## Thursday, March 1, 2012

### Understanding Vertical Gear Effect

Most people understand horizontal gear effect.

From heel to toe, the clubface of a driver in curved to a small degree. This curve, from heel-to-toe is called the ‘face bulge.’ It’s designed to help with the horizontal gear effect.

First, let’s understand that the sweetspot of the driver is in line with the Center of Gravity of the driver head. It’s about the size of a needle point and is close to the middle of the clubface, sorta like this diagram shows.

The sweetspot on the driver is NOT an area, like this diagram infers.

So, a golfer can hit a drive that feels good, but just miss that sweetspot and they could never really feel the difference. That’s because the area around that sweetspot is where the clubhead’s highest Moment of Inertia exists. The further away from the sweetspot, the MOI decreases.

When we miss the sweetspot by hitting it on the toe, that will create a hook spin axis on the ball. Off the heel…slice spin axis.

What horizontal gear effect does is if you hit the ball off the toe, it will send the ball initially to the right. And because the ball has a hook spin, it will increase your odds of finding the fairway because the ball is more likely to ‘push-hook’ towards your target. Conversely, heel shots will likely start left and slice back towards the target.

Whereas Horizontal Gear Effect goes from heel to toe, Vertical Gear Effect goes from the bottom of the club to the top of the clubface.

From what I gathered from Wishon, if the ball is struck below the sweetspot of the driver, the ball will spin more. This will help that ‘thin’ shot get up in the air. Conversely, hit it above the sweetspot and the ball will spin less so it won’t sky-rocket into the air.

I find Vertical Gear Effect interesting because Wishon’s drivers practically have zero ‘face roll.’

As I’ve described in previous posts, the clubface of drivers are also vertically curved. This is called ‘face roll.’ In Wishon’s book ‘The Search For The Perfect Driver’, he discusses how face roll initially served no real purpose nor did it affect ball flight. However, as the driver heads got bigger and bigger, the face roll became more pronounced. Club manufacturers measure the loft from the middle of the clubface. But now with the more pronounced face roll, the loft higher up on the face would increase and would decrease lower on the face.

Thus, an OEM could have a driver labeled at 10° loft, which would be measured from the center of the clubface. But, below the center the loft may be 8° while above the center the loft may be 12° due the face roll.

The issue I see is that it cancels out the ‘positive’ effect that Vertical Gear Effect could have. Hitting it a little low on the face is likely to lower the initial launch anyway. But, if your 10° lofted driver is only 8° towards the bottom of the face, now the ball launches even lower and the positive effect of the increased spin from VGE is rather negligible. Same with hitting the ball above the sweetspot…the ball will go higher and perhaps too high.

Wishon’s drivers are designed with virtually no face roll. And I’ve noticed this Vertical Gear Effect since I got a shaft that better fit my swing. If I hit it a little low on the face, I can still get the ball to reach just about the same maximum height as if I hit it dead on the sweetspot. The ball does initially launch too low because with virtually no face roll, my 919THI driver is at 10° loft all over the face. The loft does not increase or decrease regardless if I hit it high or low on the face.

3JACK