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  1. #1

    why does surfboard turn?

    anybody know why a surfboard acctually turns whn you step on the rail????
    and now why does more rocker increase the turnability? and just so you know i asked this question shapers and they did not have a clue....
    Last edited by yanis; Aug 1, 2014 at 09:36 PM.

  2. #2
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    Stepping on the rail creates drag or resistance through the water, slowing that portion or side of the board. The opposite side of the board, without that added drag, is moving faster, resulting in a change of direction, or turning, toward the slow side of the board.

  3. #3
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    Quote Originally Posted by DosXX View Post
    Stepping on the rail creates drag or resistance through the water, slowing that portion or side of the board. The opposite side of the board, without that added drag, is moving faster, resulting in a change of direction, or turning, toward the slow side of the board.
    I think you're describing a skid steer.

  4. #4
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    Quote Originally Posted by ClemsonSurf View Post
    I think you're describing a skid steer.
    Hmmmm .... Sounds like a Complete KFC Turns to me....

  5. #5
    ok that makes sense. now why does more rocker increase the turnability? and just so you know i asked this question shapers and they did not have a clue....

  6. #6
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    More rocker means less rail in the water in a turn than a board of equal length that's flatter. Less rail, smaller radius, more turn.

  7. #7
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    Quote Originally Posted by cjtst11 View Post
    More rocker means less rail in the water in a turn than a board of equal length that's flatter. Less rail, smaller radius, more turn.
    I just spoke with the manager of my local Holiday INN Express and he agrees. and just so you know i asked this question to my local shaper and he did not have a clue....

  8. #8
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    Quote Originally Posted by walkingonh2o View Post
    Hmmmm .... Sounds like a Complete KFC Turns to me....
    F'ing priceless!

  9. #9
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    I'll attempt my $.02 and hope its somewhere around correct and if so, you can understand it.

    Basically a surfboard and it's components (buoyancy, volume, bottom contours, fins) are all intended to create lift. And you have to understand that the lift that is being created is up and down from the board and left and right from the fins. Your fins are not intended to create lift that brings you out of the water. Imagine you're on your board and going straight on flat water like being pulled behind a boat or dropping in before taking your bottom turn. The lift is created by the bottom of the board as your board planes over the surface keeping your toes dry and your fins are still creating lift AKA maintaining your straight line they're not fully engaged in the process.

    OK, we're about to make the bottom turn but first think of the last time you ate a watermelon that had seeds. Did you pinch the seed between your fingers and watch it fly away? Hopefully because this will be much easier to understand. Your surfboard is the watermelon seed. You are your thumb and the water is your other finger. You are constantly exerting force on the top of the board while you're riding and I'd assume the water is exerting an equivalent amount of force on the bottom of the board.

    As you begin your turn, your rail and fins become fully engaged with the water. What that means is your fin and rail are trying to push the board into the wave and your body weight (gravity) working with the water under you. The force of your weight and the water are acting as your thumb and forefinger squishing the watermelon seed. Instead of the seed flying your pump or bottom turn generates more speed and you travel up the wave. As you're making your turn you bury your rail and shift your weight to your back foot. This forces your fin's angle of attack to change and it forces more water to move past your fins as you load up your turn and push off to find your next line. Your fins are crucial to turning and the toe, cant, etc. all play a major roll. Imagine if you squeezed the watermelon seed with fins on it (completely imaginary) and just as the seed slipped through it traveled up your finger and up your arm instead of shooting out because the imaginary fins were engaged on your finger. Now an example of when the force your your weight and the water "pushing up" but your fins were not engaged would be when you make the drop and try to get your turn in but the board just slips out from under you and you and the board are airborne in opposite directions for a second. It's never happened to me but I know a guy that knows a guy that it happened to one time.

    I hope that makes sense. As far as more rockered board turning easier think of your board traveling through the water on it's side. The board with more rocker will have much more ability to turn because less of it is in the water than a board with less rocker.

    **This is with all things being constant with the board, no flex from the board or fins on perfect waves with no chop/wind/jellies/tourists/turds/manatees/etc.

  10. #10
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    And another couple of things.

    Rocker shortens your turning radius by shortening the planing surface and rail. More or less how doing a wheelie allows you to turn much harder.

    Your body weight and where you put it in relation to the fin cant will is essentially aiming your watermelon seed. When you're charging a wave your weight is central and probably forward, backside you drop you butt outside the board's area and how the water affects your board as the surfboard tries to catch up to your body. Same on front side as your back but your arms, head and torso hang outside the area of the board.

    Your body and the cant of the fins create the apex of a turn during a bottom turn or carving (I don't think this is explained right but I mean the bottom swing of a pendulum where it would be at it's fastest point). Didn't Erock try to explain the pendulum one time? When you blow out a turn or slip out at the bottom it means your fins let you slip out of the apex of the turn. You can make the apex tighter and tighter as long as everything holds including your speed but at some point your force combined with the force from the water will make one part in the equation fail including rider ability level or equipment.