Hello Colin,
Thanks for your comments. I will try to respond to your questioms in order.
The rudders are NACA 6300 series foil shapes. They are the same rudders as used on the ARC22, therefore they appear large in size for a 17ft boat but the large size is needed for reasons already mentioned. To operate in the "drag bucket" of a 6300 series foil the lift coefficient must be small. That means in general terms that the rudders are not working hard. But the rudders on the 17 are working hard going to windward. The time that the rudders can operate in the drag bucket is when the side forces are small and the boat speed is high, at a low lift coefficient. This point of sail is sailing deep downwind with the spinnaker.
I don't think two sets of foils, rudders, are necessary. The ARC17 already has large foils by industry standards. Smaller foils have been tested and that is definately the way not to go.
The design displacement for the ARC17 is 700 pounds. Now 700 pounds displacement for a lake sailing boat and 700 pounds displacement for an ocean sailing boat are two entirely different amounts of free board. You could take a foot off the bow height if the boat was a "small lake only" design. This extra free board for ocean sailing, SE coast of Florida, leads to more passanger carrying capability if that is the way you want to use it. Without the extra passangers, the extra bouyancy keeps the beams up out of the waves in the ocean.
The max hull width is 14 inches (at 2/3rds hull height) and it is the same as the old SC17 hull shape. The max waterline hull width is 12 inches.
This boat with its lower sail plan aspect ratio should be one heck of a beach cat drag racer.
Thanks for the good wishes, Colin.
Bill