Hello! I am also at the same stage as you. As a general advise, you should do some trials by working on the design of a small portion of the hull until you end up with sth satisfying before contemplating building the whole hull. To be fully honest, at first glance I thought you have designed a steam boat and was surprised that you intended to design a 18th century sail ship. I think, the curve of the hull is too sharp, you should try to you use some curved slopes. Widen the ships by 4 studs would be great as well.