Shipyard thermal distortion during construction

1 part in 20,000 tolerance for shipbuilding (vs. typical 1 part in 2,000 for general manufacturing) — the precision is so high that solar heating changes the shape of a thousand-foot ship and must be welded around. Student adds Pascagoula sun-shade practice.

If you look at manufacturing tolerances, a typical manufacturing tolerance — it doesn't matter whether you are doing semiconductors, chips, or ships — a typical tolerance is 1 part in 2,000. So if you're a machinist, and you ever work on a lathe and you're trying to machine something to one inch diameter precisely, you can get about five ten-thousandths of an inch without too much difficulty using a micrometer. You can machine it to that tolerance. That's a typical tolerance, and it doesn't matter. But if you talk about a ship that's a thousand feet long, that's a one-inch distance. If you're off by an inch, the hulls don't come together. So shipbuilding — Alan Brown from the Ocean Engineering Department pointed this whole tolerance thing out to me once — shipbuilding was the most precise manufacturing that we did in terms of parts per thousand. About one part in 20,000 in terms of the tolerances you have to put. And when the sun comes out, or a cloud goes in front of the sun, the whole ship changes shape from solar heating. And you have to weld these things so that there's not a bunch of mismatch.