Are you an expert on graphite fly rods? Most of us have too much experience - we buy enough of them. So, what do mandrels, prepreg, tow, resin, scrim, or snake belly have to do with fly rod construction?

Well, a mandrel is a carefully manufactured steel stick or rod that is shaped to determine the cross-sectional shape or the taper of your rod. Simply put, the mandrel serves as a form or mold for the rod. Most rod manufacturers have many mandrels - some say thousands. To start with, a fabric made of graphite and resin (a prepreg - probably for graphite pre-pregnated with resin) is wrapped around the mandrel, covered with a heat shrink tape and baked in a oven. After baking, the tape and mandrel are removed and you have your basic rod blank. If the blank is not sanded (to make it smooth) it will have the spiral rough finish like some Orvis or Scott rods called "snake belly".

Some fly rods are coated with an epoxy or other plastic covering. The graphite in the pre-preg fabric is dry graphic fibers combed from spools (like yarn) and called "tow." Scrim is a thin layer of fiberglass or graphite fibers that holds the fibers in the prepreg in place - it reinforces the strength of the rod. The ferrule is sometimes part of the wrapping process, or sometimes it is added later.

So how does all of this influence the performance of your fly rod? Well it should be clear that the stiffness of the rod is not only influenced by the stiffness of the graphite but also by the amount of resin. Indeed, two rods with the same IM6 graphite may differ significantly in stiffness. Other factors that influence the action of your rod are the number of wraps of the prepreg, the diameter of the mandrel, and the kind of resin in the pre-preg, in addition to the graphite. Just like there are different kinds of graphite, there also are different kinds of resin, which also vary in their properties. So as you consider purchasing that next fly rod, don't focus only on the stiffness modulus of the graphite, or the kind of graphite... there are many other variables that will influence performance of the rod.

This article was provided by the Federation of Fly Fishers. Visit their site for more articles and information about fly fishing. The Federation of Fly Fishers is a unique non-profit organization concerned with sport fishing and fisheries.