Visby-class corvette (Swedish composite frigate)

We'll talk tomorrow about how much of these things we use. But the highest tonnage of material that we ever use is gravel, and part of that is because it's cheap in terms of energy cost. In any case, all the metals — and why do we want to use metals rather than ceramics or plastics? If we're trying to use the material, why don't we make plastic ships? Well, we do. Kids use them in the bathtub, right, plastic ships. Actually you make bigger plastic ships — you make minesweepers of fiberglass, which is a plastic ship. They made the Visby — anybody know what the Visby is? The Swedes built a combat ship, sort of a corvette, called the Visby back in the mid-90s, all fiberglass basically. It was very famous at the time. Oh, the Swedes have leapfrogged this. Well, good thing they're our friends — they're actually neutral to everybody all the time.

Cited as example of low-stiffness structural materials (aluminum, composites) failing as "beam between waves" in heavy seas — modulus argument: aluminum is ~10 Msi vs. steel's ~30 Msi.

One of the problems with the Visby — do you know what the Visby is? It's the Swedish all-aluminum or composite corvette. The Visby has problems with hogging. Basically, a ship in heavy seas becomes a beam between the waves. Composites and aluminum just don't have the stiffness to make big long bridges between two waves. In heavy seas they tend to break in two. Not good.

World's largest composite ship; usable only in good weather. Cautionary tale against Navy composite-hull aspirations.

They didn't believe that at the Navy either. They thought they were going to build all-composite ships in the future, and then they built some and they found they didn't work so well. They found the modulus of steel had a certain advantage when you made big things. That's the old story of the Visby, the Swedish corvette, the world's largest composite ship — you can only take it out in good weather. Don't take it out in a storm. That's good as long as you have an agreement with the other side that they'll only do battle in good weather, right.

All-composite corvette. Insufficient modulus → flexed in North Sea conditions → cracked within ~3 years. Tom's anchor case for "modulus matters, not just weight." Paired with Admiral Grace Hopper's "ship in harbor is safe" line.

The Swedes about twenty years ago scooped the rest of the world by building an all-composite frigate called the Visby. Anybody ever heard of the Visby? It was an all-composite corvette. A corvette is smaller than a frigate. We make frigates — a destroyer is sort of a big ship, but now we've got such high-technology weapons that a destroyer probably has the firepower of an old battleship or more nowadays. So we don't build battleships, they're expensive, they're big, they're just a perfect target. We started building destroyers 25 years ago. Today we build mostly frigates because frigates are small, like small destroyers, half the size of a destroyer. A corvette's even smaller. The Israeli Navy uses lots of corvettes. It's bigger than a PT boat from World War II, but it's not a very big ship. The Swedes built the Visby out of all composites. They wanted to prove they had the technology to build the world's best ship. All the other countries thought, oh, they scooped us. Until they found out that the modulus of all those plastics — the stiffness — was such that the sea-keeping ability, when you go out there in those rough North Sea conditions, the Visby just would flex. So the Visby had a lifetime of about three years before it had so many cracks.