Freeship Curvature Plot irregularity

Discussion in 'General Computing' started by 1 Alberto, Nov 29, 2007.

  1. 1 Alberto
    Joined: Nov 2007
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Italy

    1 Alberto New Member

    I've just started designing with freeship and I do it as an hobby.

    On the drawings I made looking at Curvature Plot of Intersection Lines, these includes in some points significant irregularity which can be: from single spikes up to successive spikes of opposite sign which can smooth down or not.
    This occurs more for the Intersection Lines next to the border of the design, while Intersection Lines at the centre have smooth curvature plot, e.g.: in a 12 meter hull Curvature Plot of station 600 ad 1200 are rough specially at the ends while stations 6000, 6600 are smooth.

    On the other hand looking at Curvature Plot of Control Curves they appear pretty regular with change of tendency at each Control Point.

    I’m puzzled!
    Can anybody please let me know:
    Are my designs fair or needs some further work to make them fair?
    If the latter is true how can I achieve it?

    Thanks in advance for your help

  2. marshmat
    Joined: Apr 2005
    Posts: 4,127
    Likes: 147, Points: 0, Legacy Rep: 2043
    Location: Ontario

    marshmat Senior Member

    You'll always see the Freeship curvature plot drop to zero at the end of a curve. There's nothing beyond there with which to compare the curvature of the surface. But the curvature plot does have to be continuous, and as smooth as you can get it; discontinuities of any sort indicate a point where the surface is not fair.
    Inversions in the direction of the curvature plot are OK, provided that (1) you really do want concavity there, and (2) the inversion plots out as smooth and continuous with its surroundings.
    If your control curves look fair, but some intersections don't, try turning the model precision up to maximum/highest. If you're analyzing the hull as a small number of large facets, you may have discontinuities appear as a result of too low a precision, thus too little detail in a tight area, when the higher-precision analysis may reveal that the surface is, in fact, fair.
  3. 1 Alberto
    Joined: Nov 2007
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Italy

    1 Alberto New Member

    Some more info on Curvature Plot

    Dear Matt

    Thanks for your help.
    Sorry for not being so fast in replying as you did, unfortunately I’ve got to work!

    I've been doing some trial, changing the level of precision to highest but results were not so good.
    I’m attaching three screen dump to show the results.

    First screen dump (High Watline.JPG) is curvature plot of (lowest) waterline with precision set to high.

    Second screen dump (Higst Watline.JPG) is with precision set to highest, spikes get narrower and higher.
    It looks like the waterline, rather than a curvature, as angles in some points, though are not visible.

    Third screen dump (Higst Contr Curv.JPG) is Curvature Plot for two Control Curves with highest precision, in this case plots looks good to me.

    The scale of Curvature Plot was changed so profiles are not directly comparable in amplitude.


    Attached Files:

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.