when comparing a heavy power rod versus a medium power rod the heavy power rod is usually a lot thicker. is this due to more material there to make the rod stiffer overall? if this has been talked about already sorry ahead of time.

Lots of reasons. There's thick wall design, thick butt design, and so forth.

All have their place to achieve whatever the blank designer is trying to make it do. Typically the thinner butts will have thicker walls and thicker butts will have thinner walls. It's all about achieving hoop strength - in other words not letting the tube (the rod) go flat when flexed. It the rod goes flat, it can fail (break). I'm putting that in real simple terms - maybe over simplifying.

The wall thickness through the length of the blank may vary to achieve the desired stiffness in sections.

Basically it boils down to a difference in design. Both have their place.

very interesting, thanks for the input:)

One of several articles from the library here:

http://www.bassresource.com/fishing/rod-actions-power.html

Rod diameter does not equate to power. I can show you two rods, with different diameters that have the same power.

Hoop strength is basically the ability of the rod to maintain it's structural integrity.

Scrim (additional glass or carbon fiber add to align fibers and resins) and elastic modulus (aka Young's modulus - stiffness of the fiber) and tensile strength (force required to pull fibers apart - or break them) go into the equation.

From St Croix:

Advanced Reinforcing Technology (ART) is a proprietary St. Croix manufacturing process that adds strength to our rods in critical locations without adding weight or increasing the rod's diameter. By adding a very thin layer of special graphite fibers wrapped around the blank at right angles to the regular longitudinal fibers, ART significantly increases the hoop strength of the blank by preventing it from deforming or "ovaling" under severe a load, such as a powerful hook set.