Silhouette with Delftship Professional for Maxsurf Stability

Discussion in 'Software' started by Rabah, Jun 5, 2016.

  1. Rabah
    Joined: Mar 2014
    Posts: 247
    Likes: 7, Points: 18, Legacy Rep: 50
    Location: Bulgaria

    Rabah Senior Member

    I would like to say some words about how I calculate Windage area and area centroid height with the fastest method and how to put it in calculations of the intact stability with Maxsurf Stability.
    I shall start with that as in Maxsurf Modeler and in Delftship Pro there is a function for use of the Background Image. In first-order for them it is necessary to be a general base point, then the Image it is scaled on a length of the model / if to impose on the side projection either on the deck view / or on breadth / if to impose on the Body plan / .
    Thus we can impose the side elevation of the Background Image of the prototype on the projection of our model. Very important is that the prototype had close ship dimensions, especially on the length.
    As I use for this purpose Delftship Pro, shall prolong explanations on it.

    On the Sheer plan we press with the right mouse button. Then follow Background-Load.
    After occurrence Background Image we select Background-Origin.
    We select a point from Image and transfer the Image with the left-handed buttons up to the model - approximately the upper point of the transom.

    We point a cursor the overall point of the models stem and we note coordinates X and Z if we do not have advance identification information about these values.
    Follows Background - Set scale.
    Then we point the cursor on the too Background Images point of the stem. There is an approval table with coordinates Background images which it is necessary to change - here it is necessary to put coordinates X and Z points of the models stem and to press enter.
    At once Background Image it is scaled.
    We test and if it is necessary again with Background - Origin it is transferred before coincidence BL Images with BL models. If not good coincidence was received, we iterate Set scale. Then save.

    On Fig 1 the Side elevation of the model is shown.
    On Fig 2 the Side elevation of the model and the imposed Background Image of the prototype is shown.
    In the upper right angle the window with coordinates X and Z is visible. If bypass the all superstructure on the contour and with the cursor to indicate the reference points, we shall see their coordinates on X and Z concerning the adopted beginning of the coordinate system. We note these coordinates.
    By cursor we select the button “Input and edit Wind Silhouettes”.
    The silhouette of hull - Fig 3 is at first seen only.
    For the remaining areas, component of the Silhouette, for each separately we use points with recorded coordinates, entering them as directed programs.
    On Fig 4 arrangement of points of the superstructure is visible.
    On Fig 5 see the final output of calculation.
    The calculation it is necessary will execute two times - once for draft of total displacement and second - for draft at displacement of 10 % store and fuel. It is received through change only the draft in Main Dimensions.
    Points of Silhouette are entered only once.
    After that the received outcomes should be introduced in criteria about an intact stability, chosen in Maxsurf Stability in point “Severe wind and rolling” as “total area A” and “area centroid height h”– see Fig 6.
    It too is necessary to make two times. We enter for 100 % and execute the calculations of the intact stability. Then we change criteria for 10 % and again make the calculations.
    But what would be desirable to update. According to Rules of Classification organizations Windage area of the not solid surfaces of elements of the vessel - handrails, masts, ropes, etc. it is approximately taken into account by increase of the calculated total area of solid surfaces at 5 %, and its statical moment concerning BL of the vessel - on 10 % ,i.е.

    Windage area Aw = 1,05 ∑Awi
    Area centroid height Zw or h = 1,1 ∑Awi*hi / Aw

    How made these corrections.

    In the precomputations of the intact stability the shown method is allowable as we use as a first approximation the silhouette of the superstructure of the prototype. When we already have ultimate General arrangement of the project then in new calculation it is possible to add particulars for handrails, etc. as a percent increase.

    _____________________
    NA Razmik Baharyan
     

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