reinventing the wheel

Discussion in 'Hydrodynamics and Aerodynamics' started by nusantara, May 2, 2016.

  1. nusantara
    Joined: May 2016
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    nusantara New Member

    Aloha Gang

    Could you all please help us.

    Could you all share the basics of different planing hull features so to improve big wave surfboard performance. Most are in agreement that currently the equipment out there is largely insufficient to do the job.


    I believe the largest of problems in the current designs is that to paddle fast enough to catch large swells requires a surfboard with quite a lot of volume.(in the order of 10'6" long , 21 " wide, and 3.5" thick). I believe the largest problem with this is that while falling down a steep wave face with some surface bump the 3" thick rails and excessive width of these 'gun' surfboards are too buoyant for the riders to" bury" or 'knife" quickly and deeply. The rail cutting into the wave face is where the rider transfers his effort to initiate that crucial first turn that redirects us perpendicularly to the direction of the wave.If performed around mid way down the wave face we are often able to keep that rail buried and "trim" harness the speed of the wave however as long and fast she goes in that mid face trim.
    Another problem with current designs is that usually the small surface bump encountered while planing on our mostly flat bottom boards makes for a challenging high speed chattery bumpy feel, commonly making the rider effort to barely hold on , and therefore missing the time to bury that rail so crucial to success . I wonder if there is a way to make all that board forward of the front foot of the rider to pierce the bump a bit more therefore damping the "chatter". without creating a design that is too slow or tracking.

    Enormously larger and faster waves then those currently paddled into are ridden vey successfully with the use of jet skis for initial propulsion (instead of paddling) and a "TOW surfboard. These boards are only 6 ' long ,16"wide,and 1" thick. They are weighted to 25 lbs have windsurfer like foot straps bindings, and allow for precision turning at high speed making the job at hand some what easy.(to the point that a beginner tow surfer can successfully ride what a professional surfer can not by paddling.) tow boards volume is so low it could never be paddled

    My obvious conclusion is to use the traditional volume but go longer so that width and thickness may be trimmed. This is concept is yet to be tested For that reason I am here at the forum trying to understand more about planing hull types so that we may incorporate additional features providing control and speed.

    I am trying to keep the volume known needed to paddle fast for the big ones but trim rail thickness with some shape of channel dug out of the rail to reduce volume on that important rail.That is one of the lines of thought I had , but please if anyone can think of something outside "my box" please do tell?

    Also so I don't assume anything incorrect , I would like to list below some surfboard design features and their characteristics according to our ignorant surfers/shaper collaboration and not hydrodynamic fact.

    Please fill in the blanks, elaborate, and correct anything that looks suspect below.

    wide point forward = better paddle and drive (always positive forward feel?)

    wide point further back more maneuverable

    rocker=flater is faster , but more rocker more maneuverable

    panel vee = stability but sacrifice speed?

    rolled vee= even more stability but more speed reduction then panel vee ?

    hard chine = (on bottom edge of rail ) = more directional holding stability

    concave bottoms=added speed when under powered/less stability at speed/sometimes sticking/tracking to water feel.

    strakes or channels = added control and drive/ but too much cavitation and loss of control in choppy conditions?

    surfboard fins
    single foiled =faster, livelier
    double foiled=more control

    well sorry to ramble ..thats enough for the first post..

    mahalo justin
     
  2. gonzo
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    gonzo Senior Member

    Traditionally the "elephant gun" boards were rather thin, narrow and long. They didn't have a huge amount of volume. On the other hand, if you want volume, there is no need to have thick rounded edges. They can be sharp on the bottom and have a sharp taper. Another design feature is a concave bottom on the front area to make the edges sharper. I think Joey Cabell was the first to come up with it.
     
  3. Barry
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    Barry Senior Member

    http://www.onthesnow.ca/news/a/27567/ski-technology-explainer-

    Attached are some design concepts that the downhill ski industry has seen in recent years.

    Camber changes and the sidecut might be options to consider for increased maneuverability. Additionally, most new downhill skis are shorter and wider than the skis from the 80's and 90's.

    For planing hulls, to increase lift, it is more effective to increase the width instead of the length at the speeds that you will be travelling at, So perhaps, a shorter wider board might be a consideration. The shorter wider board would be quicker to turn and when you shift your weight to one side, the edge would cut in a little deeper for better control

    With a flat bottom surface, lift strakes would have to be turned downward to gain additional lift but will resist turning
     
  4. Barry
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    Barry Senior Member

  5. nusantara
    Joined: May 2016
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    nusantara New Member

    thank you fellows for the info.

    great stuff on wind and snow barry

    gonzo i actually lived kauai for 15 years and had seen cabells' white ghost in cow dens shop...wish i would have paid more attention to it then...all i can remember was how thick it was.
     
  6. HJS
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    HJS Member

    A different way of thinking

    I would open up for a different way of thinking. Rather than try to create one shape that can handle everything so think about creating two forms and put them together.

    This would correspond to what Phil Bolger did with his step sharpie, an optimized hull for planing under a hull for displacement and static stability. It is the same thinking that I have in my boats with double chine, two in one.

    js
     
  7. gonzo
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    gonzo Senior Member

    Is Joey still around? You could always ask him. I got to surf a couple of boards he made and the shape was very sophisticated. Small details put them ahead of the competition.
     
  8. Doug Lord
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    Doug Lord Flight Ready

    Would diagonal fins just aft of the middle of the board help?

    [​IMG]
     
  9. nusantara
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    nusantara New Member

    yes doug lord

    actually what i was thinking was some type of channel or tunnel to take area out of the rail that also would create an appendage of sorts with a hard edge that would aide in engagement of the rail.
     
  10. gonzo
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    gonzo Senior Member

    That is what the convex bottoms do. They've been around since at leas the late 60's. You got to get used to how hard they bite and turn hard.
     
  11. nusantara
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    nusantara New Member

    Gonzo you mean like vee bottom , or rolled vee?
    Convex bottom?
     
  12. gonzo
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    gonzo Senior Member

    No, I mean convex as where the middle is higher than the edges.
     
  13. gonzo
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    gonzo Senior Member

    OOPS. Yes, I meant concave.
     

  14. sigurd
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    sigurd Pompuous Pangolin

    My lightwind windsurf shortboard has an elliptical section bow ('rolled V') with round rails, an inverted V (concave) middle, then a flat tail with sharper rails. This gives a flatter main rocker for planing but a more curved rail rocker for turning. Designer says the flow of the rocker lines is important, he prefers parabolas. Less and less arc towards tail. Mine has a flexible tail which also helps turning, but his non-flex boards share the above as well.
    They too have three fins, side fins smaller, somewhat forward of the main fin, and angled a bit inwards, maybe 2 degrees?
     
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