In order to preclude a firestorm of topics that have been beat to death, I want to preface my question with a couple of statements. I am not, in any way, refering to castability (distance or accuracy). I also realize that the rods pitch and yaw axes are controlled by the angler and the roll axis is controlled also by the angler wit;h definate input from guide (torque arm/ lever arm) configuration. Also, I am refraining from even using the term spine.

My question is from a durability/longevity standpoint. If a blank wants to flex in a given position (be it a result of manufacturing, voodo, or a force from a galaxy far far away) am I possibly causing any decrease in it's life by forcing it to flex in a different position.

I hope some of the pros will chime in, as I only build as a hobby and one breakage for me would be a larger percentage than one out of hundreds.

What prompted this question, is that a pretty reknowned blank/rod manufacturer stated ,on another forum, that when they started building on the spine, that their breakage returns decreased.

It sorta makes sense. Everything in nature that has a spine or comparatively more rigid structure within it has evolved in some way to take advantage of that structure. The stronger it is, the more structurally relevant it becomes, and the weaker it is the more irrelevanf.
The spine in a rod exists for a mechanical reason determined in its particular structure.. Perhaps a minor reaon, but it exists. For the maker you mention, are the spines very noticable?

I understand work hardening, that is part of why I posed the question. I couldn't say about his blanks, as I have not used one, but they are very popular.

No you will not shorten the life of the blank by disregarding the spine. Remember, the lever arm effect of the guides will dictate what the blank will be forced to do. Twisting a blank is bad business, past a certain point. As long as it doesn't twist you're okay. And, blanks are made to withstand at least some amount of torsional force. No matter where you orient the spine, you aren't going to hurt it as long as any twist doesn't become excessive.

Remember that when you flex a blank a lot of things are taking place internally - a lot of forces are opposing each other and that's why the blank resists flexing. But the spine effect is of little consequence. The natural ovalling of the blank is of far greater concern.

Then you get into the problem of exactly where is this spine effect at any certain degree of flex? Because it's an effect and not a thing, and because it tends to rotate around the blank as you deepen the flex, which axis/spine is the manufacturer building on? I don't want to downplay anything that a manufacturer feels is reducing breakage, but I'd question the scientific nature of any such statements against the actual data they're comparing to.

G. Loomis built a device some years ago that loaded a blank and then rotated it in a continuous 360 degree manner. They often did this for days on end and their feeling was that a blank is equally strong in all positions and no particular axis would prove more durable than another. They did feel that spiral wrapping casting rods would prevent rod twist and reduce breakage on that count, but their early spiral wrap offerings did not sell well so they dropped them.

There have been a lot of very knowledgeable people in the blank business over the years. Jimmy and Don Green (no relation), Gary Loomis, Steve Rajeff, Dick Kantner, Wade Cunningham and others. I've known and spoken with all of them about the very thing you ask about and not a single one believed that building on the spine reduced breakage or somehow made the rod more durable.


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And that's why Todd builds on the spine. Now which side, outside or inside of the curve, I don't know, but I would think, he would be more than happy to tell you if you ask him.

Seems to always break down into camps in the past, largely based on folks defending what they themselves do.. I think a reasonable middle ground is that if only takes a few seconds to locate, then why not? One camp says it makes no difference, so then orienting to the spine should make zero difference to them. The other camp believes it makes a difference, and so you are catering to that side as well.
Basically, seems you can do no wrong building to the spine, it is just that it may make no measurable physical difference. It may make a significant marketing difference, however, as a spin to differentiate yourself from, and elevate yourself above, competition. An illusion perhaps, but illusions are powerful things.

Whatever works for you is the way to build them.

Mike (Southgate, MI)
If I don't want to, I don't have to and nobody can make me (except my wife) cuz I'm RETIRED!!

C Royce,
I think that is a very good question. Fiberglass will lose its strength over time with use but I do not think that either carbon fiber or fiberglass will work harden like a metal. The reason being that with excessive stress they do not pass from elasticity to plasticity like a metal and work hardening is the result of plastic deformation or exceeding the plastic limit.

It is hard to argue with a manufacturer that believes that they have less breakage due to aligning the guides with the spine. But I guess that I would sure like to see the data and know how the testing was done. If you look at the individual factors that cause what we call spine, the blank not being perfectly straight, the material not being uniformly distributed around the blank, the blank being slightly elliptical, voids in the material etc. you can imagine how these might cause spots or localized areas in the blank where the stresses could build up. But frankly I cannot see how rotating any of these factors relative to the guides would result in higher stresses at one angle of rotation versus another. In other words I cannot see how what axis the guides were mounted on would significantly change the stresses on the blank which is what will have to happen to increase the breakage.
Do you have any more information about this?

Emory, I don't really have any other information on this. I may be in that proverbial apples/oranges area. A couple of things that added to my curiosity here were in the case of a valve spring, in a competition engine, each cycle of compression/expansion doesn't take it to it's plastic region but the repeatitions will eventually take it's toll. Granted, in that instance, we're looking at 60 plus times per second. Also many bolt manufacturers and end users have limits on how many times a bolt should be torqued.

That got me thinking about repeated flexing of the rod with normal use.

I don't think that they were actually putting those rods through a testing process or at least his post did not mention that. He just stated that their breakage dropped from 5% down to 2% and they had made no other changes in their preceedure. I think that I am correctly remembering those percentages.

Not wanting to appear like gossiping across the back yard fence, but that was Todd Vivian on the guild's forum and I certainly would not have the knowledge or expertise to challenge it. By the same token, that also applies to me challenging any others with differing theories.

The fatigue life of most carbon fibers is extraordinarily high compared to some of the other materials you mention. And I doubt it'll change regardless of where you opt to orient the spine.

A manufacturer could certainly do a scientific analysis of breakage percentage for various spine orientations. But he'd have to utilize a truly large number of rods, half built one way and the other half a different way. It would not be be a fair nor scientific test to use data from previous models or years against something current, as you'd be introducing a host of other variables into the equation. And even with the same model, half built one way and half another, you'd have to spread this out over many tens of thousands of blanks due to the variables introduced by fishermen themselves and how the rods may have been broken.

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C Royce,
I do not know about your bolts or valves you may be right. I know Todd very well and know him to be very knowledgeable and also very honest and very direct, he does not blow smoke. But having said that the more I think about it the more trouble that I have believing it. If you look at the main ways that rods are broken, over stressing by high sticking, impact or hitting them against something or stress concentration in front of ferrules I do not see any connection with any of these and spine that would result in more breakage. Plus if you just think about the simple fact that the spine is the axis that the blank is the weakest it does not make sense. You would think that if there were a correlation between spine and breakage that the rod would be more likely to break with the guides on on the weakest axis or on the spine.
You have aroused my curiosity, maybe I will give Todd a call.

Tom,
You and I must have been typing at the same time. You make a good point. During the time that Lamiglas was collecting the data they no doubt had model changes, design changes of the same models, changes in prepreg or prepreg suppliers and a host of other things could have changed. On the other hand you would think that they would keep pretty close tabs on breakage because of the affect that it would have on profitability. A 5% change would be very significant to them.

Guides on top - Load rod
Results in bend plus torsional stress - cyclic torsional stress + cyclic bending stress = total stress

Guides on bottom - Load rod
Results in bend stress only = total stress

I would suspect that the numbers the manufacturers possess will support a lower breakage rate for spinning rods vs casting rods in the same weight class. I would think that the five percent difference noted above would be on the low end of the scale. If Todd builds production rods on the spine he could verify if there was a difference.

I am sure the manufacturers have this type of data for warranty cost calculations. It sure would be nice, if it was not propieatary, and they would care to share some of the knowledge that they have. Without this type of information it would be difficult for them to offer the lifetime warranty that goes with the initial purchase of a rod. This type of post has been made a number of times in the past and none of the designers have chosen to comment. Must be top secret!

That's why little ole me, the guy building 6 to 10 rods per year is dependant upon the expertise here on the forum to try and have a clue.

I really doubt that any manufacturer, no matter how good, would want their breakage rates known to the competition or the consumer. That wouldjust open the doors to ad's like "Our rods break 10% less than _____. That wouldn't be very bright on their part to release numbers like that

Mike (Southgate, MI)
If I don't want to, I don't have to and nobody can make me (except my wife) cuz I'm RETIRED!!



Edited 1 time(s). Last edit at 08/22/2007 05:20PM by Mike Barkley.

Mike, I would agree with you, however he posted it on that forum roughly a year ago, where I would suppose anyone could read it. It was during one of those mile long threads about spining rods.

As an added thoutht, I hope that I'm not causing anyone any grief,by mentioning it.

Bill,

Keep in mind that the spine and the stiffest axis are not opposite each other. It is a common misconception that one side of the blank will put you on the softest axis and the opposite axis will be the stiffest. That's not how it is.


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Mike,

Most of the rod and blank manufacturers I have spoken with over the years speak of a true defect rate (rods that break for reasons other than fisherman abuse or accident) running at 2% or less. When the number climbs above this, you have to make some changes.

A lot more rods than that get broken or fail, but not usually because they contained a structural defect.


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Edited 1 time(s). Last edit at 08/22/2007 05:23PM by Tom Kirkman.

I understand the need for them to be aware of, and track the numbers, but I'm really surprised that they release them to the public or competition! I just don't see where there is any upside for them to do so.

Mike (Southgate, MI)
If I don't want to, I don't have to and nobody can make me (except my wife) cuz I'm RETIRED!!

I don't think that they release them to the public. I'm not aware of anyone using them in any advertising or anything like that.

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