When you’re sick, you call a doctor. When your car breaks down, you call a mechanic. When your drain is clogged, you call a plumber.
When your 32-foot-long rudders and 18-foot-in-diameter propellers get stuck in the muck on the floor of San Diego Bay, you call a . . . well . . . who do you call?
For the last 19 years, the USS Midway Museum has been berthed at Navy Pier with the ship’s stern immediately adjacent to the bay’s shallow shoreline. Although the carrier weighs nearly 70,000 tons, it still floats freely – 99 percent of the time. When the low tide approaches a negative one to two feet, however, Midway’s massive rudders and colossal propellers make contact with the bay’s muddy bottom.
“Over time, tidal effects have increased the buildup of silt under Midway’s stern,” said Len Santiago, Midway’s chief engineer. “We began experiencing abnormal stress on the rudders and propeller blades, which no ship is designed to accept. Although Midway is all steel and built to absorb a lot of damage in war, the ship was not constructed to receive up to one million pounds of pressure pushing upward on the aft portion of the ship.”
These occasional, but recurring, upward forces were causing undue strain on the propeller shafts and high vibrations on vertical support bulkheads and the fantail. The ship is not able to withstand these periodic dynamic tensions over extended periods of time.
Options were not only limited, but complicated. An extensive dredging operation could be undertaken to remove silt from below the ship, but it would only be a short-term solution. The other option was to literally remove Midway’s rudder and propellers, which would decrease the amount of propulsion and steering components extending below the water line as well as reduce the weight of the ship.
“After an in-depth analysis by naval architectural engineers, who conducted vibration analysis and hydrographic scanning of the bottom of the ship, it was decided the best options was to remove the rudders and propellers,” said Len, whose engineering team is responsible for the ship’s preservation.
An operation this extensive and complex on a ship as immense as an aircraft carrier would normally be accomplished in a gigantic dry dock. Unfortunately, that was not a possibility for Midway.
The search began for a maritime repair and maintenance company that could handle a rudder and propeller modification project on a scale rarely seen. Phoenix International answered the call.
Phoenix is a globally renowned and highly-respected ship engineering and repair company that provides a broad range of underwater services including maintenance, welding, construction, inspections and testing. But Midway’s project requirements were a bit out of the ordinary.
“Phoenix was privileged to help plan and execute this complex pierside operation,” said Travis Niederhauser, the Hawaii area manager for Phoenix. “The single biggest challenge of this project was planning cuts around very short tide windows while the stern of the vessel was afloat.”
After further review by the Phoenix’s diving engineers, it was determined only the lower portion of the rudders and several of propeller blades needed to be removed.
“Since there was limited water depth, traditional rudder and propeller removal procedures could not be utilized,” said Travis, who has been with Phoenix for nine years. “Our engineering and operations team had to develop a comprehensive rigging and cutting plan.”
Phoenix, along with its project partners, Bluegrass Company and Pacific Maritime Group, had three major issues that needed to be solved. The first, and most critical, was ensuring the safety of their divers during cutting operations. The teams also needed to ensure they had enough time to complete a cut before the ship settled into the silt during low tide, and to then have sufficient clearance between the hull and the bottom of the bay to actually recover the portions of the rudders and propeller blades once they finished a cut.
Using custom built diamond-wire rail saws, designed by Bluegrass, seven and a half feet of each of the two rudders were removed as well as seven of the 14 propeller blades. Because of the operational intricacies, nearly three months was needed to complete the project.
“With this rudder-propendectomy, we ultimately reduced the weight at the back of the ship by nearly 32 tons,” said Len, who has a master’s degree in mechanical engineering from the Naval Postgraduate School. “Midway now sits about a foot higher in the water.”
Because of the in-depth preparation, Phoenix was able to complete the project with only minor modifications to the plan.
“Our divers employed a variety of tools and techniques,” said Travis, who earned a bachelor’s degree in geotechnology from the University of Hawaii. “Very rarely do we get to implement this many underwater techniques on one project. Completing a project is always a great feeling, however, success on a project of this complexity was not possible without the right team.”
“These guys were the ultimate professionals,” said Len, relieved that the pressure on the 77-year-old ship’s hull has been finally erased. “Their hearts, hands and expertise were dedicated to Midway’s preservation.”
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