Thanks, and I'm glad you're still enjoying it.
I initially worked on getting a physics model that felt reasonable to me, but did not have too much data on actual speeds at different points of sail, and especially when turning. Then I found some more numbers, and players contributed some of their sources, and by tuning various lift and drag parameters it seems to match fairly well. See here: Historical data - A Painted Ocean by Neil Thapen (itch.io)