airsail said...
The BWS Drifter and the Slinshot Celeritas both use the large concave, probably others too that I haven't seen.
Probably an easy thing to do when CNC shaped, takes more effort when hand shaping. Just wondered if it was worth the effort, flat is pretty easy.
Agree that the concave may help reduce the requirement for fin size, thus less drag. And the concave would have a similar effect to a slight V, smoothing out the slap of the nose, we used a slight V on sailboards for this reason.
I guess it is worth a try, blanks are pretty cheap. I am finding production boards are too heavy for jumps (strapless), they have to be or they would break too often.
Shaping them into the bottom by hand isn't that hard either (though does take a bit of practice I guess). Here is how I do it though there are likely hundreds of different approaches get your boards flat and true across the bottom, then take your planer on a light cut and run it down the guts a few times starting at the middle (lengthwise) and then progress each cut out towards the ends, if your good with a planer you can then blend this out to the rails with that otherwise get the surform and sandpaper out (try not to sand too far out onto the rail until you are down to you finer grades).
On a flat day grab a board with flat or V bottom and then one with concave and push them both along, have a look at the front where the water does and doesn't accumulate (get less of this with concave - my theory is this translates to early planing) then look at the tail where water releases you'll find the water sucks up more into the concave and follows the rocker CL more (my theory is this is where better hold/smoother ride comes from). The concave also will tend to accentuate the angle between the bottom and the first rail tangent a little (less snappy as SQ said)
2c
^^^
