What things affect the rod's Power.

 

Is it simply the diameter of the blank? I assume also the thickness of the blank's walls also.

 

What makes 1 rod a Medium vs a M/H? Is it merely that a M/H is larger in diameter with thicker walls, and thus is stronger?

Power is/was rated by lifting a dead weight to the point the bottoms out. Bottoming out is subjective let’s say bending to a parabolic curve at 90 degrees. You attach a weight with the reel mounted and line through all the guides and attach the line to a weight. Now lift the weight off the floor while letting the rod bend about 90 degrees. If a 1 pound weight can be lifted with the full rod bend the power is 1 or light.

Repeating the lifting with 2 pound weight = medium light.

Lifting a 3 pound weight = Medium power

4 pound weight = Medium heavy.

5 pound = Heavy

6 pound =extra Heavy.

Since there isn’t a standard this is subjective.

Tom

 

Thanks for the way they are rated Tom, but sorry Baz - i don't know how they are built either, Good question, never even thought about it.

This link from the Mudhole has a good explanation

https://mudhole.com/blogs/tips-tricks/rod-blank-action-vs-power-explained

Thanks all.

It’s all physics.  Blank diameter, wall thickness, and material stiffness.  Bigger diameter, thicker walls, and stiffer material will all make a blank stiffer. Balancing all of those factors is what turns engineering into art.  The material that makes a rod blank is a big sheet of graphite ‘scrim’ which is like saying a big bedsheet of woven graphite fibers.  The sheet gets wrapped around a metal rod and then baked in an oven until all the layers cute into each other.  But since the blank has to taper, the graphite isn’t a straight line- it is more like a weird uneven parallelogram.  And the metal rod is also tapered.  the metal rod makes the inside diameter and then how much graphite you wrap (and where) makes the outside diameter. You can take a skinny inside diameter and wrap the graphite really thick to make it stiff.  it will be a little heavier, but it will have the same stiffness.  Or you can make a really big diameter but only use a little graphite to have the same stiffness.  If you look at a lot of more inexpensive blanks right now, they are larger diameter and really thin walled.  That makes for a lighter blank with less graphite and/or lower stiffness graphite all of which make for a less expensive blank that feels higher end.  But it comes at the cost of durability.  Just a bit more wall thickness means that impacts are better absorbed. But then increasing the wall thickness makes it heavier unless you use a lighter (per thickness) graphite in the first place.  So it is all a balancing act.

The reason I use lifting power for a bass rod is that is what a fishing rod does regarding power. I disagree with MudHole explanation it’s force needed to bend the rod to it’s action shape, that only takes a few ounces.

Trying to explain a tapering tube hoop strength for a wide variety of materials is meaning less to a bass anglers needs.
Tom

There are basically two approaches to blank design. One is thin wall, larger diameter. Second is thicker wall, smaller diameter. Neither is right or wrong, just two paths to a similar destination.  Regardless of which construction method is employed, as a consumer heavier power rods are more resistant to flex. Each heavier power will have a higher lure weight range and corresponding stronger backbone. How strong, you can’t tell as all labels are subjective with no industry standard. 

Power vs action can be tricky especially if you are new to fishing...Generally speaking I'd say think of power as how much weight it takes for a rod to 'load up' which is to say how much weight can be put on it before it bends as much as it 'should' under ideal conditions...another way to think of power is just look at the max lure weight rating they give you...that's going to be an estimate and it isn't always right but usually close...