He proposed a doubling of wave drag with increasing speed over the wave velocity (“Now, you can easily double 15% and have the beach cat hardly notice much difference”). Do we really know this number? We do not know whether it actually increases by a factor of 5 at 20 knots... ... It has been proposed that wave drag is of similar magnitude as viscous drag in kayaks already at 7 knots!
We don't know this number, because we can measure only the total drag, but we can calculate a drag break down. Wave drag and viscous drag are plotted in this two diagrams: http://www.catsailor.com/gallery/thumbnails.php?album=lastupby&uid=230 Please note, that the speed is in m/s which is about 0.5m/s = 1kts. I selected a scale to unrealistic high speeds, just to show the behaviour at high speeds. Also note that only wave and viscous drag is shown, but no induced drag. And the displacement, pitch and heeling attitude is constant over speed in this calculation. The method used is called "michlet" and is free available. You can see, the higher the speed, the lower the wave drag ratio. That is because after a certain speed, the wave drag is more or less constant, while the viscous (friction) drag raises and raises.
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When it comes to hydrodynamics of hulls and foils, a lot is empirically derived knowledge rather than formulas. We need more empirical data.
There is nothing mystical about hydrodynamics. A lot of knowledge is available for free. However your skills has to be trained to use it, it is sometimes difficult to understand.
Finally even if you can predict the drag of the boat, it is a different job to optimise a boat, which requires interdisciplinary skills. A homebuilder can still hit the right design to achieve high speeds and give boat development a new momentum, without any CFD calculation and experts. However the probability...
Your catamarans speed is limited by drag and sail power at light winds, by capsizing at strong winds and up wind courses and by pitchpoling at strong winds on the other courses. So yes, foils or ballast tanks may help on certain courses and conditions.
