Maybe you have been walking along the beach in Aquatic Park and noticed two huge propellers sitting in the sand near the east roundhouse. I've been walking by those for years and decided to do some investigating.
What is cavitation and how can it pulverize steel? This phenomenon can occur under certain conditions during the rotation of a screw propeller. In the turbulent water around the propeller air bubbles can't escape so they implode, releasing energy, and causing physical damage to parts of the prop.
See you in the park and try not to trip over those props!
Park Ranger Christine
Did You Know?
San Francisco Maritime is the only NPS site that has a cable car turnaround adjacent to the park. Riders disembark and workers push the cars around on the track to position them for the next journey back up steep Hyde Street.