Nimitz-class carrier weight creep

Carriers gain 250 tons/year, growing from ~60-65K tons at class introduction to ~90K tons 60 years later, mostly at the top of the ship. The economic driver for the HSLA-65 feasibility study that follows.

To give you an example — and I reference this in here — the US Navy was worried about the weight of aircraft carriers. Aircraft carriers gain 250 tons a year. If your spouse is giving you a hard time about gaining weight, tell them you don't gain as much as an aircraft carrier each year. The Nimitz class started like 60,000 or 65,000 tons, and it was up toward 90,000 tons 60 years later. Most of the weight is up at the top. The aircraft carrier gains 250 tons a year, and they needed to make it lighter weight because it was going to cost them 50 million dollars to design the new hull.

Nimitz-class carriers gain 250 tons per year over the hull life, mostly topside. Drove the HSLA-60 investigation: Newport News estimated 2,000 tons savings if HSLA-60 substituted for lower-strength components.

But the real point is, if I'm going to make something and sell it for less than two dollars a pound, my metal choice comes down to steel. Another rule of thumb is that the metal cost for the fabricated structure is about ten percent of the overall structural cost. One time NAVSEA, back in the days when the aircraft carriers were starting to gain weight — the Nimitz-class carriers gain weight at 250 tons a year. That doesn't sound like a whole lot, but if you plot the weight of a Nimitz carrier over the sixty or seventy years of the hull, they gained 250 tons a year. And it's not down in the keel, it's mostly up top. That's not good. That means you have to put more lead in the bottom. Trying to save all this weight in the ship and then you put more lead in the bottom anyway.

250 tons/year weight gain across the class from the early 1960s through 2000, used to motivate the structural lightweighting program.

In any case, in the early eighties the Navy was trying to do waffle-membrane construction of the superstructures. They've got to be light, so they were using high-strength sheet-metal steel and making something that looked like a cross-section of corrugated cardboard in steel, to replace the lightweight aluminum structures. It's a serious problem for ships in general. Does anyone know what an aircraft carrier gains per year in weight? 250 tons a year. If you plot the Nimitz-class carriers from the early sixties all the way up through 2000 or so, they gained 250 tons a year. And most of it's up top.