Clean surface is fast surface... not bad. Let's take it this way: planning is due to hydrodynamic lift. Water is pushed down as the board goes forward. Flat or concave are more effcient than vee shapes because they trap water better. But air is also trapped with water. A wetted hull will roll over air bubbles with minimum interaction while a non wetted hull will stay in touch with air longer and "drag" the bubbles. However at some stage water comes in touch with this hull, otherwise it would not plane. The additional surface energy needs to be taken somewhere. As we can assume the water/air ratio under the hull to be consistent, this energy is given back somewhere. I tend to believe it causes additional spray. Does it make a significant difference? I'm not sure.
Last edited by Farlo; 23rd May 2009 at 12:38 AM.