Ferry woes may be a matter of too much propeller

Published 8:35 am Friday, August 13, 2010

It looks like the source of vibrations in the brand new and overdue state ferry is known.

Finding a fix may take a bit longer and it’s still not known when the vessel will be put into service carrying cars and passengers between Port Townsend and Whidbey Island.

As the Herald’s Bill Sheets reports today:

“The ferry’s diesel engine appears to be turning the propeller so fast that it’s vaporizing the water around it and spinning in a pocket of air, causing it to vibrate, said George Capacci, deputy chief of operations and construction for the ferry system.

More air is then sucked in, creating a tornadolike effect, Capacci said.

When the boat slows down, the spinning propeller slows down too much. The propeller and the engine then “chase each other back and forth,” Capacci said.

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Here’s the story.