lostcarpark | Anyone know about solar sails?

Some of you know I'm writing a novel. It's been slow progress since the first intense month. However every so moment I have an "aha!" moment and mentally rewrite a few chapters. I had one such moment yesterday, and a whole bunch ideas came together in a rather cool way.

I've been thinking about solar sails as a means of interstellar travel for years, and would like to feature it as one of the many methods used in the book. What I'm trying to figure out is exactly how fast a sail of a given size could drag a ship of a given mass. I've found a couple of websites which hint at the equations I'd need to use, but I haven't made much headway. So if you understand the maths/physics involved, or you know somebody who does, or you read an interesting website on it, please drop me a note.