What produces a spine in the rod blank?

[mrbrklyn]

What produces a spine in the rod blank?

[Midway Tommy]

There are a couple of things that create the spline. The material is cut in a triangular shape and then wrapped around tapered metal mandrels designed for specific weight & use finished rod blanks.

It is a combination of overlapping edges of the material causing one side of the blank wall to be slightly thicker than the opposite side, the sanding operation somewhat exacerbating it and the epoxy curing a little faster on the thicker side of the blank.

[swill88]

There are a couple of things that create the spline. The material is cut in a triangular shape and then wrapped around tapered metal mandrels designed for specific weight & use finished rod blanks.

It is a combination of overlapping edges of the material causing one side of the blank wall to be slightly thicker than the opposite side, the sanding operation somewhat exacerbating it and the epoxy curing a little faster on the thicker side of the blank.

Interesting.  How do you wrap traingles?  I am having a problem visualizing this.

If you wrap a rectangle around a mandrel it will be the same thickness at both ends.  Wrap a triangle will be thicker at one end thinner at the other.

hard to wrap perfectly so there is a spline.


i think.
steve

[Midway Tommy]

Interesting.  How do you wrap traingles?  I am having a problem visualizing this.

Visualize a mandrel 1/2" diameter on the butt end, 6' long and tapered to 1/64" diameter on the tip end. Now visualize a piece of fabric 6' long cut at an angle to 3" wide for the butt end and 1" wide at the tip end. I didn't use geometric equations to calculate the taper, I just used 2 numbers as an example. Rod manufactures have that all calculated to perfection. Then they roll the fabric over the mandrel so the the calculated wall thickness will be uniform. Then they wrap it with cellophane and bake it. After the epoxy sets up they sand it smooth and trim the ends.

Here's the entire process:
     

[mo65]

That is an interesting process...thanks for posting that Tommy.

[Jeri]

The spine of a blank is where during the rolling process 359 degrees of the blank get say 5 wraps of carbon cloth, and at the overlap there is a 6th layer. This infinitely small section is therefore slightly stronger than the remaining 2359 degrees of the blank. Imagine rolling a piece of precisely cut paper round a pencil - to wrap twice around most of it, and at one particular place there will be 3 wraps.

Hope that visualisation makes it simple.

[oc1]

I've seen some old fiberglass blanks where that last wrap of the cloth came up just shy of a complete revolution or just a tad longer than a complete revolution.  A thick spot in the wall will make a spine.  A thin spot in the blank will make sort of an anti-spine (that part will bend more easily).

Here's a bit of useless trivia...  Phenolic resin was used to make most tubular fiberglass blanks up into the 1970's when everyone switched to epoxy.  Phenolic resin is very resistant to just about all chemicals except acetone.  If you soak a phenolic resin blank in acetone for about a week, the resin pretty much dissolves.  You can then unroll the fiberglass flag it was made from.  If you or your company were rolling rods you could unroll blanks made by the competition to inspect the weave, cloth weight and dimension of the flag. I've never tried to unroll a whole blank, but here is a short section from a Harnell 640 spinning rod.  Some of the black surface coat had been scraped off.



After soaking in acetone.





I haven't tried it with epoxy resin or carbon fiber cloth.
-steve