Last week I dried out on a concrete pad with posts. I have a shallow draft and the rudder is almost the same depth as the keel. I had a line on the stern holding the stern up in case, but the rudder took some weight. The fore water tank was empty and the stern one nearly full and the fuel tank half full. The question is, if the stern water tank was empty would there be no weight on the rudder? If I stopped the boat just short of the concrete with the rudder hanging over the edge of the sill, would the stern line/cleat take a great deal of strain? What is the design balance fore and aft? Is there a design specification manual?
