Trim Software

Discussion in 'Software' started by fallguy, Oct 30, 2022.

  1. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    I'd like to enter some of my cat hull data into software and determine the effect of moving mass or changing mass in certain areas of the boat.

    I'm looking for no or low cost software.
     
  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    If you have calculated the hydrostatics (longitudinal CoB) for various trims, for which there are free programs (Delftship, for example), a simple spreadsheet can help you, knowing, of course, that it will be an approximation of the real value and whenever we talk about small angles of trim.
     
  3. fallguy
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    fallguy Senior Member

    I have not met the conditional you mention.
     
  4. TANSL
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    TANSL Senior Member

    As you know, in the equilibrium position, the center of buoyancy and the CoG must be in the same vertical. By changing the displacement (only when weights are added or removed) or by changing the longitudinal position of the CoG (trimming), the longitudinal position of the CoB also changes so that the vertical line that the CoB and CoG were initially on is no longer on. it's not the same. That is precisely why the boat is tilted until both points are again in the same vertical.
    DelftShip, surely you have heard of it, is a free software that allows you to calculate the hydrostatics of a hull but, of course, you have to create the 3D model of the hull. Without that it will not be easy for you to carry out your studies.
     
  5. fallguy
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    fallguy Senior Member

    Just for a moment, discussing only the cob/cog conceptually, if the cog is forward of the cob, an excess mass is forward and the buoyancy aft, is it not possible for the two to not be vertically aligned? Or does the cob move?

    Would Delftship work for a catamaran with weights on the bridgedeck?
     
  6. TANSL
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    TANSL Senior Member

    When trimming the boat the cob moves.
    I don't know if DelftShip works for catamarans, probably it will.
     
  7. fallguy
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    fallguy Senior Member

    Thanks. This was the part I had been struggling with. If my boat's cog is a bit too far forward, and the cob too far aft, then the boat tips forward, but the cob must move then....thanks
     
  8. Heimfried
    Joined: Apr 2015
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    Heimfried Senior Member

    Hi Dan,
    what kind of cat hull data do you have? If you are able to provide a particular set of cartesic coordinates of hull points, the trim (and heel and draft) of your hull is easily calculated online and graphically displayed on screen. Then you can shift weights from position A to position B and look at the canges in trim.

    Is your boat yet in the water? Then you can determinate the relation between change in trim and applied moment experimentally.
    Example.jpg
     

  9. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    My boat was in and is out now for winter and I am getting good support for changes from @Ad Hoc , but I want to get a good understanding of when I place 12 people at position X or change 15 pounds in the settee, what changes do I get..
     
    Last edited: Oct 31, 2022
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