Hello everyone,

Does anyone know the formula used to calculate ERNs in the Common Sense System? The Rosetta Stone Chart only goes up to an ERN of 16.0.

I'm asking because I noticed that PacBay lists the IP for some blanks in grams, while NFC lists the IP for their blanks in ERNs. I was wanting to compare the numbers but didn't have a method to convert Grams to ERN and vice versa above an ERN of 16.0. I could just use the NFC chart in the Library on CCS (It goes to an ERN of 200), but that involves a lot of extrapolation from a graph and that is not always accurate (and NFC lists the ERN of their blanks to 2 decimal points... so there must be a way to calculate it).

Any help is much appreciated!

Thanks,
Gib

P.S. Has any one checked the NFC chart that relates IP (grains) to ERN, TP, and PR for accuracy? I ask because I was analyzing it to see if I could figure out the formula myself, and found the figure for an ERN of 23 to be way out of the norm compared to the other figures.... and, of course, being an engineer by education, that leads me to question everything about the chart. I'm quirky that way. See below for what I mean:


ERN Grains Delta
1 550
2 790 240
3 1050 260
4 1310 260
5 1570 260
6 1830 260
7 2115 285
8 2425 310
9 2760 335
10 3170 410
11 3680 510
12 4240 560
13 4900 660
14 5560 660
15 6120 560
16 6680 560
17 7240 560
18 7800 560
19 8360 560
20 8920 560
21 9480 560
22 10040 560
23 10060 20 <------ This number seems out of line compared to the others around it.
24 11160 1100
25 11720 560
30 15750 4030
40 21000 5250
50 28000 7000
60 42000 14000
70 52500 10500
80 63000 10500
90 73500 10500
100 84000 10500
125 94500 10500
150 105000 10500
175 115500 10500
200 126000 10500

Father to William (15 yrs), who I hope has found his passion in custom rod building!

Here is the universal chart: [www.rodbuilding.org]

The comparison between numbers is not a vertical line - please read the instructions on how to use the chart found here: [northforkcomposites.com]

.............

Yes 23 ERN should be 10600 grains, or 686.88 grams or 274.75 cents. The universal chart is correct but the sidebar has that single mistake.
Norm

The universal chart should be plenty accurate. Keep in mind there is likely a few percent variability in measurements on the blanks, so the chart is plenty good. No need for calculations.

Since we're not measuring fly blanks past 16, is the ERN really that important, can't we just use the amount of cents, or grains, or grams and still get the job done?

I agree with Spencer, ERN is a superfluous measurement for non fly rods. The Intrinsic power rating (in Cents, grams or grains) and AA gives me what I need to compare rods.
Norm

It's all the same thing. ERN isn't about fly rods. It's just a relative power rating. I can assure you that a blank with an ERN of 40 is more powerful than one with an ERN of 20, just as one you'd mark as a 300 cent rod is more powerful than one you mark as a 150 cent rod. It makes no difference.

If you want to use grams, number of cents, etc., it makes no difference. It's all the same thing. ERN is just the nomenclature the inventor chose.

...........

Tom, There is no question about that, but my point was that you do not need to look up the ERN for a rod when the intrinsic power number tells you the same thing. ERN is not directly measurable whereas intrinsic power is. As far as I know, there is really no mathematical formula that can be used to calculate an ERN from a given intrinsic power number; I.e. ERNs are not linearly related to intrinsic power. Dr Hanneman came up with the ERN nomenclature so that intrinsic power could be related to fly line weights, and fly line weights are not linearly related to each other. However, ERN is very convenient for a fly rod because it not only gives a relative power rating but also gives one an idea of the appropriate fly line to use, but this is not needed for non fly rods. I think the ERN nomenclature has confused a lot of people into mistakenly thinking that ERN (and in extension CCS) applies only to fly rods.
Norm

It probably has as most won't read the entire article/s. But it's also easier to carry simple ERN figures in your head in the same way that folks used to talk about Fenwick rods being a "2-power" or "5-power" etc. But again my point is that it doesn't make any difference which one you use - they're all the same insofar as being relative across the board.

...................

I gotta agree with Norman. I know that intrinsic power and ERN go hand in hand, but as I know nothing about how much more powerful an 8 weight fly rod is compared to a 4 weight fly rod, a higher ERN simply means the rod is more powerful.

For me its like a rod manufacturer that uses numbers to delineate their power ratings. A 4 power is more powerful than a 2 power, but how much more powerful?

Thanks to the CCS I can convert the weight of a penny to grains, grains to grams, and grams to ounces. For a non fly rod person, seeing the difference in how much weight each rod is rated for would make it easier for me to esitmate just how much more or less powerful one rod is compared to another.



Edited 1 time(s). Last edit at 03/31/2017 08:42AM by David Baylor.

That is a very good point. ERNs are easier to carry around in your head when compared to intrinsic power numbers. Dr Hanneman also recommended that ERN and AA be given together when describing a rod. My only problem with ERN is that when 'I' measure a rods intrinsic power I could not directly calculate the ERN from it. For example, Point Blanks give their CCS values as ERN and AA, as recommended, but at the time I could not take the ERN and directly compare it to my intrinsic power measurements I obtained from a given rod. I was only able to do this when the NFC chart was sent to me by Jim Spooner and yourself. This chart has made it much easier to compare rods.
Gib, I hope these exchanges are making sense and are helpful to you. If not chime in.
Norm

David and I were posting at the same time. David is correct in that ERN is a relative number and IP is a direct measurable number. For example, a rod with an ERN of 20 (IP=231 cents) is not twice as powerful as a rod with an ERN of 10.(IP=82 cents), it is more like 2.8 X more powerful.
Norm

David Baylor Wrote:
-------------------------------------------------------
> I gotta agree with Norman. I know that intrinsic
> power and ERN go hand in hand, but as I know
> nothing about how much more powerful an 8 weight
> fly rod is compared to a 4 weight fly rod, a
> higher ERN simply means the rod is more powerful.
>
> For me its like a rod manufacturer that uses
> numbers to delineate their power ratings. A 4
> power is more powerful than a 2 power, but how
> much more powerful?
>
> Thanks to the CCS I can convert the weight of a
> penny to grains, grains to grams, and grams to
> ounces. For a non fly rod person, seeing the
> difference in how much weight each rod is rated
> for would make it easier for me to esitmate just
> how much more or less powerful one rod is compared
> to another.


Be very careful here - I think I know what David meant, but for anyone else reading this, the number of grains, grams, pennies, required to obtain the measurement deflection, is NOT what the rod is rated for. If you attempt to cast the rod with that much weight you will most likely break it.

.................

Tom, you're right. I was speaking in terms of the overall power of the rod, not its casting weight range.

I believe I've asked the question before: What benefit is there to calculating the ERN at all for non-fly purposes? Is the ERN useful for something else besides determining an ELN for a fly application? I just can't wrap my head around using a calculated value like the ERN instead of the raw IP value in whichever weight unit one prefers (I like grams.) I find the IP value to be much more useful in terms of power comparison between blanks. If I'm missing something, someone please educate me so I and others can get the most out of the CCS. Thanks.

-The Batson TEAM
BatsonEnterprises.com

I do not think there is any real benefit for determining the ERN for a non fly rod, other than it is easier to remember than an IP number. As I mentioned above the ERN nomenclature has created confusion among many in thinking it only applies to fly rods. If all manufactures would give IP (in grams) and AA for thier blanks, I would be happy, and I think this would help end some confusion concerning CCS.
Norm

I have started a new thread for a "database" of CCS info for non fly rods. I am listing the IP in grams vs ERNs or Grains. But the spreadsheet does have a calculator. It displays ERN, Cents, Grains, & Grams. You can input any one of those numbers and the other three will be calculated for you.

Geoff, I think it would be useful to have the IP and AA information of a blank just like it is to know the length, number of pieces, etc. As has been pointed out on this board many times, the current power and action terms used by manufacturers are so subjective, it is impossible to compare one against another. But if I am familiar with a blank already (and know it's IP and AA), then I can more appropriately compare how a similarly styled blank by a different manufacturer to my baseline blank. I don't have the experience to know what all the blanks feel like or perform like in use and I don't have the budget to just buy 1 of everything to feel the difference personally. But at least knowing the IP and AA gives me more information to make a "hands off" comparison than just having the subjective power and action terms.

Father to William (15 yrs), who I hope has found his passion in custom rod building!

I have started a new thread for a "database" of CCS info for non fly rods. I am listing the IP in grams vs ERNs or Grains. But the spreadsheet does have a calculator. It displays ERN, Cents, Grains, & Grams. You can input any one of those numbers and the other three will be calculated for you.

Geoff, I think it would be useful to have the IP and AA information of a blank just like it is to know the length, number of pieces, etc. As has been pointed out on this board many times, the current power and action terms used by manufacturers are so subjective, it is impossible to compare one against another. But if I am familiar with a blank already (and know it's IP and AA), then I can more appropriately compare how a similarly styled blank by a different manufacturer to my baseline blank. I don't have the experience to know what all the blanks feel like or perform like in use and I don't have the budget to just buy 1 of everything to feel the difference personally. But at least knowing the IP and AA gives me more information to make a "hands off" comparison than just having the subjective power and action terms.

Father to William (15 yrs), who I hope has found his passion in custom rod building!

Geoff Staples Wrote:
-------------------------------------------------------
> I believe I've asked the question before: What
> benefit is there to calculating the ERN at all for
> non-fly purposes? Is the ERN useful for something
> else besides determining an ELN for a fly
> application? I just can't wrap my head around
> using a calculated value like the ERN instead of
> the raw IP value in whichever weight unit one
> prefers (I like grams.) I find the IP value to be
> much more useful in terms of power comparison
> between blanks. If I'm missing something, someone
> please educate me so I and others can get the most
> out of the CCS. Thanks.


Since a blank has no idea what it is going to be used for, a single power rating of some sort is useful. Dr. Hanneman intended that to be ERN. Because it's a more simple character, and doesn't mislead the less informed public that it's not the weight the rod is rated to cast (some people have broken blanks thinking they could cast the weight of the IP in grains or grams), it puts us back to simple relative power ratings. It's fine to use IP or whatever, as they're all the same in terms of being relative figures, but at some point you have to decide how many different ways you want to list relative rod power.

.................

This thread has been extremely helpful to me. Relieved some of my questions about ERN. So thanks to all.