## Thursday, July 16, 2009

Trackman has a newsletter that I really need to read more. Here's a bunch of excerpts from its latest newsletter...just great great stuff (http://trackman.dk/getmedia/2f6c5cdc-e153-466c-9e1a-f8b612947435/TMNewsJul2009_1.aspx)

What are the keys to achieving the optimal, straight shot?

In terms of club delivery, it is fairly simple since there are just three
parameters in play. To hit a straight and effective shot at the target,
you need:

1. Club Path ZERO
2. Face Angle ZERO
3. Impact in the center of the clubface.
Please note a couple of things. The old TGM laws would say that the face needed to be slightly open at impact to hit a straight shot at the target. Also, it was thought that a mis-hit would cause a loss in distance. Trackman is saying that it also causes a loss in accuracy.

For a 6 iron, if the club path and face angle are both between +/-1°, this would, more or less, guarantee a straight shot (assuming center hit). But for the Driver, it is required that the club path and face angle are both between +/- 0.5° to achieve the straight shot (assuming center hit).

Why is it more sensitive for the Driver than for the 6 iron?

As a rule of thumb, for a 6 iron the ball’s spin axis will be tilted two times the difference between the face angle and the club path, whereas for the Driver, the ball’s spin axis will be tilted 4 times the difference between the club path and the face angle. So if face angle is 5° and club path is 3°, then for a driver the spin axis will be around 8°, whereas for a 6 iron the spin axis would be around 4°. To understand why, we have to look at the so-called D-plane.
So when you want to understand why it is harder to hit a driver well versus hitting an iron well, spin axis provides an answer.

For years we have heard the mantra ‘swing all clubs the same way’. But I would not agree to that. Golfers need different swings to be most effective with their shots. In order to take a divot after impacting the ball (irons), you need to hit down on the ball – negative Attack Angle. Conversely, hitting up on the ball – positive Attack Angle – with the driver enables you to maximize your distance for your club head speed.

So, let’s assume that your vertical swing plane with a 6 iron is 60° and your attack angle is -5°. In order to create a straight shot, your goal is a club path of 0°. How can this be achieved? The answer is a Horizontal Swing Plane of -2.5°, which means aim 2.5° left of the target line with your swing plane.

In summary, for a swing having a 60° vertical swing plane, an attack angle of -5°, and a horizontal swing plane of -2.5°, the result will be a club path of 0°.

These charts and figures can be rather academic. Can you explain it in a very down to earth way?

I can try: We can say that with the driver you need the same value for attack angle and horizontal swing plane in order to obtain a 0° club path – for example if your attack angle is +3°, the horizontal swing plane needs to be +3° to obtain a club path of 0°. And for irons it is half effect – for example if attack angle is -4°, the horizontal swing plane needs to be -2° to obtain zero club path. In short,
aim left when hitting down on the ball and aim right when hitting up upon the ball. And remember when I say ‘aim left’ I mean the swing plane, the face angle should always be aligned towards the target line.
Okay, KEY POINTS HERE.

Vertical Swing Plane = Angle of Attack.

Horizontal Swing Plane = Swinging 'Right' or 'Swinging left.'

And for reference, the a positive degrees for horizontal plane means the path is 'inside-to-out' or 'swinging out to the right.' A negative degress for horizontal plane means the path is 'outside-to-in' or 'swinging to the left.'

I will use two examples.

Christy Kerr hits up with her driver about 5*. With the driver, in order to obtain a perfectly straight shot and that 0* 'true path', she needs to swing out to the right by about 5*.

Tiger Wood on the other hand hits about 3* down with the driver. In order to hit a perfectly straight shot and get that 0* true path, Tiger needs to swing out to the left by about 3*.

Of course, this changes with the irons because of the spin axis. If I hit 5* down with a 7-iron, then I have to swing 2.5* left in order to hit a perfectly straight shot. If I then grab a PW and hit 8* down, then I need to swing about 4* left to hit that perfectly straight shot.

Ball position is an issue here as well?

Absolutely. If you move the ball back towards your right foot for the same horizontal swing plane, the effect will be a steeper attack angle (more negative) and a more inside-out club path (more positive). So, in order to maintain a zero club path while moving the ball further back in your stance, you simply have to rotate your horizontal swing plane towards the left (more open stance).
One of the things that is taught by many TGM'ers is that if you want to hit a draw, you should put the ball back further in your stance and open the face slightly. Trackman is saying that when you do that, you effectively cause the angle of attack to be steeper. This means the golfer now has to swing more left to hit the ball perfectly straight. But moving the ball back in your stance also causes the clubpath to be more inside-to-outside as well. So what we know about the 'new ball flight laws', curvature of the ball is caused by the clubpath in relation to the face angle at impact (actually it's seperation, but to make it easy we'll say impact.) So by moving the ball back in your stance, you're just causing more of an inside-to-outside path which creates a hook spin. And by opening the face, you're allowing the ball to start out to the right and then draw back towards the target.

Now let's take a look at what Trackman has to say about mis-hits and their effect on ball flight.

How close to center impact do you need to be? How big is the effect of off-center hits?

Impact location and gear effect have a surprisingly significant effect on the curvature of a golf shot. If we start with the ideal situation with a face angle of 0° and a club path of 0° and impacting the ball in the center of gravity of the club face, then the ball will go straight. However, if you impact the ball just 1 dimple (0.14 inch) towards the heel of your driver, it creates a spin axis of +6° (fade spin) and the ball will end up 10 yards right of the target line on a 250 yards carry shot.

You will probably be on the fairway, but in a major with very narrow landing areas and firm turf conditions, the shot may be in jeopardy of missing the fairway. If you impact as much as half an inch towards the Toe, the dispersion will be 35 yards left of the target on a 250 yards carry!

Luckily the club manufactures have added a curvature to the club face (the bulge) on woods and drivers. This means that when you impact the ball on the heel your face angle at the impact point will most likely be closed, hereby starting the ball more left and tilting the D-plane towards a draw spin. The net effect will be a much straighter shot compared to the zero face angle situation.
DRIVER: EFFECT ON OFF-CENTER HITS (W/ZERO DEGREE FACE ANGLE AND CLUB PATH

1 dimple towards the heel (0.14" towards heel = 10 yards to the right at 250 yards

1/2" towards the heel = 35 yards to the right at 250 yards.

6-iron: EFFECT ON OFF-CENTER HITS (W/ZERO DEGREE FACE ANGLE AND CLUB PATH

1 dimple towards the toe (0.14" towards heel = 2 1/2 yards to the left at 170 yards

1/2" towards the toe = 8 yards to the left at 170 yards.

All of this being said, a golfer needs to obtain the basic fundamentals of the golf swing and the 3 imperatives according to The Golfing Machine are a good place to start. There's also a difference between coming over the top and 'swinging left.' But I would work on those TGM imperatives first and once they are executed consistently, then start to focus on horizontal swing plane.

3JACK