Understanding Shaft Geometry and the Effects on Ball Flight
Key Golf Shaft Variables To Learn When Shopping For Your Next Set of Clubs or Re-Shaft Project
Following our back-to-school theme, last week I spoke about how the geometric shape of your putter grip could improve you putting. Today, we are going to switch to golf shafts and show you a few things to look for when looking to re-shaft or purchase your next set of clubs.
Did you ever wonder why certain golf shafts hit the ball higher or to the left or right more than others?
This has to do with a number of parameters, one of which is the shape or geometry of the shaft. Let’s take for example parallel tip steel iron shafts. The majority of men’s flex parallel tip steel iron shafts have a tip diameter of 0.370” so they can fit into numerous heads across the industry and a butt diameter of 0.600” to accommodate the majority of golf grips. The geometry between these areas is what alters the ball flight.
If you look at steel iron shafts, each model has its’ own unique step pattern. The stepping is done to change diameters or the rate of taper and ultimately the geometry of the shaft. The same thing occurs on non-stepped shafts as well; the shaft becomes larger in diameter from the tip to the butt end.
The step pattern may be constant, like the True Temper Dynamic Gold Taper Tip with consistent 1.75” steps or an FST 115 with 1” steps. The shaft might have variable steps such as an Apollo Shadow Lite with 9 small ½” steps and then increasingly larger steps as you go toward the butt end. The stepping helps to identify a model.
Why does a more flexible shaft hit the ball higher in the same pattern of shaft? This goes back to geometry as the step pattern will be the same, but the more flexible shaft will have a longer parallel tip section and shorter parallel butt section. Since the shaft is skinnier near the tip, it will allow the shaft the bend further forward prior to impact creating more dynamic loft and/or a more closed face. Conversely, if you want to stiffen a parallel tip shaft, you do so by taking more off of the tip and that will resist the forward bending.
EI Profile Machine Testing
Less than a year ago, we added a piece of equipment to help us measure shafts more precisely. We have measured quite a few shafts already. Two of which are the Apollo Acculite 85 S-flex and a True Temper Dynalite Gold SL S-flex. These might not be common shafts that our readers have had an opportunity to hit, but both are listed a high launching by the respectively manufacturers, had nearly the identical final frequency for a 5-iron and they are pretty close in cut weight (Acculite 85 at 87.3g and Dynalite Gold SL at 93.1g). On paper these would appear to be similar.
Our shaft profiler measures the deflection or stiffness along the length of the shaft so you get more of a complete picture. The following chart shows the deflection of the two shafts with the left side showing the tip end and the right side is the butt. More flex is indicated when the line is higher on the chart.
From about 14” up from the tip to the butt end, these two shafts are nearly identical. Where you can see the main difference is tip section as the Dynalite Gold SL being much stiffer. This is due to the fact that the shaft tapers quickly. Instead of the entire parallel tip section remaining 0.370” up to the first step, both of these shafts has a tapered section before the first step to give them stability. Just underneath the 1st step the Acculite 85 is 0.400”, but the Dynalite Gold SL is a whopping 0.445” below the first step!
That explains the difference as the larger cross section or shaft diameter, the stiffer the shaft becomes. I shafted these up into identical heads and head to the range for me and others to hit as we could look at the effect on ball flight when one area of the shaft is decidedly different. What we witnessed was the Acculite 85 would hit the ball more to the left than the Dynalite Gold SL (we were all right handed). For those that fade or push the ball would prefer the Acculite 85 as the softer tip will help close the face at impact. For those that pull or draw will prefer the Dynalite Gold SL. Or is it simple as that?
The reason I bring this question up has to do with clubhead selection. While we saw a definite change in ball flight between the two shafts in the same head, we could have placed the Dynalite Gold SL in a head with more offset and the Acculite 85 in a model with less offset and you might hit the ball the same direction and height. Just as easily, we could have had placed the Acculite 85 in a high offset head and created a draw or hook and the Dynalite Gold SL in a low offset head and produced a fade or slice.
Remember that a club is a system consisting of the head, shaft, grip and length. This is where fitting is extremely important and how an interchangeable fitting system can help identify combinations of heads and shafts that will work harmoniously with a given player’s swing. But now you may look at the shaft geometry in a different perspective and understand better why you may like or not like a certain shaft or why.
