Fly Line Memory & Stretching
Bruce Richards, Scientific Anglers

All fly lines have memory - they "remember" the shape they are stored in, usually coils on a reel or on a storage spool.The reason is simple: most lines are made with nylon cores and PVC coatings, and both materials tend to hold and retain their shape. But memory in these materials is also temperature dependent, and the colder the line, the stiffer it will be, and the memory more tenacious.

As fly fishers, we know that to achieve maximum casting performance and to minimize tangling, lines should be as straight as possible. Lines made for fishing in cooler climates and waters, like trout specific lines, are made with softer coatings and cores to minimize memory in lower temperatures.

Lines designed for use in tropical heat are usually made with harder, stiffer coatings and cores. Cool weather lines used in tropical heat will be very soft, shoot poorly and tangle badly. Tropical lines fished in cool weather will be quite stiff and will be difficult to straighten and will require repeated stretching if the line is returned to the reel for even a short period of storage. So, what is the best plan for optimizing line performance?

First, get the right line for your application. If you expect your steelhead line to work equally well for bonefish, you will be disappointed. If you take your tarpon line salmon fishing, you will spend more time fighting your line
than fish. Although softer lines made for use in temperate climates do have some memory, in many cases, unless the weather is unusually cold, the memory can be "fished" out of the line in the first few casts. If you don't want to wait, or the weather is cooler than normal, give the line a quick stretch. And in lines made for the tropics, it's just about impossible to cast the memory out of the line.

The best method for stretching either type of line is to hook a large fish on your first cast and let the fish do the work. Easy enough, right? The best method for stretching either type of line is to hook a large fish on your first cast and let the fish do the work. Easy enough, right? Well, if like most of us your fishing skills aren't aren't refined to the point where you can accomplish that task reliably, try this. Strip 3-4 feet of line from your reel and stretch it between your hands. You can pull quite hard; even light trout fly lines are 18-20 lb. test and hard to break, and tarpon lines usually test out at above 40 pounds. Repeat this process until you have the amount of line you intend to cast stretched straight. Tropical lines fished in cool climates will require a vigorous stretch, but will work very well once straight. If you are fishing from a boat, remember to make a clearing cast before you start fishing, the line will be stacked on the deck "upside down" after stretching and will most likely tangle if you don't rearrange it.

Some have advised against stretching fly lines, thinking that stretching will somehow damage the line coating. But consider the following. Most fly lines will stretch 25-30% before they break. If the line coating didn't stretch as much as the core, stretching could indeed damage the coating. But in fact the PVC coatings used today stretch even more than nylon line cores so stretching causes no damage. Speaking of core stretch, with the advent of gel spun polyethylene backing and other high-tech, high-strength fibers, many have asked why these materials aren't used for fly line cores. The main reason is that all these new fibers have very low stretch. And the only way to effectively straighten a line in the field is to stretch the coating. If the line is made on a core that prevents stretching, memory can't be removed, and the line will retain its troublesome coils all day. A few years ago an English company introduced lines made on no stretch Kevlar cores and they all experienced incurable memory problems.

Today's fly lines are more trouble-free than any lines in history, but one thing manufacturers haven't been able to make much progress on is memory. The vast majority of lines are still made on nylon cores with PVC coatings - both materials that have been around a long time. Hopefully someday there will be lines that come off the reel straight and work equally well in hot and cold climates. But don't hold your breath.