I have noticed that many blanks/rods have an ern much higher than the factory designation. If a 9' 5wt. rod tests out to an ERN of say, 8.5, does that mean that this blank would be suited to use like an 8 wt. rod for larger fish - salmon/ steelhead even though it may have a smaller butt diameter and tip and weigh alot less?

To a great extent, yes. Remember, the factory designations aren't based on any sort of universal standard - it's just a subjective opinion based on the maker's oun idea of what an "8-weight" should be. (Doesn't mean he's wrong - just that his idea of an "8-weight" and somebody else's may be too entirely different things.)

Comparing butt and tip diamaters along with weight can be risky business due to the fact that you may not be comparing apples to apples. The materials the blanks are made from along with the design philosophy may be completely different (large diameter/thin wall vs. small diameter/thick wall).

You also need to factor in the AA of a blank. Two blank with similar ERN's but markedly different AA readings will not necessarily have the same distribution of power.

Any fly rod blank that tests out to an ERN of 8.5 is a fairly powerful blank and can handle a pretty decent load. You still have to be reasonable however, and your experience as a rod builder should guide you as to just how much load or what type fishing the blank will ultimately be able to handle.

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Edited 1 time(s). Last edit at 01/02/2005 11:30AM by Tom Kirkman.