Wondering if anyone has tried this. Over the winter I shaped a 5’8"x20.5" swallow tail small wave thruster. Ive had some amazing sessions on it over the first few months of 2021 in SE NC where I live.
I wanted this board for the bottom end of the wave spectrum up to head high or so. On pretty much every board I’ve shaped (around 15 or so) I’ve done single to double concave as I felt this was something that has been established as a reliable contour setup. For this board I remembered a post I read on here from years back where someone stated “flat is fast”. Makes sense to me so I ran flat under the front foot to a little vee out of the tail.
What happened was a board that was really quick down the line but lacked that “bite” that I feel with similar boards with single to doubles. Very similar to my 14’ flat bottomed Carolina skiff. Hauls ass in a straight line but skips out when you go to turn it at any sort of speed.
So what I’m coming to you guys with is this: has anyone here had the experience of shaping in a concave to an already finished board? I figure it’ll be a lot of unnecessary work but I’m a tinkerer so the time isn’t really an issue. I guess the way I’d accomplish this is to cut out a patch on the bottom under the front foot, shape in a single concave, and reglass. I think this same method could be used to thin out a board that ends up too thick by cutting out the deck and reglassing, which is something I’ve also toyed with. For some reason a shaped blank and finished board can feel totally different under my arm.
(chuckling) You had me with the Carolina Skiff reference. As I have called them in the past, and I used 'em in the shellfish biz, A really good boat… for something that was really meant to be a shoebox. They go sideways real well… and pound? Hooboy. In any event…
Couple of things:
First off, you might want to just build another board identical to this one but with a little concave in it. And you’ll be able to really compare the two, see what’s what. With a reshaped and reglassed board you’ve got other things going on to confuse the issue.
Next, you can modify the existing board, yeah, but try a blast from the past: beaded rails. Sand the rails lightly from the tail to about midway. Tape along the bottom, sticking out . Hotcoat that area, lightly sand, and hotcoat again, build up some resin along the botton corner so that after you pull the tape you can gently sand a harder rail along the bottom, fairing it out but a harder, sharper angle that will grip/hold better. See how you like it, if you don’t then you can sand it off, if you do you can maybe repeat the process if you want for a harder rail still and see how you like that.
I’m with McDing (not his real name) and Doc. Before I’d start ripping off fiberglass, I’d build another board and bench mark them on the same day.
OTOH, I’m a big Greg Griffin fan. Flat is fast. And I don’t want to repeat a thread on concaves and speed, and bottoms, etc, but “bite” is what fins are for. Maybe consider dialing in your fins better. Maybe add a twinzer set or whatever.
Also, I really like experimenting like Doc said. I used Bondo because it stayed in place better while placing it. It is ugly as a final product, but you will see where you placed it as opposed to clear resin. And it doesn’t run.
I remember watching Greg Loehr put bondo all over a board bottom as he experimented. I thought he was crazy at the time. The board looked awful. But he easily developed really good info about what worked what didn’t. Generally speaking, he settled on single concave. I don’t know this for a fact, but I think he did this because every board is different and you really can’t know the optimum placement for fins for every board. The cheat is to enhance bite with a single concave.
One last comment on concaves. In hydraulics and fluid flow, an axiom is that making water change directions comes with a cost called drag. And the often discussed Venturi effect isn’t free either.
I hope you will do some experimenting and report back here. Good luck.
Thank you so much for the ideas guys. I’m going to try a couple different things and will report back. First thing was setting some fcs plugs to run it as a quad. Waiting on waves now.
the bondo idea has the gears in my head turning. It’s cool to hear that Loher experimented in that way
I used to rankle Griffin and his skin was too thin, so he therefore took me too personal. But the philosophy that Mr. Tate has herein stated regarding flat bottom = speed and fins are for bite is certainly correct .