Small Hydroplane centre of gravity/balance point??

Discussion in 'Boat Design' started by Sooty, Jun 19, 2007.

  1. Sooty
    Joined: Jul 2006
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    Location: UK

    Sooty New Member

    Hi Chaps

    I have a small (3.5mtr) racing hydroplane to which I need to add some ballast to meet class racing rules.


    The thought of where to I put the lead has made me wonder "where do I put it?!"

    Is there a set formula for working out where the static centre of gravity should be?

    Any help, guidance, answers really appreciated.

  2. Victor Lemmi
    Joined: Jun 2004
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    Location: Sao Jose dos Campos- Brazil

    Victor Lemmi Junior Member


    How didi you get the plans?
    I would like to build one similar
    Happy new year
  3. kach22i
    Joined: Feb 2005
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    Location: Michigan

    kach22i Architect

    I don't have your answer, but I'd like to think out loud for a moment if you do not mind too much.

    1. Adding all the weight to the center of buoyancy is a fine solution if you always plan to be at rest.

    2. Adding all the weight to the center of lift as located while up on plane at a steady top speed may not reflect the "shift" which may occur from deceleration and acceleration as the result of resistance/torque caused by the water.

    3. If I recall correctly, getting up over the "hump wave" at the starting line is very important, maybe this is one aspect which should be a priority when locating the weight.

    4. One may locate the extra weight at or just below below the center line of mass to enhance stability and help prevent it from becoming top heavy.

    5. On such a small craft operator/pilot leaning and shifting of weight may be an important control factor (it is in small hovercraft). Do the rules allow for the weight to be in added the form a weight belt? If so, being able to move or shift the weight could be an advantage at start up and at plane out and especially in turns.

    6. Take any friendly advice you can from old timers and racers who are not directly competing against you or who are helping out another team. Weigh the advice carefully, everyone has an opinion and not all are equal.

  4. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    There are some older, free plans here that might interest you...
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