Fly Lines weights

[kbproctor]

You know, I still don't get it. Yes, rods work better with appropriate lines, but either a line OR a rod may be off from the labeled designation. Maybe my rod is actually a 4.95 an the line is a 5.1 - what am I to do?!!
I wonder if you are concerned about casting a specific distance. In the example you listed for Cortland lines, 33.48ft of the lighter line = 30ft of the heavier line, so if you cast those amounts of those lines the rod should feel the same (but your timing will have to change). If you want to cast 10ft or 40ft, what are you going to do? By changing line lengths you changing the 'virtual' weight designation, the rod will not be casting the ideal weight, and the feel of the cast will change.
You might actually want to cast the heavier line if your casts are all short (or you tend to shoot line on the cast). Or use the lighter line if you are casting farther or prefer to arialise a lot of line rather than shoot. This is where the plan of the perfectly weighed line to match the common-cents rod fails. If you always cast long, then you are casting 6wt of line regardless of the 5wt rod designation. This is why most respondents to this thread are promoting FEEL over measurements. The line may be Rocket Taper, but this is not rocket science.

Ideally your ERN (Effective Rod Number) and ELN (Effective Line Number) should match, but that is something that probably will not happen. I think it is good within a quarter step. With your example above, you are already close enough to call spot on. The rod should load properly for an average caster under average conditions. All of the other things you mention still come into play.

The "feel" is absolutely important. I drag out my TFO Pro Series 5w and it "feels" better with the Bass Pro CV2 5w line than the Dogwood Canyon 6W did with the 6w line. I could cast the TFO much easier and had that "feel" of a nice cast more often. I struggled with the 6w. Well, it is not really a 6w. Turns out it has an ERN of 5.65, almost a spot on 5w, and it "feels" much better with the 5w line I normally use with the TFO. So here is a rod that even the folks at Bass Pro Shop that sold it to me say is a "cheap rod" and not to expect too much out of it, that is now a keeper. The cool part is that I understand why it was such a clunker and figured it out all by myself.

All this does is give me a head start on figuring out which way to go with a method I am comfortable with due to the way I think. Both methods get us to the same place.

It may not be practical to get the information I am looking for. I have been swapping emails with SA on it, but it occurs to me that while an individual run of 3w Sharkskin lines might run 102 grains, that the next run could be different. We will see what we will see.

I'm having fun with this. Isn't that what it's about?