OceanBlue64 said...
Is a soft rail when its is rounded off and a hard rail when it goes to a hard edge? What effect does the different shapes have?
Yep, soft = round, hard = square, especially the bottom edge.
Basically for most purposes you want hard rails at the back for speed.
On trailing edges soft rails create "suck" (negative lift).
Mid to forward rails are better soft for ease of handling, earlier slalom boards had hard rails every where and made them very unforgiving down wind in chop at speed, the forward rail catches the chop in even the smallest spin out, the rail will dig and the board will turn over, sending rider into a catapult. Also gybing is much harder, for a similar reason, the forward rail digs in causing the board to go in a straight line, if you're leaning out, splasho.