How slight is a concave and what is the general objective when creating one? Do you include the stringer in the depression? How does a vee seperate itself from a concave?
Shallow concave is about 1/8" deep. It includes the stringer (except maybe through the fins, but the stringer should be shaped down first, then add a little double, which makes the stringer seem to be sticking up).
Deep concave is about 1/4" or more.
Concaves may intuitively seem to give lift although they actually ride lower in the water than, say, a flat bottom or a shallow con-bottom.
The general objective for this contour seems to be two-fold.
First the concave makes the board feel like it is retaining some energy for a moment that you can exhert when coming out of a compressive move like a bottom turn.
Second, the concave definitely gives the board more bite, which can allow a rider to apply some physical input and translate it into forward progression.
The vee that is seen in most concave bottoms is actually the middle portion of a double concave which is embedded in the greater single concave (ie. triple concave, or single-to-double). These contours usually involve most of the bottom but not always.
Another variation is a single concave that goes from the nose to the fins, where the single concave quickly diminishes and the bottom goes momentarily flat, then rapidly goes into a vee off the tail. This works especially well on swallowtails and wider-tailed boards…
I just finished a reverse v to single concave with a flat transition between the two. Thought about nudging the concave up into the v as a double, but went with the simpler configuration the first time around. The v is deepest around the nose and chest, then flattens out mid board, then progresses into single concave through the tail.
Mr. OregonPeter,
Those are great bottoms, esp in juice conditions (which I am sure you’ve got). Very carvy and very good control. The doubles transitioning from the vee to the con would not hurt (when very subtle). Seen a lot of Simon Anderson’s and Maurice Cole’s shapes with this bottom in the Mentawais and they seem to go unreal.
Very important how that single progresses off the tail as they have a tendency to “lock up” if they don’t relieve the energy trapped by the front fins. Definitely worthwhile to dump out the con after is passes the front fins and goes toward the tail. This can be done by reducing the con and/or kicking the tail rocker (kick affects drive though).
Try to see the front fins acting as “fences” keeping the pressure in; be sure to let it go somehow after that…