Large, high MOI drivers require tip-stiff shafts to reduce bending
It's almost a cliché to say the shaft is the engine of the golf club. But when the performance characteristics of the chassis changes, do you need to fine-tune the engine as well? In a word, yes.
Shaftmakers say that when the properties of the clubhead are altered, shafts need to adapt. This is especially true when moments of inertia jump above 4,500. According to John Oldenburg, VP of engineering and product development for Aldila, shaft designers first had to understand what was changing in the driver head. "It's not enough to know it's bigger or has a higher MOI," said Oldenburg. "You need to know what is going on inside the head."
What shaft R&D minds found was the center of gravity not only moved farther back and lower, but also shifted farther from the shaft. This combination does three things: It puts additional stress on the shaft (especially in the tip section); it adds torque at impact; and it effectively increases the loft and thus the launch angle.
"The larger heads led to a bigger bending load on the shaft," said Oldenburg. To combat that shaft designers had to make the tip sections stiffer for more stability while also reducing the torque.
One of the reasons for lowering torque is a technological tug-of-war. When the center of gravity is moved back and deep on a driver head, the more the head wants to close during the swing. A stiffer torque in the tip section helps prevent that.
The modern driver presents other issues. "A high MOI driver allows players to swing harder," said Alex Dee, engineering manager for Fujikura. "Since the drop-off in performance isn't so bad on off-center hits, some players go to a longer shaft to try and boost their clubhead speed even more." Which leads to another challenge: swingweight and mass balance.
Oldenburg says one of the tools to achieve greater MOI is to make a clubhead heavier by moving the weight to the extreme edges. But clubs still need to stay in the same swingweight range. To do this, the shaft's balance point needs to move toward the grip end of the shaft, which keeps the swingweight down. To that end, Oldenburg said he is working on a high-balance-point shaft specifically geared to high MOI drivers.
What does this mean for the everyday player? If you're looking at a high (more than 5,000) MOI driver, the stock shaft might not be your best choice. Get on a launch monitor and get properly fit. That new driver you're eyeing might also require a new engine to go with it.
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