My mind is racing this morning. Now I see that Pacbay has a new fly rod blank series and shows the CCS numbers for the blanks. So how come they rate a blank with an ERN of 5.5 as a 4wt???

FAF904-4 QUICKLINE 9’0” 4pc 4weight $98.26 weight 1.3 butt dia. .34 tip size 3.5 ERN 5.5 AA 72 CCF86

Simple - ERN is a relative power rating, not a fly line number. A rod with an ERN of 5.5 will perform very well with a 4-weight line, albeit plenty of it.

Keep in mind the inventor's equation for line matching: ERN=ELN with about 30 feet of line aerialized. So when you see a 4-weight rod with an ERN of 5.5 you should instantly recognize that it will perform best for most anglers with more than 30 feet of 4-weight line beyond the tip. Or... with 30 feet of 5-weight line beyond the tip.

The "4-weight" rod designation is simply a subjective rating by the manufacturer. The ERN is a quantifiable power measurement. Once understood, the ERN provides information about what lines and distances the rod may perform best with.

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The ERN is more informative than the mfg's line rating. Fly line weight doesn't remain constant. It changes with more or less of it out there past the tip of the rod. This is why two fishermen with the same rod will have completely different impressions of it. One will say they found it easy to load while the other will say they couldn't get it to load at all. The answer is that they were using the same line but at different distances. Totally different weights involved.

With an ERN of 5.5 I would envision a rod that inside of thirty feet would do best with a #6 line. Around 30 or so feet I would use a #5 line. Moving out much more than that I would use a #4 line. Most any fly rod will handle three different line weights but not all at the same distance. The ERN makes it easy to lock in the best three line weights and at what average distances each one will work best at.

All blanks cast or throw a weight of some sort, be it a lure or a fly line. But it is still weight.

Bill - willierods.com