USGA on U grooves: Impact on GCA?

[TEPaul]

"I think so much more is understood now about golf equipment and swing dynamics that the manufacturers and players will find a way to hit a more optimal high flat trajectory even with a higher spinning ball.  But, only time will tell."

Bryan:

You're right. That is a reality today as it always has been in the past. Anyone in the USGA Tech Center back then from Frank Thomas on down would tell you that the tech center was just about always in a "react mode" to what came down the pipeline at them and what the real "in play" consequences of it were. Sometimes they had to even create new tests and testing equipment themselves just to try to figure out what it meant in play, and after the fact of being deemed conforming. Basically the whole COR issue was such a case----eg they didn't even understand why it was happening until it was already out there.

Since 2002 the USGA has dedicated 10 million dollars to study all the characteristics and ramifications of all these various combinations of conforming balls and equipment. They had never done that before. They merely wrote I&B Rules and Regs they thought could do the best to control things. Obviously those old Rules and Regs didn't work as intended.

I once asked Frank Thomas what the computerization of I&B analysis (optimization) had done via the manufacturers and he said a ton. I asked him why they'd never done it before and he just said the world hadn't gotten there yet in golf I&B.

They have now. The USGA has obviously gotten into this bigtime and will continue to do more of it. They've done this for one reason alone---eg to try to overcome that old inevitability of their "react mode" to what came down the I&B pipeline at them.  

The world of ball and club manufacturing has always been a cat and mouse game with the regulators (USGA/R&A) and will obviously continue to be. But the more the USGA's tech center knows about this entire technological dynamic of balls and clubs the more effective they will be in writing rules and regs to control what comes down the pipeline at them into the future.

And don't forget, even if they fail to spot the technical ramifications in play of something that is done within their own rules and regs and is not performing the way they expected within their I&B Rules and Regs they have put the manufacturing world on notice in 2002 that they do reserve the right to deem anything nonconforming for any reason at all, now even including "athleticism".

The latter is new as of 2002. In the past the USGA said that athleticism was beyond their I&B Rules and Regs and control and should be.

Apparently not any more. Read their "Joint Statement of Principles" and you will see it.

[TEPaul]

"But there's still the two questions of why those wound Balata balls were necessarily way toward the high-spin/low-launch end of the tradeoff when hit hard (it has to with the fact that they deformed so much but once again the details are vague in my memory) as well as the whole lift/drag thing."

My understanding is that those higher spin rate balls created greater drag which is what keeps the ball down like that initially.

But the point seems to be even with high spin rate balls they still have to be hit around 105 and above to create that kind of initial spin that creates that amount of drag to keep them down like that initially.

Physics seems to say that given the various characteristics of those old high spin balls that golfers who cannot swing at 105MPH are not capable of creating that kind of drag and consequently are incapable of keeping the ball down initially like that.

[Bryan Izatt]

Tom, Brent,

The launch angle is determined by the dynamic loft of the club face  at impact.  The dynamic loft depends on the loft of the club, the kick point of the shaft, and the swing plane.  It is virtually never the same as the loft of the club.  The launch angle does not depend on spin rate.

If you remember the old guys hitting it low to start it's because they were using drivers with 6 to 8* of loft compared to today's drivers being at 9 to 10*.  The low hitters were also hitting it with a descending or level stroke.  Today players try to play the driver forward and hit an ascending blow.  And, people have figured out that a higher launch angle is better for carry distance, so they adjusted their swings accordingly.

Once the ball is in flight it will rise if the backspin is sufficient for the Bernouilli effect to outweigh gravity.  The Bernoulli effect explains why airplane wings create lift, why curve balls curve, and why slices slice - and upshooters upshoot.  It does not have to do with drag. If you hit a ball with lots of backspin and at high speed there will be a lift force created that will cause the ball to rise.

End of lesson.

[Garland Bayley]

...The launch angle does not depend on spin rate.
...

Exactamundo!

[Brent Hutto]

In my job they pay me to go to the library and dig up references when I say things. If I'm not getting paid I'd rather do other things with my time. So while you don't necessarily have to take my word for it...it does happen to be is true that backspin and launch angle are inversely related at any given impact conditions

[Garland Bayley]

In my job they pay me to go to the library and dig up references when I say things. If I'm not getting paid I'd rather do other things with my time. So while you don't necessarily have to take my word for it...it does happen to be is true that backspin and launch angle are inversely related at any given impact conditions

Brent,

I guess I am going to have to sick Pat Mucci on you!    

[Bryan Izatt]

...The launch angle does not depend on spin rate.
...

Exactamundo!

Garland,

Is that a technical term?  

Brent,

Interesting.  I'm always prepared to be wrong.  I'm not prepared to pay you but it would be interesing to know the source that has demonstrated this relationship.  Do you remember the strength of the relationship?

One plausible explanation might be that less spin is generated through shorter residence time of the ball on the clubface.  In that shorter residence time, the dynamic loft of the face would not increase as much.  I would think that would be microseconds of less residence time and consequently a minute change in launch angle.  Hence it would be interesting to know the strength of the relationship you saw in your readings.

[Brent Hutto]

I don't know of a reference for the exact form of the relationship I stated but it is implied by the physics discussed in The Physics of Golf by T.P. Jorgensen (1994) and The Search for the Perfect Swing by Cochran and Stobbs (1968) just to list the two canonical reference I'm most familiar with.

Here it is from first principles in 100 words or less...

1) At impact, the ball briefly rolls up the face of the driver because it's an elastic, oblique collision (perfectly inelastic ball and clubface result in zero backspin and clubface-normal launch IIRC). Rolling motion produces backspin.

2) The more the ball compresses (ignoring clubface flex) the longer it dwells and the more accelerated the roll/spin.

3) The energy (or is it momentum?) used to induce spin comes from the launch-velocity component parallel to the clubface i.e. less vertical velocity and lower launch angle.

[TEPaul]

"If you remember the old guys hitting it low to start it's because they were using drivers with 6 to 8* of loft compared to today's drivers being at 9 to 10*.  The low hitters were also hitting it with a descending or level stroke.  Today players try to play the driver forward and hit an ascending blow.  And, people have figured out that a higher launch angle is better for carry distance, so they adjusted their swings accordingly."

Bryan;

I don't believe that makes too much sense to me. First of all those high swing speed players back then were not trying to hit the ball low initially. Why would they do that?

I'm sure they understood that a higher trajectory or a higher initial launch angle translated into increased carry distance just as well as today's players do. And that low flat initial trajectory followed by that steep incline certainly was not the way to maximize carry distance.

Furthermore once the ball got out there 100 or so yards on that low flat initial trajectory what was it that made it then rise steeply?

[Bryan Izatt]

Brent,

Thanks.

I'm OK with the first two points.  The third one, less so.

Energy is scalar, so there is no vertical component to it.

Momentum is a vector.  The collision of club and ball is governed by conservation of momentum.  But, I see no reason to understand that only the vertical component of momentum would be reduced.  Or by how much?  And whether it would have a measurable impact on launch angle.

Here's a quote from Golfworks that summarizes my understanding of factors affecting launch angle.  

"The loft of the club is only one of many factors that effect the launch angle and ultimately the total distance a player can hit a driver. Other factors are: tee height, ball type, shaft type, weather conditions, turf conditions, ball position, face material, the materials characteristics, face height, vertical roll of the face, ball contact point on the face, and the center of gravity location of the head."

Is it possible that the understanding of the club/ball interaction and launch angle is better understood now than in 1968 and 1994?  Is it possible that the effect if it exists is negligibly small compared to other factors?

[Bryan Izatt]

Tom,

Oh well, as long as it makes sense to me.  

If they weren't trying to hit it low, why use a 6* driver.  Probably because higher lofted drivers imparted more spin and accentuated the upshoot effect. You'd have to work to hit a 6* driver high initially

I think it a stretch to think that they thought much about launch angles, trajectories, or spin rates back in the day.  Maybe they wanted low ball flight to generate more roll.  Is the aerial  all carry game a modern phenomenon?

The late upshoot is a function of the initial ball speed and the lift created by the spin.  The faster the initial horizontal speed the longer it would take for the lift to overcome the horizontal speed.  Why does a curve ball curve over the plate rather than out of the pitchers hand?  The harder throwers have curve balls or sliders that break later.  Same concept.

[Brent Hutto]

The list of factors in the Golfworks quote (other than "ball type") are all covered in my phrase "at any given impact conditions". Once the clubface arrives at the ball with some particular velocity vector I'm describing the difference between balls of different characteristics. A ball that comes off the clubface with more spin also comes off the clubface at a lower (more horizontal) initial angle and vice versa.

If you write out three equations (containing terms for the ball characteristics and the impact velocity vector) for the spin and two perpendicular velocity scalars and do the algebra to reduce them down the launch velocity component parallel to the face is the one that changes inverse-linearly with the backspin rate. It just works out that way.

I guess they're conservation-of-momentum equations...or maybe it's energy. It's been a decade or so since I last saw it worked out in detail.

[Bryan Izatt]

Brent,

If you ever see it again, post it, or send me a copy.   I'd like to see if it makes any sense to my rusty brain. Right now it doesn't make sense.  Do you have any idea if it's a significant or insignificant effect?  If the rpms were 500 less does that make the launch angle 1* higher?  I must say I've never seen this referenced anywhere else and I've read a lot about launch monitoring.  But never say never.  There's always new things to learn.  

[Doug Siebert]

Bryan,

The 6* drivers weren't chosen to hit the ball low, per se, but to allow the ball to hit the ground with some forward momentum and get some roll.  It was a tradeoff of a bit of carry distance in exchange for more than that in roll.  In windier areas, it was also to get better performance on drives into the wind.

The trajectory of drives with the pre-Pro V1 type balls would rise to a peak and then fall rather steeply, especially with higher lofts.  The Pro V1's reduced spin at launch allowed its trajectory to flatten at the top, allowing for increased carry distance with higher lofted drivers.  It also had a side effect of lessening the effect of wind upon the ball, meaning you didn't need to worry about keeping the ball down when driving into the wind (it might help a bit to do it, but it is no longer a necessary skill by any means)

In sum, players used to use lower lofted drivers to trade carry distance for increased roll.  Today they use higher lofted drivers to trade roll for increased carry distance.  All made possible by a ball that spins less off a driver while maintaining similar spin characteristics off shorter iron shots.  Thus making architecture less important, because stuff you can carry your ball over bothers you less than stuff you have to roll your ball past.

[James Bennett]

In sum, players used to use lower lofted drivers to trade carry distance for increased roll.  Today they use higher lofted drivers to trade roll for increased carry distance.  All made possible by a ball that spins less off a driver while maintaining similar spin characteristics off shorter iron shots.  

Thus making architecture less important, because stuff you can carry your ball over bothers you less than stuff you have to roll your ball past.

That post is worth repeating.

[Bryan Izatt]

Doug,

I agree that'd be a reason for using 6* drivers. Less loft also reduces spin which would increase roll.  Interestingly the latest direction in club fitting is to try to fit for the best landing angle (on top of launch angle, spin rate and ball speed) to optimize the roll out as well as the carry.

Agree on the rest, although we could debate that the aerial approach to the game pre-dated the Pro V1 era, albeit on shorter courses at the Tour level.

[Brent Hutto]

Do you have any idea if it's a significant or insignificant effect?  If the rpms were 500 less does that make the launch angle 1* higher?

It's not a huge effect with a driver. Something like a a couple of degrees launch angle difference between a high-spin ball and a low-spin one. Then again, some people doing club fitting will spend a lot of time trying to get one more degree more or less launch angle.

Here's how it shows up. If you were to measure the three important impact angles (clubface loft, added dynamic loft due to the shaft kicking forward, upward travel of the clubhead due to playing the ball forward and teeing it high) then you might expect the sum of those to give you the inital launch angle of the ball. In the real world the ball always comes off anywhere from a couple degrees to several degrees lower than that effective total clubface angle. That's because it rolls up the clubface, producing spin in the process.

Keep in mind that this works in the direction that the typical high swing speed player is trying to get. They want high launch and low spin off the driver. Well, getting the ball to spin a couple thousand rpm less also makes it launch a degree higher so if anything it just makes spin/launch fitting work a bit easier than if it worked the other way around.

With wedges and short irons it's a big deal. I think a high-spin ball comes off a pitching wedge as much as four degrees lower than a low-spin ball.

[TEPaul]

"The late upshoot is a function of the initial ball speed and the lift created by the spin.  The faster the initial horizontal speed the longer it would take for the lift to overcome the horizontal speed."

Bryan:

Does a modern age ball like a ProV have less initial horizontal speed than the old high spin softer balata ball?

And if it doesn't then why doesn't it stay down initially like the old high spin ball did?

And what about the difference in spin rate between the two balls regarding that initial low trajectory (or not)?

It may've been just a ballpark remark but i recall the tech center mentioning the old balata ball probably had a spin rate of around 3,000rpm while these modern age balls are closer to 2,000rpm.

[TEPaul]

"Today they use higher lofted drivers to trade roll for increased carry distance.  All made possible by a ball that spins less off a driver while maintaining similar spin characteristics off shorter iron shots.  Thus making architecture less important, because stuff you can carry your ball over bothers you less than stuff you have to roll your ball past."

That certainly is a remark worth repeating.

I just wonder what it is about the ball used today by the high swing speed player that allows it to launch really high compared to that old initial flat trajectory of high swing speed players of yesteryear with those old high spin rate balls. It seems like it must be the difference in spin rate.

If it was possible 20 years ago to use a combination of clubface loft, flex or whatever else to get the kind of initial high trajectory they do today with these new balls then why didn't any high swing speed players back then ever do it?

I played a lot of golf against some high swing speed players back then (Jay Sigel being the best example--eg he was as long as any of the tour players back then) and I never saw him hit a drive with that really high initial launch and trajectory that I see these high swing speed players today producing. His trajectory was that initially flat one like all the high swing speed players back then seemed to produce.

How much of that had to do with that old really high spin rate three piece ball they all used to use?

 

[Brent Hutto]

It seems to me that if you start an old Balata ball on a high initial trajectory it will start high and then upshoot even higher.

If your only choice is between hitting it low at the beginning and then upshooting or hitting it high at the beginning then upshooting even more, wouldn't a good golfer choose to start it low? Of course they could have always tried a Pinnacle...

[TEPaul]

"If your only choice is between hitting it low at the beginning and then upshooting or hitting it high at the beginning then upshooting even more, wouldn't a good golfer choose to start it low? Of course they could have always tried a Pinnacle..."

Brent:

First of all years of observation has told me that those high swing speed players back then with those old high spin rate three piece soft balls didn't have a choice. Basically if they hit those old high spin rate balls hard they just stayed flat for about a hundred yards or so before really launching.

In all the years I played tournament golf I never saw one of those really high swing speed players hit a drive with those old high spin rate ball with the type of trajectory the high swing speed players do today with these new age balls.

Golfers, particularly good ones are pretty intuitive and if they realized they could hit those old high spin rate balls with the same trajectory (high launch) they do today there is no reason at all they wouldn't have done that in a heart beat.

They most certainly could've used a Pinnacle and they  would've gotten just about the same high launch trajectory that they do today with these new age balls.

Don't you wonder why that's so or certainly why they almost never used Pinnacles?

BTW, my definition of a high swing speed player with a driver is around 110mph and up. To be honest there weren't many of them around but Sigel was definitely one of them. Here's a relative measure of his power; He told us at a tournament that he played a couple of days at the Masters with two of the longest players of his era----Norman and Ballesteros. He said he was interested to find out how his length stacked up against them and he said he was surprised to see neither one got in past him all day long.

[Brent Hutto]

Golfers, particularly good ones are pretty intuitive and if they realized they could hit those old high spin rate balls with the same trajectory (high launch) they do today there is no reason at all they wouldn't have done that in a heart beat.

Tom, my point was that they didn't have the option of a modern trajectory. If you launch a ProV1 high and hit it hard it will carry a long, long way. If you had launched a Tour Balata high and hit it hard it would start out high, upshoot higher and fall nigh vertically out of the sky after about 200 or so yards. That's why the low spin is such a big deal.

I meant the Pinnacle comment as a joke. I don't necessarily think it would carry like a ProV1 and it certainly wouldn't have been playble from 100 yards in for a good player.

[TEPaul]

"Tom, my point was that they didn't have the option of a modern trajectory."

Brent:

That is precisely my point too.

"If you launch a ProV1 high and hit it hard it will carry a long, long way."

I think we all realize that.

"If you had launched a Tour Balata high and hit it hard it would start out high, upshoot higher and fall nigh vertically out of the sky after about 200 or so yards."

Brent, that is something I basically never saw in about twenty years of playing tournament golf against high swing speed players using high spin rate balls. Basically if they hit the ball hard with a driver it would just stay flat for about a hundred yards. The only good player I ever saw who teed the ball really high (as high as most do today) and tried to sweep way up on it probably did hit it a little higher initially but not by much. He was fairly long but I doubt his swing speed was 110 or plus either (the mph and plus that really seemed to keep those high spin rate balls down). I did see a few high swing speed players hit a high spin-rate ball really high initially but unfortunately that's what we all called a "pop-up" and I think we all know what caused that.  


"That's why the low spin is such a big deal."

I realize that and that's been my exact point all along (for a couple of years now)---eg so much of this is about spin rate.

[TEPaul]

"I meant the Pinnacle comment as a joke. I don't necessarily think it would carry like a ProV1 and it certainly wouldn't have been playble from 100 yards in for a good player."

I realize it was a joke and I think we both know the real reason why good high swing speed players basically never used a ball like a Pinnacle.

It seems like the Tech Center feels that given the same clubs used today a high swing speed player could hit one of those old low spin rate Pinnacles about as far as they hit the new age low spin rate balls today. The reason for that appears to be all about spin rate.

Also, they seem to suggest that given the same swing speed (in this case the ODS protocol of 120mph) a low spin ball (Pinnacle or these new age ProVs) vs a high spin ball like those old three piece balls would carry up to 30 yards further because of its trajectory.

[Garland Bayley]

Do you have any idea if it's a significant or insignificant effect?  If the rpms were 500 less does that make the launch angle 1* higher?

It's not a huge effect with a driver. Something like a a couple of degrees launch angle difference between a high-spin ball and a low-spin one. Then again, some people doing club fitting will spend a lot of time trying to get one more degree more or less launch angle.

Here's how it shows up. If you were to measure the three important impact angles (clubface loft, added dynamic loft due to the shaft kicking forward, upward travel of the clubhead due to playing the ball forward and teeing it high) then you might expect the sum of those to give you the inital launch angle of the ball. In the real world the ball always comes off anywhere from a couple degrees to several degrees lower than that effective total clubface angle. That's because it rolls up the clubface, producing spin in the process.

Keep in mind that this works in the direction that the typical high swing speed player is trying to get. They want high launch and low spin off the driver. Well, getting the ball to spin a couple thousand rpm less also makes it launch a degree higher so if anything it just makes spin/launch fitting work a bit easier than if it worked the other way around.

With wedges and short irons it's a big deal. I think a high-spin ball comes off a pitching wedge as much as four degrees lower than a low-spin ball.

OK Brent,

You put this stuff out there once and I find it counter intuitive. Now if you are going to keep repeating it, I for one would like to see the references!