CaptnWil: >>That does not change the thrust of the post. Yes, the basic premise is the same. In order to exceed theoretical hull speed, enough additional power must be applied to have the boat climb over her boat wave. >>Full displacement vessels of good design can be driven well above hull >>speed with acceptable fuel consumption when compared to other vessels at >>comparable S/L ratios. I suspect the top speed is somewhere around S/L = >>1.65. I really hesitate to use words like "top speed". Obviously if you belayed a tow line between a full displacement boat and the QE2 (as a horrible example) you would go as fast as she did.... That is, until she ran aground again. ;-) The same would apply in the case of providing enough on-board power, but efficiency does suffer. Al Golden / International Marine Insurance Services