So which would be stiffer a solid graphite rod or one with a tube design? Assuming that both are the same weight?

If they are both the same weight, that means they have the same amount of material in them. That would then mean that the tubular blank would be larger in diameter and therefore stiffer than the smaller diameter solid blank.

A tube offers the most stiffness for the weight/material involved.

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OK, thanks.

John ,
The question that you need to ask is this:

Which is stiffer.
If you compare two equally sided graphite blanks - one tubular and one solid graphite - which is stiffer?

I suspect that you won't find much difference. Certainly the solid graphite will be heavier and it will also be quite a bit stronger. But with respect to flex, one would have to test to see. My guess is that there woundn;t be a lot of difference, because I think that flex is largely determined by the diameter of the tube.

Take care
Roger

You are correct Roger about the stiffness being mainly a function of the diameter. Stiffness goes up at the third power of diameter for a tubular blank and at the fourth power for a solid blank so there will be some difference but not a huge difference. However, the solid blank will have much higher hoop strength or strength against shear, torsion and crush. The difference in hoop strength will depend on the wall thickness of the tubular blank. And as Tom points out the solid blank will be heavier and again the difference will be a function of the wall thickness of the tubular blank.