More On Spine

By Tom Kirkman

Here's a question from the Volume 2 - Issue #4 issue of RodMaker magazine:

RodMaker Magazine

" . . . I have followed the debate on finding and using the spine with great interest. Very briefly, in my mind, there are 4 main 'lines' along the blank. When bending the blank, holding the tip and placing the butt on a table, during the 360 degree rotation I encounter two "stiff" (unstable) positions where the blank wants to move further down into either of two "softer" (stable) positions. Trying to twist the blank out of either of the stable positions takes a bit of force. On most of my blanks the "built-in" curve of the blank follows one of the stiff positions, very easy to notice on my Scott.

I have considered placing guides along either of the two stable curves, because I thought that during casting this would stabilize the movement, i.e., the rod would not have this tendency to twist away from the unstable position. Words fail me here, but with your experience, I think you know what I mean.

Any help will be greatly appreciated, so I don't spend several more months wondering about what I do. . .Sigurd . .Norway

Glad to see that you realize the importance of utilizing the spine in rod making. There are so many theories and concepts concerning the spine that it is often difficult to make a dicision on the best way to utilize it, let alone find it!

The spine of a blank, which is the outside curve when the blank is in its relaxed position, is caused by the fact that the wall thickness around the blank varies due to the intricacies of the prepeg pattern and how it is wrapped around the mandrel during the manufacturing process. In your case, I would suggest locating the more pronounced of the "softer" positions and using that as your reference point, marking the outside of that curve as the spine.

As you have noticed, the stiffest plane or axis usually follows any natural curvature of the blank, but may or may not be exactly 180-degrees opposite the spine. In this instance, you will have to decide what particular performance characteristics you deem most important and locate your guides accordingly. If casting is your main concern, some test casting with the guides both on and opposite the sprine should be undertaken and will make it easy where the guides should be located. If fish fighting is the primary objective, you may find that locating the blank so that the stiffest side is presented to the fish (this would usually put the blank in a concave position following its natural curvature as it is help parallel to the ground) yields the best results.

I always strongly suggest attaching the handle in a temporary fashion and taping the guides on the blank in various positions relative to the spine and then going out and doing some test casting and fighting/lifting. Doing so will teach you a good deal more about how the spine relates to rod performance then any amount of reading or considering theories ever will. Good luck. ~ Tom Kirkman

Publishers note:

If you have any tips or techniques, send them along! Help out your fellow rodmakers! ~ Publisher, FAOL

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