Tuesday, April 24, 2012

Underrated Aspects of Driver Head Designs

One of the big eye openers for me when I started learning about club design, club making and club fitting was from Tom Wishon’s book ‘The Search For The Perfect Driver.’

In the book, he discusses the fallacy of the ‘hot spot’ of the driver. The fallacy goes as this….there’s supposed to be a ‘hot’ spot of the driver head up towards the top of the face (near the crown). This is a fallacy rampant throughout the golf industry. I’ve seen Martin Hall talk about the ‘hot spot’ in his show on The Golf Channel and heard this quite a bit at the PGA Merchandise Show this year.


Wishon’s explanation of the fallacy was that the face of the driver curves vertically (bottom to the top of the face). This is called the ‘face roll.’ With 460cc driver heads, the clubface became longer both vertically and horizontally. Since the face became longer vertically, the face roll became more pronounced. And when that happened, the clubface would increase in loft towards the top of the face and decrease in loft towards the bottom of the face.


Face roll wasn’t a problem pre-titanium. As you can see the difference between a persimmon driver and the titanium driver in the photo above, the pre-titanium driver heads were so small that the face roll was not as pronounced.


With the driver it’s ultra-important to fit for loft. 1° of loft difference in a driver can greatly influence how well you hit a driver. However, Wishon recommends that you first look at clubhead speed in order to start to fit for loft. The more clubhead speed, the less loft a golfer should use. And of course, attack angle plays a factor as well. But most of the time, it’s far more about clubhead speed in loft fitting than it is attack angle. This is something most golfers either don’t get or go the opposite way (thinking attack angle first, then clubhead speed)


So according to Wishon, the reason for the fallacy of the ‘hot spot’ was that golfers were playing with drivers that had too low of a loft for their clubhead speed. They would then hit the occasional shot up high on the face where there was more loft which fit their swing better. So a golfer who swings the driver at 100 mph may be best off with a driver with a 11-12° of loft. Instead, they are using a 9.5° lofted driver head. Eventually they discover when they hit the ball up high on the face, they hit it longer. But in reality they are just hitting the ball on the part of the clubface more where the loft is comparable to their swing speed.



One of the things I hear some clubmakers talk about is how the Quality Control of OEM drivers is poor. I usually hear that the lofts are higher than the what they are stamped on the club. So, you may hear a clubmaker say that he has a driver that has a stamped 10° loft, but when they measured the loft, it was actually more like 11.5° loft.

Obviously, a club can have the incorrectly stated loft from time to time. However, the loft of a driver is measured from the center of the face. Thus, if a clubmaker is measuring an OEM driver and happens to measure more above the center of the face where the loft has increased because of face roll, then they are not quite getting the most accurate measurement of loft.



One of the questions that a reader asked me was ‘if you can hit the ball further by hitting above the sweetspot, then why not just keep hitting the ball above the sweetspot?’

I thought about this for a while and I’ve come up with a few reasons to avoid this:

1. Toe shots

From my personal experience of believing in the hot spot hype and then getting out of that hype is that my toe shots off the tee dramatically decreased just by no longer trying to hit that ‘hot spot.’ First, the ‘hot spot’ is alleged to be slightly towards the toe. So, if you try to hit slightly towards the toe…your chances of hitting one woefully off the toe increases. I also find that swing mechanics wise, if you try to hit the ‘hot spot’ and in particular try to hit up on the driver and hit the ‘hot spot’, I think that tends to cause your swing mechanics to be more likely to hit that toe-hook shot. I don’t have a problem with hitting up with the driver, but you should hit up and try to hit the actual sweetspot instead of trying to hit up and hit the faux ‘hot spot.’

2. Less Distance Off The Hot Spot

The closer you are to the sweetspot (somewhere in the center of the face, aligned with the clubhead’s Center of Gravity), the clubhead’s Moment of Inertia is at its highest. The higher the MOI, the less twisting of the clubhead as the ball hits it.

You will hit the ball further with less twisting from the sweetspot than from the Hot Spot. I don’t think it’s a giant difference because I think the ‘hot spot’ still has a rather high MOI, but not as much as the optimal MOI of the sweetspot.

In general, I think golfers will be much more accurate and consistent to avoid trying to hit the faux ‘hot spot.’ But, I think those 2 reasons above are the things that become obvious once you stop believing in the hot spot hype.


One of the things Wishon Golf decided to do was to counter how much the loft of the driver can change because of the pronounced face roll. So what they created was something they call ‘Graduated Roll Technology.’

Graduated Roll Technology (GRT) keeps the face roll down to a minimum.



The main benefit I’ve found of GRT is that it allows the golfer to increase their distance off the tee *over the course of a round.*

What I mean by this is that a properly fitted Wishon driver and a properly fitted OEM driver will likely go about the same distance when they hit the ball on the sweetspot.

However, we don’t always hit the sweetspot. And often times we may not hit it off the toe or the heel, but just miss the sweetspot by hitting it a little too high or too low off the face. Usually these shots wind up fine, but they just don’t go quite as far as we would like.


Recently I discussed something called ‘vertical gear effect.’ Vertical Gear Effect is similar to Horizontal Gear Effect in that it helps ‘self-correct’ the golfer’s ball flight when they miss the sweetspot.

For example, with horizontal gear effect…if I hit a shot off the toe the ball will have hook spin to it. So the horizontal gear effect will launch the ball out to the right and the ball’s hook spin will bring it back towards the target. Without horizontal gear effect, we would miss the target badly every time we missed the sweetspot.

Vertical gear effect works in a bit of a similar fashion.

If I hit a shot with the driver above the sweetspot, the ball will initially launch higher. You can lose a lot of distance, but the vertical gear effect will produce less spin. The lower spin allows the ball to not go too high. This is another reason behind the ‘fallacy of the hot spot.’ Golfers would hit the ‘hot spot’ and the ball would carry better for them and with less spin.

Conversely, if you hit below the sweetspot, the initial launch of the shot will be lower. So the vertical gear effect kicks in and the ball will spin more to help bring the trajectory up.

So, let’s take the difference between a driver with GRT and one without. We will say that both are optimally fitted for the golfer and the golfer understands the fallacy of the sweetspot.


Here the golfer is using an 11° loft driver in both cases as that is what they were optimally fitted for.

Hits Above The Sweetspot

The golfer will actually hit the GRT driver further because while the loft is higher with each driver, the GRT loft is more in line with what they were fitted for. The vertical gear effect will help bring both trajectories down. The difference in lofts here above the sweetspot is 1.5°.

Hits Below The Sweetspot

The GRT driver will go much further because the loft has not changed from what they were fitted for. However, the non-GRT driver has a much, much lower loft. The difference in lofts is now 3°. Imagine having the choice of buying 2 drivers with a difference in 3° of loft. That’s a massive difference.

So over the course of a round, the golfer would likely pick up yardage because when they go above or below the sweetspot, the GRT driver consistently allows them to hit the ball further.



With all of this being said, another benefit is that better players are in a better position to hit driver off the deck with a GRT driver than a non-GRT driver.

Think about it for a second. If you hit a driver off the deck, the ball contact will be lower on the face. With a non-GRT driver, the loft will be very low on that part of the face. While the Vertical Gear Effect can help, the loft may just be entirely too low with the non-GRT driver off the deck.

Perhaps the player on Tour that uses the driver off the deck the most is Bubba Watson. I think Bubba faces the same issues with his non-GRT PING driver. However, his clubhead speed is so high (around 125 mph), that allows him to more easily (and naturally) get the ball up in the air. But for mere mortals, even those who generate a good amount of clubhead speed (say, 112-115 mph), using a non-GRT driver off the deck is a difficult proposition

The main point in all of this is to really try and understand your equipment. Even if you utilize a non-GRT driver, you can still hit a driver really well. But, you are likely to become a better driver if you truly understand the features of the clubhead design than if you are going into it blind.


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