Unlike traditional ship launchings, where the hull slides down the building ways, launching the hull from the final assembly bay at Austal USA and into the water is a much more controlled process.
After the customary christening ceremony, when the dignitaries and guests depart and the bunting and chairs are put away, Austal prepares to launch the ship.
The location of Austal’s manufacturing facility on the wide Mobile River allows the company to roll its ships out directly from their final assembly bays and onto an awaiting barge on the river. Meanwhile, final assembly construction on the next ship begins just minutes after the one ahead has been moved out.
Navy ships traditionally have been constructed on a building ways. The keel would be laid, and the ship built up from there. The ship would be sitting at an angle so when it’s “launched,” it would slide down the ways – either stern first or sideways into the water where it could be brought alongside a pier where construction and outfitting could be completed.
Austal teamed with Berard Transport of New Iberia, Louisiana, to get the future USS Manchester (LCS 14) off the land and into the water. At full-rate production, Austal rolled in the first modules of the future USS Charleston (LCS 18) right on the heels of the Manchester heading out the bay doors.
According to Braedon Berard, the company’s chief operating officer, a significant amount of engineering and planning is conducted before the ship is made ready for launching. Berard’s scope of work is to loadout and transfer the USS Manchester onto BAE Systems Ship Repair’s floating dry-dock Alabama, and encompasses engineering, project management, logistics, heavy transport equipment, labor supervision, barge ballasting and mooring to ensure the Manchester move is conducted safely and efficiently.
Self-propelled modular transporters (SPMTs) made by Scheuerle in Germany, are connected together like a train and placed under the ship. SPMTs are capable of loading and unloading their cargo with twenty-four inches of hydraulic compensation. When connected, a single operator using a hand-held remote control can transport, steer, brake, level and elevate the modules as a single entity. In the case of the USS Manchester, BTI configures its SPMTs into five files totaling 108 axle lines. “When the SPMTs are all connected via data lines a network is created and [they] become one,” Berard says.
“After the SPMTs are in place and connected, we pressure it up, making sure the pressures in the hydraulic zones are correct, and elevate the ship,” Berard says. “We do a test run and make sure the SPMTs are fully functional. At sunrise on the following day, the barge is set into place and final barge preparations are done to ensure the barge is level. We have to constantly adjust the ballast as the ship is moved onto the barge to compensate for the weight of the ship to keep the barge trim.”
The barge is moored and held in place by single drum winches and winch trucks that are attached to the barge and large bollards on the pier. The mooring plan is designed to keep the barge stationary for a 20 knot wind.
Once the ship is positioned on the barge, it is lowered back onto its keel stands to spread the load. “When we lower the hull, we shed 50 percent of the load, which is picked up by the keel stand,” Berard says.
The winch trucks are disconnected and the barge is cast off to be towed stern first down the river to BAE Systems Ship Repair’s Mobile yard.
Sea Trade and Chouest provided the tugs, and the barge was supplied by Crowley.
At the BAE Systems Ship Repair yard, two winch trucks are placed on the floating drydock Alabama, and another on the pier, to hold the barge and dock together, and the dock to the breasting piers. After the barge is made up to the dock, the transporters lift the ship off the keel blocks and roll it onto the Alabama. This is a challenge as the drydock has a tapered floor. The team carefully watches the ballasting of the barge and drydock to ensure they both remain level.
Once on the drydock, the Manchester is lowered onto the blocks, and the SPMTs and winch trucks are removed. The barge is moved away, and the drydock can be slowly flooded. Once afloat, the ship can be moved out of the dock and positioned with tugs to Austal’s nearby outfitting piers.
Altogether, it takes about one day to move the ship out of the assembly building down to the dry dock, and another day to undock the ship and move it to the vessel completion yard (VCY) piers.
Manchester and her sister ships are trimarans with a large center hull and two side hulls – also called outriggers or amas – for stability. The wide center hull bears the weight during movement, while the sidehulls are very narrow and are empty, contributing to stability.
Austal USA is also building the Expeditionary Fast Transport (EPF), formerly known as the Joint High Speed Vessel (JHSV). The EPF is a catamaran, with two relatively narrow sidehulls that also contain the diesel engines.
Berard says moving EPF follows the same basic process, but, he says, the EPF “has its own unique challenges.”
Courtesy of Surface SITREP. Republished with the permission of the Surface Navy Association (www.navysna.org).