Golf Club Shafts

Lessons from ShaftLab
TrueTemper 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. 

All About Spines
An 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.

The Physics of FLO
• Why is FLO important? Because it is the most simple and direct measure of the real direction of the spine and NBP.
• Why does a "spiny" shaft 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 are trigonometriphobes.

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.

Frequency Matching With a Meter
The question comes up every month or so on various golf forums: "I just got a frequency meter. Now... how do I build a frequency-matched set of clubs with it?" Here's how 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 deal with: How do I choose a frequency or frequency slope? That's a design issue. This article is limited to shop practice. It assumes you know the frequencies you want, and describes how to build the clubs to those frequencies.

Frequency 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
Even 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.

Shaft Profiling

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 frequency 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.

An 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 profiling.

Plotting the data
It is difficult to learn much about a shaft profile from a raw plot of deflection vs beam length. In the previous article, 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 other shaft.