Modulus vs Rod Action-- how related???

[Orthoman]

What is the relationship between rod action (fast, moderately fast, slow) and Modulus?

In attempting to buy a fast action blank of 57,000,000 modulus to build a new rod, I called a supplier and was advised they could not get the blank I wanted -- it was back ordered and delivery date was unknown. The company then I called suggested that I buy a 37,000,000 modulus blank instead and that it would be as fast or faster than the 57,000,000 blank. This doesn't make sense to me as I have typically used a relatively fast action Sage XP that I believe also has a relatively high modulus.

Althought fast, moderate, and slow action may be somewhat subjective,it would seem to me the faster action rods will also be of a higher modulus.

Can anyone out help me out on this issue?

[taoski]

I would agree with Mer. To expand on that, if the 57,000 ksi and 37,000 ksi rod have the exact same action, the 37,0000 rod will PROBABLY be heavier and probably have a slow recovery speed.

I say probably because modulus only refers to the carbon fibers, and doesn't account for the resins and scrim. So it only relates to one ingredient, not the overal product.

That said, I wouldn't focus so much on rod modulus. Compare action, power, and blank weight-- that will give you a better comparison. And if you want to get technical, do a search on the common cents system, that is truly the best way to compare blanks, short of casting each one.

Modulus is a measurment of a materials resistance to bending in relation to its weight. Steel has a modulus, wood, fiberglass, telephone poles.
The higher the modulus the more resistant to bending the material is. With high modulus graphite you can make a rod that is very light weight and very stiff......but you dont have to.

[kengore]

modulus short for an enginnering term 'modulus of elasticity' This is one of the basic mechanical properties of a material. It's a measure of how much a material changes shape when subjected to a load. In engineering terms the modulus of elasticity = stress/strain. The higher the value the 'stiffer' the material is.

For any given material the taper design, wall thickness and fiber orientaion will predict the action of the rod, much more than the material it's made from. I could build very stiff rod from a low modulus material such as wood (like a broom stick),or a very soft rod from high modulus material such as steel (like a radio antenna).

With that said, for the same flex charactoristics a rod made from high modulus material would have less mass than the same rod made from lower modulus material. This is because it would require less material to achive the same flex charactoristics. I think this is why rod manufactors are always advertising the 'high modulus' graphite.

It means they can build a stiff fast rod with a thinner, lighter (and more brittle) wall section. The new high modulus graphite rods weigh very little compared to older fiberglass or cane rods. They also break more easily since they have much thinner wall sections.

Just because a rod is light, fast or made from the latest most expensive material doesn't mean it feels good in the hand. I suggest you actually cast a rod before you make your choice. There are a lot of lower modulus rods that cast beautifully. And some of those fancy high modulus rods feel like a club in my hands...

Stiffer doesn't always mean better, but in material properties terms it usually means more expensive.

[Orthoman]

Thank's guys -- you have help me understand modulus vs taper and how they effect action.
I appreciate all of your input.

[dleo6446]

Kengore nailed it. the modulus refers to 2 things, modulus of elasticity, and modulus of rupture...the bending points and breaking point. The action of the rod is determined by the taper design of the rod.
Great explanation Kengore