Wedges: Friction and Trajectory

The other day during a Three Day Golf School I hit four demonstration pitch shots for my students. My intent was to repeat the same shot in each attempt, with the only difference being how I manipulated the amount of friction between the club face and the ball.

The amount of loft I was able to deliver for each of the four shots was between 44.3º and 45.3º - the best I've been able to do! The interesting part is that the launch angles ranged from 30.4º tall the way up to 40.0º. How does that happen?

The Four Shots

The reasons why the launch angles are different is something that too few golfers (and coaches) understand and while I've written on this before it's a mission of mine to get the good word out. My intent was to carry each shot 50 yards and they are all played in the same fashion, with the same club except for shot 4.

Shot 1 - clean, dry club face and a clean, dry range ball. Spin rate - 6246 rpm. Launch is a respectable 32.1º

Shot 2 - clean, wet club face and a clean, wet range ball. Spin rate - 2782 rpm. Launch is a whopping 40º

Shot 3 - clean, dry club face and a clean, dry premium ball. Spin rate 6923 rpm. Launch is the lowest at 30.4º

Shot 4 - clean, dry grooveless club face and a clean, dry range ball. Spin rate is 5837 rpm. Launch is decent at 33.6º

I must mention that in order to 'manage' the friction between the club face and the ball each of these shots is played off a tee so as to eliminate grass and outside matter from interfering.

While the loft is maintained the launch, spin rate and peak height can be greatly influenced by the amount of friction generated between the club face and the ball. The moral of the story here is that the best pitchers in the world hit low launching, high spinning shots when the conditions allow. There is more at play than simply the loft at impact determining the launch angle. As you can tell friction plays a massive role too. It is my hope that in understanding this you will be less likely to try and 'fix' something that isn't broken. Hope this helps and thanks for reading!

Luke Donald

Wedges and Water

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:

The Science Behind Superb Wedges: Part I | Andrew Rice Golf

The Science Behind Superb Wedges: Part II | Andrew Rice Golf