Over the last year i've seen quite a few shapers producing boards with concave decks. Experience from my skateboarding days helps me to see how this would have many benefits but are there any draw backs? I'm thinking of shaping a concave deck into my next small wave board but is it as simple as scooping out a bit from the middle? Is there a general concave plan shape and how deep should they be?
Some info from those in the know would be appreciated.
I don’t know a lot about concave decks. But one thing I know is that the reason skateboards have them is for stiffness, wich is not the case for surfboards.
That’s all I know
I do my own thing... It works for me.
I make the "belly" area of the deck @ 3/8" thicker and scoop it out a bit... for where my chest is and my front foot.
My experience with skateboards tells me concave is for control. Old school decks were pretty flat with a mild concave under the front foot, then when the twin-tip boards came out the concave ran the lenght of the deck for riding switch. Riding a flat skateboard vs. one with concave the benefits are immediately obvious.
There are lots of guys doing concave decks on surfboards as well. Stamps, Pavel and many others I can’t think of off the top of my head.
I just sent this picture to my shaper the other day as a reference for my next 5’10" x 21 x 2 3/8 board:
Back in the early 80s I did a lot of concave decks, I did it for the foot ''control'' and to take a little meat out of center. Boards had heaps of volume so losing a little to the concave didn't matter. Getting your feet closer to bottom was also part of my ''theory'' at the time. If you're riding 80s style volume this could still apply.
On modern boards, the thinner profile and foiled rails don't really mesh that well with deck concaves, IMO. We are usually trying to hide a little volume on center rather than taking it out with concave.
Of course, if you like thick rails but don't want too much volume, scooping out the deck makes perfect sense.
Ok sorry, seems like your experience is better than mine 
I started doing concave decks after Bert suggested it and every one since! As I remember… his thought was that with a flat bottom, when the board flexed it would give contour to the bottom?
I like the way it feels when I’m paddling and standing up. I feel more a part of the board. When I trade with someone to let them try my boards I seem to loose my balance quicker on a domed deck board.
But… I like a long board (9-10’6") AND I like to knee paddle so I make them thick (3-31/2") so I do a deep concave and step the nose and tail (S-Deck?)
I’ll see if I can get a pic… OK got one, it’s a profile and you can’t see the concave deck (that’s a tough shot) but you can see the step, sorry. The concave is between the front and rear step. This board is 9’2"x3 1/2" the concave is about 1/2". The rails, I’ve been told, are Brewer’esq? The high point is about 4" in from the rail and slope radically to about 1 1/2" diameter rail at wide point.
And… shaping… I do the concave last, whole board is shaped, deck flat. Then I take two passes down the middle with my planner, then one pass on each side of that, one down the middle one on each side of that, one on each side of that, etc. Till I get the depth I want then go to a fairing board to smooth everything out.
Les
https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/deck_0.JPG
Thanks for the input!
I think this is going to be a case of getting on with it and testing the results. I am hoping that the concave will give me a feeling of being closer to the board and having the edges curved up at my toe and heel maybe more responsive? The only downside i could think of was the reduced volume so i will have to make sure that i start off pretty thick, that and maybe more water on the deck?
Thanks for the heads up on shaping it Les although i'm still a little nervous with my electric planer so i might finish with my surform. Glassing could be interesting...........
Never thought about putting a concave in a surfboarddeck but thinking of it …
I do quite a bit of downhill longboarding and slalom and built my own boards to and there concaves are a major deal…
they are used a bit differently than in the already mentioned twintip skateboard.
nowadays in slalom skateboards you have a heavy concave up front for control since thats where you steer
and a kick at the tail thats sometimes convex to push the rear trucks down so you don´t slide out.
The concave gives you a bigger lever, therefore less power needed to do a turn resulting in more control
there was a domed slalomboard out in the 70`s i think it was the TURNER summerski…way before my time
probably doesn´t help you to much … anyways
in the 1970’s GS waterskates had them, kneeboards and greenough spoons too.
read Bert’s post on how with a flexing perimeter railed composite structure with a concave deck can morph a flat bottom into a concave when you need it. His “Magic Carpet” is an excellent example as is Josh Dowling’s(speedneedle) dual concave rear deck foothold design.
Greater control over you skateboad is the reason for concaves. Flip tricks in particular… heelflips, kickflips are all made possible by the concave in the deck… or at leas much easier for an experienced rider to pull off.
I’ll admit that I have never shaped a concave deck, but am eager to try one. I like the idea of being wedged in when paddling… kinda like if you are lying in the sand and scoop out the sand around you… feels much nicer than a convex surface. This sounds intruiguing to me. I’ve ridden a few paddleboards that have a concave surface area for you to lie on and you could approach that same feeling on a surfbaord.
Performance-wise I am not sure what the advantages are. I don;t plan on trying many kickflips on a surfboard. I guess you could expect an increased leverage on your rail when leaning into a turn. But then again, the water doesn’t know if your deck is concave or not, it’s still providing a base for your rail to slide through regardless of it;s shape. I would think that it would take less pressure to be put on the rail to get it to lay over thus possibly making it feel tighter and more “raily”…
Totally rambling.
I’ll post more when i actually shape and ride one rather than speculate
Drew