Gary Stavrou could get a degree in Naval Architecture or 40+ years of design experience. Failing that he needs to understand that a lot of the formulas that are applied in naval architecture [as in mechanics and many branches of physics] are empirically based. Froudes Law is a mathematical expression based on a set of observations made by Froude of the performance of existing boats . The number that is under consideration here is the Displacement/length [please do stop calling it weight!] ratio. Basically this describes the observed performance of hulls of varying displacements. A higher value for this ratio tells a designer that this boat will be slower than one with a lower displacement/length ratio. ie: more displacement on the same length = slower boat, or a boat that takes more power to push. The actual physics involved is immaterial it is an observed "fact". In his book "The Physics Of Sailing" H.F.Kay says "Also boats of greater displacement will, for any similar wavemaking condition, show greater hull drag simply because a greater volume of water is displaced". It just takes more energy to move more water. Of course this is not the only number to be considered when designing a boat. There are a large number of variables and the interactions are a lot more complex than Mr. Stavrou ever dreamed. Regards, Malcolm Tennant. ARINA MA Malcolm Tennant Multihull Design Ltd e-mail malcolm@tennantdesign.co.nz www.tennantdesign.co.nz www.catdesigners.com