When I started on this forum almost two years ago, I had never even heard of hull speed. Now I think I understand it on a basic level. It seems the main parameter required to determine hull speed is the length of the boat at the water line. If I understand correctly, the width and shape of the hull affect it, but not very much. That being said, does a dual hull boat (like a cat or a pontoon boat) have a similar hull speed to a single hull boat? I am guessing yes from a practical experience point of view, but how is that explained in theory? I would think a pontoon would be more efficient than a full hull at any given speed, but then, of course, the motor has to drive two of them through the water.
My only practical example is my 24' pontoon boat. It's max speed is about 5.5 knots using 4KW (a Torqeedo Cruise 4). A more typical crusing speed is 3.5 knots which requires 1200 to 1500 Watts.
The standard formula for hull speed says my boat's hull speed should be a little over 6.5 knots. So, 4KW gives me about 85% of hull speed. From the many posts I have read here, that seems about right.
So, back to my question, from a theoretical point of view, does each of my pontoons have a hull speed higher than the standard formula would indicate but after figuring in two of them, the hull speed is similar to that of a full hull boat?
Pat
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