Pre-Inclining Inclining

Discussion in 'Stability' started by fdmsiv, Oct 5, 2016.

  1. fdmsiv
    Joined: Sep 2016
    Posts: 2
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    Location: Houston, TX

    fdmsiv New Member

    I have been asked to perform an inclining on a private boat that will not be classed, more for the owners peace of mind. The boat was built pre WWII and through the years the superstructure has grown while the documentation has vanished. I have a lines plan and a table of offsets and have generated a stability model. The project was described as a casual update but the most recent pics they've sent now has a rib and crane mounted on the top of the house.

    In my previous inclines we had weight estimates or previous inclining so we at least had a ballpark idea. My concern going into this incline is I have no idea what the KG is. My concern is the GM could be negative before we begin inclining.

    Has anyone run into a situation like this before or have any thoughts on the best way to approach this?
  2. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    The situation is similar to when one makes a totally new project. You have to make an estimate of the weights and the position of their centers of gravity. You, in this case, have the advantage of knowing what the drafts fore and aft so you can calculate the total weight of the boat and the longitudinal position of its center of gravity. With this information, you follow the normal procedure.
  3. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    I agree with TANSL. Unless the vessel has a obvious dangerous loll/list, sound (or press up) the tanks, pump bilges, do the displacement check (including water temp & density), calculate the 5 deg (or wall sided if less) heel moment, then do the inclining. If she's lolling, the inclining will show it. You can then use the loll intercepts to calculate a KG which can then be used to calculate stability with the RIB on the crane.

    Remember that negative GM at zero heel has little to do with ultimate stability. If KG is high enough to endanger ultimate stability (i.e. large negative GM just off zero heel), then a normal hull form will show significant loll.
    Last edited: Oct 5, 2016
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