# The D-Plane, Trackman, NBFL, etc. thread

Since there’s people asking for it, I have no problem starting a thread over here.

The ‘new ball flight laws’ is really another way of stating the ‘correct’ ball flight laws as the PGA has gotten the laws of ball flight wrong for years. I believe that the ‘correct ball flight laws’ were really brought into light from Dr. Theodore Jorgenson’s 1991 book ‘The Physics of Golf.’ In it he goes into detail of what he coined ‘D-Plane’ or ‘Descriptive Plane.’ In reality, D-Plane = the new ball flight laws.

I’ve heard that the rules are that the initial direction of the ball is 70-87% responsible for the initial ball flight. The other 13-30% is due to where the clubhead path is going at impact. Curvature of the ball flight is due to where the path is going in relation to the FACE at impact.

Trackman measures the clubhead and clubface dimensions thru impact (as well as other things). I highly recommend golfers to check out their newsletters that can be found at trackman.dk/Media/Newsletter.aspx

I don’t agree with all of the Trackman philosophies. For instance, they believe that golfers should hit upward with the driver because that optimizes distance. I do agree that you can hit the ball dead straight while hitting up on the driver, but I also believe that factors like wind and personal preference mean that not all golfers should try and hit up with the driver. IMO, the greatest measurement that Trackman provides is the attack angle. By accurately measuring the attack angle, it’s made interesting, new studies in relation to the swing. Also the ‘horizontal swing plane’, which in my mind is basically measuring where the clubhead is going after impact is an important measurement as it shows the effect of ‘swinging left’ and what it has on the ball.

I wrote a blog post on this and how Hogan more or less figured out D-Plane for himself as evidenced by his stance diagram in 5 Lessons. You can read that at 3jack.blogspot.com/2010/04/mr-ho … plane.html

I notice that Mac O’Grady uses the ‘swing left’ release and uses the same stance with different clubs like Mr. Hogan describes in 5 Lessons.

3JACK

Thanks for starting this up 3J.

robbo

The following is a brief excerpt (pages taken from ‘The physics of golf’ (2nd ed.), by Theodore P. Jorgensen. (It explains D-Plane, and it’s practical application.)
I’m sorry about the long post, but think it’s good to have some reference material to make sure everybody is talking about the same stuff

The D Plane
Euclid, the famous geometer, says something to the effect that two intersecting lines determine a plane. The normal to the clubface and
the line along which the clubhead is moving at impact intersect at the ball and therefore determine a plane. The line along which the ball
leaves the clubhead also lies in this plane. We shall call this plane the D plane because it is descriptive of the collision between the clubhead
and the ball.
Consider a collision for which the clubhead at impact is moving directly toward the chosen target and the normal to the clubface is
directed to a point exactly above the target. The D plane for such a collision contains the target, and the plane is vertical. After the colli-
sion, the ball will be moving in this plane toward the target with the line of flight a little below the normal to the clubface…

Equations Give Some Results
After the speed of the clubhead is given, the mathematical equations may be used to determine approximately what is happening after the
collision is over. They will tell us the speed of the clubhead, the speed and direction of the flight of the ball, and the rate of spin of the ball.
The velocity vector of the flight of the ball after the collision is below the normal to the clubface at impact. For similar swings the angle
between these two vectors increases almost directly with the loft of the club.
The rate of spin of the ball depends directly on the speed of the clubhead at impact. The golfer who can move the clubhead at a higher
speed will put more spin on the ball, and consequently, the ball will experience a greater lift. The lift will be greater because it increases
with the spin of the ball and it also increases with the speed of the ball through the air. With the greater lift, the ball will be held up longer, it
will not fall as fast, and with the higher speed it will fly farther before it hits the ground. This is true even though the drag also increases with
the speed of the ball.
The rate of spin of the ball depends directly on the speed of the ball as it leaves the club and almost directly on the angle between the
normal to the clubface and the line of the flight of the ball as it leaves the club. For a given speed of the ball, the spin rate is about three times
greater with a five iron and about five times greater with a nine iron than with a driver.

Collision Theory
The theory of collisions indicates that if a very light perfectly elastic ball is hit with a very heavy club with no loft, the ball will leave the
clubhead with almost twice the speed of the clubhead before impact. This is an upper limit. For the ordinary ball and an ordinary club, the
ball will be sent off at a slower speed. For a driver, five iron, and nine iron, the factors are 1.46, 1.30, and 1.12 for the three clubs, respec-
tively, according to our theoretical results. The photograph of Bobby Jones swinging his driver [4] shows the ball’s speed to be 1.4 times the
clubhead’s speed before impact. The agreement between 1.4 and 1.46 is better than we have any reason to expect because of possible experi-
mental error in determining the speeds involved and also in determining the coefficient of restitution of the golf ball. The agreement
suggests, however, that our theoretical results are not too far out of line. We may use the theoretical results to calculate the rate of spin of the
ball. Some experimental determinations of both the rate of spin and the speed of the ball are available [7]. These data are for the swing of a five
iron by a professional golfer, and the exact orientation of the clubface at impact is not given. By using a 5 deg angle between the normal to the
clubface and the line along which the ball leaves the clubface and a ball speed of 145 ft per second for a five iron, the theory gives a calcu-
lated rate of spin of 72 revolutions per second. For a five iron the measured spin rate for this ball speed averaged about 80 revolutions
per second. Perhaps a difference of this magnitude should be expected as a result of the approximations made in setting up the original math-
ematical expressions.
The spin put on the ball when it is hit correctly, so that it rolls up the clubface during the collision, is such that it appears to rotate in a
counterclockwise sense as seen by an observer facing a right-handed golfer. The ball is given what has been called underspin. A ball must
rotate with underspin in order that the aerodynamic forces give the ball the necessary lift. If the ball is hit with the edge of the club above the
center of the ball, the ball will be given topspin. Such a topped ball will have negative lift. This negative lift accounts for the quickly diving
flight of a topped ball. When the ball is hit out of deep rough and a layer of grass lubricates the contact between the clubface and the ball, there
may not be enough friction to give the ball the usual amount of spin. Under this condition the ball may leave the clubface along a line closer to
the normal than usual. Expert golfers have learned that a nine-iron shot from deep rough will not bite the green as does a shot with the
usual amount of backspin.

The D Plane as a Practical Tool
The D plane for a golf swing contains the path along which the clubhead is moving at impact, the normal to the clubface, and the initial
path of the ball after impact. The D plane also contains the aerodynamic lift force, since the lift force is perpendicular to the axis of spin
and this axis is perpendicular to the D plane. A diagram of the D plane for a possible five-iron shot is given in Fig. 9.2. A copy of this diagram
on a card will facilitate the reading of the following discussion.
It is suggested that a golfer take a five iron in hand as he reads this description of the use of the D plane. If the reader takes the usual
stance with a five iron and swings the club directly in the direction of an assumed target with the clubface square to the target, neither toed in
or toed out, then the D plane for the swing will be a vertical plane containing the velocity of the clubhead, the velocity vectors of the ball
and the normal to the clubface, and the target. To illustrate this swing, the card representing the D plane should be held so that the line repre-
senting the clubhead motion points horizontally toward the target and the line representing the normal to the clubface points directly toward
but above the target. For such a swing, in the absence of a crosswind, the ball will fly directly toward but above the target without a hook or
a slice.
Next, let the reader open the face of the club so that the normal to the clubface points to the right and above the target. The club has been
toed out. This is done while retaining the original intention of swinging the club directly at the target. To represent this swing of the
club, the D plane is tilted to the right. The line representing the direction of the clubhead motion is still horizontal and points toward the
target. The line representing the normal to the clubface points above and to the right of the target. The card shows that the path of the ball
will also be to the right of the target but not as far to the right as the normal to the clubface. Since the lift force lies in the D plane, the lift
force will have a component to the right, and this component will produce a slicing motion of the ball.
For a club that has been toed in, the D plane is tilted to the left, and the previous discussion applies except that “left” replaces “right” and
the component of the lift force to the left will produce a hooking motion.
Many swings with a golf club are made in which the clubhead is not directed toward the intended target. For such swings, the line on the D
plane card representing the direction of the clubhead motion, while still horizontal, must be directed either to the right or to the left of the
target. If the swing is described by a vertical D plane, the ball will go to the right or to the left without hooking or slicing. The reason for this is
that the horizontal component of the normal to the clubface also points along the direction of the clubhead motion. However, if for these cases
where the clubhead motion is not toward the target, and the clubface is toed out or toed in, the D plane is tilted as before, and the ball will have
a slicing or a hooking motion.
It is usually taught that a swing of a clubhead from outside in will produce a slice, but we see that a slice will result only if the swing can
be described by a D plane tilted to the right, and if the D plane is tilted to the left, the ball will have a hooking motion in spite of the motion of
the clubhead from the outside in.
The analysis involving the D plane may be used in diagnosing any swing producing an aberrant flight of the ball. Consider the problem
facing a young man who played a round of golf with me. His tee shots consistently started off to the left and sliced back to the right. The
slicing flight of the ball tells us that the D plane for his tee shots was tilted to the right; the aerodynamic lift force had a component to the
right producing the slice. Since the ball started off along a line to the left of the target and this line is in the D plane, we know that the
clubhead at impact was also moving along a line pointing to the left of the target. Since the normal to the clubface is in the tilted D plane and
lies above the line along which the clubhead is moving at impact, the normal to the clubface must point to the right of this line. We have thus
determined that the young man was swinging the clubhead from the outside in across the line to the target and the face of the club was open
to the path of the clubhead. Our diagnosis was confirmed when on one of the tees, his driver cut through the grass below his ball. The grass
was removed along a path pointing several degrees to the left of the green. A diagram of the tilted D plane for this kind of shot is shown in
Fig. 9.1.
The analysis involving the D plane may also be used to design swings to produce intentional hooks and slices. The club must be toed
in or toed out to tilt the D plane to the left or right. If the ball is to be kept in the fairway, the line along which the clubhead is swung must
be pointed to the right of the target for the intentional hook and to the left for the intentional slice. Figure 9.1 shows how the D plane must be
oriented for the intentional slice.
Many golf instruction books treat the subject of sidehill lies. When the ball lies lower than your feet, you are to play for a slice, and when
the ball lies higher than your feet, you are to play for a hook. The D plane may be used to understand why. Consider a sidehill lie with the
ball higher than your feet. If you stand to the ball with your usual stance, the normal to the clubface will naturally point to the left of the
target. This will tilt the D plane to the left, and the ball will have a hooking flight. The golfer has two possible ways to correct this flight of
the ball. He may, as the books advise, play for a hook and aim to the right of the target. The question is, How much to the right of the target
should he aim? He may toe the club out a bit so that the normal to the clubface and the direction of the motion of the clubhead at impact
indicate a D plane that is vertical and contains the target. There will be no hook for a vertical D plane, but the toeing out of the club will give
the club more loft. Thus for a given swing the ball will not go as far as one might expect for a given club. Then the question is, How far will
the ball go? In either case the shot requires considerable judgment. In considering what happens when the clubhead meets the ball, we
have assumed that the ball makes contact with the center of the clubface, at the “sweet spot.” For such a shot there is no torque about the
shaft of the club to produce a change in the orientation of the clubface.
If the ball makes contact with the clubface off-center, the clubhead will turn under the torque produced by the large force between the club-
head and the ball. If the ball is hit too close to the toe of the club, the club will turn to a toed-out position before the ball leaves the clubhead,
putting the normal to the clubhead farther to the right than was intended. The ball will then fade to the right.

FIGURE 9.1. The plane containing three directed line segments represents the D plane for a slicing golf shot. In the diagram the ball is on the
tee at A. The line AT represents the line from the ball to the target. The line AB represents the normal to the clubface at impact with
the ball, the line AD represents the velocity vector of the clubhead after impact, and the line AC represents the velocity vector of the
ball just after impact. For this shot the clubhead is moving from the outside in across the line from the ball to the target, and the ball
will start off to the left of the target line and slice back toward the target line, since the lift vector is tilted to the right.

Thanks.

I’ve only read small bits of The Physics of Golf. Trackman really explains all of the factors quite well in their newsletters. The effect attack angle has on path really blew my mind, but the more I thought of it, the more it made sense.

For instance, when I try to hit a very low punch shot to keep the ball under some trees, the ball almost always has some hook spin on it. D-Plane explains that as basically with that shot I’m moving the ball position back which creates a steeper attack angle which moves the path out to the right.

They also blew my mind with the ‘swinging left’ and the effect it has on path. I believe ‘swinging left’ has 2 huge functions.

1. You really can’t swing left unless you have a pivot driven swing. I firmly believe that pivot driven swings make the golfer far less reliant on hand-eye coordination and ‘timing’ and ‘talent’ to control the clubface and the low point.

2. Swinging left is needed, particularly with the irons, square up the path and allow the golfer to hit it dead straight.

That’s a big reason why I decided to get into ABS. I understood the importance of ‘swinging left’ and thought Lag could teach it. Then I was pleasantly surprised with the effect that Module 2 has had on my ballstriking along with going to heavier, flatter clubs.

3JACK

Richie
I am blown away by the effect of the attack angle on the path as well but still cant get an explanation as to how it actually does it.

It’s just the geometry of a circular type path if I understand what you’re asking Macs.

Is this what you’re trying to understand?

Thanks Steb
That is an imprtant beggining but leading to more questions in my head. From the picture it seems that a steeper AA(attack angle) or impact at an earlier part of the circle will lead to a more right releaseand vice versa. But the R3J puts it says that with a steeper AA you need to siwng it more left (horizontal swing plain) and vice versa.
Or is this related more to swinging in a tighter circle (as Lag recommends) so that the leftward part of the circle comes sooner after impact. I have just started seeeing a J shaped divot on my better iron strikes and it amzes me as to how tight and sever the rotation is in an ABS swing . Enter impact inside out and exit the divot out side in. Will also coinside with Lags prefernce to play the ball back in your stance and from the steepes angle possible from a deeply laid 0430 position. It sounds crazy but basically you have to produce a lot of opposing actions in golf. BUT I AM ALL EARS ON THIS ONE.

If I am understanding this angle of attack concept, it is saying that a steep angle of attack goes with( causes?, or is associated with?) an in to out path, but is it not possible to have a steep angle of attack, and still have an outside to inside, or OTT, swing?

Or will moving the ball back in the stance toward the trail foot be the absolute cure for someone afflicted with an OTT swing?
thanks/eagle

Sorry to butt in here on the thread, but happy to sit aside while other questions are being answered first…

RJ3,

Thanks for re-opening my eyes to the D-Plane…I remember seeing it a few years ago on Manzella before working with ABS and didn’t get that much out of it at the time.

I’ve got two questions for you when you have a chance. 1) If you are using the D-Plane correctly, do your draw shots now fly the shortest? with the straight-one going longer and the fade going the furthest?

Also, 2) what does Trackman numbers (or what have you found) say for HSP if play you intend to play a fade with the driver if your angle of attack is +3 degrees? Do you have a square face at impact and only +1 degrees of HSP instead of the normal +3?

The picture just gives a look at what happens hitting before low point given a simplified arc. But the real swing is not such a simple arc. If your arms and wrists were keep rigid through the swing, the arc would have a constant radius throughout - ie. a circle. Introduce arm movement and the circle starts to distort depending on when the arms are moved. Then add in the wrists and further distortion occurs. Add in loss of spine and sway during the downswing and more distortion occurs. What we end up with is not an ellipse but a very complex, irregular curve dependent on the timing of all the parts constructing it. Anything is possible!

I haven’t reached module 3 yet Macs and it still sounds amazing timing to me that this 2nd stage pivot thrust can actually be seen in the hook on a divot, if I understand its cause correctly. I look forward to it.

At one of our Hawaii golf schools this winter, I was doing my usual lecture/demo on the Old vs the New Ball Flight Laws, and said something like, “…the weird thing is, the Old laws seemed to work really well for almost every good player I have known, even though the science has proven some of those Laws to be incorrect” and one of the students who is an engineer and science geek said something like “…well if empirically the old Laws worked, ie pros who used them created consistently accurate hooks and slices on command for example, then the new 'science” is simply wrong - empirical evidence trumps theory". And I would add to that, I never met a single good player who believed that the starting direction of ball flight was ONLY caused by path with no influence of clubface angle at impact. Maybe it was more intuitive knowledge, but I certainly believed that it was a blend of both that created the starting direction. It seemed pretty clear to me that the ball would leave the face more or less perpendicular to the face angle, after all this was patently obvious in putting, for instance.

I think a lot of this controversy is due to some common perceptual errors along with linguistic confusion. I can move the clubface independently - either open or closed - of the clubhead path, through wrist and forearm muscles rolling the face open or closed. This will have no effect whatsoever (physically - although we all know how we can alter path based on feeling a too open or shut clubface, ie a compensation move)on the clubhead path or in other terms, the clubshaft plane angle. But whenever I move the clubhead in a certain direction, ie path - the clubface goes along for the ride so to speak. The clubface is an integral part of the clubhead so of course it is also moving with the path. If you have a good grip and understand how to cock your wrists and release that angle properly, and you dont change your original grip pressure, and you grip it with the face square to start with there is no physical force that will alter the face angle, ie it will stay “square” in its orientation, moving with the clubhead path, almost until impact, when there will be some rolling closed of the face due to CF and momentum, unless you have a very weak grip and/or very tight grip pressure.

In other words, changing the face angle does not alter the path but changing the path will always alter the face angle. Using target line as the reference point. Once you get this, a lot of this old vs new laws starts to make sense.

I think sometimes this is why I prefer to emphasize shaft plane angle instead of clubhead path in my teaching, since it avoids to some degree this widespread confusion.

That’s a good question and something to be judged on Trackman, which I haven’t used in over a year. The big thing would be just measuring the carry of the ball, which Trackman does very accurately.

One thing to remember, golfers who hit golf shots do not create ‘overspin.’ Draws/hooks roll more because they have less backspin, but do not have overspin.

Like I stated with irons, in order to square the path up to the target, the golfer needs to have a HSP that is approximately 1/2 of the attack angle (there’s other factors that play into this, most notably the downswing plane, aka vertical swing plane).

However, with the DRIVER, it’s slightly different because the spin axis that drivers put on the ball is different from the irons. With the DRIVER, the HSP needs to APPROXIMATELY match the attack angle in order to square up the path. So, if you wanted to square up the path and you have a +3 attack angle with the driver (remember, you don’t swing upward with irons), you need to have a HSP that is APPROXIMATELY +3*, which is out to the right.

Thus, it’s not that hard to hit a controlled fade with the driver if you have an upward attack angle. Let’s say that attack angle is +3*, your HSP can be +2* and it’s likely to create a path that is going left (outside-to-in) to some degree. One of the things you’ll see with today’s golfers, particularly the long hitters, is that they can swing out to the right and fling the arms off the chest and hit their driver well and long. I think it’s because today’s modern drivers make it much easier for golfers to hit with an upward attack angle. I have a persimmon and hitting up with that is just too risky because I’ll either catch one off the toe or sky the ball. However when these golfers use an iron and ‘swing out to the right’, they are usually not as effective because they really need to ‘swing left’ like Lag teaches. I think the big advantage of ‘swinging left’ like Lag teaches is that you can still hit the driver long and straight if you know how to aim your body. And then of course, you’ll hit the irons really well. With the ‘swinging out to the right’ release, you’re relying a lot on hand-eye coordination and probably going tho hit a draw instead of a dead straight iron shot.

3JAC

One of the best natural golfers I’ve ever played with, a tour winner and consistent performer, always told me that he got more backspin on the greens when he hit draws- unfortunately I used to laugh when he said it because I ‘knew’ that a fade comes down softer . It makes a lot of sense to the original question about draws going shorter, and when thinking that a steeper angle of attack causes hooks/draws, but doesn’t add up when looking at the above comment regarding draws rolling more because of less backspin. If a draw is caused by a steeper angle, and a steeper angle causes more backspin, then it all seems a little crazy don’t you guys think?
Any thoughts?

Seems pretty goofy to me. I’ve looked at some of the TM stuff and the only thing that has caught my attention a little is “going left” to counter descending angles and “going right” for ascending angles. Kinda makes sense, but I would like to see someone actually know precisely where 3* to the right is. I think it’s something you just have to feel where it is.

Going left…perhaps a different story. If skipping stones on a lake, the motion is downward with the stone, but I don’t think there is much left going on to “square the path”. Just some idle rat thoughts. RR

A draw isn’t caused by a steeper attack angle. It’s caused by the path being more out to the right than the clubface at impact. A steeper attack angle can cause a draw in the end, but a ball won’t draw just because the attack angle is steeper.

PROVIDED that you take your normal golf swing and all you do is increase your attack angle, the path will rotate out to the right. The path still has to be further out to the right than the face at impact. But the reason why moving the handle forward and the ball position back can make for an easy draw is because you’re still taking the normal swing, just making some slight adjustments at address.

The thing is, typically golfers who swing out to the right see their attack angle shallow out as well. That’s a big reason why many of the long hitters hit a draw. They swing out to the right which shallows the attack angle for them. They’ve just learned to get the clubface open (in relation to the target) so they can hit that push-draw/push-hook at the target. Then the ball has less spin so it rolls more.

But a draw, provided you hit the sweetspot flush and there’s no wind, is caused by the path being right of the face at impact (provided you are a right handed golfer).

3JACK

That’s why Trackman is a good teaching tool. I think one would be able to control where they ‘swinging left’ or ‘swinging out to the right’ by using Lag’s ‘swing left’ release instead of using the ‘swing out to the right’ release. All you really need to do with swinging left is just change where your body is aligned given the club you are using. With Trackman, you can hit a shot and see what it says your club is releasing. If it’s too far out to the right for your tastes, try to swing more left. Work until you get it down and then try to grasp what it feels like.

3JACK

Thanks for your detailed responses 3J.

FWIW, the more I think about it, for the easy draw shot recipe I was probably adding a little loft at address for me. My next shag session I’m going to toe in the face slightly as I move the handle forward but still have the face pointing to the right of the target. That might get the iron draw shot a little more finely tuned in.

An open clubface will add loft to the clubhead as well. A closed clubface will de-loft the club. My old man is a great example. He hits a low pull slice and struggles to get distance. In order to hit a pull slice, the clubface will be closed to the target at impact and the path will be going further left than where the clubface is pointing.

At the top of my dad’s swing, you can see he has a very closed clubface, and if you’ve ever seen a video of his swing, the clubface is very closed on the downswing. So it’s easy to logically assume that the clubface is closed at impact. But because it’s closed at impact, the ball starts out left and low. One thing I always emphasize to amateurs that are high handicappers is that if they want distance off the tee, they need to hit the ball higher than they already are and that the RE-Max long distance drivers are not hitting low bullets out there, they are hitting shots that are going a mile high. Many amateurs I’ve come across still think of the credo ‘tee it high, watch it fly, tee it low watch it go’ and think that height of trajectory of the ball flight doesn’t effect distance.

Anyway, getting back to my dad’s swing, he’s got such a closed clubface that it starts the ball out left and low and then comes so much over the top on the downswing that it causes the ball to slice, but also it’s hard to generate clubhead speed when you are that far over the top because little angular momentum is created. Thus he hits the low, pull slice that doesn’t go very far.

For him though, he just wants to shoot somewhere between mid-80’s to low 90’s and not find a lot of trouble hitting a golf ball, so that’s all he wants and he is pretty consistent doing that.

But the other obvious part is that more clubhead speed generally gets the ball going higher as well.

I’ve discussed this here a bit, but I’m really more interested in having a stock shot that is straight. While a controlled push-draw or a pull-fade can work and many people prefer it, the chance of double corssing it can result in disaster. Whereas if I can hit it pretty much straight quite often, then if it happens to fade or draw, I can usually still find the fairway or the green. I do find what Lag says about today’s golf being harder to ‘work’ being true and because it flyies higher and further, I don’t think the golfer needs to work the ball that much compared to yesteryear. I think ‘working the ball’ today should be more focused on hitting the ball low and high and all various degrees of height instead of worrying so much on hitting fades and draws on command. Don’t get me wrong, I think a serious golfer should know how to hit a fade or draw on command, but I don’t think they’ll have to do it nearly as much as a golfer had to do back 20-40 years ago.

Nice Discussion guys
2 quick ones??
The HSP is these many degrees left of what? Trackman obviously does not know where the target line is. Does it mean the plane the club is moving 3 deg left at separation compared to the plane when it initially made contact then it would make a lot of sense. That is I think one of the holy grails of ABS to enter from in to out and exit out to in as shown by the J shaped divot.
Does moving the handle forward means shaft lean and does just leaning the shaft at address has to do so much with impact dynamics.;