Reducing Pitch

Discussion in 'Boat Design' started by makobuilders, Oct 5, 2014.

  1. makobuilders
    Joined: Feb 2009
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    makobuilders Member

    What are some methods of reducing pitch (through design) for a small boat? Bulbous bows seem impractical. Is it just limited to fine entry versus a bluff bow? What about a bluff bow but with little flare on the topsides?
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Full ends helps. What kind of small boat ?
     
  3. TANSL
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    TANSL Senior Member

    Try redistributing the weights, or move the center of buoyancy forward, changing forms (add volume at the bow and / or decrease volume aft)
     
  4. makobuilders
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    makobuilders Member

    We're talking about a powerboat of around 40ft length. Would seem to be that full ends as you mention would be worse, no?
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Planing or displacement ?
     
  6. makobuilders
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    makobuilders Member

    Displacement. 25 tons.
     
  7. philSweet
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    philSweet Senior Member

    Okay, displacement type 25 tons.

    Now, are you referring to a static nose up trim or an oscillating motion due to waves?
     
  8. makobuilders
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    makobuilders Member

    Reference to active motion due to waves. It's tough to change the entry angle of the design but I suppose the topsides flare could be reduced. Just looking for other ideas.
     
  9. kapnD
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    kapnD Senior Member

    I am not an engineer, but have spent lots of sea time in boats of this size range. In my very seat of the pants opinion, the best way to minimize pitch is to increase the waterline length. At 40' you have just made the first step, and will not see huge improvement until approaching 70'. I think this has a lot more to do with the distance between the waves than the hull design.
     

  10. TANSL
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    TANSL Senior Member

    kapnD, you seem to be an experienced man and you are probably right. In a way we're both saying the same thing because increasing the waterline length (without changing anything else), among others, has the effect of displacing the volume of buoyancy to the bow.
     
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