Technical stuff – Performance

The performance of the board when flying is determined by the wings almost exclusively, the efficiency of a wing is expressed as L/D – the Lift:Drag ratio.  The L/D of wings goes from a superb 200:1 in a turbine blade to maybe just 5:1 in a paper airplane – L/D in an airplane is equivalent to the ‘glide path’, that is how far forward it will go for a given drop in altitude.  If an airplane, in still air, has an overall L/D (including the L/D of the body) of 35:1 then it requites 1/35 Th. of its weight in thrust from the engine to fly level and, if the engine stops it will descend one foot for every 35 it goes forward.
It turns out that L/D also equals the slope of the water surface needed to fly any surf rider – if you are dependent on a planing surface, like a surfboard, to provide the lift you’re stuck with only being able to ride water steeper than the miserable L/D of planing surfaces, maybe 5:1, at best 10:1.  This means you are restricted to only the zones of extreme power concentrations in the wave.  But try to visualise having a L/D four times or more greater than that of a normal board and traveling fast over a region of water that has just one foot of fall per 30 or 40 ft – it’s amazing and will open up new vistas in surfing.
A note about speed, lift and wing area – expressing this stuff in old fashioned ‘imperial’ units is remarkably convenient when dealing with wings in water, so that’s what I’ll do.   A wing traveling at 10 feet per second in water and having an area of one square foot, at a coefficient of lift of 1.0 (about 10 deg angle of attack) will generate approx. 100 pounds of lift.  It’s the speed squared that determines the result so at 20 feet per second it will generate 400 pounds of lift and at 30 fps it is capable of 900 lb. etc.
But before this speed is reached the auto-adjusting wings of the wingboard will have reduced their angle of attack to a much lower setting, generating only enough lift as your weight requires and thereby minimising drag.   The faster the better as far as the efficiency of the wing goes.  I don’t know how fast surfers generally travel but the wingboard prefers fast – faster than 30 fps (20 mph) is ideal – at speed, a smaller set of wings will generate ample lift at low drag but will have higher drag when forced to generate that lift at lower speed.