Justin,
I live in Annapolis and keep my boat at Jabin's on Back Creek. I forget where Fairwinds is...on the Magothy, I think? Anyhow, my boat
WITH good fresh bottom paint (Micron CSC) gets slimy in a week on Back Creek. If I didn't take it out every 6-10 days or so and run it at 20 knts to scrub everything off, it would be a total mess in 2 weeks. And that's WITH bottom paint. Without bottom paint, I can't imagine how clogged up and slimy it would get in short order.
Now, if you're on the Magothy, it might be a little less bad up there, but not much. If you keep it in the water w/ bare gelcoat, no paint, you'd have to be cleaning it thoroughly every 3-4 days, in my opinion.
And unfortunately, bottom painting a boat for the first time is an expensive, fairly challenging project best left to the pro's. To do it right, you've got to de-wax the gelcoat, sand everything with at least 80 grit, put on a two-part barrier coat, and then finally 1-2 coats of the antifouling paint.
Regarding canvas of any kind, there's one place that can't be beat: ACYC in Annapolis. Ask for Dan. They are really good.
http://annapolis-custom-yacht-canvas.com/
Good luck,
Rob