Finding the Spine on a Fishing Rod Blank [Rod Building Guide]

the Spine on a Fishing Rod Blank

Locating a spine along the fishing blank is one of the most important reasons why custom rods perform better than mass produced.

By loading and bending the rod with the spine being perfectly aligned on the outside of the curve, you will get better casting abilities and a stronger rod.

Rod spine can be observed as a human one. You are the most efficient and strongest while bending forward, not to the side or backward. 

No matter whether are you building a casting rod, spinning rod, or fly rod, it is equally important to check and find it before proceeding with other parts. 

Finding it is not hard, especially on a one-piece rod, and it is crucial to find it before mounting your rod guides and reel. 

So, here is a short guide that will help you find the spine on any rod and create a perfectly tailored, high-performing, piece of fishing equipment!



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What is the Spine in a Fishing Rod Blank?

Before continuing about performance, the rod part along the fishing blank, referred to as the spine, is the strongest part of it.

When materials are assembled and layered together, in the manufacturing process, there are always some minor differences along the blank. Even a slight deviation in the material can have an impact. Those are not visible, and you can't see them, but you can feel and discover them with a simple test I will mention later. 

This spine part is stiffer than the opposite one ...

Due to this spine, the rod has a natural way of bending and flexing where the stiffer side is on the outside of the curve. Of course, the rod will flex in all directions, and mass-produced rods are not considering it, however, following a natural curve has various benefits

It can improve casting distance and precision, allow deeper motion without breaking, and give more strength under load. Those differences are very subtle and complete fishing beginners may not feel them at first, but experienced anglers will notice.

Finding Spine on Fishing Rod - Spinning

Why is Important to Find the Spine?

When you find it, that is the baseline for mounting all other parts on the rod.

When building a spinning rod, line guides should be located along the inner part of the spine perfectly aligned so that they hang below the spine, inside of the curve. The same goes for mounting a reel. 

When talking about casting rods, rod guides will be located on the outside part of the curve (the spine side) together with the reel. 

This will enable natural bending where the stiffer side is on the outside when the rod is loaded and flexed under pressure. 

All of this will also avoid potential performance problems, especially when building a multi-piece rod. If the spine is not taken into consideration, you may get uneven load distribution which can lead to damage or a bit worse handling experience.

Finding Fishing Rod Spine - Guides 

How to Find The Spine On A Fishing Rod Blank?

Here is a process I do - just follow the steps below:

  • STEP #1: Gather all the tools - you need a flat surface like a table, mask tape, and china marker (grease pen).

  • STEP #2: Use the tape around the middle to create a "flag" on the rod blank. Wrap it around and attach the two ends to stick out about half an inch.

  • STEP #3: Place the rod butt on the table. Use one hand to hold the rod near the top, in the upper fourth of length. Rod and table surface should be at around 30 degree angle.

  • STEP #4: Use your other hand to apply pressure onto the blank. Place that hand slightly above the half of the length.

  • STEP #5: When pressure is applied roll the blank and observe the flag from tape. Rod should "pop" into a position from which it rotates harder. When you find this position, you have located the spine.

  • STEP #6: Repeat the process a few times. It may have more than one spine, however you are searching for the strongest or most pronounced spine.

  • STEP #7: When you find it, use a grease pen to mark the spine (outer part of the curve for casting rods) or to mark the opposite side (inner part for spinning rods). Make a line along the blank a few inches long.

  • STEP #8: And that's it! You have a baseline to add other parts. 

Finding Fishing Rod Spine - Bend

You can also use a spine finder which is a tool that resembles a rod holder. You insert the butt and apply pressure with your hands in the same way as described. Rod will turn itself into the natural position without you rolling it.

How do you Find the Spine of a Two (or More) Piece Rod?

When building two piece rod, you need to do the process described above in both sections.

Then connect them and repeat to see if the whole unit works. If you located the spine correctly on both sections, when connected and tested again, you will get the same result. If not, maybe one of the pieces has more than one spine and you need to test again.

Also, you need to carefully check that the spines are aligned (use the markings created by the grease pen) when connecting the pieces. 

The same goes for three or four pieces, however, the top two will be easy to test, but the lower ones will be much harder to flex. Sometimes, it will even be impossible. 

In such a case, just observe the bottom section of the rod blank, feel it, and look along it to visually choose the straightest axis. 

Does Finding Spine Really Matter in Rod Building?

There are divided opinions about this topic, but those who know me know that I like to check data and scientific research. So here is a short recap of the one I found in Rod Maker Magazine

Two groups of 50 blanks were tested under load. Half of them were loaded in line with the stiffest, and half with the softest axis. A bucket of water (20lbs) was the load and water was added gradually. 

Keep in mind that those that failed under very high or low loads were not calculated here to exclude manufacturing deficiencies. One 10th of an ounce was added at times until the blank failed. Every number that the blank withstood was recorded. 

The final result showed that typical failure on the soft axis was 22.5 lbs and on the hard axis 23.7 lbs.

This is around 6% difference. Considering that you are casting and reeling in the fish under various directions (for example sideways) and flexing the rod in different ways, 6% is a minimal difference in real-life conditions. But think about getting a 6% raise in salary? Would you say "No thanks, it's not a lot."? It seems insignificant but those 6% can mean a lot in the right conditions. 

I think that building a rod but skipping this simple check is simply lazy. You have nothing to lose but a lot to possibly gain.

Experienced rod builders and their customers know the importance of the slightest details, including this one. All the details together have quite an impact on the final product.

Finding Spine on Fishing Rod - Research


As you can see, finding a spine is an important moment in your rod-building experience. It enhances performance and prolongs your rods life, especially if used under heavy load. 

The process takes only a couple of minutes, and even complete beginners can do it without any special tools or advanced knowledge. 

So, before you start mounting your fancy guides and reels, check for the backbone of your new rod!

About Me

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I am Siniša Pintar (friends call me Sina), the guy behind and eBook writer. This site is base camp for fishing enthusiasts from all over the world. I love fishing and want to share all my stories, knowledge and my experience with any and all potential anglers. Read more ...

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