Hi! puzzled about the relationship of all three components of topic
Just recently shaped a 5’11 x 20 3/8 x 2 3/4 (15" tail) single behind nose area to double concave to flat at tail. It would be a quad fin setup. got placement and toe in set but puzzled on the relationship between the double concave and the Fin CANT for this board.
Concaves will typically pull your finbox cant in toward the stringer a degree or two depending on the curve and size of the concave. For instance, an FCS fusion 5 degree box installed on the curve of a concave will most likely make the fin cant around 4 degrees (measured perpendicularly to the stringer’s flat plane). We mostly use 9 degree Fusions for concave bottoms that interact with the fin area…
ProBox allows you to change the cant inserts and experiement so it’s not critical what cant you choose in relation to concave when designing the board.
Futures has cant built into the fins, the box has no cant. So it is important (and a little more difficult in a concave) to set the true cant you want since it is hard to measure the angle from a concave surface.
In most cases for any fin system just set it close and forget it. You’ll never know the difference, there’re so many variables going on in a surfboard and wave interaction there’s no use trying to be dead on with any dimension.
In addition, a Vee bottom will kick the finbox cant out a degree or 2 towards the rail relative to the perpendicular plane…
~Brian
Great insight! thanks! that info truly helps… =)