The state ferry Taku won't sail again until Monday, as maintenance workers repair recently discovered damage from a mechanical problem that occurred this week.
The Taku was in Chatham Strait en route to Sitka on Monday carrying 79 passengers and 10 vehicles when the crew found that a bearing in its drive mechanism had overheated. The drive mechanism transmits the diesel engine's power to the propeller.
George Poor, senior port engineer for the Alaska Marine Highway System, said the starboard main shaft thrust bearing also was damaged. That bearing, which is part of the ship's reduction gear, handles the thrust generated when the propeller spins.
"The nut on the thrust bearing came loose and it wasn't handling the thrust of the propeller," Poor said.
As a result, the first bearing had to carry the thrust bearing's load, and it failed, he said.
Monday's incident was the second mechanical problem that has held up the ferry this season. The Taku is the third of the Alaska Marine Highway System's seven Southeast ferries to be sidelined in the past month. A generator fire hit the Columbia as it sailed through Wrangell Narrows on May 28, and the Kennicott hit a rock outside of Wrangell on June 3. Both are back in service.
Ferry system Capt. Jack Meyers said the incidents are not connected.
"One was a fire, and one was a vessel that hit a rock, and this was a casualty to the shaft. I wouldn't even speculate as to why. Things happening in threes, or something, I don't know," Meyers said.
The Taku began having problems with its shaft clutch assembly last week as it sailed from Auke Bay to Haines and Skagway. The Aurora, a smaller ferry, was brought up from southern Southeast to cover the Taku's weekend Lynn Canal runs.
According to Poor, Lufkin Industries, a Texas company that manufactures bearings used in the Taku, said there have been problems with the bearing loosening.
"It's not a maintenance issue. It's a design fault which we're now going to correct. We're going to modify it so it can't ever come loose again," he said.
Poor said ferry crews will take measurements to make sure a similar bearing on the port side of the ship doesn't come loose. He said the Taku is the system's only ship that uses that model of reduction gear.
For ferry schedule updates, call 465-3941 or check www.dot.state.ak.us/amhs/.