I trust that you have taken Pars advice by consulting John Gardners book. The Banks dory is capable of sailing fairly well but it can not tolerate too much sail or too high a sail. A lug rig or a peak sprit rig will likely be the best choice. The general idea is to keep the center of area low.
The dory that you have built has the advantage of easy adjustment of fore/aft mast position. Once you put the centerboard case or the dagger board case in place it becomes a fixed entity. Luckily the mast is movable with only minor modifications.
The location of the sailing rig parts are subject to experimentation but you can get into the ball park by using some fairly simple calculations. First make your best estimate of the location of the sail center of effort. That'll be somewhere aft of the mast of course. Now make an informed estimate of the center of lateral resistance of the hull and board. You may want to fiddle the locationof the board in the process of these calculations. Let the center of lateral resistance, the CLR, fall somewhere in the neighborhood of five to eight percent of the waterline forward, not aft, of the center of sail effort (CE). That is counter intuitive but that is the way that it usually works out.
After you try the boat under sail, you will have determined whether weather helm or lee helm is in effect. You will want some weather helm, not much but enough to feel in the tiller when going to windward. Lee helm is a no no. Now you will know whether to move the mast or not. Keep in mind that the Banks type is cranky when heeled. Very much heel and the boat will want to steer itself despite rudder input. As a matter of fact you can steer one of these boats by merely heeling it one way or the other.
The cypress boat is going to be heavy by todays standards. Cypress is a magnificent wood but it is a thirsty wood. It will "take up" some weight if you leave the boat in the water for any but the shortest time intervals. I suggest that you epoxy saturate the cypress to keep it from taking up more water that you'd like. If left in the water for long periods of time, it can easily take up half its weight in water soakage unless you head that soakage off at the pass.
Keep us informed about your progress. Your dory is an interesting project.
