Influence of a humidor on the aerodynamics of baseballs

TL;DR

This study examines how humidity levels in a humidor affect baseball aerodynamics and flight distance, revealing that drier balls curve more and are slightly more affected by aerodynamic forces, but overall distance is influenced by other factors.

Contribution

It provides new insights into how controlled humidity storage impacts baseball aerodynamics and flight, combining experimental measurements with trajectory modeling.

Findings

Drier baseballs curve slightly more than humidified ones.

Aerodynamics can add approximately 2 feet to hit distance.

Humidity affects the coefficient of restitution, influencing overall distance.

Abstract

We investigate whether storing baseballs in a controlled humidity environment significantly affects their aerodynamic properties. To do this, we measure the change in diameter and mass of baseballs as a function of relative humidity (RH) in which the balls are stored. We then model trajectories for pitched and batted baseballs to assess the difference between those stored at 30% RH versus 50% RH. The results show that a drier baseball may be expected to curve slightly more than a humidified one for a given pitch velocity. We also find that the aerodynamics alone would add ~2 feet to the distance a moister ball is hit. However, this is compensated by a ~6 foot reduction in batted distance due to the well known change in coefficient of restitution of the ball. We discuss consequences of these results for baseball played at Coors Field in Denver, where baseballs have been stored in a humidor at 50% RH since 2002.