Posts Tagged ‘friction’
I recently stumbled onto an interesting tidbit whilst working with a young professional on his wedge game. It was early in the morning and we had been hitting beautiful 50 yard pitches the afternoon before and suddenly he could not get the ball to launch low enough with the spin rate he had been generating the day before. Now as you may know I’ve tested almost all there is to test in regards to a 50 yard wedge shot and of course I had looked into the effect of water interfering with the friction between the face and the ball. One problem – I had tested a wet club striking a dry ball. My results from the earlier test showed very little difference in launch and spin when there was water involved and I had since adopted that belief.
As I watched the young pro struggle to lower his launch in the morning dew it came to me – there was a difference between a wet club striking a dry ball and a dry club striking a wet ball! I had to run the test again.
I had to be very careful with the test in that I needed to use the same club, my 54 degree sand wedge, in very controlled conditions, with golf balls that were consistent. I used brand new Titleist NXT Tour golf balls and made sure that I cleaned the grooves and clubface off between each shot. I attempted to hit each shot to carry 50 yards flat and hit eight shots for each portion of the test. I removed the two shots that had the lowest spin from each portion. With the help of my TrackMan here are the results:
Wet club and dry ball:
- Launch angle was 27.8 degrees
- Spin rate was 5463 rpm
- Height was 26.5 feet
Dry club and wet ball:
- Launch angle was 30.1 degrees
- Spin rate was 5291 rpm
- Height was 28.4 feet
Dry club and dry ball:
- Launch angle was 25.4 degrees
- Spin rate was 6603 rpm
- Height was 21.2 feet
The interesting thing in looking at the trajectory chart is how much lower the dry club and dry ball (purple) shots flew. Clearly there was more friction between the face and ball which led to a lower launch with substantially more spin. The dry club and wet ball (yellow) sample flew the highest as the water on the ball greatly decreased friction which led to higher launch, due to slippage and thus decreased spin – certainly not the optimal shot.
The interesting thing when comparing the wet club/dry ball versus the dry club/wet ball results was that the spin and launch were better when the BALL was dry. This was due to the water being forced off the clubhead and into the groove channels during the motion of the swing. Not to mention that the air dried the face during the swing too.
Moral of the story – always clean the clubface (unless it has sand on it) and dry the club and ball when possible. If you happen to have an early morning tee time and you’re a dew sweeper, don’t plan on hitting any low spinners! The drier the ball and club, the better the friction and the better the quality of shots you will hit.
Please read my first two articles on wedges and pitching:
In my quest to better understand pitching, chipping, and more specifically the low spinning wedge shot I needed to watch different professional players hit a variety of shots and be able to track the data from each shot. My objective was to understand how friction or grip between the face and the ball influenced the launch angle, height and spin rate. I have named the measurement of this grip and it’s influence on the golf ball – friction launch.
I need to explain some fairly detailed physics as to how I measure friction launch, so bear with me. The golf ball always launches somewhere between where the face is angled and where the clubhead is travelling – on both a vertical and horizontal plane. The ball also always launches closer to where the face is angled than where the clubhead is travelling. Where the ball launches between the face angle and the clubpath is primarily determined by club speed and friction between the face and ball. I needed to measure this friction in order to see how it effected the trajectory and spin on wedge shots.
With the help of Mark Reilly and Edoardo Molinari, we came up with the following formula to determine friction launch:
(Dynamic Loft – Launch Angle) x 100/Spin Loft = Friction Launch
This formula informs us where the ball launches between the face and path. The percentage indicates how far below the face angle the ball launched. A friction launch of 0% indicates that there was absolutely no grip at impact and the ball launched in the direction the face was angled at impact. A friction launch of 50% would indicate that the ball launched directly between the face angle and the clubpath and the grip was exceedingly high. By the way – neither of these are possible under normal conditions. The smaller the percentage, the higher the launch and lower the spin and vice versa.
With all the various situations I tested I needed to keep certain factors constant in order to be able to detect why the trajectory and spin rate of each shot was altered. My constants were TrackMan – to record the data; the golf club – a Titleist Vokey SM4 54 degree wedge; and the distance of each shot studied – 50 yards. If any ball landed short of 40 yards or longer than 60 yards it’s data was thrown out. The factors I controlled were the quality of the lie and playing surface, the grass and dirt in the grooves and on the face and the type of golf ball.
Here are the average results attained from three professional golfers hitting 10 shots each in 7 different situations:
1. Clubface packed with dirt and grass/ProV1/off lie board (to eliminate additional matter)
- Friction Launch 17.9 degrees/Spin Rate 4408/Launch Angle 34.9 degrees/Height 31.9ft/Carry 51.6yds
2. Clean clubface/ProV1/off lie board (to eliminate additional matter)
- Friction Launch 28.1 degrees/Spin Rate 6501/Launch Angle 28.4 degrees/Height 25.1ft/Carry 50.3yds
3. Wet clubface/ProV1/off lie board (to eliminate additional matter)
- Friction Launch 28.1 degrees/Spin Rate 6564/Launch Angle 28.7 degrees/Height 25.7ft/Carry 50.4yds
4. Clean clubface/ProV1/off turf/preferred lie
- Friction Launch 31.9 degrees/Spin Rate 7178/Launch Angle 26.1 degrees/Height 22.3ft/Carry 48.9yds
5. Clean clubface/hard range ball/off turf/preferred lie
- Friction Launch 28.8 degrees/Spin Rate 6625/Launch Angle 27.6 degrees/Height 25.1ft/Carry 50.8yds
6. Clean clubface/ProV1/off a new mat
- Friction Launch 30.4 degrees/Spin Rate 6859/Launch Angle 26.8 degrees/Height 23.3ft/Carry 49.2yds
7. Clean clubface/ProV1/Off a tee
- Friction Launch 30.6 degrees/Spin Rate 7259/Launch Angle 27.6 degrees/Height 24.8ft/Carry 51.2yds
Edoardo Molinari was also kind enough to submit his TrackMan data to me from the 10 shots he hit with his 60 degree wedge and 10 more with his 56 degree wedge: (the following shots were hit with premium golfballs, off preferred lies and cleaning the clubface between each shot)
60 Degree Wedge
- Friction Launch 22.9 degrees/Spin Rate 6048/Launch Angle 36.2 degrees/Height 34.8ft/Carry 51.0yds
56 Degree Wedge
- Friction Launch 24.4 degrees/Spin Rate 6046/Launch Angle 34.2 degrees/Height 31.5ft/Carry 50.5yds
NOTE: After a few weeks of practice Edoardo has improved his 10 shot average with his 60 degree to a spin rate of 8700rpm and a Launch angle of 26.1 degrees! There is something to this…
The deductions I took from the above tests are as follows:
- Shots out of the rough, first cut or even into the grain lies are always going to launch higher, spin less and as a result fall out the sky faster and roll more after landing – no matter how good you or your wedge is. There simply is too much ‘matter’ involved between face and ball to create optimal friction.
- A wet clubface actually makes very little difference in determining how much friction, and thus spin, is imparted on the ball.
- A premium golfball makes a noticeable difference with the wedges. Not only will it add distance off the tee, but it will also allow you to hit better and more predictable short shots.
- If the rules allow you to tee the ball up – go ahead and do so. You increase your ability to place the clubface cleanly on the back of the golf ball.
- Hitting pitch shots off mats is a fantasy world and can only increase the ‘illusion of competence’. No bad lies, nothing between the face and the ball, minimal consequence to heavy shots...
- For pitch shots, higher lofted clubs do not spin the ball significantly more than the next wedge down (60*vs56*). They do, however, get the ball to stop slightly faster due to a steeper landing angle.
- Average friction launch for a 50 yard shot is around 25%. The lowest friction launch was out of the poorest lie (18%) and the best results came from an ideal fairway lie, a new and clean wedge along with a premium golfball (32%).
- The quality of the lie is the most important factor in allowing a golfer to control the trajectory and spin of the wedge shot they are about to play.
Let’s take a look at the factors that influence friction launch:
The Golf Club
- The sharpness of the top edge of the groove will effect spin, yet most of the spin on a shot comes from the roughness of the area between the grooves.
- In my opinion the wedges that provide the highest amount of spin are the models that have the roughest surface between the grooves – the new TaylorMade ATV and the Nike Vr Pro wedges seem to do an excellent job with ‘between groove’ treatment.
- An excellent way to improve spin with your current wedges is to have the face sandblasted with normal aluminum oxide sand. This will provide a rougher, more ‘grippy’ texture to the face.
- The number of groove edges that come into contact with the ball also effects backspin. In pushing the limit of the groove rules manufacturers can now put five grooves on the surface of the ball at impact versus the traditional three.
- Grooves channel away some of the moisture and matter from rough that gets between the ball and face – but seldom all of it.
- The grooves and face of your wedges should always be very clean – even when you’re practicing. Keep a towel or brush handy to clean the club after every few shots.
- If you are serious about competitive golf I would recommend having a tournament set of wedges and a set you use in practice. Every shot you hit wears down the face which reduces friction at impact.
- In fact Gary Player would ensure that his caddie never cleaned his wedge after hitting a sand shot – the sand particles on the face helped to create more friction between the face and ball for his next shot.
Turf Type and the Quality of the Lie:
- When you are into the grain you will often get grass caught between the ball and the face, thus reducing grip. A down grain shot will ‘cut’ very little grass and thus allow for clean contact and increased grip.
- Different turf types are thicker and stronger and thus, even at fairway height, support the ball enough to keep it up and away from the grass. This makes it easier to have a higher friction launch factor. If you’ve ever played off kikuyu grass you’ll know what I mean.
- When laying up on a par five understand the value of high friction launch – lay up in the fairway and don’t be greedy.
- This is where I am now focusing my efforts. There does seem to be a method that DOES NOT involve a more open face, increased speed, higher launch or a cutting action that seems to produce a lower trajectory with a much higher spin rate. Stay tuned…..
Read part one of this article HERE
For years golfers have asked me how to hit low, spinning wedge shots and I’ve never been able to give them a confident response. After the research I’ve put in over the past few weeks I can give them a certain answer – and perhaps even explain a few other interesting shots we encounter on the course.
In polling better golfers regarding what really good pitch shots look like, the response has almost unanimously been that they tend to be lower with more spin. Edoardo Molinari, the European Ryder Cup golfer and former US Amateur champion was kind enough to help with the research for this article and he stated,
I’ve watched Tiger, Mickelson and Ernie hit hundreds of 50 yds shots, I’ve played with them and they all seem to deloft the club without taking much divot.
Which I agree with by the way – the best pitchers always seem to have a knack for nipping the ball off the turf without much divot and then firing the ball in there low and spinning. The problem with this shot has always been how to hit it low, yet make it spin at the same time….
If you hit down on the ball you’ll be able to hit it lower, but hitting down more only lowers height and does not, as is commonly believed, make the ball spin more. So that option is out. If we take a more lofted club to spin it more then we may get a little extra spin (although that’s not a given), but now the shot will fly too high.
Here is where we need to get a little technical and talk about the forces and angles the club is imparting on the ball at impact. TrackMan uses a term spin loft and it refers to the vertical difference between where the clubhead is travelling at impact (attack angle) and where the clubface is angled at impact (dynamic loft). My research shows that good wedge players have a narrower spin loft (dynamic loft minus attack angle). Let’s get a better understanding of these important factors:
Attack Angle (angle that indicates if the clubhead is travelling up or down, relative to the ground at impact)
In studying hundreds of 50 yard pitch shots on TrackMan over the last few weeks I have found that good pitchers tend to not take very large divots. Yes, they always contact the ground, but the club ‘bruises’ the turf more so than cuts it. This would indicate that the attack angle is shallow – it is down but not hugely so. Now hold on for the following part, because this should not change the way you think about a club striking a ball: my research shows that the attack angle should be shallow enough so that the sole of the club (bounce) actually makes contact with the grass/ground before the ball. And this occurs even on ideal hits…..
Dynamic Loft (the angle of the face/loft at impact)
Really good pitchers have the ability to deloft the club without hitting down more. This means that the hands are in front of the ball at impact and the loft on the clubface is often more than 10 degrees less than the static loft. For example in much of the testing a 54 degree wedge would apply 41-44 degrees of dynamic loft to the ball.
Spin Loft (dynamic loft – attack angle)
This is a very important factor as it contributes to, but does not solely determine, how much spin and loft each shot will have. If you hit a pitch shot with 42 degrees of dynamic loft and you have an attack angle of -3 degrees (the minus indicates a downward hit) your spin loft would be 45 degrees. Common wisdom indicates that a broader spin loft (eg. 50 degrees) would create more spin and height, yet my research indicates that when it comes to chipping and pitching a slightly narrower spin loft (without much downward hit), coupled with clean contact between ball and face increases the golfers ability to hit low spinning wedges. An easy way to narrow your spin loft with pitch shots is to take a lesser lofted club. My students have had tremendous results by using the lob wedge less and getting a little more accustomed to hitting a variety of shots with the pitching wedge.
Friction Launch (the amount of grip between face and ball and how that effects launch conditions)
This type of strike on the ball leads to a scenario where the friction between the face and the ball is far higher than normal. This increased friction leads to a lower launch and trajectory with a substantially higher spin rate. This grip between the ball and face is what I call ‘friction launch’ and just like the term spin loft it addresses the friction and launch of any shot.
As golfers we’ve all hit that pitch shot that comes off the face very low and the moment you strike the ball you know it’s going to grab as soon as it hits the green. Your playing partners are yelling bite and as soon as the ball gets near the hole it comes to a screeching halt! You have just experienced high friction launch.
Please check back in a few days for the follow up post The Science Behind Superb Wedges: Part II where I’ll discuss friction launch in detail and show the results of much of the research I’ve done.
To get a much better look at the data be sure to read Part II HERE