Placing weight fore and aft in a planning cat

Discussion in 'Boat Design' started by Bullshipper, Jun 29, 2019.

  1. Bullshipper
    Joined: May 2008
    Posts: 106
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    Location: Mexico

    Bullshipper Bullshipper

    Its my understanding that the straight keel lines of a planning cat should incline between 3-4 degrees up when the hull is under power on plane.

    My question is, when I set the rest of the components weights forward to aft in this bare hull AT REST FLOATING STILL in water, should I try to move stuff so that the bows sit at the same 3-4 degree angle at rest, providing I also center the fuel over the hulls fulcrum or tipping point?

    I realize that testing with installed motors would be a much better test, but spending $40K US is a tough pill to swallow. Any guidance you can give will be much appreciated.
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    What is the at rest trim angle now ? A lot depends on the characteristics of the particular boat, but power cats are sensitive to fore-and-aft weight placement. We need more information and pictures if available.
     
  3. Bullshipper
    Joined: May 2008
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    Location: Mexico

    Bullshipper Bullshipper

    Its a bare hull, 28x10 with no floors, bulkheads. It floats about 3" down at the bow with its higher sides and more weight up front
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    That would be fairly normal, with no motors fitted. Your fuel tanks really ought to be placed such that differences in fuel load have the least influence on running angle, which is pretty standard for all boats.
     

  5. Bullshipper
    Joined: May 2008
    Posts: 106
    Likes: 1, Points: 18, Legacy Rep: 21
    Location: Mexico

    Bullshipper Bullshipper

    As no one knew or cared to answer, I checked a couple of cats in the marina and their decks slanted up between 1.1 and 1.3%. Still have to check 2 more to draw my conclusion aas I suspect it will be more on CC's than on the express cats I measured first. Thanks Mr E for giving it a try.
     
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