Orca3D Holtrop analysis Cp 1/2 of correct value

Discussion in 'Software' started by DCockey, Oct 27, 2021.

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  1. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

    I am running the Holtrop analysis on a series of boats, and on some but not all of the models the Cp value is 1/2 of the correct value, for example 0.265 instead of 0.230. The stability analysis calculates the correct value. The models are of the entire hull. I have versions with and without decks which does not appear to make a difference.

    Has anyone else encountered this problem? If so did you find a fix?
     
  2. DCockey
    Joined: Oct 2009
    Posts: 5,023
    Likes: 512, Points: 113, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    I also sent an inquiry to the Orca3D team and received a very quick response.

    The Orca3D Holtrop analysis expects a half hull model while I've been using a full hull model. I can easily create a half hull model to solve the problem.
     
    Tad and kaptcatb like this.
  3. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    Well that's just a stupid limitation. So to use Orca's resistance prediction you have to run it on a half hull?
     

  4. DCockey
    Joined: Oct 2009
    Posts: 5,023
    Likes: 512, Points: 113, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    I believe the Holtrop method is limited to transverse symmetric hulls. My guess, and only a guess, is the limitation of using only half hull models in the Orca3D Holtrop analysis is intended to ensure only symmetric hulls shapes are analyzed.
     
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