The specific blank model we used for our dead lift (overload) failures were a St. Croix model. All were tested and found to capable of sustaining 23 pounds of dead-lift load. At some point between 23.5 and 24 pounds, every single one of them failed, regardless of where the spine was oriented. I'd have to go back and look at the records but I think we ended up busting about 3 dozen or so of this model during that phase. If there was any difference in actual dead-lifting capability between spine orientations, it was extremely slight. There was only a half pound difference in break strength in this lot of blanks. That sounds like about 2% at the most. (Pretty good quality control on St. Croix's part for all to be so close.)

Again, since we don't fish on a single axis it would be hard to use this to any practical advantage. Although, if you put the thicker side of the blank on the bottom (assuming that most of the flex will be down or somewhat down rather than somewhat up) you will find that what you have done is use the straightest axis and oriented it so the tip and butt are high and the belly of the blank is low.

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Great topic, so many thoughts here is one more. If when building a fly rod I mount the guides on the soft side modified or rolled to straightest axis. During the back cast this puts more load on the blank and therefore more drive into the forecast. What do you think?

JLS Custom Rods
Cassadaga, NY

Remember that what you call the "soft side" is not opposite the "hard side." And the difference between the two is generally very small. If you run the CCS ERN numbers on both, you're apt to find less than a .2 difference.

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Tom,
So what you are saying is, where you place the guides (hard vs soft, strong vs weak, convex vs concave or whatever terms) will make very little difference in the casting performance of blank. Is that a correct interpretation?

John

That depends on what you mean by "performance." If you're talking accuracy, it makes no difference. If you're talking distance that depends on how well the casting weight (or fly line) plus your input load the rod on that particular axis. Even then, it makes only a very, very slight difference.


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In my judgment the spine is a manufacturing flaw and the smaller the spine, in other words, the more uniform a blank is on any plane on which it is being deflected the better the blank. Tom is probably correct that with todays manufacturing processes all blanks will have some spine but I think that rod blank manufacturers should be attempting to eliminate any spine just as the carbon fiber golf club manufacturers are. I think in time both blank and golf club shaft manufacturers will elinimate the problems associated with spine.
I think that many rod builders only have a vague idea about what spine is, what causes it and why it occurs where it occurs. There are some application notes on a web site that explains it very well. The web site is {CSFA.com}. The web site is the work of a very sharp mechanical engineer who is interested mainly in golf club shafts but his work applies to rod blanks as well. If you are interested go to the web site and look for the technical notes. There are several technical notes that pertain to spine.

Unless the industry starts making blanks in a completely different fashion (pressure molding, etc.) you aren't going to eliminate having a "spine", curvatures (however slight), weaknesses at transition points, etc. Even with ART (St Croix's method of stabilizing inherently weak spots) you simply reallocate and widen "stress points". The ONLY way to have consistent results is through consistent manufacturing processes. Those processes would have to eliminate human hands AND "start/stop" points in materials, among other things.

I don't know as much as you guys. But I can still have an opinion. I do not believe a rod is going to fail because the guides were put on some wrong axis of the blank. I have never had a rod fail just fishing for the species that I want to with that particular rod. I think failures come from damage to the rod, nicks, hits with a beadhead fly, etc. Some defect introduced into the rod. As a fly rod, I have never had one fail. Period.

I do not believe that placing the guides ON the effective spine....or opposite the effective spine is going to enable better casting, hook setting, or landing a fish. It...in my mind is such a small insignificant effect that it becomes irrevelant.

Now on big rods like probably ocean rods....I dunno...never done it...but those may be important to spine alignment because of the load....the torque might have an effect. But normal fly rods I think not.

'tis a big waste of time I think.....

Torque is cased by guide position, not spine alignment.

In short, there is no "wrong" nor "right" axis upon which to orient the rod.

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