ROD BUILDING TIPS
Damping?

By Tom Kirkman, (RodMaker Magazine)

Here's a question from the November/December 2000 issue of RodMaker magazine:

"I am confused about the term damping and what it means to a rod builder when selecting or building rods. I was under the impression that a damp rod was a soft rod. Is it? Really, what is it and what does it mean? James. . . Oakland, California

RodMaker Magazine

In the purest technical sense a system exhibits damping if the system producing the motion also produces a force that inhibits the motion. (Think about that for a few seconds.) On a fishing rod the resistance between the air and the blank as the rod oscillates would be a damping force. Because friction is caused and occurs as the rod moves through the air and because that friction inhibits the rod's motion, we could say the rod exhibits damping. The greater the force which is generated to inhibit the motion the greater the damping force is said to be.

In the terminology used by most rod builders, however, the term damping or dampening is normally used to depict something a tad different. After a cast most rods will oscillate/vibrate for a certain period of time. Rods with a high stiffness-to-weight ratio normally stop oscillating sooner than rods with a lower stiffness-to weight ratio and thus are said to "dampen" or "damp" more quickly. In this cast however, the difference in oscillation times can be directly traced to the difference in stiffness-to-weight ratio and all the things that happen when you set any mass in motion rather than external forces which inhibit the motion. Whether right or wrong in the purely technical sense of the terminology, rod builders normally use the term damping to describe how long a rod takes to stop oscillating. "This rod damps quickly" would be an example of the usage and would depict a rod that stops oscillating sooner rather than later.

Calling a soft rod "damp" is technically incorrect, but many rod builders do use that terminology. ~ Tom Kirkman

Publishers note:

If you have any tips or techniques, send them along! Help out your fellow rodmakers! ~ Publisher, FAOL

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