That's interesting that even up on foils they were slower, but maybe the foils were too small and required too much angle of attack (and thus drag) to get it airborne? Of course if you go with longer foils you also incure more drag...it sure seems to work for the Moths, I wonder why not for the cats.
Weight is one big thing working against the catamaran....it does have twice the hulls...and if you think about it, if you're going to try and spend most of your time airborn, why have two hulls?
Next you have a LOT of power in the rig. The foils have to resist that power that tries to press the leeward hull into the water (and tries to lift the windward hull)..so the lifting force required by the foil increases dramatically because of the lever between the foil and the sail power (beam). As a result, having to lift more weight means the foil has to be larger (or at an extreme angle) and more inefficient. A moth foil doesn't have to deal with but a fraction of the leverage forces since it is mostly in column with the sail drive.
