Skim Online's Summary

This is undoubtedly the most complete mathematical treatment of skimboarding hydrodynamics ever published.  The author assumes that the board is a round disc with no rocker and that the rider is riding over very shallow water.  Several factors are neglected in order to keep it simple (believe it or not...).  The author makes the shallow water assumption to keep the formulas simple.  He says that the more complicated deep water treatment is "not particularly illuminating" which we can probably take to mean not altogether different.

The end result declares mathematically that the trim of the board is directly proportional to how fast a rider has to be moving relative to the water in order to stay afloat.  Not surprisingly it says that a given rider will be able to maximize his ability to stay afloat by centering his weight over the board (actually, it says something slightly different, but common sense says that if you lean too far forward you dig your rail and stop).

One of the most interesting things that can be taken from the paper is that there is very little dependence on the size of the skimboard in determining how far a rider may travel.  A larger board increases the distance from the rail to the center and therefore modifies the lower speed boundary upwards.  However, the difference between a larger board and a smaller board is almost always less than an inch of the "radius" these days.  That inch represents about 8% of the overall radius and since the relationship is linear, it has only minimal impact.  Much more important than that inch is the riders ability to trim the board properly.  This follows my own experience that a larger board definitely helps you get out further, but there is no substitute for skill.  Then again, sometimes you need that 8%....