Spin off of mats vs grass, what is the technical cause?

[Howard_Jones]

Let me try again then....

 

Ball compression takes TIME, so the longer time we are given the more the ball will be compressed.

If turf conditions helps to hold the ball back a fragment of a second longer before it takes off, spin will be higher and launch will be lower, just like the old grooves did, it kept the ball on the face for a fragment of a second longer.

 

This will change with AOA so with a shallow AOA we want see much of a difference between turf and synthetic surfaces like a mat, but as soon as AOA becomes negative this difference will be visible like in that Trackman test.

 

Club speed and delivery is the same, so its not a higher club speed of a different loft at impact who caused higher spin and lower launch from the turf, it was the turf who gave the ball a fragment of a second longer time on the face who helped to compress the ball better than from the mats where is takes of a tad to early.

 

It will need high speed cameras to show it off, but this is the only reasonable explanation to it, based on what we already know about what the ball does under certain conditions, and here we know it from both ends, from club speed and compression with the driver, and the time issue on high lofted clubs like wedges. Irons falls in-between, so why should there be another reason for it with irons?

 

If Time on the face changes, so does ball compression, and by that, spin and launch value from the same club delivery

 

This is more visible for a player with a high PTR value and steep AOA vs the oposit, so if the player DONT compress the ball good under normal turf condition, he want see much of a change to a synthetic math, and thats why there is no fixed numbers for conversion between this 2 surfaces.

 

Let anyone with access to a LM try it off.

Hit 10 balls from each surface

AOA must be -2* or steeper

he should see a difference of about 4-500 rpms HIGHER spin from the turf vs the math for each degree he is down in the ball so at -2 AOA we should expect to see 800-1000 rpms of spin difference, while launch should be in the area of 0.5 degree launch for each - AOA so at -2 on AOA launch should be about 1 lower out of the turf compared to the mat

 

That was the numbers we saw (me and my local PGA trainer), when we tried this off back in 2011 or 2012, and i used those numbers as averages so i was able to judge indoor numbers for what we would expect to see out door from the same.

[Stuart_G]

Give me just one single argument for why ball compression should NOT make a difference to spin and launch from mats vs turf, when ball compression is the reason on high vs low club speed or new vs old grooves. Why is what we know about ball flight all of a sudden invalid, or dont you even acknowledge that club speed is a factor for spin,

 

You misunderstand. My argument is not about whether it could or not. My argument is that it's far from conclusive and the matter is far from being closed. Yes, it certainly could be a contributing factor and is a theory that should be considered and pursued.

 

But there is some (also inconclusive) evidence against the theory as well. First off all, high speed video shows no evidence that the amount of compression or deformation actually does change. Now those videos were not shot for that particular purpose and usually the comparison is across different set-ups, so the accuracy is certainly suspect.

 

Then there is the fact tat, if there was a significant amount of additional resistance between the surface and the ball, such resistance only acts at that point where contact exists. And since that's at the bottom of the ball, it means it would also impart an moment arm about the ball c.g. that should (in theory) add a torsional force to the ball that would decrease spin, not increase it. Of course, that would have to be balanced against any possible changes in the interaction between the ball and face, or even how a different deformation might influence the movement of the balls center of mass as it deforms. It doesn't necessarily mean the net change has to be toward less spin.

 

 

Yes, deformation takes time - and I agree that is a VERY important consideration - but what most do not consider is that it also means that it takes time before the deformation reaches the point where changes to the ball-ground interaction would take place. Right at impact, the initial deformation of the ball only occurs right where it is contact with the face. As we take very small time steps, that deformation will spread throughout the ball and finally reach the point where the ball touches the ground. Before that point, the only thing that's 'holding back' the ball is it's own mass. The ground plays no part what-so-ever.

 

Now, once it does reach that ball-ground contact point(s), it's only at this point in time that any forces between the ground and ball could potentially be generated and start to influence the results in any way. Then on top of that, then it would take even more time for those (potential) changes to 'rebound' and travel back to the ball-face interaction point(s). Only then, can there be a potential change to the ball-face interaction - friction, slip, etc...

 

I suspect, but don't know, that at that later point in time, it's actually too late to have a significant impact - even IF the forces produced between the ball and the ground were significant enough to have any influence (another potential hole in the theory is that there is not enough change in those forces). To me that's the biggest potential fault in the theory trying to equate what we see here with what happened with the grooves. The influence of the grooves - as part of the ball face interaction will effectively be immediate - there is no delay like there is when we consider influences from any ball-ground interaction. Some ball designers may have an understanding of the actual time frames we're dealing with here - but I doubt anyone else would. Even I could only guess.

 

That's also why I'd me more inclined to suspect that the interaction between the club and the ground would more likely be a contributing factor. Relative to the ball, there is virtually no deformation in the club, so the influence would be much more immediate. And we know for a fact (via our friend gear effect) that changes to the relative motion of the face at the point of impact in a direction parallel to the face - can have a noticeable influence on the spin.

[Howard_Jones]

OK fine but it dont think its that hard to explain at all.

 

we know that its FRICTION on the face who decide if the ball stay and compress or skids off, and for drivers club speed or impact force makes that friction higher or lower.

 

When we play the ball from the ground, we have 2 surfaces with friction involved we "trap the ball between"

Face friction is the same (same loft at impact), while the surface friction from turf to a matt will vary, so the effect of face friction will vary, (with or without help from the surface the ball lies on)

 

If the surface has friction like turf has, the effect from face friction will go up, just like a higher impact speed does, just like the old grooves did....keep the ball on the face a fragment of a second longer

 

We normally dont see so large differences as the Trackman test, because most of us dont have such a high PTR value to start with, and we are a bit more shallow as average vs that player, so the Trackman test shows off the extreme, not what we all should expect, and again, both mats and turf vary as they are, so we can never find a fix number for conversion here.

 

So it boils down to how good of a grip we get on the ball, thats what decide how good we can compress it or not and the surface we hit the ball from is as we can see, a part of it all, and since that surface did NOT change club datas, FRICTION is whats left and the only way a higher ball compression can occur, and by that, higher spin but lower launch from turf vs mats.

[Stuart_G]

Yes, but changes to that friction between the face and the ball will really only occur early in the time sequence I discussed. The friction comes from the deformation of the ball near the face. Once the deformation of the ball (only where it contacts the face) get to a certain point - the normal forces combined with the increased surface area of contact are just too large to change any potential relative motion between the ball and the face.

 

IMO, the concept of the ball actually getting trapping against the ground and it's influence on ball compression is as outdated as the old original ball flight "laws". To certain people they seemed perfectly logical and make complete sense - right up until the time they learn that they don't ;-)

 

 

EDIT - Now whether that thought or visualization may help someone during the swing to get a better delivery is a completely different question. But much about many common swing feels have little to do with reality.

 

 

Oh well, I think it's time to move on. We seem to have exhausted the possibilities of this part of the discussion.

[bladehunter]

Howard. I applaud you for saying what some of us have known for ourselves for a long time.

 

If you’re a good ball striker you can tell immediately how a shot is going to spin based on the strike .. the strike is dependent in part on the turf it sits on. This part we can actually read. Or forecast.

 

A good example. A lie such as one sitting clean but on a thin bed of mulch. Or a soft fairway bunker with ball sitting clean. You simply cannot compress it like you can on firm turf. Even catching it very clean it won’t fly as far. And you must adjust for it. Usually taking more club .

 

But we have many tell us over and over that compressing the ball is a myth. I’ve always believed it’s those who’ve never struck the ball well enough to experience it that perpetuate that myth.

 

If you could, please elaborate on the technical reason the ground has that effect on your shots as it relates the the OP.

 

Also, given what you said, would a soft tee peg that you hit the ball off of present the same problem as your mulch lie or sand lie?

 

Edit: just to clarify what i mean, imagine a golf tee in very soft ground, such that it barely holds up a golf ball much like i imagine the soft lies you describe would. Would a ball struck off a tee inserted into a very soft tee box then make a difference on spin and launch angle vs a ball struck off a tee inserted into a firm tee box?

 

Well

 

I don’t know exactly how to explain it. But you see this more clearly with a sharp thin soled iron or wedge. But when you properly strike a ball off of firm turf or even hard pan , you get the sensation of the ball staying on the face longer and you know the ball is coming off with lots of spin.

 

Exact opposite is the soft sand or mulch lie I described. You can get ball first ( so a good strike ) and yet the ball will not come off the same. These shots I’ve heard described by pros on tv as “ the lie exploded on him “. Which is exactly the sensation I’ve had. It’s as if there wasn’t anything under the ball when you got through the shot. Nothing to hold the ball onto the face. Comes out low spin and hard to control and usually less distance.

 

 

I’ll also add that a ball feed up does the same. I tee up 2-3 irons some times and pick them off a tee to gain height and hit the low spin bomb on a par 4 tee. Nothing down there again to hold the ball onto the face.

 

I usually describe this to blank stares. Most people do not compress the balll and do not know what I’m talking about.and most still believe the “ balls gone long before any turf interaction “ nonsense. Yes the ball is gone before the main pelt of the divot flies. But. The ball is not gone when the iron gets to the turf if the ball is compressed properly. Can’t explain the spin and flight differences away. Much less the feel.

[cxx]

I think that the idea that even with a descending strike that the club pushes the ball into the turf is incorrect. There may be another reason, but that one doesn't work. Here is a link related to drivers, but the underlying model works for all clubs.

 

https://www.researchgate.net/publication/243492348_The_physics_of_golf_The_optimum_loft_of_a_driver

 

Figure 1 shows the forces acting during the strike. The club face exerts a force that has a component normal to its surface and one that is parallel to the surface based on its path. This results in the balls initial direction and speed as well as its initial spin. The initial direction of flight is a combination of the normal component and the component parallel to the face resulting in what you would expect, a lower trajectory than the normal but a positive direction relative to the ground. This is true even with a descending strike or the ball would never get airborne.

 

In this analysis, which is like all the others I've seen, the impact itself is too complicated to model analytically and is replaced with the coefficient of restitution for the ball. This accounts for energy lost in compressing the ball. The pre and post collision momentum must balance out. The analysis in the link shows the post collision ball speed direction and spin. These results are pretty much what was expected.

 

The thing is, if you look at the force diagrams from the strike, there is nothing that is pushing the ball down even with a descending blow.

 

About the only thing that might support that idea is the deformation of the ball, but the magnitude of that effect would seem to be small.

 

A finite element analysis might lead to some insight, but actually calibrating such a model would be a huge undertaking.

[cxx]

Howard. I applaud you for saying what some of us have known for ourselves for a long time.

 

If you're a good ball striker you can tell immediately how a shot is going to spin based on the strike .. the strike is dependent in part on the turf it sits on. This part we can actually read. Or forecast.

 

A good example. A lie such as one sitting clean but on a thin bed of mulch. Or a soft fairway bunker with ball sitting clean. You simply cannot compress it like you can on firm turf. Even catching it very clean it won't fly as far. And you must adjust for it. Usually taking more club .

 

But we have many tell us over and over that compressing the ball is a myth. I've always believed it's those who've never struck the ball well enough to experience it that perpetuate that myth.

 

If you could, please elaborate on the technical reason the ground has that effect on your shots as it relates the the OP.

 

Also, given what you said, would a soft tee peg that you hit the ball off of present the same problem as your mulch lie or sand lie?

 

Edit: just to clarify what i mean, imagine a golf tee in very soft ground, such that it barely holds up a golf ball much like i imagine the soft lies you describe would. Would a ball struck off a tee inserted into a very soft tee box then make a difference on spin and launch angle vs a ball struck off a tee inserted into a firm tee box?

 

Well

 

I don't know exactly how to explain it. But you see this more clearly with a sharp thin soled iron or wedge. But when you properly strike a ball off of firm turf or even hard pan , you get the sensation of the ball staying on the face longer and you know the ball is coming off with lots of spin.

 

Exact opposite is the soft sand or mulch lie I described. You can get ball first ( so a good strike ) and yet the ball will not come off the same. These shots I've heard described by pros on tv as " the lie exploded on him ". Which is exactly the sensation I've had. It's as if there wasn't anything under the ball when you got through the shot. Nothing to hold the ball onto the face. Comes out low spin and hard to control and usually less distance.

 

 

I'll also add that a ball feed up does the same. I tee up 2-3 irons some times and pick them off a tee to gain height and hit the low spin bomb on a par 4 tee. Nothing down there again to hold the ball onto the face.

 

I usually describe this to blank stares. Most people do not compress the balll and do not know what I'm talking about.and most still believe the " balls gone long before any turf interaction " nonsense. Yes the ball is gone before the main pelt of the divot flies. But. The ball is not gone when the iron gets to the turf if the ball is compressed properly. Can't explain the spin and flight differences away. Much less the feel.

 

Even a 50 yard pitch shot compresses the ball.

[Stuart_G]

the impact itself is too complicated to model analytically

 

A bit more accurate to say it's very complicated to allow for the type of explicitly analytical solution most people think of (no single equation can be used). There are plenty of other ways it can be modeled and solved - usually involving a lot of computational power. If I ever get some time I might give it a try, it's just that even the set-up is fairly time consuming. After that you just let the computer do all the work.

 

About the only thing that might support that idea is the deformation of the ball, but the magnitude of that effect would seem to be small.

 

The only thing that comes to mind would be as the ball compresses in the normal plane to the face, it also, in turn, expands a bit in the parallel plane - which if enough resistance to that expansion exists from the ground, might cause the ball's center of mass to move upward more than it would otherwise. But I agree I wouldn't expect it to be enough to see the 2k spin reduction we sometimes do see at times with mats.

[clevited]

Howard. I applaud you for saying what some of us have known for ourselves for a long time.

 

If you’re a good ball striker you can tell immediately how a shot is going to spin based on the strike .. the strike is dependent in part on the turf it sits on. This part we can actually read. Or forecast.

 

A good example. A lie such as one sitting clean but on a thin bed of mulch. Or a soft fairway bunker with ball sitting clean. You simply cannot compress it like you can on firm turf. Even catching it very clean it won’t fly as far. And you must adjust for it. Usually taking more club .

 

But we have many tell us over and over that compressing the ball is a myth. I’ve always believed it’s those who’ve never struck the ball well enough to experience it that perpetuate that myth.

 

If you could, please elaborate on the technical reason the ground has that effect on your shots as it relates the the OP.

 

Also, given what you said, would a soft tee peg that you hit the ball off of present the same problem as your mulch lie or sand lie?

 

Edit: just to clarify what i mean, imagine a golf tee in very soft ground, such that it barely holds up a golf ball much like i imagine the soft lies you describe would. Would a ball struck off a tee inserted into a very soft tee box then make a difference on spin and launch angle vs a ball struck off a tee inserted into a firm tee box?

 

Well

 

I don’t know exactly how to explain it. But you see this more clearly with a sharp thin soled iron or wedge. But when you properly strike a ball off of firm turf or even hard pan , you get the sensation of the ball staying on the face longer and you know the ball is coming off with lots of spin.

 

Exact opposite is the soft sand or mulch lie I described. You can get ball first ( so a good strike ) and yet the ball will not come off the same. These shots I’ve heard described by pros on tv as “ the lie exploded on him “. Which is exactly the sensation I’ve had. It’s as if there wasn’t anything under the ball when you got through the shot. Nothing to hold the ball onto the face. Comes out low spin and hard to control and usually less distance.

 

 

I’ll also add that a ball feed up does the same. I tee up 2-3 irons some times and pick them off a tee to gain height and hit the low spin bomb on a par 4 tee. Nothing down there again to hold the ball onto the face.

 

I usually describe this to blank stares. Most people do not compress the balll and do not know what I’m talking about.and most still believe the “ balls gone long before any turf interaction “ nonsense. Yes the ball is gone before the main pelt of the divot flies. But. The ball is not gone when the iron gets to the turf if the ball is compressed properly. Can’t explain the spin and flight differences away. Much less the feel.

 

Thank you, that was a good explanation of what you were trying to get at before. I will summarize the ideas presented in here in another post and see if we can figure out exactly what is going on.

[cxx]

the impact itself is too complicated to model analytically

 

A bit more accurate to say it's very complicated to allow for the type of explicitly analytical solution most people think of (no single equation can be used). There are plenty of other ways it can be modeled and solved - usually involving a lot of computational power. If I ever get some time I might give it a try, it's just that even the set-up is fairly time consuming. After that you just let the computer do all the work.

 

 

I was thinking more about validating the small scale parameters that would be required so that the model would agree with the data that is known. Compute power is cheap and fast but the answers are only as good as the info you put in.

[clevited]

So a little summary of the main ideas being talked about in here. I will focus on the 3 biggies.

 

1) Given identical strikes, the friction of the surface being hit off of, briefly impedes the rotation of a golf ball and if substantial enough, makes it pop upwards vs a surface of lesser friction. Less friction creates more spin and lower launch. Striking off a tee would create more spin potentially than off of a grass lie or off a mat due to potentially lower friction. A ball struck off of a fluffy lie where there is no grass between ball and clubface, would show similar launch spin and angle as would be seen off of a typical grass lie. This is all assuming the ball is struck the same across all shots, that is a downward strike intent on creating reasonable spin and launch angle.

 

2) Assuming that there is a pinching or compressive like effect that occurs between the golf ball and the surface being hit off of, a soft lie will cause lower spin and higher launch vs a firm lie. In my mind, this could be visualized by stepping on a golf ball and squirting it out from under your foot. Hard surface it will shoot out low and perhaps with lots of spin. A softer surface it perhaps shoots out higher and with lower spin.

 

3) Given the pinching or compression idea of #2, the surface friction rather than the surface firmness causes the changes seen when hitting off a mat vs grass. In this case, higher friction between ball and surface creates more time on the clubface and promotes more spin and lower launch angle when compared to a lower friction lie. This is also assuming identical downward strikes intent on creating reasonable spin and launch angle.

 

Please anyone correct me if I have these ideas wrong or if there are details I should add. With these here, we can discuss these ideas more in detail to see if either has any substance.

[bladehunter]

Howard. I applaud you for saying what some of us have known for ourselves for a long time.

 

If you're a good ball striker you can tell immediately how a shot is going to spin based on the strike .. the strike is dependent in part on the turf it sits on. This part we can actually read. Or forecast.

 

A good example. A lie such as one sitting clean but on a thin bed of mulch. Or a soft fairway bunker with ball sitting clean. You simply cannot compress it like you can on firm turf. Even catching it very clean it won't fly as far. And you must adjust for it. Usually taking more club .

 

But we have many tell us over and over that compressing the ball is a myth. I've always believed it's those who've never struck the ball well enough to experience it that perpetuate that myth.

 

If you could, please elaborate on the technical reason the ground has that effect on your shots as it relates the the OP.

 

Also, given what you said, would a soft tee peg that you hit the ball off of present the same problem as your mulch lie or sand lie?

 

Edit: just to clarify what i mean, imagine a golf tee in very soft ground, such that it barely holds up a golf ball much like i imagine the soft lies you describe would. Would a ball struck off a tee inserted into a very soft tee box then make a difference on spin and launch angle vs a ball struck off a tee inserted into a firm tee box?

 

Well

 

I don't know exactly how to explain it. But you see this more clearly with a sharp thin soled iron or wedge. But when you properly strike a ball off of firm turf or even hard pan , you get the sensation of the ball staying on the face longer and you know the ball is coming off with lots of spin.

 

Exact opposite is the soft sand or mulch lie I described. You can get ball first ( so a good strike ) and yet the ball will not come off the same. These shots I've heard described by pros on tv as " the lie exploded on him ". Which is exactly the sensation I've had. It's as if there wasn't anything under the ball when you got through the shot. Nothing to hold the ball onto the face. Comes out low spin and hard to control and usually less distance.

 

 

I'll also add that a ball feed up does the same. I tee up 2-3 irons some times and pick them off a tee to gain height and hit the low spin bomb on a par 4 tee. Nothing down there again to hold the ball onto the face.

 

I usually describe this to blank stares. Most people do not compress the balll and do not know what I'm talking about.and most still believe the " balls gone long before any turf interaction " nonsense. Yes the ball is gone before the main pelt of the divot flies. But. The ball is not gone when the iron gets to the turf if the ball is compressed properly. Can't explain the spin and flight differences away. Much less the feel.

 

Even a 50 yard pitch shot compresses the ball.

 

 

Like I said I can’t exactly explain it. And never ever has anyone read me say I’m a scientist and quote theories or laws on anything except my own experiences. I’m quite the opposite. But I do know that the surface the ball sits on matters. A lot.

 

 

Another good example are the super wet conditions we have down south right now. Every shot that isn’t a super high point on a fairway is a “ explosive lie “ situation. Very hard to get full distance from a shot. I’m taking full distance after adjustments for temp , wind , layers of clothing etc. why ? I feel like it’s because the lie explodes from underneath the ball. Nothing to hold it on the face to collect that full shot of energy is my sensation for those lies.

[cxx]

I have seen in abstracts that more recent papers about spin during the ball strike uses a different, simplified model. Like the compression spring notion that is used to represent the ball jumping off the face, some of the literature is modeling the spin producing part of the collision as a torsional spring along the surface of the ball. I guess everyone realized from the high speed pictures that the ball wasn't rolling up the face (which implies some initial slippage) but that the release of the torsion along the surface was producing the spin.

 

I haven't found a full text one that isn't behind a journal paywall.

[cxx]

Howard. I applaud you for saying what some of us have known for ourselves for a long time.

 

If you're a good ball striker you can tell immediately how a shot is going to spin based on the strike .. the strike is dependent in part on the turf it sits on. This part we can actually read. Or forecast.

 

A good example. A lie such as one sitting clean but on a thin bed of mulch. Or a soft fairway bunker with ball sitting clean. You simply cannot compress it like you can on firm turf. Even catching it very clean it won't fly as far. And you must adjust for it. Usually taking more club .

 

But we have many tell us over and over that compressing the ball is a myth. I've always believed it's those who've never struck the ball well enough to experience it that perpetuate that myth.

 

If you could, please elaborate on the technical reason the ground has that effect on your shots as it relates the the OP.

 

Also, given what you said, would a soft tee peg that you hit the ball off of present the same problem as your mulch lie or sand lie?

 

Edit: just to clarify what i mean, imagine a golf tee in very soft ground, such that it barely holds up a golf ball much like i imagine the soft lies you describe would. Would a ball struck off a tee inserted into a very soft tee box then make a difference on spin and launch angle vs a ball struck off a tee inserted into a firm tee box?

 

Well

 

I don't know exactly how to explain it. But you see this more clearly with a sharp thin soled iron or wedge. But when you properly strike a ball off of firm turf or even hard pan , you get the sensation of the ball staying on the face longer and you know the ball is coming off with lots of spin.

 

Exact opposite is the soft sand or mulch lie I described. You can get ball first ( so a good strike ) and yet the ball will not come off the same. These shots I've heard described by pros on tv as " the lie exploded on him ". Which is exactly the sensation I've had. It's as if there wasn't anything under the ball when you got through the shot. Nothing to hold the ball onto the face. Comes out low spin and hard to control and usually less distance.

 

 

I'll also add that a ball feed up does the same. I tee up 2-3 irons some times and pick them off a tee to gain height and hit the low spin bomb on a par 4 tee. Nothing down there again to hold the ball onto the face.

 

I usually describe this to blank stares. Most people do not compress the balll and do not know what I'm talking about.and most still believe the " balls gone long before any turf interaction " nonsense. Yes the ball is gone before the main pelt of the divot flies. But. The ball is not gone when the iron gets to the turf if the ball is compressed properly. Can't explain the spin and flight differences away. Much less the feel.

 

Even a 50 yard pitch shot compresses the ball.

 

 

Like I said I can't exactly explain it. And never ever has anyone read me say I'm a scientist and quote theories or laws on anything except my own experiences. I'm quite the opposite. But I do know that the surface the ball sits on matters. A lot.

 

 

Another good example are the super wet conditions we have down south right now. Every shot that isn't a super high point on a fairway is a " explosive lie " situation. Very hard to get full distance from a shot. I'm taking full distance after adjustments for temp , wind , layers of clothing etc. why ? I feel like it's because the lie explodes from underneath the ball. Nothing to hold it on the face to collect that full shot of energy is my sensation for those lies.

 

It is incredibly wet out there. Fortunately there has been enough daily rain to keep me off the course. The thing is even with a very steep angle of attack that to get the club on the ball with the VCOG of the club below the COG of the ball you are going to have to touch the grass before the ball. No trouble in tight dry fairways. In these super soaked conditions, it might be a problem.

[Stuart_G]

the impact itself is too complicated to model analytically

 

A bit more accurate to say it's very complicated to allow for the type of explicitly analytical solution most people think of (no single equation can be used). There are plenty of other ways it can be modeled and solved - usually involving a lot of computational power. If I ever get some time I might give it a try, it's just that even the set-up is fairly time consuming. After that you just let the computer do all the work.

 

 

I was thinking more about validating the small scale parameters that would be required so that the model would agree with the data that is known. Compute power is cheap and fast but the answers are only as good as the info you put in.

 

Actually they don't really need to be all that exact to get the point where one can get some pretty good answers to what's happening and why. The ball park staring points are pretty well known (in part thanks to the ruling bodies compliance testing). And material properties and boundary conditions are easy to tweak and play around with different values for various runs.

[sadclevelandsports]

Somewhat peripherally on the original topic, do distances drop proportionally from turf to mat or is it all over the map? For instance, if someone has perfect 12 yard gaps between clubs on the mat, is he going to have 12 yard gaps at a reduced distance on grass or is it not that straightforward?

[MP4444]

I hit off a mat with a SkyTrak for ball data and I find that my real life turf distances seem very close to what I am seeing on the launch monitor within a few yards.

My guess for me is that with my ball speeds, launching lower with more spin off turf produces similar carry to launching higher with less spin off a mat.

I think that at higher ball speeds the difference gap should be smaller and at lower ball speeds the gap should get larger.

[Howard_Jones]

We should expect distance gaps to be the same indoor vs outdoor, but its really hopeless to say "thats how it is", because there is so large varieties between different mats and different turf, so we really never have the same surface or launch conditions twice during play, even with the same club.

The Trackman study who caused all this head scratching is good as a input, but its only a single example, and if you look at the video made by TXG who is quite popular here on WRX, the mat they are using dont give any differences compared to the turf area they tested from.

So...if you have gaps on 12 yards carry indoor, expect the gaps to be 12 yards out door, while both launch, spin, apex, descent and carry MIGHT vary from indoor datas, but with no fixed conversion factors...each club fitter have to test his own fitting mat and judge this things by himself.

 

TXG Mats vs grasshttps://www.youtube.com/watch?v=F-Nhl9CKAAY

 

Trackman blog. mats vs grasshttps://blog.trackmangolf.com/mats-vs-grass-whats-difference/

[sadclevelandsports]

Thanks, I was not aware that TXG had done a comparison. I was aware of the Trackman case study, which was the only available data to me, so I almost took it as mantra that I would lose height, gain spin, and lose distance. Thanks!

[Stuart_G]

I was not a big fan of the TXG video for a couple reasons.

1) They didn't show AoA numbers. (that's more for my own curiosity) Or even test against different AoA numbers.

2) The put the mat on top of turf which I don't see as very representative of how mats are more commonly used. Most people hit off of mats that are on much harder surfaces - typically a concrete base.

 

 

 

[clevited]

I agree with you. I like a lot of their videos but for my mind, they aren't careful enough with how they present their findings too often. I found that turf video bothersome but for another example, they did a test with a 20+ year old wound ball and presented it as fact without mentioning its age, and no doubt, significant elastic degradation. I think they noticed that it was smaller but didn't seem to realize that it wasn't supposed to be smaller. Wound balls tend to shrink over time. They also did a cold golf ball test and that bothered me too. Sorry, had to get my TXG rant in after you mentioned it. Thought I was the only one that didn't like that video.

[JCAG]

As I said earlier: In a well it iron shot the ball has left the face of the club before the club sole hits the ground. What I do think it that many being fitted on a mat hit normally for a few swings but they do not like the feel of hitting the mat so they change their swing to accommodate this. Like they start "picking" instead of going down and through. As Stuart said, most mat fittings are done with the mat on a hard (typically concrete) surface. Of course places that only do off a mat fitting are going to try and prove there is no difference. I do say a driver fitting is a different animal as one is picking the ball off a tee so the ground surface means nothing other than between one's ears.

Some years back there was an indoor mat where the hitting area was mounted on springs running vertically, under the hitting area. It was very expensive and it also required buying not just the hitting area but building (or buying from them) a special hitting mat (raised some 3-5in) to have your feet at the same level as the hitting area. That said, it truly felt like hitting off of good turf.