Sail Area to Displacement Ratio... that's... SA/(Volume^(2/3)). Now...make sure where I say displacement to use the weight in pounds, and when I say Volume, use the volume of the  water it displaces. The factor is the density of the water (either fresh or salt). Fun geek homework task is to get a list of your favorite boats or whatever you'd like to compare, and go into Excel, record  all of their prinkers, and calculate out all of these values, and hemm and haww over the resulting charts. Did you ever get Larsson and Eliasson's book? You know what, though, get that book by Dave Gerr that Rachel mentioned.  Now that I've gone through and written all of this... maybe it's better to just look at Ted Brewer's website, which doubtless  wasn't written hastily on a lunch break and didn't comprise the entire bit of naval architecture Ted did in one day, myself  now being a too highly educated drafter at the moment.  http://www.tedbrewer.com/yachtdesign.html  He has a book as well.  That's the most important thing to read right now, with you building that boat. You can start your design career once  you're done doing your building internship. 124