Just did a quick search to confirm my faded memory from reading "Chapman's" boating book years ago when my dad had a sailboat. Below is a link that explains it. Looks like in most situations the sailboat has right of way.
I was reminded of a time years ago salmon fishing with my brother in law off of Shilshole on a foggy rainy day with the canvas snapped up and poles sticking out. We drifted into a sailboat race and almost got run over by a 30 footer! Talk about a wake up!!

http://www.boatsafe.com/nauticalknowhow/boating/6_2_b.htm