Over-Lining Answered

For years saltwater fly rodders have been going back and forth about the practrice of over-lining their fly rods. Some rods seem to perform better when their recommended line-weight ratings are increased by one or two weights. Some don't. Saltwater fly rodders are in agreement about that much, but that's usually where agreement ends. It is common for different anglers to load the exact same rod with different weight lines. Why?
If everything was supposed to have been standardized by the AFTMA Line/Rod Weight Rating Table, why should a 10-weight Sage load differently than a 10-weight G. Loomis, Winston, T&T, etc., etc?
The cause appeared to be the rod, the angler or both. It was logical to assume that different standards should apply to stiffer rods made of modern high modulus graphite materials, but there was the fact that manufacturers continued to make 10-weight rods which loaded better with 11-weight lines. It was just as logical to assume that none us cast quite alike, so the same rod in another's hands might perform quite differently. Through it all, there has also been a nagging suspicion that rod manufacturers' line-weight ratings just weren't all they're cracked up to be.
Finally, the questions have been answered, and quite thoroughly, by Bruce Richards of 3M Scientific Anglers which should give you a clue about the true nature of over-lining. It's not the rod. It's not the fly rodder. It's the line, or to be more precise, the line's design.
Richards lays it all out in one of the volumes of the Lefty's Little Library series of books, called Modern Fly Lines. He explains that fly rods are rated using the lowest common denominator weight-forward fly line -- one with a standard length head of approximately 40 feet. The trouble is, almost every fly line these days has been specialized to suit a specific fly fishing situation.
A saltwater fly rodder would never think of spooling a line labeled Salmon/Steelhead even if the weight was a match, and rightly so. Most saltwater fly lines are designed to turn-over large patterns and to provide more punch for distance, so they're designed with a somewhat shorter head. Meanwhile, other specialty lines are designed with long heads, medium heads, fat heads, skinny heads.
All of the different designs still match their labeled weight ratings according to the AFTMA standard, but only as far as the working portion of the line is concerned. When it comes to the short-head saltwater lines, more of the thinner, lighter running line will be extended beyond the tip when you're going for a distance cast.
A lot has to do with the physical dynamics of various fly line designs during a cast as well, but I'll leave that and all of the rest to Richards.
The bottomline, he writes, is "anglers planning to purchase a short-head line specifically for bass, saltwater or other applications would be well advised to buy a line one size heavier than the rod recommends to insure proper loading."
As for shooting heads, when I interviewed Richards for an item in our special edition 1996 Nor'east Saltwater Fly Fishing magazine, he recommended increasing the recommended rod rating by two line weights because the dynamics of a full fly line do not apply to shooting heads. However, I've found there seem to be some slow to moderate action rods which cannot handle a two-line weight increase. What I didn't consider when I was fooling around with various shooting head line weights was that I was actually lengthening the heavy portion of the line by reversing the head. That is, rigging the heavy portion forward and connecting the tapered portion to the shooting line. It works well to turn over large saltwater patterns, but my slower action rods wouldn't take an increase of more than one line weight over their ratings. After reading Richards' book, I dusted off one of my older, slower rods, re-installed a shooting head with the taper forward and sure enough, it felt as if it could use a little more oomph. By reversing the shooting head, I was really changing the line's design, having a long, heavy portion carry the loop forward. Still, I would recommend that you try both the standard and the reversed setups and see which works best for you.
Of course, there's much more involved than I can go into here and Richards, who probably knows about the workings of fly line designs than anyone, goes into great detail, even suggesting methods for re-vamping the line-weight standardization charts.
Originally, fly lines were classified by diameter under the old alpha code ratings. Along about 1960, the American Fishing Tackle Manufacturers Association decided weight was the way to go, giving us our current line weight ratings standards. Richards feels that modern fly line designs call for yet another revision and he recommends that this one be based upon length.
It can all be a little too technical at times, but it is worth your time to read and re-read his examination. It is an excellent explanation of how to get the most out of your entire set-up, including leaders, and why it all does what it does.
Lefty's Little Library books have been around for a few years and are available via mail order. If you've ever subscribed to a fly fishing magazine, you've probably already been showered with the direct mail campaign. Advertisements still pop up from time to time as well. You may find the books in shops, but the only sure way I know of to get them is to enroll, meaning you'll receive a book every other month or so, sight unseen.
Some of the books are specific to types of fly fishing you may not care about. Some may totally miss the mark for you. In that case, you have to go through the hassle of returning the parcel. You'll probably put it off long enough to end up buying a book you don't really want. I did enough times and I eventually dropped my enrollment, but after borrowing Richard's book, I'm sorry I did.
Your membership begins with Lefty Kreh's book on casting and it carries on from there. You don't have the option of selecting previously published books from a list, but I'm told you can request to begin with any specific title in the series if you call in your membership. Modern Fly Lines wouldn't be a bad place to start.