Wake gates for Ski Nautique HydroGate, lifting pads

Discussion in 'Boat Design' started by FMSki, Oct 5, 2022.

  1. FMSki
    Joined: Oct 2022
    Posts: 5
    Likes: 2, Points: 3
    Location: Sproat Lake

    FMSki Junior Member

    Ski Nautique (1997 hull): I am building stereo wake gates which are flat plates that drop down off the transom. This is to create lift similar to trim tabs. I did have tabs there, and now moving to a more compact plate design.

    The idea is to lift at say 55 km/h and flatten the wake and to perfectly balance the hull side to side.

    Since about 2006, Ski Nautique uses a hydrogate which is a flat plate that closes a center tunnel, to create lift... and a jet of spray off the thing. For 2022 they added blades left/right called wake tuners that deploy electrically.

    While egregious design, I think the abrupt edges create a bit of a padding effect so it's not as bad as it looks. Therefore the amount of plate depth is kinda equal to the total downward deflection of a trim tab.

    The water collides, drives down and creates the lift. They also employed lifting pads gel'd into the hull. These are ledges that impact the flow, direct spray sideways and lift.

    Needless to say not very energy efficient. I don't understand why a manufacturer hasn't gone to mild foil treatments to do the same thing - using a wing on the tracking fins and a wing on the rudder to list the boat.

    Curious if the boat design community knew this existed and thoughts on the approach!
     
  2. FMSki
    Joined: Oct 2022
    Posts: 5
    Likes: 2, Points: 3
    Location: Sproat Lake

    FMSki Junior Member

    Here are my trim "gate" plates
    And transoms of the hull iterations, with the hydrogate style
    [​IMG]

    FM Ski design below -( had a trim tab style there before)
    [​IMG]
     

    Attached Files:

    Last edited: Oct 8, 2022
  3. baeckmo
    Joined: Jun 2009
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    Location: Sweden

    baeckmo Hydrodynamics

    Still not clear what you mean with "stereo wake gates". The quadruple pics show planing hulls with hull shapes suitable for towing ski, and the IMG 2588 seems to show a similar hull with what looks like a standard interceptor installation. I wonder what is your point, what am I missing here?
     
  4. FMSki
    Joined: Oct 2022
    Posts: 5
    Likes: 2, Points: 3
    Location: Sproat Lake

    FMSki Junior Member

    thks for the comments. Stereo refers to left and right plates vs down the middle gate.
    I added a picture from URL of the plates I designed for the original TSC (TSC1) hull. Yoiu might notice the speedo pickup tubes on the image "TSC". I used those holes in hull to mount my plate bases.

    The TSC1 has a center "V" keel, they called the padded keel. That keel creates lift at speed, which is good thing. I think the skiers/designers in subsequent iterations flattened the hull thinking it would reduce the wake disturbance. They also played a bit of shell game moving the fuel tank and changing the strut angle.

    My observations and formula are pretty simple : The size of the divot the boat makes = the disturbance affecting skier performance.

    Divot = Weight /Hull surface area

    I reduced weight by using an Anti-gravity battery, carbon-composite motor box, ply floor panel, removed interior panels/equipment/hardware, light helm seat, smaller fuel tank, remove ISO damp, lighter carpet. I could add a ply swim platform too.
    The stock fuel tank is HUGE 120L I went with a 40L tank.

    The TSC1 1997-2000 doesn't have a super deep keel entry so is not as smooth over large waves as the newer hulls (2010 +)
     
  5. baeckmo
    Joined: Jun 2009
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    Location: Sweden

    baeckmo Hydrodynamics

    Ok, so your point is that you have applied a pair of interceptors, which is the standard engineering name of the device. And yes, it is very well known by those of us involved in the operation and design of high speed hulls.

    I might add that the efficiency (in terms of lift/drag ratio) depends on the shape of the blade edge and the width/depth ratio. The details of your devices are not quite clear from the pics, but fyi the lower front edge of the interceptor blade shall be sharp and the spacer should be flush with the hull bottom, so that there is no disturbance to the flow until it hits the blade.
     

  6. FMSki
    Joined: Oct 2022
    Posts: 5
    Likes: 2, Points: 3
    Location: Sproat Lake

    FMSki Junior Member

    Thanks so much for the info on interceptors! I had absolutely no idea they existed as such. My design is 1st rev & what I visualized over a few bike rides. Acetal base, screwed + 3M 5200 to transom. Two M6 thumbscrews with the slotted 0.10" 5052 plate, SS washers. I made these by hand but mill CNC'd the slotted holes. ( I have our water-ski shop here on the lake)

    Yes the base is flush to hull and I figured 3/8" deployment was about right. Have yet to water test tho! But that engineering information is very encouraging that it should work as intended, once I get it back in the water.

    The lift at the transom trims things out for an increase in wetted surface, thus reducing "divot" and wake of course. Which is what we look for in slalom skiing.
     
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