Why doesn’t the rail catch? If you look at almost any surfing photo, you will notice that the flow is almost always outward from under the board. The flow on the wave side rail continues up the face of the wave, and the flow on the shore side rail has been reversed in the spray root region. You’ll also notice the rail shape above the bottom is very conventional. You’ll only catch a rail on a Camber Surfboard under the same circumstances you would catch a rail on a conventional board.
Does the angle of the rail create more “grip?” The bottom contour along the rail provides a bit more force drawing the board up the face of the wave. This enables the rider to trim the nose down a little, generating more speed while maintaining a similar line on the wave.
Why is the bottom flat across the center? It turns out the most effective way to increase bottom pressure and, therefore, lift is to concentrate the curvature of the bottom out near the rail.
Does it ride differently? The surfer should notice greater speed, especially going down the line, when the transverse flow is the greatest. Some riders mention upon first riding one, that it feels like the nose wants to lift. That is because the whole rail is providing lift whereas a conventional shortboard has a shallow concave with a low exit angle typically placed under the rider’s back foot and slightly forward. On a Camber Surfboard, the entire rail lifts. Speed is generated when the rider leans forward into a turn and pushes back. The harder the rider pushes, the faster the board will go. Lean forward and in!
Does the board feel stiffer? A flap at the back of an airfoil slows down the flow on the bottom of the foil, and increases pressure across the entire bottom surface of the airfoil. The same thing happens on the bottom of a Camber Surfboard. The increased pressure across the entire bottom makes a Camber Surfboard feel like it is pushing back harder as the surfer rolls into a turn. Because a Camber Surfboard more efficiently generates bottom pressure and force that opposes the weight or G forces of the rider in a turn, you carry more speed through the turn. The harder the surfer pushes, the harder the board will push back, and more speed that will be generated. Turning up the face is actually easier because the entire rail is lifting the surfer up the wave.
Isn’t a flap on a surfboard bottom slow at top speed because “flaps down” is slow on an airplane once it reaches cruising altitude and speed? The important difference is that the flow across the bottom of a surfboard is moving at angle relative to the centerline of the board. The contour of the rail is designed to slow the transverse flow and increase pressure, not slow the axial flow on the board.