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  1. #1
    Join Date
    Jul 2012
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    Manahawkin
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    54

    Concave on the bottom of your board .

    . Right now I have this 5'10vert Lib tech water board I been fooling around with . This thing is pretty rugged . I have had this thing get smashed over some shore break in nc this last fall. Not even a scratch . I love to kite surf on it because of the feel of it. But I have been trying to get use to surfing it , but It has a different feel to it . Seems to be loose on the front foot when driving forward . I have changed out the fins , moved them back and forward( option on this board). Put Fcs fins in there . It almost has the same rails , rocker and shape as an Al Merrick proton . Other than the contour of the bottom . The proton has single to double , were as the lib has no concave at all .
    So my question is . So having no concave on this board has loosened it up compared to having concave ?

  2. #2
    Join Date
    Oct 2013
    Location
    Atlantic City
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    1,296

    Thumbs down concaves

    never had a concaved board that went well unless the concaves were soft - real soft. if a shaper
    or intermediate tells you they work, well, let their surfing talent (on that concaved board) be
    the final answer.

  3. #3
    Join Date
    Nov 2009
    Location
    in the grace of the most holy FSM
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    3,067
    Quote Originally Posted by baddy trailerpark View Post
    never had a concaved board that went well unless the concaves were soft - real soft. if a shaper
    or intermediate tells you they work, well, let their surfing talent (on that concaved board) be
    the final answer.

    yea, concaves don't work...


  4. #4
    Join Date
    Nov 2009
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    in the grace of the most holy FSM
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    Quote Originally Posted by surfin View Post
    It almost has the same rails , rocker and shape as an Al Merrick proton . Other than the contour of the bottom .
    in other words, it's a basic hpsb, but made by libtech instead of ci.


    Quote Originally Posted by surfin View Post
    The proton has single to double
    not true...the proton has a very significant single concave running all the way through the board.


    Quote Originally Posted by surfin View Post
    So my question is . So having no concave on this board has loosened it up compared to having concave ?
    i'm assuming that your previous board was a proton, since that's what you referenced. the combo of extreme continuous rocker throughout the length of the proton, combo'd w/ the deep single concave, makes for a board very much designed for aggressive, in-the-pocket surfing in good or great waves. it's not an "everyday" type of board. the libtech, while maintaining a relatively high rocker, is actually fairly full-railed & full(ish) bodied, based on the dimensions from their website. that, combined w/ the flat bottom, makes for a board that is going to seem looser.

    of course, if you could be a bit more specific in what you mean by, "looser on the front foot when driving forward," that'd be really helpful.

  5. #5
    Join Date
    Nov 2013
    Location
    East Coast
    Posts
    321
    Concave is a very useful feature on a surfboard. Single concave in the front of the board will initially bring speed. When it fades back to the double concave toward the tail it creates better lift and also gives some direction keeping.

    It allows water to flow through the contours of the board to naturally give you some speed and helps the rider calculate/predict the board’s abilities in various conditions.

    When kite boarding you have a source of power constantly pulling you. This makes concave less important overall, as you do not need to generate lots of speed from the wave.

    As far as surfing this board and it being loose on the front foot – when you have a board that is relatively flat throughout the shape, and you lean on the front foot, it takes a lot of stress off the fins and makes your pivot point slightly forward of the fins. What this does is make your board a little better for the small days hacking off the top and spinning 360’s. What you give up with no concave? Speed and overall momentum will be most of the sacrifice.

    It will be difficult, though not impossible, to pull huge bottom turns and round house cut backs. If you are a power surfer you may enjoy this board while surfing for the mid wave range but in head high plus you ay struggle a little bit with holding your line. Also if you get into a steep pit, you may be wishing you had some concave in the back toward the fins.

    On a side note to popular boards and their specific concaves – They have developed a specific set of contours based on performance, rider feedback, and computer calculations to make their boards describable. What I mean by that is when Al Merrick or AJW makes a board, they say it can do certain things because it “Should” be able to based on testing and reported results.

    Hope this helps you out a little bit.

  6. #6
    Join Date
    Aug 2009
    Location
    Monmouth Beach, NJ
    Posts
    2,412
    Concaves are the standard on most surfboards today. They're a proven design feature that do a number of things... much of which has been said in the above posts. They flatten the rocker down the middle of the board, while maintaining curve along the rail line. They create lift by helping to capture the energy of the water moving up the face of the wave, and help direct the flow of water out the back of the board, rather than across the bottom and out the rail, which also helps facilitate lift generated by the fins. All of this translates into generating speed.

    But another thing concaves do is slightly stiffen the board, by adding structural support feature. This is a pretty complicated topic, but simply put... features like concaves, bottom channels, domed decks and rail channels do the same thing. This is where materials and design have to work together... some materials are stiffer, and if you use them, you can get some stiffness back in the absence of concaves or other design features that reduce flex. Lib Tech supposedly uses pretty exotic materials, and that's their claim to fame. All of that toughness comes at a price... it creates a stiff board. So my guess is they're making up the difference where they can... design. Flat bottoms, flat decks, plenty of rocker throughout... all these things get some flex back, but the feel will be completely different than what you're used to.
    Last edited by LBCrew; Jan 19, 2014 at 01:24 PM.

  7. #7
    Join Date
    Jun 2013
    Location
    Singer Island
    Posts
    1,112
    My shaper friend, who specializes in small hpsb designs for aggro surfing, and hydrofoil shapes for tow ins explained it to me like this: The opposite of concave is vee. If you have lots of vee in the back, the board goes rail to rail real easy. Concave makes the board stick to the wave going rail to rail. It facilitates forward movement, not lateral motion. A single to double concave gives you the benefits of concave forward speed, and also allows for some vee in the tail which loosens it up a bit on smaller waves. On big hollow waves concave works great for the speed you need to make the wave. If you put channels in you board it really gives it forward speed, but it's a pain in the ass and he will only do channels for himself.

  8. #8
    Join Date
    Oct 2013
    Location
    Atlantic City
    Posts
    1,296

    Thumbs down don't get me wrong; i want concaves to work.

    so a photo of a well lit/centered/focused rider falling backwards for a photog is proof?
    got anything better?

  9. #9
    Join Date
    Apr 2013
    Location
    highlands, nj
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    21
    I have a 5-8 Walden fish with fcs thruster set up, fins set up similar to yours with 3 slots, move up or down according to wave size. Its has a set up that looks like an exaggerated concave till you get about 4 inches to the rail where it flattens out till the rail, seemingly killing the concave idea. Its a really fun mush wave board but on anything stomach and up sized sets its way too loose, which I never thought would be an issue. Anyway if I put in keel big twinnie set up with middle plugs open the thing is super loose, turns way easily but doesn't hold the rail in any power. So most of the time I use it in thruster set up with medium fins. Its a really fun board and when im not surfing well with my board (a thinner copy of thr hypto krypto) I take the Walden out to have fun and throw skatey turns. Sorry, my mind wanders, just wanted to share that my Walden looks cool but handles strangely at times because of the weird concave and rails. I will post a picture when I get home, maybe one of you dudes could enlighten me as to the objective of the Walden's silly concave and rails.

  10. #10
    Join Date
    Apr 2013
    Location
    highlands, nj
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    21
    WaldenConcave1.jpgWaldenConcave2.jpg

    Here's the pics of the aforementioned Walden with concave that flattens to wide flat rails. It's a great board, but oh so loose, which I imagine was Walden's objective. Any ideas?