Twin-keeled boats are quite popular in southern England and northern France because of the many harbors that dry out at low tide. The wind tends to be fairly strong, so the increased drag can be overcome by the sails fairly easily, to provide acceptable performance. (These are NOT high-performance racing boats, but generally smaller weekend cruiser types.) Besides the English builders, Jeanneau, Beneteau and Kirie have all made many models with twin keels. A newer variation is a double -in-line keel that is supposed to offer shallow draft with less better performance than the twin-keel design. I believe Etap makes these. With so many possible builders, if you're still trying to identify your boat's model or manufacturer, we're going to need a picture.