Quite a bit has been written about batted ball data the past few seasons since the information has become publicly available. Fantasy owners have taken notice and are trying to find that next hitter who is raising his launch angle to be part of the “Flyball Revolution”. One major issue which is not being publicly discussed is the major effects backspin has on the ball. By knowing a hit’s spin rate, some of the anomalies seen between launch angle and exit velocity can be explained. The spin rate is a major batted ball component but is generally an unknown factor.
The importance of batted ball spin comes down to this simple table and explanation by Dr. Alan Nathan in a piece he wrote at the Hardball Times.
Finally, I want to take advantage of the fact that we have an aerodynamic model that accounts for most of the features of the data to investigate how flyball distance depends on the amount of backspin, here for a fixed exit speed of 103 mph and launch angle of 27 degrees. The results are given in the table below. They show that distance increases rapidly as the backspin increases from zero but eventually saturates, with very little gain in distance for spin rates exceeding about 1,500 rpm. The reason for the saturation is partly because air drag increases with increasing spin, essentially canceling the increase in lift.
Same launch angle. Same exit velocity. And the ball travels an additional 64 feet of distance because of backspin. Simply, how is a factor which can add an additional 60+ feet in travel distance not be part of our analysis?
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