CMC said...
Most people think of concaves and look at them from rail to rail cross ways on the boards bottom. A better way to look at them is lengthways. A concave or vee is a function of the stringer versus the rail line. Imagine taking a board with a lot of rocker and then reducing the rocker down the stringer line only leaving the rail line curved. This creates a flat rockered board when sitting flat on the waters surface (not often in reality) and keeps the curve in the rail line. The flatter rocker creates speed, the curve creates looseness. The increased angle of the bottom due to the concave on the horizontal plane rail to rail also increases the pressure in relation the waters moving across it and creates lift.
A vee bottom is the opposite to the above and is used to control speed rather than create it. That is why guns have vee, to control the speed and to reduce pressure against sinking a rail at high speeds.
Hope this makes sense. My recommendation would be to talk to a designer that has been making surfboards about your next board as the design features above only really work when combined with the right rockers, outlines etc. A lot of board to me look like design features are added for perceived value not in consideration of the way they relate to other factors of design.
cmc is pretty onto it here...
Concave is a must in a surfing sup... But as stated needs to be combined with rocker line, foils and rail lines etc and depths of concave and where to start stop and fade in and out but any good sup shaper should know this, one would think...
I prefer deep concaves in my personal boards and wouldnt shape a board without one then fading out to vee through the fins
