Rods used for tenkara are long, really long. We all know this. We use log rods. This fact, as well as the fact that we don't use a reel which acts as a counter weight, means that often times the rods we use feel tip heavy. This is the cantilever effect. The fulcrum of a tenkara rod is low down on the handle (where we place our hand) -- everything proximal to this point acts as a cantilever beam. It is our hand that anchors the cantilever beam and provides the counter weight for the rod.
Why is it then that some rods feel tip heavy? For the fact that its balance point is further up the rod than other rods. This is part of the rod's design. Again, rods used for tenkara are particularly prone to tip heaviness because there is nothing to counterbalance all that carbon hanging out in space.
In
a previous post, I showed that sometimes the tip heaviness between rods can be dramatic -- making one rod feel "heavier" than another of the same or similar length. This "heaviness" feeling may be independent from the rod's actual physical weight. I compared the AllFishingBuy Kasugo-4209 to the Tenkara USA Amago. Although they weigh about the same, the Amago feels much more tip heavy than the Kasugo.
For some time now I have wanted to test the cantilever force for the 380-390 cm rods (advertised length) that I currently own. I define the cantilever force as the amount of weight in grams required to balance the tip of the fully extended rod at 30 degrees above horizontal. At this time I have not measured my 360 cm or shorter rods since tip heaviness seems much less of an issue.
Method: The rod is fully extended. The actual length of the rod is measured in cm to where the lilian bends near the tip (this may be different from the advertised length -- see image below). The rod is placed on a box that has two V-notches cut into it. The rod is adjusted so that the handle butt is 12.5 cm behind the rear V-notch (this corresponds approximately to the mid point of most cork handled rods -- this is the fulcrum point for the test). To keep all things equal across different rods, this fulcrum point (12.5 cm proximal to the handle butt) was used on all rods, cork handled or non-cork handled. Weights were then applied to the butt of the rod until the tip of the rod was raised and balanced at 30 degrees from horizontal. The weight was applied, or removed, to bring the rod barely in contact with the cross bar -- ideally the rod would hover or balance just under the 30 degree cross bar. The applied weight in grams was measured to the nearest US penny (2.5 g).
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| Length of Shimano Kozuka 39NT: 385.5 cm |
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| AllFishingBuy Hirame-ML-3909 --- just hovering under 30 degree bar |
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| Tenkara USA Ayu-II |
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| Tenkara World River Master |
Results: Here are the results of the rods that I tested. I would like to test other rods but I only tested the 380-390 cm rods that I currently have.
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| Most tip heavy (top) to least tip heavy (bottom) |
Conclusion: Rods that have a smaller cantilever force have less tip heaviness than rods that have a larger force. This may translate to less fishing fatigue after hours on the water and hundreds of casts. Tenkara rod designers should take into account the amount of weight used to raise the rod as measured from the midpoint of the handle, not just the static balance point of the rod.
What do you do with this information? I don't know -- whatever you want! :o)
It's interesting that a few of the rods are longer then advertised.
ReplyDeleteI think the advertised length is only a ball park for most rods.
Delete-Tom
Am I wrong or would not finding the center of gravity of the extended pole give a result that would speak much the same. The center of gravity (COG) of a tip-heavy pole should be further away from the butt of the rod. The measure of length from the butt-end to COG divided by the overall length of the rod should yield a fraction (or percent if you prefer) which would in comparison would relatively show which of two rods is tip-heavy.
ReplyDeleteJust wondering if that might be what Gamakatsu had in mind with their measure of "moment" from their website I mentioned in the previous post.
I have had a thought rattling around in my head for some time now that it may be easy to overcome a tip-heavy tenkara or keiryu rod if one did not mind added weight. That screw-in butt plug provides a place to add some easy weight by replacing the existing plug with a weighted one (might be a nice side industry if the screw size didn't change from rod to rod). The only problem may be that it is too close to the fulcrum point depending upon how one holds the rod to cast it.
Measuring the COG would give a estimation of the tip heaviness of the rod. It's just a different way to measure it. The COG does change as the angle of the rod rises, though. Since we fish the rod between 30 and 50 degrees (to keep the line off the water) a better estimation of tip heaviness is made at some angle in that range. It is more cumbersome however. I chose 30 degrees due to my ceiling height.
Delete-Tom
Anothr very nice post Tom.
ReplyDeleteThis information, in my opinion, would be a very iportant one (if not the most),
in makiking a rod buying decision. Good feel and confort are a must to those who fish and cast a rod all day. Feeling light for me is more important than being light.
Sure, if you can have both the better.
Very interesting way to look at it. In western fly fishing, although not ideal, one can compensate for tip-bulk by balancing with a heavier than normal reel. In Tenkara good balance is set by the designer. Hand position makes some difference, however a tip heavy T rod is just less pleasant to cast and fish. It seems likely that some current rods will be completely refined, not just with added weight to the butt section, in such a manner that justifies the good money we are paying for the product. It is not surprising that the Japanese made (or at least Japanese marketed) tenkara (and some sieryu and keiryu) rods offer the best balance and are the least tip heavy. Glad you have pointed this out.
ReplyDeleteTom,
ReplyDeleteOnce again, thanks for the numbers. It is Very surprising to see that it would take 12 ounces to "balance" the Sagiri, especially when you consider a 4 ounce reel balancing a 10' traditional rod. That forward fulcrum makes a Big difference.
On my Kozuka 39NT I added an ounce of adhesive-backed Zonker lead when I built up the butt to give me a bulb at the end. Now I know why I had a hard time noticing any difference in the feel of the rod when held at the bulb. But when I move my grip forward I Can feel the difference.
Your numbers make it clear that a good design is the only way to go. Otherwise I'd end up with a 16 ounce rod if I wanted it "balanced".
Greg
I meant "balanced" in a traditional fly fishing context - not literally. No, I do not plan on jamming the butt end of my T rod into an apple any time soon.
ReplyDeleteTom,
ReplyDeleteThis is a very nice measurement of a "feeling" that we all have as we pick up and cast a fly rod or Tenkara rod. I think it's more significant in Tenkara because the weight of a traditional flyline and reel completely changes the "tip heaviness" of a western flyrod. With nearly weightless Tenkara lines, the rod is almost all that we are supporting.
I've never held any of these rods, but looking through your data, the weight of the rod correlates reasonably well with the cantilever force that you measure. The Ayu is 1.8 time weight of the Sagiri, but the cantilever force increases a bit less than 1.6 times.
Thanks again, I really enjoy this information,