Greetings,

It seems that I asked this question before - but can't find it. Perhaps I did not.

I have some very thin walled UL blanks. These identical blanks came either in bare carbon fiber unsanded, or painted. Before painting, the surface was smoothed. Everything else is identical.

Well, the painted ones are lower powered and just right for some applications. now I want to sand down the unsanded ones to reduce the power. I realize that this is probably fraught with peril as the outermost fiber are the ones that provides the most rigidity.

To do what I want to do, to take the blanks down a bit in power, what grit do you suggest I do?

And is carbon fiber dust toxic? if yes, I'll wet sand it in the bathtub and keep washing it down.

Thanks in advance for any comments or insight.

Mo,
I recently received several NFC HM blanks that were significantly higher in power than some I currently had of the same model numbers. We’re all aware that blank power specs are likely to fluctuate somewhat within a given model, but these were dramatically different. Because the blanks in question were also much heavier, I suspected that they were not sufficiently sanded by NFC. Being unhappy with them, I figured it was worth the risk to sand them further to reduce power and weight. I was careful to make measurements at 6” intervals along the blank to ensure an even removal of material. I started with 60 grit and worked progressively to finer grits to achieve a polished finish. The process appeared to be removing far more material than what was actually being removed, so measurements were invaluable. I ended up taking from .003” (tip end) to .006” (butt end) per side. I was able to reduce power by 15% and weight by 14%. While both have since been fished rigorously and have held up fine, I wouldn’t want to make sanding blanks a common practice.
Btw, reducing the diameter does lower the resistance to bending, but the fiber strength does not vary from outermost to inner layers.

Thank you Jim. Very helpful.

I'msurprised to see the almost perfect correlation between weight and power reduction. Theoretically, the power reduction should be must faster than weight given that stiffness is cubed to thickness of a beam. Of course, that is solid square beam while blanks are hollow tubes. Good to know - very valuable data you provide. I'm grateful.

May I ask what grits you went through from 60 downwards? What did you end up with as the final grit? I would probably be afraid to start with 60 given how rough that is as my blanks are truly very very thin!

Mo,
The only thing that I would add, since you have not done this before on these blanks would be to start wtih 100 grit paper -- rather than 60 grit.

With 100 grit, the process will take longer but that grit will also be more forgiving and less likely to cause irreparable damage to the blank.

Be safe

It is a question of patience. As Roger suggests, 100 grit would be good start. I went from 60 to 150, to 220, then used green, then gray Scotch-Brite pads to polish.

Mo,
Yes, sanding down the OD of a blank will obviously reduce the power of the blank. To what extent, who knows. Additionally, and given the same amount is removed, the further up the blank = more drastic the power reduction at that point. You are a much more adventuresome sort than me!!! Typically, I would think anyone would be well advised to NOT do so, but then I am still on the upsweep of the learning curve. Personally anxious to learn more from additional posts.

Mark Talmo
FISHING IS NOT AN ESCAPE FROM LIFE BUT RATHER A DEEPER IMMERSION INTO IT!!! BUILDING YOUR OWN SIMPLY ENHANCES THE EXPERIENCE.

No one has answered the question of toxicity, but I believe it is wise to use a mask when sanding carbon fiber. It has to be a problem for the lungs.

It is hard for me to justify sanding blanks to change power when I know how many great blanks there are out there that cost less than $75 and come "ready to use," the right power, the right action, good finish, no risk of creating toxic dust, a warranty with the great customer service of every blank maker I know of. Different strokes.

Michael,
I agree with your statement.

However, I will say that one place that does work very well to sand is to sand a solid glass or graphite ice fishing blank.

Normally these blanks are quite inexpensive but at times it is difficult to find the blank of your choice with the exact action that you desire. But, by sanding, one can tailor the action of one blank to create an entirely different rod.

I also agree that it is a very good idea to use a filter mask when sanding any graphite, or fiberglass blanks.

I have glass fibers in my lungs today that happened when I did not wear a mask working for a day to take care of a house problem. I started with a mask, but it was so hot that I stupidly took the mask off about 1/2 way through the job.
As a result, I am now suspect to various lung related issues.

You only have one body - take care of it in the best way that you can.

Good luck

You could reduce a blank's power in a finished rod by cementing a mandrel on the rod's butt and attaching your grip and reel seat on this extension. This would reduce power without weakening the walls of the tip of your rod.

Phil,
Extending the rod length will actually increase the power.

My bad. Instead of weakening the tip by sanding it down saw off the butt.

Yes, trimming from butt end does lessen power, but ironically, the rod will feel stiffer.

Actually the stiffness of a round hollow beam is based primarily on the OD to the fourth power.
Length is based on a cubic relationship.
The fastest way to reduce power is reduction of the butt diameter in the lower 1/3 of the length.
This in turn will shift the CG further to the tip while reducing stiffness of the butt.
Rod response will slow decreasing the natural blank frequency.
I would think that wet sanding would be the preferred way of finishing a graphite fiber.
I wouldn't start with anything as coarse as 60. Probably choose a 180 at most and continue down from there.
Neutral axis of a hollow tube is the center of the tube.
Fibers on the outside of the bend will be placed in tension where those on the inside will be in equal and opposite compression.
Fibers in tension on the outside of the bend will be in more tension then the adjacent fibers on the ID on the outside of the bend.
How much difference is based on the ratio of the wall thickness versus the blank radius at the measurement point.
Difference will be greatest at the tip and least at the butt.

Gene Moore

Occam's razor is a reliable tool to obtain the power you want when you select a blank.

Thanks everyone for the comments. Much appreciated.

Michael Danek, I hear you, except that I have a small supply of these blanks aready so they cost me $0 at this point, and they are very special blanks that are particularly lightweight for the power and length so they are somewhat unique.

Thanks again!