Aft Bulb Hull Modelling

DELFTship forum Hull modeling Aft Bulb Hull Modelling

This topic contains 5 replies, has 2 voices, and was last updated by  Icare 5 months, 2 weeks ago.

  • Author
  • #39559

    Martin Currie

    Good day Everyone

    This is my first post here on the forum and i’m looking for some help in designing the aft bulb area on a trawler design.

    I’m fairly new to delft ship and would like to be able master this technique to allow my hull design be scaled and 3D printed as an RC Model.

    I’ve attached a screenshot of a similar design of this area to illustrate my point.

    Thanks for looking guys and i look forward to hearing from anyone that can help.


  • #39560


    Welcome on board, Martin!

    Today there’s something wrong with the pictures display (caused by my computer or by the server?).

    Broadly, a bulb is drawn by punching a hole, extruding its edge, then closing it.

    Punching a hole:
    Select a vertice and press the DEL key on your keyboard. If the convenient vertice doesn’t exist, draw it by dividing a polygon.

    Extruding the edges:
    Select the hole’s edges then press the EXTRUDE button on the toolbar. Give the direction and distance by relative coordinates.

    Close the hole:
    Since the hole is probably on the symmetry plane you’ll have to select each point on the edge, one after the other, in a logical order (clockwise or counterclockwise), then press the NEW SURFACE button on the toolbar.
    If the hole is not on the symmetry plane, you can select the vertices forming the hole’s edge and press the CLOSE button on the toolbar.

    I hope it’s clear enough. 😉

  • #39563

    Martin Currie

    Hello Icare

    Thank you for the reply to my post, unfortunately i wasn’t able to understand what you meant.

    I have attached the file i’m currently working on of a 24m Trawler hull. General shape is good still a work in progress, also i suspect something is a little off with the scaling of my stations background image.

    I was looking at the keel today and offset it on the Y axis 0.18m, but still trying to figure out the method to add the aft bulb/skeg.

    I was thinking that i’d need to have two surfaces for this hull, I’ve attached a of pictures of the aft part of the hull i got from the builders website

    Thanks for the help guys


  • #39564


    First of all, remember that each word is important (each thing has its name)… mainly when you use a foreign language… errr… when **I** use a foreign language. A well-chosen picture is more elling that a long speech.
    For me, a bulb is not a skeg, and a skeg is not a rudder.

    If you want to draw the hull’s protusion the scew’s shaft is sticking out of, I assume that reading an old topic about creating protusions and receseses on a hull will help you:

    If you need just a rudder or a wing-like keel, there’s a tool in the toolbar called KEEL AND RUDDER. It allows you to create this “fin” and to import it in your model.

    Does this help you?
    If not really, encircle on your picture the hull’s detail that’s puzzling you, and I’ll try to propose you an illustrated “how-to” guide.

    A last advice: Always read the manual, understand it, practice each operation. That’s the way I learnt using Delftship. Nothing all cooked will fall down into your mouth, as we say in french, you need to use some brain juice. 😉

  • #39565

    Martin Currie

    Hello Icare

    Thank you for your reply. Please find attached a surface of the skeg i made last night. IO created a new layer and using rows of three control points i came up with a basic surface for the skeg.

    I need to complete the final faring of the upper portion of the hull, then i’ll try find a method of intersecting the two surfaces and joining them together.

    If you have any tips i’d greatly appreciate them



  • #39566


    I can’t read your file (my old steam-powered computer allows me running only an old Delftship version).

    One year ago I wrote a how-to method for drawing a tunnel for a bow-thruster, which is an illustration of connecting a cylinder to the hull by a rounded surface. I assume reading it will help you join the skeg to the hull.

    For a sharp connection, the SURFACE INTERSECTION function can give you the connection ridge, then delete all excess surfaces on each layer *plus* a row of polygones on *only one* of the layers, finally and connect the remaining surfaces by adddina new surface on the convenient layer.
    Don’t forget to set the connection ridge as a *sharp* chine if it appears as a soft chine.

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