CCS … RFI … RM …? Acronyms can be downright confusing, especially when you’re unfamiliar. In tenkara, there are a few acronyms frequently used to describe attributes of rods in many popular rod reviews, ours included! If you’ve ever been intimidated by these terms, or still don’t undersand what they mean, this article serves as a simple glossary, and how one might use them when you come across them.
Note: If you’d rather watch a video explaining rod flex, including CCS & RFI, check out this detailed tutorial by Tom Davis on our YouTube channel!
Back to the article…
Common Cents System (CCS)
The Common Cents System was developed by Dr. William Hanneman as a way to objectively measure the power, action, and speed of any fishing rod. The core measurement when it comes to tenkara rods is the “penny rating.” (Get it, pennies… common cents?) Such a rating is determined simply based on how much weight (in pennies) it takes to bend a horizontally positioned rod’s tip straight down a distance equal to 1/3 of the rod’s length. This measurement was originally popularized in tenkara circles by Chris Stewart.
So if you have a 3.6m long tenkara rod, and you tie a little baggie to the end of the lillian, keep loading that baggie up with pennies until it bends down 1.2m. If it takes 20 pennies to do so, rod’s CCS penny rating is 20. This rating quantifies how flexible a rod is… and becomes helpful when used to compare rods of similar lengths.
Rod Flex Index (RFI)
Rod Flex Index is where things get a little more mathematical. The idea of the Rod Flex Index (as developed and popularized by Tom Davis) is to create a value we can use to compare tenkara rods of different lengths. He achieved this by applying the penny rating against the rod’s length, or mathematical terms:
Penny Rating / Rod Length (in meters) = Rod Flex Index
Example: 20 pennies / 3.6 meters = 5.6 RFI
By using the rod’s length as the denominator, it makes different rod lengths proportionately relative, and far more comparable. The rod flex index is then linked back to this table of values to determine the rod’s flex characteristic. The lower the value, the slower and more flexible the rod is. As the number rises, the rod gets faster and stiffer. That 5.6 RFI rod in our example would be a 6:4 moderate, mid flex model.
| Rod Flex Index | Characteristic |
|---|---|
| < 3.5 | 4:6 – Very Slow, Deep Flex |
| 3.5 – 4.5 | 5:5 – Slow, Full Flex |
| 4.6 – 6.5 | 6:4 – Moderate, Mid Flex |
| 6.6 – 8.5 | 7:3 – Fast, Tip Flex |
| 8.6 – 13+ | 8:2 – Very Fast, Minimal Flex |
This is convenient should you own an 11 foot rod with a certain RFI and really love it… but want to buy a new 13 foot rod that “feels the same” sight unseen. If you know that 13 foot rod’s RFI ahead of time, you could at least venture to guess if you’d enjoy that rod’s flex as well.
Note: There are many other factors that could impact the “feel” of the rod in hand. Factors such as weight are not contemplated in this calculation. So use this as a directional tool, not gospel.
Rotational Moment (RM)
Which brings us to Rotational Moment. There are a lot of measures one could use to figure out if a rod is well balanced or tip heavy. One such measurement that Gamakatsu uses (and Tom Davis has begun to reference) is rotational moment. However, Tom only references it on rods that are 4m/400cm or longer… i.e. your long, big fish rods. Shorter rods, even if “heavy” shouldn’t be an impediment to your fishing. But longer rods, especially those that feel heavy in hand may not be the most enjoyable to fish for long periods of time. That’s just a lot of mass to be swinging back and forth all day!
One additional value required besides the rod’s weight to determine the rotational moment is the rod’s center of gravity. This is the point on the rod where it balances when fully extended. Center of gravity is measured up from the bottom of the rod.
The calculation for Rotational Moment is:
Rod’s Center of Gravity in Centimeters x Rod’s Weight in Kilograms = Rotational Moment
Example: 84 centimeters x 0.096 kilograms (or 9.6 grams) = 8.1 Rotational Moment
The higher the rotational moment, the more tip heavy (and potentially fatiguing) the rod may be. Tom suggests that long rods begin to feel tip heavy with an RM slightly over 6. That weight becomes even more noticeable as they approach and exceed values of 7, 8, or greater.
Takeaways
We hope this article helps you decipher what some of the commonly thrown around acronyms mean on popular tenkara and fixed line rod review websites. CCS, RFI, & RM don’t need to be intimidating, and can be really helpful once you understand their meaning and function.
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