been there, done that
I have a 30' boat. A couple of months ago, I took my boss out. T-storms were isolated - scattered and we had a good clearing to do some nice sailing. Unfortunately, on the lee side of an island (we could not see the wind coming) we nearly had a knock down with full sails. A 35 mph straight line wind came across the beam while we were close hauled and we went over far! The T-storms were surpisingly far away to produce such a gust. . . we are both instrument pilots and considered our location safe.I started the engine right away, and told my crew to let the sheets go and start pulling in sails. Thinking quickly, my boss put the furling line on the winch and was able to get the jib in, but as I was able to power her into the wind, we got overpowered and flattened twice. At one point, the prop sprayed water behind the boat. Yes, the rudder was out of the water and the prop could not grab either - - very scary!! 2 other boats got hit with it badly after us and all we could see/hear was luffing sails, bottom paint, & crew scrambling!I never took the extra seconds to see how far we were heeled, but it must have been at least 45 degrees. I'd guess a bit more.None of this was intentional like you were doing, but I'll repeat what a very experienced cruiser used to tell me: "if you're heeling, you're doing it wrong."