At the speeds sailboats are operating, I think the drag of the winglet would be far larger then the pressure leak it eventually might stop. The added weight that far up would not do much good for pitching and sideways stability either.

Also, sails and wings are not directly comparable. AoA for a sail is at best 25-30degrees whereas a wing has an Aoa of about 1 degree. The aspect ratio is also way off. All due to the constraints of the different environments the two crafts operate in.


Just my opinion..