From: "Jim Russell" <jimrussel@sympatico.ca> To: "'East Cape Marine Ltd.'" <info@eastcapemarine.com>, "'Power Catamaran List'" <power-catamaran@lists.samurai.com> Subject: RE: [PCW] Air cushion between catamaran hulls Date: Wed, 4 Mar 2009 17:05:08 -0500 The "air cushion" effect that is referred to is really the hull's aerofoil generating aerodynamic Lift & Drag in "close ground proximity or "ground effect". Physical characteristics that affect the contribution of aero Lift of the tunnel hull's aerofoil include - tunnel height, angle of attack, wing aspect ratio (width/chord), plan area of wing, wing thickness (upper deck to tunnel roof), aerofoil shape (camber). The contribution of aerodynamic Lift (as compared to hydrodynamic lift from sponsons) can vary from 10% on heavier hulls or slower velocities to 80% to lighter hulls and high velocities. Jim Russell, P.Eng. AeroMarine Research http://www.aeromarineresearch.com -- The reason your post was delayed is that you're are not subscribed to Power Catamaran List with the email address you're using above. To subscribe, go to <http://www.trawlersandtrawlering.com/forums/powercatamaranli.html> and you're posts will go directly to the list without delay.