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