If you have a model of the SS UNITED STATES, chances are youíre looking at a waterline model - flat bottomed, and usually without propellers or rudder showing. Missing from view is 30 feet of hull depth and underbody details. Thatís the way Gibbs wanted it. Photos of the ship in drydock were not allowed. So, was the underbody the biggest secret Gibbs had?
No. Just one of many veils of secrecy directed by Gibbs and his engineers. However, the real secrets of the ship were those dictated by the Navy. Sensitive information: Speed, power ratings, plant design, auxiliary systems, hull design, navigational and communication systems. Letís start with the hull design. Measure the ship from bow back 764 feet and youíre at Frame 272. Make a cross section and it would look like this:
In the cross section above, you can see hull form for the bossings. Gibbs believed that bossings would help to stabilize the ship (help to minimize roll) - and prevent stern squatting.
Most believed struts would give the ship better performance, but Gibbs opted for enclosed (faired) shafts in bossings - even if they introduced undesired drag. He believed the bossings would better protect the drive line, given the demanding, constant high speed service requirements. Take a look at a very rare image below - revealing bossings and propeller placement.
Extensive model testing (collected by Gibbs between 1916 and 1950) revealed the best choice of design was a cruiser stern, very modest bulb and four shafts through bossings. (enclosed faired tail shafts) When comparing the Big U performance to new ship designs 50 years later, it turns out Gibbs & Cox engineers chose wisely.
18 Blades, New Design
The Navy was advancing designs for propellers and testing revealed the best approach would be to use five bladed props on the inboard shafts, and four bladed props on the outboard shafts. Itís clear, the U benefited from Gibbs close working relationship with the navy. Can you imagine a renewed U with current naval and maritime technology?
Click to enlarge the aerial image, and youíll see the four props now on the decks of the ship placed relative to their original installed positions.