Effect of Chine at Bow

Discussion in 'Powerboats' started by barrelback, Feb 27, 2018.

  1. barrelback
    Joined: Feb 2018
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    barrelback Junior Member

    Been doing a bit more studying. If I understand correctly, as a planing hull (or any other hull) moves through the water at displacement speed, there will be a wave with a crest and a trough. As the hull's velocity increases, the wavelength and amplitude will increase, moving the trough deeper and farther aft. As the planing hull rises from sitting to planing, the trough will also move to a lower waterline. Am I in error so far? If all of this is correct, am I correct to assume the chine geometry should be such that it transects the lowest point of the trough at any given velocity?
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    You sort of have it, but think of the wave train as simply separating (increasing in amplitude). In displacement mode, there's a bow wave, a midship wave and a stern wave. As speed increases the midship waves moves aft a little, while the stern wave tries it's best to stay attached. The bow wives gets bigger as it piles up against the resistance. Once you've pushed through the bow wave, the midship wave has all but moved to where the stern wave used to be and the stern wave has separated and is trailing aft of the boat, typically with a hole between it and the boat. Additionally, this now dramatically drawn out wave train presents an inclined surface for the hull, which settles into it, bow up. As speeds increase, the dynamic interaction of the flow and the hull bottom become more intertwined and the boat eventually settles to the surface contours.
  3. DCockey
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    DCockey Senior Member

  4. barrelback
    Joined: Feb 2018
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    barrelback Junior Member

    What PAR said is gonna take me a bit to digest, but it seems that if the water catches the chine aft of the trough on its way up to form another crest, it will push the craft up, and thus set the craft on plane sooner, assuming everything else is correct for a planing hull.
  5. barrelback
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    barrelback Junior Member

    I do indeed intend to consider the entire wave train, however, would it not be prudent to verify my understanding thus far before adding more elements and compounding an error?
  6. gonzo
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    gonzo Senior Member

    That is not correct. The boat does not "ride on the chine" but is lifted dynamically by the pressure along the whole bottom, and sides if they are submerged.

  7. TANSL
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    TANSL Senior Member

    That's pretty confusing, do not you think?
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