I’ve been drawing up a new shape for the rudder. After discussion with Gav it looks like a deeper, narrower rudder will be better than the one drawn. But not too deep and narrow or it will stall the boat. Quite how a “stall” manifests itself on a boat I’m not sure, but I guess it causes unnecessary drag and slows the boat.
The issue with the rudder as it stands is that any significant crew weight forward will lift the blade out of the water. This is how the Patí Català tacks -though it doesn’t have a rudder- the helmsman's wieght lifts the stern out of the water, the hull pivots on the bows and the force in the sail pushes the stern round. Neat. But I think I’ll stick with the traditional method on my Trow I don’t want to inadvertently tack every time I go forward to get a beer out of the ice-box.
Rudder design is not an exact science, at least not without a mega computer, so it will be a question of trail and error. Gav’s given me some numbers,
Drawing up the shape made me think though—how much of design is an exact science? How many “easy-to-open” milk cartons are patently design failures? And does anybody market a soy sauce bottle that doesn’t slosh sauce over the food then drip incontinently over the table?