From this (very good) FT article https://www.ft.com/content/171c92ec-0a44-4dc5-acab-81ee2620d3c1 https://www.ft.com/content/171c92ec-0a44-4dc5-acab-81ee2620d...

From this (very good) FT article https://www.ft.com/content/171c92ec-0a44-4dc5-acab-81ee2620d3c1 https://www.ft.com/content/171c92ec-0a44-4dc5-acab-81ee2620d... "But the specific engineering of container ships mean that they can’t get longer; they have to get wider. An oil tanker is a shoe box with a lid: hull on the bottom, oil in the middle, deck on top. But a container ship is a shoebox without a lid: hull on the bottom, then containers all the way up. It’s not as strong without the lid. There are definitely hydrodynamic forces in the open ocean, it’s just that the ocean is usually in charge of them. And the biggest stress on a ship’s hull in heavy weather happens along the longitudinal bending moment — lengthwise, between the bow and the stern. The longer a ship gets, the worse the stress gets when a wave pushes up in the wrong place. As far as length goes for container ships, “we are at the limitations of welding and steel quality,” says Lataire. “I will not say that it is impossible to weld thicker plates, but in a way this is the economic limit.”