Float Off—Another Big Milestone for the future USS North Dakota
By Katie Fowler, Sponsor
Katie Fowler, the boat sponsor, and her husband retired Vice Admiral Jeff Fowler, were able to participate in another special event in the construction of the future USS North Dakota. For the first time after years of being assembled in a variety of buildings, the hull of the boat, now more than 90% complete, was rolled out of the building and placed in a Dry Dock. Also, for the first time in its life, the hull was surrounded by seawater until it “floated off” the blocks that have been holding it up since the beginning of construction.
As you might imagine, many things must be completed and certified before this can happen. The exact date for this movement out of the building is impossible to predict, so Katie and Jeff waited for the report from the boat’s Captain, CDR Doug Gordon, that the North Dakota had left the building.
The 7,800 ton vessel moves on the equivalent of train tracks, first sideways, then out of the building, then sideways again onto a pontoon that is in the Dry Dock. The water is pumped out of the Dry Dock, so the pontoon settles on the bottom of the Dry Dock with the North Dakota still “high and dry” on its original blocks.
The shipyard and crew sign off all of the final checklists to ensure bringing water against the hull will be done safely. Katie and Jeff arrived the edge of the Dry Dock at 3:45 a.m. (yes, in the morning!) on Sunday September 15th, 2013 to observe the final sign offs.
The boat on its blocks in the Dry Dock truly looked like a completed submarine—no scaffolding, very few construction materials around the boat—very exciting to see it in this condition. Two young workers who were instrumental to getting the boat to this point had the honor of opening the two valves that allowed water to enter the Dry Dock. Katie was given the privilege of ordering “Open the valves!” around 4:00 a.m. to get the process going. Many photos were taken, so once they are cleared by the shipyard, I am sure we will be able to post some of them.
The filling of the Dry Dock with sea water is done very deliberately, with occasional pauses to make sure all places that might leak water are actually water tight. Katie and Jeff left so the process could move forward, and returned when there was 26 feet of water on the hull.
The actual float off is an important event. First, a naval architect has done calculations at what water level on the boat’s hull should lift the boat from the blocks. If that does not happen by a certain point, major delays and an investigation would ensue. The best analogy I can think of for the float off is when you take your fishing boat to the lake on its trailer, unhook all fasteners, then very slowly back into the water until the boat lifts off the trailer. In the case of the Dry Dock, instead of moving the boat and trailer to deeper water, the water level is raised against a stationary boat on the blocks.
To detect the slight motion of float off, the shipyard rigs a plumb hanging from a chain that just touches the upper hull of the boat. When the boat lifts off, the plumb contacts the boat and leans over. Because the boat has been compressed against the support blocks for years, there is a little friction that has to be overcome.
The young female naval architect was on the phones with her team as the water slowly rose to the expected point. Within an inch of her calculation, the North Dakota floated off for the first time at noon on September 15th, 2013. The ship’s whistle blew a loud, long blast heard up and down the Thames River, announcing “North Dakota is waterborne!”
The next big milestone will occur on November 2, when North Dakota, floating in the same Dry Dock, will be christened.