SHAPE OF THE HULL TO CHOOSE BETWEEN STABILITY AND CONCEALMENT

The US Navy is currently quietly building the DDG-1000 ship and rarely news (the delays and issues of the LCS ship problems seemed to be better known). With the first boat release scheduled (USS Zumwalt), from 3 ships into the water at the end of this year.  And will be enrolled after the end of the trial at the end of next year.

Superstructure assembly with the hull at the end of last year (Image from US Naval Sea Systems Command)

The DDG-1000 ship has a displacement tonnage over 14,000 tons, length of 180 m., and width of 24.6 m. With such enormous size, it seem that the definition of ship as the Guided-missile destroyer ship (DDG) is not suitable for the size of the ship but should be compared as a patrol boat (CG) or even better as modern battleships instead. However, the DDG-1000, emphasized the use of automatic systems to reduce the ship’s personnel down to only 130 people, which is very small compared to the ship size. (Compared to the DDG-51 ship, with a capacity of 9,000 tons with around 300 crews on board).

Back to the technology and shape of the boat. In addition to the DDG-1000 ship uses automatic technology to reduce the ship’s personnel. There’s also a new design ship which uses the new Tumblehome Hull technology, to help reduce radar reflection. The use of this new boat shape is a groundbreaking design from a conventional design from a general vessel that uses a V-shaped hull or a flare hull.

Tumblehome Hull boat shape has the appearance that the hull part above the waterline is less wide than the hull part by the waterline. The maximum width is right by the waterline or a little under the water. And this help reduces the radar reflection to the source by reflecting it to another direction. In addition to reducing radar reflection, the shape of the ship also help reduces the ship’s center of gravity height (Because the upper mass is smaller compared to the ship’s body). Making the hull more stable in the view of static stability. And helps reduce the side stabilizer due to the mass on the side of the ship also decreases. This boat-shape design is often seen in the sailing era to the Iron Clad and the early battleships. But why don’t we see this boat shape in the modern warships and current commercial ship?

Credit : kapitaennem0.wordpress.com