This is in regard to a thread on another board.
It was stated that the spine of a blank will usually be aligned along the curve or bend in the blank.
I feel that normal(and acceptable) bends and curves in a blank are NOT strongly related to spine and have liitle if any effect on spine location.
What do you guys and gals think?
Thanks,
Kevin

Kevin,
I think that you are right and those on the other board are full of prunes. The spine will sometimes but usually not be on the same axis as the curve in a blank.

The natural curve of any blank certainly contribute to where the effective spine is. It's one of about 6 or 7 manufacturing anomolies that create the spine effect.

On some tubular structures, say a PVC pipe, the spine will indeed fall along any natural bend. But only because being extruded, it will likely have verbatim wall thickness and uniformity so the natural curve or warp is the overriding factor involved. Rod blanks are not made that way - wall thickness, concentricy, voids, etc., all contribute to the spine effect. Since blanks are rarely perfectly concentric, or have verbatim wall thickness, and may have voids in the material, these factors can make the spine fall away from any natural curve.

In most cases, the effective spine will be neither on or opposite the blank's natural bend or warp. It is rare, in fact, to find one where the spine and natural bend are on the same axis. Unless you have a blank that possesses a very, very strong and distinct curve, it's not likey that the spine and either the concave or convex curve will be the same. But, the natural curve does contribute. How much so depends on how much curve we're talking about.

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Edited 1 time(s). Last edit at 01/16/2005 09:41PM by Tom Kirkman.

It's my thinking that the primary factor in the location of the spine is the coincidence (relative positions) of the inner and outer edges of the graphite cloth as they are wrapped to form the blank. Is this correct as far as anyone knows? Would this also be a primary factor as far as the natural curvature of a blank goes? If so, would this be due to less vs. more radial wall thichness + composite shrinkage upon catalyzation & curing?

Thanks guys.

Thanks Tom, I knew you'd give me a detailed answer. :-)

Kevin

Ed,
You are right that how the material (prepreg) overlaps is one of the factors that results in what we call the spine in a blank. It contributes to the spine in a couple of ways. First where the material overlaps there is in effect an extra layer of material and second this overlap results in the blank not being perfectly round or very slightly oval in shape. However, as Tom pointed out there are a number of other manufacturing anomales that also have an effect.

I've always wished that rod blanks could be extruded. This would allow for much greater control in terms of taper, concentricity, wall thickness, etc. But, I know of no extrudable materials that have sufficient modulus to create fishing rods at the performance level we've grown accustomed to. Maybe a few years down the road something will turn up.

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