by Don Irving, Artisan Golf
In this article, I would like to discuss one of the many parameters that go into fitting and building a custom set of clubs. This parameter is Shaft flex.
When fitting for shaft flex, three pieces of information are necessary in order to determine the proper flex of a shaft. One of these is clubhead speed. Clubhead speed is measured at impact by the launch monitor. To get a good fit for shaft flex, I need to know not only how fast the club is traveling but how is that speed achieved. In other words, how does the golfer swing the club? Is it a long smooth tempo type of swing or is it a quick aggressive swing. The other two swing characteristics are transition and club release point. Let us first look at the transition, the point where we go from backswing to downswing. If the golfer has a very aggressive transition, then no matter what his clubhead speed is, I am going to make his shaft flex a bit stiffer than if he had a smoother transition. Now let us look at club release. (Most amateur golfers release early.) What is club release? At the top of our backswing, there is an angle between the leading arm and the golf club’s shaft. Let us say it is 90 ˚. As a golfer progresses with his downswing, somewhere between then and impact, that angle will go from 90 ˚ to zero. The point where the golfer’s forearm and the shaft are in line (0 ˚) is the point of release. A very good golfer will time that point to be right at impact, where he or she is developing maximum clubhead speed. But, what happens when the timing is a bit off? When a golfer has an early release, he begins to release the club almost at the moment of transition. When this occurs, the club is fully released at a point somewhere before the ball, that point of release can be 2 or 3 feet before impact. The ramifications of an early release are this. The point of release is generally the point of maximum clubhead speed. Let us say that your clubhead speed with a 7 iron is 75 mph. If your release point is 2 feet before the ball contact, there is a good chance that at that point your clubhead speed was at its maximum. You can actually lose clubhead speed with an early release and we all know that clubhead speed equals distance.
So how does all this knowledge go into the build part of custom clubmaking? Once I have determined the clubhead speed for any given club, the transition characteristics and the release point, determining the correct shaft flex is quite easy. First, let me clarify that I do not build to an L, A, R, S or X flex. These are simply general terms and can get you in the right ball part of shaft flex but not in your specific seat. I build to a target frequency as determined by a frequency analyzer. I have developed a chart that gives me a specific frequency based on a given clubhead speed. For example, let us take a 7 iron clubhead speed of 75 mph. For that clubhead speed, the appropriate frequency would be 303 cycles per minute as per the frequency analyzer. If that person has a very aggressive transition, then I may add 3-6 cycles of stiffness to the shaft, based on his or her transition, or I may soften the flex by the same amount for someone with a very slow transition.
Release point is accomplished in a similar manner. Rule of thumb is that the earlier someone releases the club, the softer the flex of the shaft would be. For example, for a golfer with a 75mph clubhead speed, who releases about two feet before impact, I would probably take the flex from 303 cpm to 299 cpm or even a bit softer, based on the transition. Once I know the correct flex of a 7 iron for any gofer, it is then a matter of creating the proper flex profile based on this number and the type of swing a golfer has. A golfer with a smooth, slow swing with an early release would more than likely have a frequency matched set of irons, where the chosen frequency is the same for every club, i.e., if the 7 iron was 300 cpm then every iron in the set would be 300 cpm. This is known as flat line or single frequency matching. For a more aggressive golfer, the frequency of each shaft would get progressively stiffer, from the 4 iron down to the wedges. It may be that each club gets 2 cpm stiffer as the clubs get shorter, or it could be as much as 7 or 8 cpm per club for a very strong player. This type of frequency matching is known as slope frequency matching, where for example, if the 7 iron is 300 cpm, the 8 iron could be 304 cpm, the 9 iron 308 cpm, etc.
This type of frequency control or frequency targeting is accomplished by using shaft blanks. These are shafts that start out at a raw length of 40-41” and have a parallel tip that allows the shaft to be tip trimmed. As you trim the tip, the shaft gets stiffer. For frequency matching shafts, I dry fit the head on the shaft, mark it to the correct length and check the frequency. If the frequency is too low, I will cut more off the shaft tip, dry fit the head, measure to length and check the frequency. I simply repeat this process until I achieve the desired frequency for each club. The result is a perfectly frequency matched set of clubs.
Shaft matching is extremely important when building a set of clubs and clubhead speed is an important factor in determining that frequency. It is not all about how fast you swing a club, it is as important to know how you swing it fast. For a perfect build, I think it is important that the one who fits your clubs also builds your clubs. Then nothing is lost in translation.