Through my novice eyes and not being a fly-guy, I tend to agree with Michael and Norman in that IP may be the simplest, purest form to measure a blank’s power; it clearly requires X number of pennies to deflect a blank 1/3 of its length when held by 10% of its length.
I just took delivery of 37 vintage Conolon blanks (7 different models) and performed IP and AA measurements of those and the other Conolons already in stock. It is the first time I have had CCS measurements of so many blanks side-by-side on one sheet of paper. One thing immediately became obvious; very precise measurements are paramount! Slight differences in either IP or AA can produce a very noticeable difference in the actual blank characteristics. While the addition of pennies is quite simple and straight forward, I cannot imagine achieving accurate AA measurements without a digital level; using the same unit to set the blank to perfectly level AND to measure the tip of the blank eliminates any guesswork of leveling an angle-card and provides digital angles to the tenth of one degree.

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

ERN derived from the number of pennies, not IP.

I do not think it is important for anyone to know how much weight it took to flex the rod a distance equal to 1/3rd of its length. In fact, it only leads to confusion on the part of the end user. That's the behind the scenes stuff and is only meant to be the basis for determining relative rod power. When you start explaining to a person how much weight it took to do this or that, instead of simply being able to say "this is a 2-power rod and this is a 3-power rod" you've lost sight of why the system was invented. The idea was never to determine how much weight it takes to flex the rod the required distance, only how much more or less weight was required from one rod to the next, and then a whole, simple, relative power number assigned to that.

The inventor intended ERN to be the rod power number. I'll stick with that. Obviously, others can do what they want.

.........

Just a friendly point of disagreement. I just don't like the arbitary and non linear way ERN was derived/defined. I think it could have been defined in a much more linear and intuitive manner. But that's just my opinion, and it does not take away from the importance of using CCS data for comparing blanks. I like IP you like ERN, so be it.

Norm