Heeling

Back in Ye Olden Days (TM) ships hung sails on masts to catch the wind, so the crew didn't have to row everywhere. As techniques and technology improved, the masts got taller, to provide more sail area, so the ship could go faster. This does create issues, as the longer mast creates more leverage for the wind to tip the ship over (the technical term is heeling). This is mitigated somewhat by the fact that as the ship heels more, the sails present less surface area to the wind, decreasing its force, and, assuming the ship is loaded properly with its heavy cargo down low, gravity will help pull the ship upright as well.

Sometimes, though, a ship will be overloaded, or will be poorly loaded so that there's a lot of weight carried high in the hull, or sometimes the wind is just so strong that it pushes the ship over too far. Once water starts flowing in, it's a lot harder to get the ship to return upright, and many times there isn't even an opportunity to try. The ship just goes down.
I've been poking around trying to work out some factors for how much a ship can heel before capsizing, but there are just so many to take into account that it quickly gets unplayable (not to mention that there are few hard figures to be found on the matter). So rather than get too deep into numbers, I believe I'll fold them all into a general hazard system for sailing ships (later to come), and have it come down to a skill roll for the captain and/or crew of the ship to make to see whether they can shoot along under full sail in high winds or turn turtle and go to the bottom.