design help needed

Discussion in 'Inboards' started by waterskier, May 14, 2009.

  1. waterskier
    Joined: Apr 2009
    Posts: 5
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    Location: Queensland Australia

    waterskier Junior Member

    I am looking for assistance in designing a ski boat for disable (wheelchair) slalom waterskiers.

    The problem
    Current centre mount ski boat whilst have a small wake at able body ski speeds it is too big for wheelchair skiers.

    The idea
    Could a light weight v nose aluminum punt with centre mount ski boat be the answer.

    The fixed paramaters
    For competition the following is required.
    Centre mount motor
    Centre mount ski pole
    Boat length 6-6.5m
    Must be able to track straight whilst withstanding lateral load of skier.
    Min skiing speed 39k(22mph), max skiing speed 58k(36mph)

    Thank you
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    If the boat is smaller then it wouldn't fit the competition parameters. Which part do you want to make smaller and why?
  3. waterskier
    Joined: Apr 2009
    Posts: 5
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Queensland Australia

    waterskier Junior Member

    It is the wake that need to be smaller particularly at slower speeds. This is because the skiers sit in a seat mounted onto a wide ski (12 inches) which will launch them off the wake that would be produced by the normal type of boat.

  4. Guest625101138

    Guest625101138 Previous Member

    Anything that reduces weight will reduce the waves. If the centre of gravity is further forward it will also reduce the waves at lower speed.

    You can make a boat that makes ripples around 40mm high at the nominated speed but it has ridiculous proportions.

    Something slightly less than ridiculous is a catamaran with deep slender hulls as pictured. I did not constrain the minimum length so it is shorter than you nominated. Length is 4.3m and beam is 2.4m.

    This is going in the other direction to what you are thinking. It is not a planing hull.

    This will have waves less than 0.1m at 25 knots. It is reasonably economic. Would probably achieve your speed requirement pulling a skier with about 70HP but I have not checked this. It would take 40HP to do 25 knots without a skier.

    It needs to be built very light. I am counting on the hull being around 250kg - one reason to keep it shorter if permitted.

    Obviously it will track well; as if on rails. Turning would be another matter.

    Anyhow this is what a low wave hull would look like. It would take some work to put enough together to get a practical boat within your spec. Depends on how serious you are about minimising waves.

    Anything you can do on a planing hull to reduce weight will reduce waves.

    There are tunnel hul boats that produce reasonably low waves:
    The are primarily intended for shallow water operation.

    Rick W

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