There is always a lot of discussion and debate about building on or off the spine and how it affects the finished rod. I checked a graphite 7.5 foot blank today and this is what I found. First of all finding the spine was a piece of cake, obvious without any special tool.

THIS IS ONE BLANK. I DON'T ARGUE THAT THESE RESULTS WILL BE THE SAME FOR EVERY BLANK. But I do believe that they are about what will be found for most blanks. I recently checked a 9 wt fly blank and found about the same difference.

First check, 675 IP, 75.5 AA

Rotated 180 degrees: 650 IP, 75 AA

3.7 % difference in power, AA is probably within test error. So ON THIS BLANK building any way one would choose would probably fish the same, with no perceptible difference. The only way to know how your blank will build is to measure it.

After doing this, I let the blank remain on the latter orientation and checked it for 7 feet and 6 1/2 feet:

7 feet long, IP 650, AA 75

6 1/2 feet IP 590, AA 72.5

This verifies what has often been said about cutting from the butt, power goes down, action slows.



Edited 1 time(s). Last edit at 11/06/2023 05:11PM by Michael Danek.

Thanks for sharing, I’ll have to start testing the difference on my next builds.

Only thing I see that wasn't measured was the specs when testing on the stiffest axis. 180 degrees from the softest axis (spine) is rarely the stiffest axis. Find the stiffest axis and measure there and I think you will find just a bit more difference between that and the spine.

Straightest axis and stiffest axis go hand in hand many times.

Spencer Phipps Wrote:
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> Straightest axis and stiffest axis go hand in hand
> many times.

Yes, they go hand in hand almost always. But the softest and stiffest axis are rarely 180 degrees apart. The spine and the straightest/stiffest axis are usually anywhere from about 110 to 170 degrees apart.

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This blank is so straight that I don't recognize a "straightest axis."

You can find the stiffest axis by hand just as easily. It's not likely to be 180 degrees opposite the spine, but who knows... maybe you got lucky.

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Interesting findings. Thanks for posting!

The stiffest axis is easily found and seems to me to be close to 180 from the weakest. Maybe 170.

170 is common. Take the measurements on that axis and most likely you'll see the power come up a little bit more. Just a little bit.

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Could you clarify the data measurements you used? AA and IP? I apologize I am not familiar with that terminology.

Common Cents System. AA is action and ERN is power. Go to the magazine website and you can find and read the article on what it is and how to use it.

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Thanks! I was looking to far into the woods I see and couldn’t see the trees.

Here is a handy web site:

[common-cents.info]

The third entry down in the Library link at the top of this forum is a handy chart. You will find it here, too:

[www.rodbuilding.org]

If you decide to make a rig, and there are ways to do it that do not require the 4 x 8 sheet of pegboard, and want some tips, let me know. I check every blank that goes through my hands. It can also be done for finished rods, factory rods, any rods.