Resistance prediction

Discussion in 'Software' started by souravsandesh, Sep 30, 2014.

  1. souravsandesh
    Joined: Aug 2014
    Posts: 8
    Likes: 1, Points: 0, Legacy Rep: 33
    Location: INDIA

    souravsandesh Junior Member

    Hello all,

    I need a small clarification as to what the below text actually mean

    1 {0.93 ( / )
    0.521448 0.6906
    1 13 12
    C C lcb
    k c c B L
    P P
    − − +
    + = +

    In this formula, CP is the prismatic coefficient
    based on the waterline length, L and lcb is
    the longitudinal centre of buoyancy forward
    of 0.5L as a percentage of L??

    Please kindly tell me what the highlighted text means

    My vessel is a catamaran and am calculating resistance for a demi hull...

    My vessel length is 18m...and my LCB demi hull is 8.9m from aft

    thank you
  2. daiquiri
    Joined: May 2004
    Posts: 5,373
    Likes: 249, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Longitudinal centre of buoyancy expressed as a percentage of L, measured from the mid-ship (0.5 L). If it is forward of the mid-ship, then it is a positive value - otherwise it is negative.

    For example:
    L = 80 m
    Xlcb = 3 m aft of the midship​
    LCB = -3/80 = -0.0375​
    or, in percentage:
    LCB = -3.75%.​
    The value is negative because it is aft of the 0.5L.

    Another example:
    L = 60 m
    Xlcb = 2 m forward of the midship​
    LCB = 2/60 = 0.0333​
    or, in percentage:
    LCB = 3.33%​
    The value is positive because it is forward of the 0.5L.

    Hope it helps.
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