This led me to wonder how important height was a restriction on ships. Turns out "air draft" is reported for major ports. Some interesting findings: The Panama

This led me to wonder how important height was a restriction on ships. Turns out "air draft" is reported for major ports. Some interesting findings: The Panama Canal has an air draft of 201 ft imposed by the Bridge of the Americas; the Port of Oakland has an air draft of 220 ft imposed by the Golden Gate Bridge. Height from waterline does not appear to be typically listed for ships, but I would guess that most cargo vessels do not have 100 ft of clearance to spare. I think this means these sails would only be fitted to vessels which generally don't care about height restrictions (e.g. ships larger than Panamax) or ships running predictable routes. https://en.wikipedia.org/wiki/Air_draft https://en.wikipedia.org/wiki/Air_draft