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  1. #1
    PuprleNuprleGPR's Avatar
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    Stepped sponsons kill speed on a stock boat

    I figure that there might be people wondering what certain mods can do for their boat, so Im sharing my experience. I bolted on the cut sposons from my 04 to the 07 before my ride today. I lost 1-2mph on top, but handling difference was noticable. Chine walk is greatly reduced and the ski also feels more playful. Its a good free mod if the speed loss doesnt concern you and you like to play around on the low end


  2. #2
    Stepped sponsons become necessary when using an aftermarket angled rideplate.

  3. #3
    "Hustler" Inkaddict's Avatar
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    Quote Originally Posted by PuprleNuprleGPR View Post
    I figure that there might be people wondering what certain mods can do for their boat, so Im sharing my experience. I bolted on the cut sposons from my 04 to the 07 before my ride today. I lost 1-2mph on top, but handling difference was noticable. Chine walk is greatly reduced and the ski also feels more playful. Its a good free mod if the speed loss doesnt concern you and you like to play around on the low end
    The sponsons arent in the water at top speed.... How do they slow you down/?

  4. #4
    PuprleNuprleGPR's Avatar
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    Dont know...
    Maybe the stock plate doesnt generate enough lift to get the tips out of the water. I know that they are pretty needed with an angled plate (I used these with a J-plate on my 04), but wanted to see what happens with a 100% ski

  5. #5
    Quote Originally Posted by Inkaddict View Post
    The sponsons arent in the water at top speed.... How do they slow you down/?
    Best guess is that they act like little wings and with the water spray and wind pushing on them it keeps the rear of the ski up and the ski more level.

  6. #6
    NIXON'S BACK!! cincygpr's Avatar
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    Eh, not really. Maybe a little bit, but aerodynamics doesn't really apply until 50mph or so, and the sponsons aren't big enough to generate noticable lift.

    There's an idea though... buy one of those big aluminum wings and bolt it onto the platform behind the seat 2mph speed secret.

  7. #7
    andygpr748's Avatar
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    Eh, ya really. We're talking about top end here, 65mph and up. I'd say areodinamics have a lot to do with it. Try searching it, there have been a lot of discussion's about it.

  8. #8
    NIXON'S BACK!! cincygpr's Avatar
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    Quote Originally Posted by andygpr748 View Post
    Eh, ya really. We're talking about top end here, 65mph and up. I'd say areodinamics have a lot to do with it. Try searching it, there have been a lot of discussion's about it.
    Hydrodynamics, yes. Aerodynamics, no. Not from the sponsons. The hull itself does contribute to lift, but given the sheer amount of turbulence and drag created from the top of the ski and the person riding it, PWCs don't have the best of aerodynamics.

    I don't want to sound like a know it all... but aerodynamics is what i'm going to school for

    EDIT: Here's a link to a good discussion on this:

    http://greenhulk.net/forums/showthre...n+aerodynamics

    EDIT #2: And here's proof of my airfoil idea above ^^ I had no idea it had actually been implemented... maybe this will be a project for me this summer...

    http://greenhulk.net/forums/showpost...1&postcount=20
    Last edited by cincygpr; 05-05-2008 at 09:06 PM.

  9. #9
    Quote Originally Posted by cincygpr View Post
    Hydrodynamics, yes. Aerodynamics, no. Not from the sponsons. The hull itself does contribute to lift, but given the sheer amount of turbulence and drag created from the top of the ski and the person riding it, PWCs don't have the best of aerodynamics.

    I don't want to sound like a know it all... but aerodynamics is what i'm going to school for

    EDIT: Here's a link to a good discussion on this:

    http://greenhulk.net/forums/showthre...n+aerodynamics

    EDIT #2: And here's proof of my airfoil idea above ^^ I had no idea it had actually been implemented... maybe this will be a project for me this summer...

    http://greenhulk.net/forums/showpost...1&postcount=20
    I would love to hear YOUR explanation of how stepping the sponsons stops the ski from porpoising at high speed considering they are out of the water. I'm listening...........

  10. #10
    NIXON'S BACK!! cincygpr's Avatar
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    Quote Originally Posted by VOODOO View Post
    I would love to hear YOUR explanation of how stepping the sponsons stops the ski from porpoising at high speed considering they are out of the water. I'm listening...........
    Easy, man! I was just hoping to toss my $.02 in... I don't know much about porting, pumps, triple pipes, carb settings, but this is one thing I do look into... And I haven't heard a lot of hard theory to back up the results that people get from mods... just tried-and-true 'take it out and see if it works' testing.

    I'm not exactly SURE of how sponsons cure porpoising at speed, but honestly... the sponson isn't that big, and so, won't be causing that much lifting force, even at 70mph. Besides, it's caught in the turbulence between the boat and the water.

    With the stock rideplate, the sponsons may still be in the water (because the boat hasn't lifted enough), causing a dragging force that creates a nose-down condition. Without this drag, the hull pitch will be too great, and porpoising will happen.

    Now, I don't know about highly modded rideplates. Has there been any testing done on a Jim's FF plate or IR level-4 plate with sponsons in the 'up' position? Or how about the skis running 75+MPH? I'd like to see what happens when they leave their sponsons in the 'up' position.

    Really high speed guys probably have their skis dialed in so well that the sponsons most likely don't matter at 80MPH. I just don't want to ask them to make a speed run without the sponsons

    EDIT: I did some calcs to help me figure out what i've been saying... if anyone wants some numbers, shoot over a PM!

    I just keep thinking about this, and i've come to the conclusion that with a stock ski (NO mods), the stepped sponsons do cure porpoising because they lift the ski out of the water quicker (even though they don't add any lift in the air, they DEFINATELY add lift in the water), and once the ski's on plane, they act as a drag-inducing device that pitches the ski's nose down when it tries to porpoise... but it also slows the ski down.

    When going at higher speeds, the aftermarket rideplate, once dialed in correctly, will correct the porpoising problem itself, because like people have told me, the sponsons aren't even in the water. They still help the ski plane faster, but once it's on plane, they're out of the water and add little to the total dynamic of the ski. Other elements come into play to reduce porpoising, such as shimming down the trim tabs, because they do the same thing as the stepped sponsons on a stock ski... they add more drag and thus help to stabilize the nose of the ski from pitching up.
    Last edited by cincygpr; 05-06-2008 at 07:21 AM. Reason: I keep thinking of stuff

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