. I too feel that the cost to replace a section every once in a while is the price of using these fine, light weight rods.

Aug 17, 2019
by: Sean

No matter how segments are seated there will be stress risers at the overlap, the difference in thickness of the overlapping sections makes a sudden change in Young’s modulus. In a structure like a tenkara rod under the load of the line, the sections at the tip will primarily be under tension as each segment has bent under load. Further down the rod each segment is progressively experiencing the load less as tension and more as flexure. The discontinuities in thickness will concentrate stress at the overlaps, and leverage will result in increased hoop stress. Eventually, assuming the tip structure has enough tensile strength, one of the lowest sections experiencing the greatest flexure will fail, usually as a rupture of the fibre structure either at the lip of the lower tube of a joint, or in the structure of the lower tube overlying the end of the higher tube on the opposite side. If these areas are disproportionately reinforced, then the higher tube will tend to buckle and crush at the overlap. It’s not a design or manufacture flaw, just an inevitable result of overload.

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