Santa was especially kind to me this year and delivered a new piece of equipment (called an EI shaft profiler) to augment the equipment we already have on hand to educate you more on the proper golf club shaft choices. See, it pays to be nice! If you are not familiar with EI (short for elasticity times inertia), as few will, it is a 3-point bending test that measures the golf club shaft deflection along a span of the golf shaft. By taking measurements from the tip to the butt and plotting the results provides a more comprehensive look at the golf shaft’s stiffness distribution and a better understanding of how that shaft will react.
I began scientifically testing shafts in 1989 to more accurately compare one from to another. In 1991, I created the DSFI (Dynacraft Shaft Fitting Index) formula as a way to accurately compare shaft stiffness based on the interrelation between golf club frequencies and torque that is still published annually to this day. That was the first year the data was published to help fellow golf clubmakers fit more precisely. In 2006, I expanded it one step further and started compiling tip and butt deflections measurements and added them to the DSFI formula. This would provide a much clearer picture as how two shafts, that at least on paper appeared to be the same, could be actually quite different. With the addition of our EI shaft profiler, we hope to provide you with more accurate shaft fitting for years to come.
It will take a while to compile all the data and put in into a format that will be easy for our customer base to understand and use. I wanted to let you know we don’t rest on our laurels and hope to expand our knowledge base so that we may increase yours too. Here is a snippet with a comparison of three cut #5-iron shaft deflections. All are of the same length, frequency and weight but completely different shaft stiffness distribution profiles.
The left side of the chart represents the tip and each of the 14 data point’s measures 2” closer to the butt. The lower the reading; the stiffer the shaft is at a certain point. For example, Series 2 (or the shaft in red) has a much stiffer tip section that the other two, but is more flexible in the butt end. This shaft should produce a lower golf club launch angle, while the shaft in green will produce the highest golf club launch angle as they exhibited at the range. That is how to interpret the data.