Experienced anglers can tell when a rod "feels right" for a certain situation, such as tossing topwaters or lobbing live baits. Much of this "feel" involves how the rod flexes when casting, working lures, setting hooks and fighting fish - and all that flexing varies according to a rod's taper (also called action).
"Rod taper determines the point along a rod's length where it stops bending under a constant variable of pressure," says Justin Poe, Shimano's (http://fish.shimano.com) rod-products manager. "Blanks that continue to bend farther back from the tip have a slower action, while fast-taper rods only bend close to the tip."
Taper does not establish the degree to which a rod flexes (because applying greater pressure can make the blank arc more deeply); instead, it defines how much of the rod flexes when an angler applies that pressure. Although we have no precise, objective measuring stick to compare rod actions among different manufacturers, common tapers include extra-fast (just the tip flexes, about 10 percent of the rod's length); fast (about 20 percent of the rod's length flexes); medium-fast (about the top third bends); medium (about 40 percent); and slow (nearly the entire length of the rod scribes an arc).
Boundaries get blurry when we see terms like "heavy action" in rod descriptions. "Many fishermen mistakenly believe a rod's action indicates how hard you can pull and which strength of line to use, but these factors depend on the rod's power rating," Poe says.
To avoid confusion, most manufacturers use speed-related words ("fast," "slow") to specify action (taper) and weight-related terms ("light," "heavy") to describe power. Be careful, though, because "medium" appears in both listings. Poe warns that power ratings are relative, varying according to a rod's intended application. For example, a fast-action, medium-heavy inshore rod may have a line rating of 15 to 30 pounds, while a fast-action, medium-heavy tuna rod carries a 50- to 80-pound rating. Both of these fast-action, medium-heavy rods flex only near the tip, but different line ratings mean you must apply more force to the tuna rod to put a bend in it.
The combination of proper taper and adequate power rating unlocks the door to better rod performance in any situation.