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Spline Alignment: Does it matter?

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Spline Alignment: Does it matter?

Postby Jason Klass » Sat Mar 30, 2013 3:40 am

So, in rod building, a lot of people pay attention to aligning the splines (the stiffest part of a section of a rod blank). That's why you see those dots on some rods that you're supposed to match up when putting the pieces together. For western rods, that might mean aligning 2, 3, 4, or 5 segments. But tenkara rods have more like 9 or 10 segments. It would seem that with more segments, spline alignment would matter even more since it could have a big impact on action but I've never heard anyone talk about it and have never seen a tenkara rod with any markers to match up splines between segments. Is the thinking that it just doesn't matter? Curious to hear from Daniel and others with rod design & building experience.
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Re: Spline Alignment: Does it matter?

Postby tsegelke » Sat Mar 30, 2013 9:02 am

The reason for finding the spine on a rod is for the guides to be put on the natural curve of the rod. Some argue that it is not important on a rod. Others swear it makes a difference. Since Tenkara telescopes, and there is no way set up the rod to be cast on the same arc every time, It seems there is no reason to try and mark the spine. If they were marked, I guess you could spend the time to align them. Then you would have to line up the rod in your hand for the marks to be river side down every cast. The end result would probably be something you wont even notice. Also, the bottom section is also known to dominate the smaller sections, so the important one to find is the bottom piece or pieces. In Tenkara the bottom sections have very little of the flex action, making it less important to find the spline.

This is my understanding, and am also interested in a more experienced point of view.
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Re: Spline Alignment: Does it matter?

Postby John @ Tenkara USA » Sat Mar 30, 2013 12:32 pm

A rod builder buddy of mine brought up this same question, but they agreed that the shorter and stiffer the segments, the less important the spine becomes.

Just to humor myself, I took apart an 11' Iwana to see if I could find a spine in the sections. I could in the first three down from the tip, but found it tough as I got into the thicker sections. I've only built a couple of (western) rods, so a more experienced rod builder might be able to do better.

If a person really wanted to, they could find the spine on the sections and mark them with a dots to line up, but I honestly don't think it would be noticeable. Interesting conversation, though and if you wanted to try it, it wouldn't cost anything.
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Re: Spline Alignment: Does it matter?

Postby Karl Klavon » Tue Apr 02, 2013 10:57 am

Whether rod spline is important or not largely depends on the rod blank manufacturing process used to make up the rod blanks on Western fly rods. As has already been mentioned, spline alignment is important for the correct placement of the line guides on Western fly rods for casting accuracy and fish fighting purposes. Since Tenkara rods have no guides, this is not nearly as important an issue for fixed line rods as it is for Western fly rods.

Back in the days when making up rod blanks meant cutting a tapered swatch of resin impregnated woven rod fabrication cloth, adhering the cut pattern to the length of a steel rod mandrel of the correct taper to produce the desired rod action, and then rolling the cloth on the mandrel under pressure, heat shrink wrapping the blank and baking it vertically in a specially constructed oven to cure and form the rod blank, the alignment of the starting and ending cloth edges made thick spots in the blank that caused one side of the rod blank to be stiffer than the other sides. The concentric sanding of blanks, mostly for cosmetic appearances purposes, reduces the spine stiffness effect on the outside of the blank. Layup and helical rod construction techniques have no to significantly fewer spline stiffness problems involved in the rod making process. With the solid tips present on many Tenkara rods there would be little to no spline present in the tip sections of most T-rods. And with the many individual rod segments present on fixed line rods, if there is a spline it would tend to be scattered every which way on a fixed line rod and not line up in a single plain as the spline is aligned on fixed furled rods.

Determining the spline on the many relatively short rod sections would be next to impossible on Tenkara rods, and at any rate how the spline is aligned, if there is any spline to be aligned in the first place, does not seem to negatively impact casting accuracy to a measurable extent for most of us in our fishing. Consequently, while interesting, spline alignment isn't a big enough factor to worth consideration for most Tenkara fly fishermen in my view. Perhaps, Daniel can give us some input on TUSA's rod fabrication techniques and the importance, or lack there of, of rod spine on TUSA's rods.
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Re: Spline Alignment: Does it matter?

Postby rmcworthing » Tue Apr 02, 2013 9:14 pm

No up. No down. No spline.
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Re: Spline Alignment: Does it matter?

Postby jd_smith » Tue Apr 02, 2013 10:07 pm

Tenkara rods do not have a spline. Sorry Karl and Rob I couldn't resist.

The individual sections do, however have a SPINE or "relaxed curve". How do I know? Because I've been a custom rod builder for more than two decades, and I had these very questions come to me as soon as I found tenkara in 2010. "Why are these sections not marked? and "Would it matter if I aligned them?" So I took apart all of my rods and tested them for spine. For the most part the generic answer is no, it really doesn't matter if you align the spine on a tenkara rod. At the most effective ranges one would generally fish their tenkara rod, spine has little bearing on how the rod casts or how accurate you can cast. At greater distances, for you long liners out there, it may be something you would like to try, it will make a difference. Also stated above is the fact that you would have to hold the rod in the correct direction to take advantage of the spine and relaxed curve.

Most rods sold do not have the guides placed on the spine or the relaxed curve. If you have no experience finding a spine on a rod and don't have experience fishing rods with this extra step incorporated into the assembly of the rod, I say don't bother. You may or may not notice any difference. It seems that the more you spend on a tenkara rod, ( big brand names) the less it matters. My lesser expensive rods (other names) are SLIGHTLY affected by spine alignment, even at close range.

The spine on the smaller sections are easy to find, and as they become bigger in diameter they are harder to determine, just like the two piece or four or six piece rods with guides. Contrary to what is stated above, the larger sections that are nearly impossible to determine a spine, have little to no bearing on how a rod will perform. It is the smaller sections that are most important to align for the rods action and performance. If I can't determine a spine neither can the line.


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Re: Spline Alignment: Does it matter?

Postby oleg » Tue Apr 02, 2013 11:36 pm

Good question, Jason. Thanks.

Every segment has spine. When the rod is extended the total spine is randomized. The result is: Every time you extend your tenkara rod, you get another tenkara rod.
The only way for manufacturer to reduce this effect is to limit segments spine, to measure it and reject the segments with extra spine before assembling the rods. Most of manufacturers, even branded Japanese, do not do that. I do…

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Re: Spline Alignment: Does it matter?

Postby Daniel @ Tenkara USA » Wed Apr 03, 2013 9:31 pm

Wish I had seen this post sooner. I'm travelling right now and don't have access to a couple of the photos I have taken before that help explain it.
But, the answers here are good. In short, yes, there is a spine, but we really work hard on minimizing that spine and it shouldn't be as pronounced as most western fly rods. And, yes, the spine really does not matter a huge amount in tenkara.
As Karl wrote "the alignment of the starting and ending cloth edges made thick spots in the blank that caused one side of the rod blank to be stiffer than the other sides."
Try opening your rod through the back, have all the segments aligned so that you can see the walls of every segment. The better rods, with less of a spine, will have a very uniform thickness throughout each segment's circumference. Our first rods will be a bit less uniform, and we have worked on improving the process so they are better with each run. Cheaper rods, and even some expensive ones will have a thinner side; incidentally this also causes more breakages.
I have to disagree that you generally get a different rod every time you open it. I work hard so that the rod is not different every time; that's one of my guiding principles in developing the rods. A rod that is different every time you open it is not a good thing.
But, because the lines are so light, tied to the tip of the rod and there is no pressure on each section as is caused by line running through guides, it shouldn't matter.
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Re: Spline Alignment: Does it matter?

Postby rmcworthing » Fri Apr 05, 2013 7:26 am

Hmm. That's interesting.

I'm not a rod builder, but this is different than the explanation of tenkara rod construction I received from two major Japanese manufacturers. They explained that there is no true spine in a tenkara rod. There is, I was told, a false spine created by the carbon fiber layering process, which the manufacturers seek to eliminate. However, I was told there is no structural spine, as would be found in a Western fly fishing rod, spincasting rod, baitcasting rod, etc.

One manufacturer told me that some tenkara rods were made with a sinusoidal or spiral structural spine variation, but this was not the rule.

Daniel, could you clarify? Would you classify the spine you describe on Tenkara USA rods as a false spine or structural spine? Or am I just way off on my understanding?

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Re: Spline Alignment: Does it matter?

Postby pechelman » Fri Apr 05, 2013 8:25 am

sounds like what Daniel said above would classify it as a false spine, simply due to the fact that the rods are constructed with woven cloth that is wrapped on a mandrel.

Wrapping cloth on a mandrel means you have a location where the cloth starts and ends, which depending on how things are trimmed and how precisely the fabric is placed, may or may not overlap or terminate exactly how one wants.

The only way to effectively eliminate this phenomena is by using more advanced manf techniques like tape placement....which might be extremely difficult at these smaller sizes. Even then, given these small diameters and relatively thin sections, you'll probably still have some measure of asymmetry in your A, B, and D stiffnesses.

A structural spine would be created by physically adding material to a location or designing in for the cloth to overlap by a certain amount so you have more material\fibers at that lap.
Or as others have mentioned, is a by product of the rod building process where the guide feet cause a rod to stiffen a little.

maybe a better distinction here, since any spine in the sense I described above is still "structural", would be whether or not the spine is "Intentional\Unintentional" or "Expected\Unexpected"

double edit (what does it mean!? )
To answer Jason's question;
I'm a pretty picky, detailed oriented engineer, and while I have thought about this issue when I first got the rod in hand, I never once felt it was worth my time to worry about.
I suppose if I was a picky, detail oriented mathematician, I would lose sleep over this question.....but if I was a picky, detail oriented mathematician, I'd certainly have a lot more issues than this :lol:
I've never noticed any difference in how a rod casts either as Daniel mentions above.
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