Paikea:
If you are talking about a "normal", ballasted 30' keel boat with reasonably healthy design characteristics it would take a real pro to "capsize " it in anything short of a full gale with breaking seas and too much sail up.
A few years back I got a call from a couple in SF The were new owners of a Nordic 40. It was their FIRST sailboat! They were worried about being "knocked down". They were looking for a "manual" for the boat that would give them instructions. They were clearly very new to sailing. After a short chat I made the offhand comment that I could teach them to safely sail the new boat in a day if I flew down. The husband said, 'When do you want to come down?" Oh. Well it would e nice to sail a new 40 on the Bay for a couple of days, I thought. " You pay my expenses and I'll come down on Thursday."
I went down and sailed with them for two days. The owner sailed the boat for a while then I took the helm. I sheeted everything in and hardened up and laid the boat over to about a 26 degree heel angle and of we shot. The husband said, "I didn't know you could do that." When he steered the moment the boat started to heel he luffed up and kept repeating this process. " Don't do that. Just let the boat heel over and get in the groove. Everything will be fine." It was a revelation to this guy, a smart guy. We sailed for two days. I had fun and they learned a lot.
Mostly they learned to have confidence in the boat.
Tilting was OK.