what's the name of these ?

Discussion in 'Fiberglass and Composite Boat Building' started by hyboats, Mar 19, 2013.

  1. hyboats
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    hyboats Junior Member

    look at the photo.
    high speed boat usually come with that, i know what it used for, but I don't know the name .
     

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  2. tunnels

    tunnels Previous Member

    vent !!! :confused:
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

  4. gonzo
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    gonzo Senior Member

    They also make the boat run in trim with less sensitivity to fore and aft loads.
     
  5. tunnels

    tunnels Previous Member

    So the vents allow air to come in from the side of the hull to reduce skin friction and airate the surface between the hull and the water and yes they are used with STEPS :D:p
    But there is a popular brand of boat that has 2 VENTS eachside to let air in the down turned chined edge of there DYNA hull !!and the hull dosent have steps !!:D:p
     
  6. gonzo
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    gonzo Senior Member

    Not really. What they do is make the water touch only the aft end of the steps, with a reduction in wetted surface. They are not vents. You can maybe visualize them as a series of trim tabs. The original design in the 20s was called a "shingle bottom" and was promptly banned from racing.
     
  7. tunnels

    tunnels Previous Member

    ITS A VENT !!!:eek::D
     
  8. PAR
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    PAR Yacht Designer/Builder

    Actually they are ventilated steps. You can have steps without vents, though vents make them more effective. Shape, size and location can be (usually is) critical. The dynamics of their application are pretty easy to see, if you look at high speed tank test video.
     
  9. rxcomposite
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    rxcomposite Senior Member

    You hit the nail right on the head! Here is what Sorensen's guide to Powerboat has to say.
     

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  10. daiquiri
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    daiquiri Engineering and Design

    LOL! :D

    Yeah, but actually both vents and steps can be seen in the pic. So you all guys are right. ;) :p
     
  11. gonzo
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    gonzo Senior Member

    I suppose it would be possible to install some kind of endplates to prevent the steps from venting. I think that there is a lot of confusion, mainly caused by advertising, about "air lubrication" and other related claims.
     
  12. daiquiri
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    daiquiri Engineering and Design

    Why would one want to do that?? :confused:
     
  13. IMP-ish
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    IMP-ish powerboater

    I think he's saying most steps are small vents because they're cut up into the hull. That makes an opening at the chine. To not be a vent some kind of end plate would have to block off the opening.

    Some steps have bigger vent openings than others:

    Active Thunder's "Patented DDC Ventilated Step (#36879)"
    http://www.activethunderboats.com/37.html
     

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  14. IMP-ish
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    IMP-ish powerboater

    Here's an outerlimits 40 with a much larger vent opening on the step
     

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  15. daiquiri
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    daiquiri Engineering and Design

    Cool boats :)
     
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