The main sections of the CDA file are described below:
1.The ID section. The keyword is ID in the first two columns. The section can contain any identification, such as the name of ship, project or file, followed by a '$' sign.
2.The PP section. It starts with the keyword PP in column 1-2. PP stands for Project parameters. There can be up to 100 project parameters, but only the first 16 parameters are used.
The meaning is as tabulated below. Parameters given in boldface must be specified using correct values. The other parameters can be set to 1.0 or 0.0.
PP No. / Parameter / Description1 / fac / Scale factor for plotting (set to 1.0)
2 / LPP / Length between perpendiculars
3 / B/2 / Half breadth of the ship at the waterline
4 / D / Depth of the ship (including superstructure, if applicable)
amidships
5 / RBIL / Bilge radius
6 / ZFLAS / Raise of floor
7 / TRIM / Rake of keel
8 / BKEEL / Keel breadth
9 / XMID / X-coordinate of midship section
10 / LORD / Distance between stations (LPP/20)
11 / LMIN / Smallest X-coordinate in file (0.0)
12 / LMAX / Largest X-coordinate in file (LPP)
13 / HMIN / Lowest Z-coordinate in file (negative in case of a sonardrome)
14 / HMAX / Highest Z-coordinate in file
15 / BMIN / Smallest Y-coordinate (0.0)
16 / BMAX / Largest Y-coordinate in file
The PP section is concluded with a dollar sign.
3.The section describing the contours of the stations (cross sections). The keyword is TY = zz in column 1-5. Here zz stands for the type of contour. There are 6 types of contours that are commonly used:
- FRfor frame sections
- WLfor waterlines
- BTfor buttocks
- KNfor knuckle lines
- ALfor angle lines
- SCfor space curves
This document only describes FR type definitions. For both FREDYN and SHIPMO input, frame sections are sufficient, i.e. TY=FR always. The keyword TY=FR is followed by the station number, in the format N=aaaaaaa. Here aaaaaaa is any decimal or integer number. It must be typed directly after 'N='. This number enables the program to distinguish between different contours of the same type.
The next line contains the station distance from aft perpendicular, in mm. For the first station this must always be 0.0. Hence, TY=FR, N=2.0 6105.0 defines a section FR No. 2.0 at a distance of 6105 mm from the aft perpendicular.
The following text describes the type and the coordinates of the specified contour points (see the figures on the previous page).
The type of a point can be:
-TNfor a normal smooth point. This is the default type.
-TKfor a knuckle type point.
-TRfor a straight line to this point, and a curved line thereafter.
-TGfor a curved line to this point and a straight line thereafter.
-THcan be used when the contour must pass the point with a specific angle with respect to the vertical axis. The angle is given as an integer number of degrees. TA90 forces the contour to be horizontal, (= 90 degrees from the vertical), whereas TA82 specifies a rise of floor of (90-82 =) 8 degrees. TH is normally used to specify extreme values. It is equivalent to specify two normal points at a small distance.
The first offset point to be specified must be the lowest section point located at the centre line (Y=0.0). The last section point to be specified does not have to lie on the centre line; in that case CDAWSP will connect the last point (e.g. the deck edge) by a straight horizontal line to the centre line to complete the contour specification. The coordinates of each point must be given in mm; first the vertical distance with respect to the base line (upward is positive), followed by the transverse offset. It is possible, but not recommended, to specify two points (i.e. combinations of Y and Z) on one line of the input file. A (watertight) superstructure can be included in the contour definition.
The offset type and location must be specified in consecutive columns, where a column has a fixed width of 8 characters. The first data space starts in column 1, the second in column 9, the third in column 17, etc. In the example below, first line, TK could start in column 9, 4652.0 in column 17, and 6089.0 in column 25.
Conclude each contour by a dollar sign on a new line.
The end of the hull form definition file is indicated by the keyword 'LC' in columns 1-2.
Part of a sample input file is shown below:
TK 4652.0 6089.0
5000.0 6209.5
TK 5245.0 6268.0
5500.0 6357.4
6162.8 6500.0
CThe following dollar sign signals the end of the definition of FR0.000
$
CThe following line signals the definition of FR1.000
TY=FR,N=1.000
5705.0
3060.3 0.0
3290.3 1000.0
3386.7 1500.0
3481.1 2000.0
3577.5 2500.0
...... until the end of the last contour
TK 9050.0 46315.0
TK 10310.0 91080.0
12440.0 120400.0
$
CThe following line signals the end of the definition
LC