[yardie]

I've actually seen one of these at sea. Not this particular one but a similar autonomous vessel. Large swells aren't a problem. If it floats a swell will pass under it. Breaking swells are a concern and usually occur under gale force winds.

A boat has a displacement that is less than water. Which is how it floats. A small weighted bulb in the keel keeps everything pointing upright. You can mitigate the forces on a sail through 2 ways: heeling is when the entire boat leans to one side, heading up is pointing the wing sail into the wind.

Wingsails are pretty well understood and used extensively in racing. Volvo Ocean Racing (VOR) and America's Cup are 2 examples.

[cromulent]

Back when I was a kid sailing dinghies, we did a competition on the lake of the designer of Miss Nylex. An early and primitive wing sail design, it still kicked ass in high winds and could apparently tow a waterskier.

https://en.wikipedia.org/wiki/Miss_Nylex_catamaran

[__aeneas]

Nice, thank you for taking the time to explain this!