sail size?

Question
I am just beginning to get into windsurfing. I just purchased an old O'brian board from a guy I met at an auction, who didn't really know what it was. Unfortunately I am only slightly ahead of him. I know what it is but I don't know what I really need for my area. I live in Kalispell, Montana near Flathead lake. We get 15 - 20 mph winds, and I am wondering how big of a sail I need to get around quickly yet still be good to handle for a beginner. Any help would be great.

Thanks, Excited Novice

Answer
Hi,
I would need to know what size board it is to give you an accurate answer.  Obrian boards are very old.  The older the board the more user unfriendly it tends to be so be aware it may take you much longer to learn on older equipment.  Older equipment tends to be much heavier so the frustration quotient is much higher.  I don't want to put a damper on your enthusiasm but without knowing this you may get turned off really fast.  The equipment made in the last 10 years or so is much more user friendly and easier to learn on. Your best bet to learn quickly would be to locate a local windsurf shop and get a lesson on their new equipment.