How do large ships survive being tossed and heaved by waves on a rough open sea without breaking apart?
In: Engineering
There are other answers here explaining how they don’t always survive, but none giving you the actual reason why boats CAN handle this treatment and survive.
The answer to this is weight displacement and distribution and is basically the same reason the boat floats in the first place. Namely the boat displaces as much water equal to its weight. When the boat is getting tossed around, it is still displacing as much as it weighs, so it’s not going to sink. Add to this that boat designers design the boat so its balanced to always return to an upright position. When a boat gets tossed upwards and strikes the sea on the way back down, the impact force is evenly spread across the area that impacts the water, and as its displacing its own weight, its no big deal. Imagine throwing a rubber duck into your bath and see how it “bounces” off the water. Basically the same effect.
Likewise, when huge waves wash over the boat and spill all over the decks, the water isn’t actually doing anything other than washing over it and off. The boat is sealed and unless the water gets inside and starts to lower the boats attitude in the water, its not gonna do much. Imagine trying to sink a rubber duck bath toy by pouring water over it. You will never do it. Cut a hole in the top and pour the water inside the duck though and eventually it will sink. And while thousands and thousands of gallons of sea water might weigh a huge amount to me and you, comparitively to the ship, it’s nothing.
So basically, enclosed boat is full of air and displaces the water it sits on. Without being able to overcome that, waves can’t sink the boat. Waves don’t break the boat apart because the energy of the water is quite spead out across the ship.
Having said that, as others pointed out sometimes boats do go down due to severe waves and stormy seas. However this tends to be because the boat is either capsized (Rolled over and unable to right itself), or other mechanical defects that allows water to breach the boat and get inside it, thus making it heavier and heavier till it takes on too much water. In fact in most modern ships, this is 99% the cause of ships going down in rough weather, and it’s now rare when mechanical reasons aren’t counted. A mechanically intact and correctly run ship can take on some truly horrendous seas just fine.
[Here’s a famous example](https://www.youtube.com/watch?v=DMNhO8dKJjQ) of a ship being broken up by heavy (Actually not considered all that bad by most maritimers) seas. The cause? Poor maintenance and an even poorer inspection programme for the ship.
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