first time post: did some searches and found just enough info to peak my interest on this idea.
keep in mind that i am not a shaper, but like anyone, am always contemplating equipment in this era of so many options.
so some basic principles im basing my asumptions on. more rocker = better turning but slower. less rocker = harder turning but faster.
so it seems like everyone would love to get both.
people have been experimenting with bottom concaves and vees for along time. most of these experiments seem to focus on water flow and stuff that is probably too complicated to be analyzed effectively (at least by me) on the other hand it does seem like bottom concaves could be used to try to get the best of both worlds of rocker (flat-fast and rockered-loose). starting with a baseline rockered board. putting concave under the front foot, would tend to flatten out the rocker at the stringer without effecting the rocker at the rails. vee placed in the tail section would seem to increase rocker at the rail without increasing rocker at the stringer.
so how would this behave in various conditions.
going straight (on rail in the pocket) - water should be able to take a relatively straight line from rail in contact with water back diagonally and troough fin box. the wather will be travelling not horizontal in relation to board but slightly up (i know this is confusing) so the rail will have a sharper attack to the face of the wave - this seems good
turning (on rail) - rail rocker is maximized
going straight through flats - the flat rocker through middle of board will hopefully provide extra planing for maximum speed.
i have a feeling that these concepts are fairly basic, but id like to hear some comment on if this thinking is correct, who has experimented with these conecpts, how far it can be taken and where does it go next.
The concave(s) help more when planing and coming out of turns, when you push on the front foot (gas pedal) and it helps acceleration because of the flatter rocker in the concave.
Vee does increase the tail rail rocker for turns (slightly) without increasing the whole tail rocker, and it helps going rail to rail a little in wider tails and faster waves. But with a narrow tail and slower waves it really isn’t necessary. It can even tend to bog a little in slower waves because the tail will sit down in the water more and not plane as well. This also can offset the lifting effect of high cant fins, or multi-foils like the vector 3/2s.
There really is no one right answer because of so many other contributing factors that those two elements can compliment, offset, or work against. I’m sure Bill, Greg, Bert, or some of the other big dawgs in here can give a much better answer than I can.
“it helps acceleration because of the flatter rocker in the concave.”
This may be part of it but Dale Solomonson told me he has done extensive experiments altering bottom contours on a given board by adding/subracting Bondo or some such and even starting w/ flat rocker as in a flexspoon and adding concave which actually creates reverse rocker, it still adds noticable speed. What to make of this I don’t know as far as theory goes…
I read something about this in one of the older posts…to paraphrase:
The surfboard gets its speed from the amount of water rushing underneath it the more ‘hard’ water that’s underneath you, the faster you go (i think its like that physics idea of mass and velocity relationship, squeezing the garden hose comes to mind) . So by using a concave, you actually force water through the ‘hull’ of the surfboard and increasing the water going underneath the board. This helps not just with speed but also lifting the board for flatter sections. Also, the concaves are helpful not just for when you are riding the waves but increasing your paddling efficiency as it flattens out the rocker.
Ok i think that was the gist of what I read…I hope someone can correct me if I’m wrong.