I built one recently to mostly help myself visualize how sail trim worked and how various boat controls like mainsheet and backstay affected sail shapes, various forces and boat performance. It uses a physics-based VPP and I calibrated it against Catalina 36 polar charts, so should be pretty precise!

I plan to integrate the simulator with the sail trim guide I'm building to help people learn.

It's a WIP, but accessible at https://www.sailrhythm.com/

Happy to answer any questions!