Backspin on Drivers

 

Frank,

I'm confused about some contradictory statements I've read concerning the desirability of backspin (or lack of it) when one hits a driver off the tee. The February 2008 issue of Golf Digest states, " . . . you want to hit the ball just above the true middle of the face to launch it high without too much backspin" (p. 123). On the other hand, a book entitled Newton on the Tee: A Good Walk Through the Science of Golf states, "The force of the air on a dimpled golf ball with backspin provides lift . . ." (p. 81). The author elaborates that the rotating ball creates a downward force on the air, and "according to Newton's Third Law, the air must, in turn, create an upward lifting force on the ball" (P. 83). This lifting force, he concludes, alters the ball's trajectory in an upward direction.

The implication of both of these contradictory points of view is that a golfer will get more distance from his drives.

What is your view on the backspin issue?

 

--Tom

 

Tom,

 

Believe it or not these statements are not contradictory.  A ball without back spin will fly about 140 yards compared 260 yards with backspin. This assumes all other launch conditions – speed, launch angle etc – are the same.

 

The dimples on a golf ball actually reduce the drag force through the air at speeds the ball normally experiences in flight. But it is very important to have the right amount of backspin to get the maximum distance. It is only recently -- in the last twenty years -- that we have really understood the total effect of spin in combination with launch angle and ball speed to get maximum distance. Because of the equipment these launch conditions were not achievable to the likes of Jack Nicklaus and golfers of his era.

 

When the ball spins – backspin is on every shot irrespective of what some TV announcers suggest -- the air flow over the ball is such that it creates a differential in air pressure above and below the ball – high pressure below and low pressure above. This allows the ball to experience a lift force creating a gliding trajectory through the air rather than take on the trajectory of a stone or bullet.

 

The problem about backspin is, that too much actually creates more drag forces giving the ball a lift force sending it into a ballooning trajectory and reduces the distance. So backspin is important, but the right amount is needed in combination with ball speed and launch angle to get maximum distance.

 

The reason why it has been suggested one hits the ball high on the club face is to take advantage of the vertical gear effect which will help reduce the spin getting it closer to the optimum, e.g. about 2,500 rpm for a 13 degree launch angle and a head speed of about  90 mph. In the past we have found it difficult to get this low spin rate with a 13 degree launch angle because as the launch angle increases so does the spin rate. Today drivers in combination with the multi-layered balls allow us to get close to optimum launch conditions.

Hope this helps clear up the confusion.

Frank