Shaft University – Design 101 – Part II

In Part I, we left off with a brief mention of Fujikura’s proprietary motion capture software, ENSO.

Internally it’s described as an MRI for golf shafts, and with three systems in existence (two of which are owned by Fujikura – PING has the other one), it’s not as though this type of technology is commonplace. The point is that Fujikura is the only shaft manufacturer with this setup, though every major shaft company has an arsenal of research tools at its disposal.

Enso is unique because it can quantify the dynamic relationship between the shaft and the golfer. Humans play golf, not robots and so when trying to understand how a shaft bends, deflects, and twists, it happens as a result of both the who (golfer) and the what (specific shaft characteristics). Both the golfer and the shaft play a role in the overall performance of a club so, ideally, both should be included in the design process.

If this sounds complex, it is, but the ENSO does the heavy lifting and helps take the guesswork out of shaft design, and allows Fujikura’s design team to access a blue ocean of information from the system. More specifically, ENSO uses ten high-speed motion capture cameras (capturing at +1,000 frames per second) with at least three cameras tracking each of the sensors (the same sensors that are used in CGI animation for box office films) located on the shaft and clubhead throughout the golf swing.

As we said, it’s a powerful system.

The real-world applications of ENSO are such that it allows Fujikura to streamline the R&D/prototyping process and how different shafts work with individual swings.

Based on this data gathering process, shaft designers hone in on a couple of fundamental questions:

1)How does it need to perform?

2)Who will the design benefit?

With that, there are four primary parameters designers address to change the recipe, and with it, performance. While the typical golfer might not understand the full implication of tweaking each parameter, it’s boilerplate stuff for shaft engineers. Here’s a quick overview of the basics.

Stiffness 

• Increasing the length of the butt parallel section will increase stiffness.
• Increasing the inner diameter of a design will increase stiffness.
• Decreasing the length of the tip parallel section will increase stiffness. A parallel tip section is typically 2.5”-3”.
• Adding stiffer materials to both the 0 degree (fibers along the length of the shaft that affect bending) and +/- 45 degree orientations (known as the bias layer, fibers across the length of the shaft that affect twisting) will increase stiffness.

Launch/Spin 

• Increasing the stiffness in the mid and tip section will lower launch and decrease spin.
• Lowering torque also lowers launch and spin.

Torque 

• Stronger and stiffer materials applied as the first plies at a bias (45-degree angle) to the tip section reduces torque.
• Increasing the length of the butt parallel section will reduce torque.

Weight 

• Increasing the amount of materials will increase weight.
• Increasing the number of layers of material around the mandrel will increase weight.
• Adding heavier materials to a design will increase weight.

Quick quiz – Let’s say you go to a fitting and notice your fairway wood is launching too low with too little spin to maximize carry distance. Your fitter suggests a new shaft. As compared to your current shaft, the new one should:

1. A) Be exactly the same, but a different color.
2. B) Have a slightly longer butt parallel section.
3. C) Have decreased stiffness in the mid and tip sections.
4. D) Have a shorter parallel tip section.

 

Feel 

Then there’s the subjective world of feel. Let’s be clear, feel, and performance aren’t directly related. One doesn’t necessarily dictate the other. That said, designers do tweak a shaft’s geometry to alter feel based on the target audience.

For example, to create what’s described as a smoother and easy-loading feel within a shaft, designers might focus on accelerating the taper rate from the butt to mid-section. Conversely, a longer butt parallel section will create a more stable, rigid feel throughout the shaft. Note that both of these examples center on changes to the grip section of the shaft.

But wait, hold up a sec, what’s taper rate?

At the butt end, a shaft’s diameter is +/- .600”. At the tip, it’s either .335” (drivers and fairway woods), .355″ (taper tip irons) or .370” (hybrids and parallel tip irons). The general sloping (and rate of change of that slope) from butt to tip is called the tapering of the shaft. Also, keep in mind shafts are every bit as regulated by the USGA as club heads, grooves, and balls.

For reference, here are the two most important regulations:

2a: Straightness:

“The shaft of the club must be straight from the top of the grip to a point not more than 5 inches (127 mm) above the sole, measured from the point where the shaft ceases to be straight along the axis of the bent part of the shaft and/or socket.”

2b: Bending and Twisting Properties:

“At any point along its length, the shaft must: (i) bend in such a way that the deflection is the same regardless of how the shaft is rotated about its longitudinal axis; and (ii) twist the same amount in both directions.”

APPLICATION

Once designers know what they want the shaft to do, they have to strategically use materials, geometry, and technology to combine all of these components into a structure. The process is made more complex when engineers want the final product to maintain uniform concentricity (meaning: the shaft will produce the same performance regardless of how it’s oriented during installation). Concentricity also implies that a shaft should offer nearly identical performance in any orientation. This is particularly important when a shaft is paired with an adjustable hosel that allows the golfer to change the loft/face angle of the club.

As a slight tangent, we’ve received several questions as to whether or not spining/floing is beneficial. It’s a topic which deserves its own space, and we will save the particulars for that occasion, but you might want to wait for that information before you drop tons of extra cash for the service.

As we mentioned in Materials 101, graphite shafts are made with advanced composite materials known as CFRP (carbon fiber reinforced plastics). The orientation of these composite materials in a design is as important as the materials themselves.

Like the perfectly baked birthday cake, every shaft production process starts with having the right ingredients (materials). Quality results aren’t dictated by materials alone, nor is it the result of X number of quality control checkpoints. Manufacturers which produce the most consistent products also generally control more steps of the production process. This tends to be true whether we’re discussing shafts, balls, or other hard goods (equipment). Think of it this way: anyone can order generic materials to build a garden shed, but how would the Home Depot kit compare to one made by a skilled craftsman who purchased specific types of materials, which were delivered and stored at certain temperatures, and were used in a building process according to precise CAD designs – not to mention the craftsman’s several decades of experience? You likely see where this is headed.

In the case of Fujikura, it requires all suppliers to deliver materials in specific nominal states to center material tolerances. It also stores all materials at a constant 40 degrees Fahrenheit to ensure consistency from design to finished specs. This extra step in the design process tightens material tolerances reducing the variance between shafts produced throughout a product’s lifecycle. Effectively, it means the production tolerances remain the same whether a shaft is manufactured in December of 2019 or March of 2021.

GEOMETRY

We’re not talking about Pythagoras, Euclid, or right-triangles, but because shafts have a shape, they also have geometry – or relationships between different dimensions. Since there are fixed dimensions (see USGA rules above) it becomes imperative that shaft manufacturers understand every facet of design and how changes in geometry impact the performance characteristics of the final product.

Also, keep in mind that as a result of modern equipment designs OEMs have more or less locked-in butt and tip diameters, as well as the length of the parallel tip section. The result is a relatively confined sandbox in which shaft companies can play. This is where the flexibility of composite materials gives them a distinct advantage over steel, where its isometric qualities are more limiting.

As mentioned previously, composites allow manufactures to independently modify bending and twisting stiffness, weight, and flex throughout every millimeter in a design. It’s like selecting a different type of wood for every square foot of your kitchen floor as opposed to a single type of carpet in the living room.

Some designs require only a few materials and plies applied along the full length of the shaft, while other more advanced designs utilize several materials and 15-20 plies ranging from full-length to smaller tip flags.

Shaft Sections

There are three primary sections (Tip, Mid, Handle) within in a design which can be targeted to modify performance attributes.

TIP SECTION 

• Adding a tip flag of stiffer material in the 0-degree orientation decreases launch and spin.
• Adding a tip flag of stiffer material in the bias orientation (+/- 45 degree) reduces torque and increases the rigidity.
• Incorporating softer materials in the tip section will increase launch and spin and increase torque.

Example: The tip section of Fujikura Ventus is ultra-stiff in both 0-degree and bias orientations, reducing torque and decreasing the amount of twisting that occurs at impact (tightens dispersion and reduces energy loss on off-center shots).

MID SECTION 

• Adding a flag of stiffer material in the mid-section will reduce the amount of shaft lead, decreasing launch and spin. Depending on the design, this can also help shift the balance point away from the clubhead to achieve a more playable swingweight.
• Using more pliable materials will increase the shaft lead and create a softer feel.

Example: Speeder TR has a stiffened mid-section to reduce the amount of shaft lead, and decrease launch and spin for golfers with faster transitions to the ball.

HANDLE SECTION 

• Adding stiffer materials in the handle section will decrease the amount of deflection in the shaft, creating a stiffer feeling in the hands.
• Stiffening the handle section will also help to retain the load applied by more aggressive swingers. See: Johnny Vegas

Example: The three Atmos Tour Spec profiles (Red – Mid-High Launch, Blue – Mid Launch, Black – Low Launch) were designed for aggressive loaders. They feature similarly stiff handle sections that provide similar feel across the three models.

Once the specs and the materials are determined, the next step is to select the right tooling. In some cases, it’s necessary to design new tooling based on the parameters of the new concept.

The tool, in this case, is called a mandrel. Mandrels are the steel cylindrical rods around which composite materials are wrapped and cured to form a shaft. Technological and material advancements have allowed for more sophisticated mandrel designs.

While mandrels all look the same at first glance (for that matter so do shafts), each of the 1168 millimeters along the length of a mandrel has been designed to meet certain requirements.

Examples of how Fujikura has used different mandrels to create new technologies in products include:

HDCC (High-Density Composite Core) – The mandrel design for the PRO iron shafts has a truncated tip section that allows for a precise weight pocket, which is created using composites that are 62% denser than standard modulus materials. This adds weight to the design to achieve proper swing weights on standard length irons.

H.I.T. (High Inertia Tip) – The Atmos and Pro 2.0 wood and hybrid shafts have an engineered taper which is created by removing the excess materials in the tip section while maintaining the same inner wall thickness. The goal with this design is to maximize the energy generated during the downswing and release it before impact, accelerating the tip section faster to the ball.

MCT (Metal Composite Technology) –  MCT is extremely strong, but also enables us to add weight in key points in the shaft to aid in changing the balance point or to change feel. Similar to HDCC, MCT requires a mandrel that is thinned in a particular region to allow for this additional material to be integrated within a design.

Once the mandrel is selected, technicians begin the process of applying the material. Each mandrel is designed with specifically marked locations or clocking that specialists use as a guide when applying material. Each material within a design has a clocking number that tells the technician where to apply the material and how many times the material must wrap around the mandrel. This helps to ensure shape uniformity and consistent material application. Because many drivers, fairway woods, and hybrids feature adjustable hosels, the topic of concentricity continues to be a point of discussion. Again, concentricity simply means regardless of a shaft’s installed orientation (logo up, down, etc.) performance remains largely unchanged.

This might feel a little bass-ackwards, but before a shaft goes into mass production and all of the decision points around materials, tooling, and layout have been determined, the build has already been simulated through Fujikura’s proprietary 3D modeling software. Based on the parameters selected by engineers, this program produces a complete understanding of specifications surrounding such as:

• Torque
• Weight
• Balance Point
• Tip and Butt Flex
• Material Properties
• And many other data points

Computers can work infinitely faster than humans (they also don’t require sleep or vacation pay), so rather than creating and testing several physical prototypes, software programs run broad spectrum simulations to narrow in on 1-2 workable designs. Every major shaft company utilizes a version of this basic process. These prototypes are then built in a facility (hopefully nearby) and tested to confirm the specifications created in the design program. If these prototypes pass the necessary specifications checkpoints, they are then moved into the testing phase, which is a topic we’ll save for another day…

And….exhale. That’s more than a metric ton of information, but before we go, here’s a brief homework assignment.

Do an inventory check. Look through your bag and see if you can determine the bend profile of each shaft. Once you’ve done this, what does this information tell you about the performance of each club?