TBAR™ vs. KICK (BEND) POINT
By Carter Penley
The term “kick point”, originally referred to as bend point, has been a popular term for many years by many shaft manufactures and yet the most misunderstood and least useful term applied to the performance criteria of a golf shaft.
I once heard it summed up in this manner:
- 50% of the players think they know what it is!
- 50% of the players don’t know what it is!
- 100% of the players don’t know why or how the measurement is made?
- 101% of the players have little or no idea at what position or point these measurements are on a golf shaft!
Originally “bend point” (kick point) was considered a simple black and white measurement; something a club maker could use as a way of differentiating how ‘soft’ or how ‘stiff’ the tip section of a golf shaft is.
In reality this is not the best indication or measurement of the golf shafts tip section stiffness.
By using this measurement as indicated by the golf shaft manufacture and as it is printed on the shaft, a club maker would determine how to fit his customer. A high bend point equates to a lower ball trajectory and a low bend point a higher ball trajectory.
To a point the above statement is true; but not because high bend (kick) point and low bend (kick) point as measured on a golf shaft actually yields the above result. The fact of the matter is that the golf shaft manufacturers have accepted and adopted this theory. Therefore bend point now became the term ‘kick’ point and manufacturers now determine ‘kick point’ by hitting the golf clubs and observing the ball trajectory and have labeled the golf shafts accordingly.
If the ball appears to go higher then the golf shaft is labeled ‘low’ kick point and if the ball appears to go lower the golf shaft is labeled ‘high’ kick point and ‘mid’ kick point is somewhere in between. When in reality, I have measured shafts for bend (kick) point position and discovered in some cases that a Senior (‘A’ flex) shaft could have a higher kick point than a high modulus (‘X’ flex). How is that possible, you say? Well let me explain how this measurement is made and what influences bend (kick) point and where on the golf shaft these kick points are located.
Originally the kick point measurement was determined by compressing a golf shaft from tip to butt using over center clamps and a tooling ball fitted to accept the small (tip) ID and the big end (butt) ID of the golf shaft being measured. The over center clamp is closed and the golf shaft is compressed to a length of approximately ¼’’ to ½’’ less than its uncompressed free length. The golf shaft would then bow (up) and the highest point between the two centers on its ‘X’ axis measured with a DRO (Digital Read Out) unit is the bend (kick) point position of that golf shaft (usually measured in inches from the tip end of a golf shaft). You notice that I said that golf shaft, because you could test golf shafts of the same flex from ten different manufacturers you would most likely find ten different bend (kick) points measurements for reasons I will describe next.
The kick point in a golf shaft is controlled primarily by two criteria and they are geometric shape and materials selection, usually in that order. A golf shaft designed with a long parallel tip section such as a senior (‘A’ flex) or a ladies (‘L’) but not limited to these, would tend to have a low bend point. On the other hand a golf shaft designed using very stiff (high modulus) material in the tip section, like boron, could also cause a golf shaft to exhibit a low bend point, because the tip area is so stiff that the golf shaft has no opportunity to bend except at the termination of the boron or high modulus material pattern(s). Because of this fact it is sometimes possible for a senior (‘A’ flex) shaft to have a higher bend point than a high modulus (X flex) shaft but have a higher ball trajectory than a high modulus (X flex) golf shaft.
There is another misconception by many players as to just where these bend (kick) points are located on a golf shaft? The general thinking is that a low kick point is down near the club head, and a high kick point is up near or just below the grip area and a mid point is in the middle of the club, give or take. When in actuality most all kick point measurements of ‘high, mid and low’ are all within approximately a 5’’-7’’ range of each other, at about 18’’ to 25’’ from the tip of the golf shaft and when you swing a golf club it very seldom, if at all physically bends at any one of these kick points. In a carbon fiber tapered tube (golf shaft) the controlling factors are referred to as stress risers in the laminate modulus (stiffness) analysis.
To further illustrate this point concerning kick point as it relates to ball trajectory, would be to fix (clamp) the tip end of a Senior (‘A’ flex) and a high modulus (‘X’ flex) and then apply an equal load to the butt end of the Senior (‘A’ flex) golf shaft with a high bend point and a high modulus (‘X’ flex) with a lower bend point and you would observe that the Senior (‘A’ flex) golf shaft will deflect much more than the high modulus (‘X’ flex) which it should, even though it has a higher kick point. So what are we measuring? In reality, it is actually a golf shafts tip section stiffness in reference to its butt section stiffness rather than kick point. So, why is this measurement made and how useful is it?
Therefore what does influence ball trajectory and how does PENLEY design to and more accurately measure a golf shafts ability to launch at a higher or lower ball trajectory? The answer is the “TBAR™ “(Tip to Butt Aspect Ratio) algorithm.
Copyright © 2002, 2015 Carter Penley. All Rights Reserved
(all theories and analysis are still pertinent)