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### Rod Flex Index Chart

It is difficult for any person to guess the action of an unknown rod unless there are some objective data that has been published.  Although there is no standardized method for measuring the flex of a tenkara rod, there are two easily performed and reproducible measurements may help give the investigator an initial idea of how any given rod may behave. These measurements are the Common Cents System measurement and the Rod Flex Index. The Rod Flex Index (RFI) is the Common Cents System (CCS) measurement of a rod (in US pennies minted after 1996) divided by the rods length (in meters). This simple rating gives a person an estimate of how a rod's action might feel in comparison to other rods of any given length.

For instance, if Rod A has a CCS of 21 pennies and it is 360 cm long the RFI would be (21 divided by 3.6) 5.8. That would give the rod a mid flex action in the 6:4 flex range. If Rod B had a CCS of 28 and its length is also 360 cm, then its RFI would be 7.8. This would predict the rod of having a tip flex 7:3 action. Therefore one would be able to predict that Rod A would feel "softer" in action than Rod B. Now, if we have a shorter rod, say Rod C at 310 cm, and its CCS is 18 pennies, it would have an RFI of 5.8. From this we can tell that even though they are of different lengths, Rod A and Rod C would feel very similar in their flex actions. This is useful data if you are considering purchasing Rod C but you have never laid hands on it, but you have Rod A.

For a more complete explanation of these measurements, see my article at the A Treatise on Static Rod Testing tab on this blog.