44417287-Rhino-Ship-Hull-Tutorial

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Ship Hull Creation Tutorial
Developed by Mark Pavkov for
The Center for Innovation in Ship Design, Intern
Program
Naval Surface Warfare Center, Carderock Division
9500 MacArthur Blvd
Building 1
West Bethesda, MD 20817-5700
2007©

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Introduction
This tutorial has been designed to give the reader an understanding of the
different methods that can be used to model a ship‟s hull in Rhino through a series of pre-
designed offsets. These offsets are produced from when the hull form is portrayed
graphically by the lines plan (see: Introduction to Naval Architecture). This shows the
various curves of intersection between the hull and the three sets of orthogonal planes. In
merchant ships the transverse sections are numbered from aft to forward. In Warships
(U.S.) they are numbered from forward to aft. The distances of the various intersection
points from the middle line plane are called offsets. There are a various ways to complete
this modeling task and in no way does this tutorial purport to be the best way. It will
however introduce some techniques, developing a useable skill set in surface modeling.
In this case, the body plane was scanned and offset points were created with a piece of
software called SHCP (Ship Hull Characteristic Program). This is a very fast, albeit
inaccurate way to create a table of offsets. Techniques will be introduced to help align
these inaccuracies and solve the problem of the “sloppy offsets”.
This tutorial will lead the reader through the following steps to complete the
modeling of the ship‟s hull:
Introduction ..................................................................................................................... 2
1. Generating the Offsets ................................................................................................ 4
2. Generating a Rhino Points Cloud ............................................................................... 6
3. Generating Station Curves .......................................................................................... 8
4. Refining the Curves .................................................................................................. 10
5. Introducing Special Features ..................................................................................... 15
6. Generating the Main Hull Body ................................................................................ 17
7. Generating Waterlines .............................................................................................. 20
8. Generating Bow & Stern Surfaces ............................................................................ 23
9. Mirror the Hull .......................................................................................................... 31

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Useful Commands:
Hide: Left click the icon and either select an object to hide or drag the selection box
over a group of objects by depression and holding the left mouse button. Then by hitting
the Enter key or right clicking the mouse, the selected items will then be hidden. By right
clicking the icon, all hidden objects will reappear on the screen. It should be noted that
this applies only to active layers; hidden objects on inactive layer will remain hidden.
This command is quite useful when the need arises to work on an object that is obscured
by another or when there is simply too much clutter on the screen.
Zoom window/ Zoom target: This icon will zoom onto selected areas. Keep in mind
that this command can be executed in the middle of another command, for example to
pull the distant terminus of a line into view. In the Perspective view, it has the added
benefit of relocating the axis of rotation for all objects to the center of the selected area,
which is very convenient when doing close up work on an object.
Press ‘U’ in Middle of Command: This is an „undo‟ command to return to the previous
step in the overall command.
Command Bar: It is useful to keep an eye on the „command bar‟ as this will indicate any
errors in the command and can be used for problem solving of incorrect modeling.
Double Click on View Fields: You can „double click‟ on view fields such as front or
perspective to enlarge them to a full screen. The double click can also be used to escape
back to the original four window view.

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1. Generating the Offsets
AIM: To edit the SHCP table of offsets into a Rhino compatible form.
METHOD: By editing the table in Excel
In order for Rhino to the use the offset data produced by the software package
SHCP it must first be put into the correct form. Open the Excel file Containership lines.
The format of the table of offsets is in a typical Cartesian system, with one anomaly: the x
coordinates are given in a different scale then the y and z. The x scale in this case is not a
scale at all, but a division of the ship called “stations.” As explained stations are a series
of transverse cuts at defined increments from the forward perpendicular (FP) aft (negative
x coordinates define the bow section forward of the FP).
There are usually 10, 20, or 40 stations in a typical table of offsets. In this case there are
20 stations and several partial stations where the curvature is complex. To make this
table compatible with Rhino the following editing must be performed:
 Delete row 1, which is text and unreadable to Rhino.
 Delete column D, to remove the redundant 88888 station breakers produced by
the SHCP program.
Once this is done we must transform the scale of the stations. The y column is in
meters and defines the point from the ship centerline (the transverse middle of the ship
running fore and aft), where as the z column defines the point from the ship baseline or
the bottom of the keel plate. The spacing between stations is 9.875 meters.
 multiply column A by 9.875 in order to get the correct longitudinal spacing of the
points.
 Put the calculated values into column A in a new sheet using the Special Paste
command in the Edit dropdown menu, while selecting the values radio button.
Once you do this the spread sheet should look like this:

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 Now save this spread sheet as a common delaminated file (*.CSV), using the
Save As command and changing the file type in the drop-down menu. Give it the
name Offsets for Rhino. Two warnings may come up. Just select Okay or yes for
both.
This will create a copy of the file in the new format and can be opened or modified in for
Notepad or Excel. The Data file is now ready for Rhino to read.
NEXT STEP: This Rhino compatible „Ship Hull Offsets‟ table can now be used to
generate a ship hull‟s „Points Cloud‟.