Golf Club Shafts
manufactured a very expensive instrument called ShaftLab, for measuring
shaft flex during the swing. It was sold as a shaft-fitting tool, but
IMHO is far more useful as a research tool. I have had the opportunity
to play with one for a few hours and several golfers, and look at the
ShaftLab data for a lot more golfers -- including well-known touring
pros. Here's what I've learned from all this.
engineer's view of spines, spine finding, and spine alignment. Be
forewarned, it isn't the usual clubmaker's view. We cover terminology,
the physics of shaft bending, spine-finding and measuring, and the
practice and theory of spine alignment.
Physics of FLO
• Why is FLO
Because it is the most simple and direct measure of the real direction
of the spine and NBP.
• Why does a
wobble when plucked? Because the spring forces due to
bending the shaft are not in the same direction as the bend itself.
This article explores the above questions, with illustrations,
analysis, and even some math -- sorry 'bout that to those of you who
How Shafts Bend (first installment)
When you rotate a flexed shaft around its axis, does the bend rotate with it?
How stringy is the shaft at impact?
Since the 1990s, I've been saying, "The shaft is a string at impact!"
to anybody who will listen. I still believe it is a good rule of thumb.
Is it absolutely true? Of course not! Here we explore the limits of
approximating the shaft as a string during the moment of impact.
Matching With a Meter
The question comes up every month or so on various golf forums: "I just got a frequency meter.
do I build a frequency-matched set of clubs with it?"
I do it. It may be a little different from others, but it works for me.
Let's also keep in mind that
this article does not
How do I choose a frequency or
frequency slope? That's a design
This article is limited to shop
practice. It assumes you know the frequencies you want,
describes how to build the clubs to those frequencies.
Matching Without a Meter
In early 1996, when I first did this work, most clubmakers did not have
a frequency meter. In fact, I didn't have one. So I did some analysis
to predict how to trim shafts to get the frequency slope you want. Paul
Nickles (then of Raven Golf) provided a bunch of empirical data to test
my analytical results.
While almost all serious clubmakers now have a frequency
meter -- and all
serious clubmakers have some
way to measure and put a
quantitative value on the stiffness of a shaft -- the analysis in this
article is still interesting. For instance, it tells the truth about
how to trim for a "flatline" set. Hint: it usually isn't to tip-trim
all shafts the same.
Finding Spines with a Non-Differential Instrument
if you are stuck with an instrument like the GolfMechanix Auditor, the
NeuFinder 2, or the Apache Multi-Match -- which were never designed to
do differential deflection -- there is still a way to accurately locate
the spine. Here's how.
Quick Guesses about the Nunchuk Shaft
Around the beginning of 2011, NVentix introduced the
Nunchuk shaft. Are
its rather radical claims and design a good thing or bad? My quick
evaluation, based on their claims and specs, and what I know of shaft
science. I have not actually tried or measured one.
Over the past eight years,
increasing attention is being paid to the
way the flex varies over the length of the shaft. This variation,
commonly called the "flex profile", is now deemed as important to
clubfitting as frequency was a decade ago. It is usually done as
profiling (often called "zone
frequency"), but deflection can be as good or better than
frequency for "zoning" a shaft.
I got involved in shaft profiling when I
was the engineer for the NeuFinder-4
(NF-4) shaft instrument. Here are things I have learned about it.
account of the first profiling that I did, during the alpha
test of the NF-4. It covers my first attempt at data reduction for
graphing profiles, and a comparison of frequency and deflection
It is difficult to learn much about a shaft profile from a raw plot
deflection vs beam length. In the previous
I introduced the notion of transforming the raw deflection load data to
make the graph easier to read. Here is a much-improved data reduction
transform. It is easier to understand, as well as no longer depending
measuring some "standard" shaft. Instead, the data is
subjected to a simple calculation not based on comparison with any