This question is from Volume 5, Issue #3 of RodMaker
I was looking at the FAQ on www.rodbuilding.org and
noticed you said the outside of the relaxed curve is
the effective spine. In the Flex Coat
book, it says the inside of the curve. What am I
missing? Nick via email.
First, let's understand that what we call the spine
is not an actual physical thing. Rather, it is an effect
created during the making of the blank and can be caused
by any number of anomalies during the manufacturing process.
So what we are referencing is that point in which the
blank seeks to align itself when pressured or loaded.
Once in that position, we can locate any point of
reference that allows us to remember or find that
exact same location and call it the spine. You could
locate a point 26 degrees off that location and call it
the spine, as long as you remember that the position
of the effect you are concerned with is 26 degrees
away. Get the picture?
So calling the spine the inside of the curve, or the
outside of the curve, makes little difference as long
as you remember how each reference point relates to
the position the blank will locate itself in when
The problem comes when rod builders try to converse
on the issue. Without common terminology, none of it
makes any sense when being discussed among rod builders
who may all be using different points of reference.
Therefore, most custom builders will pressure the blank
and allow it to roll/spin to its preferred location.
This will be the position where the blank naturally
locates itself and wants to stay put, under pressure,
always returning to the same position any time you
attempt to roll or turn it from that position. They
mark the outside of the "relaxed curve" and refer to
that axis as the "effective spine." Remember, this will
be the relaxed position or curve which the blank
naturally seeks when it is pressured or loaded. And
again, the outside of that curve is generally referred
to as the spine or effective spine.
I will add that some builders and a few books, continue
to call the spine the point where the blank jumps or
kicks. That point is the stiffest axis of the blank
and is neither considered the spine nor the opposite
side of the spine by most knowledgable rod builders.
It is, simply put, the stiffest axis and is something
altogether different. ~ TK