18: DXF-Export
It was an often expressed wish of the colleagues, to be able to work further on
the airplane construction in a CAD program. Thus one could save the
time-consuming, always recurring new drawing. A wide-spread file format for CAD
systems is the DXF format. This is a very old format, however it is supported
by many programs.
The following text describes, how one can generate a DXF-file in FLZ_Vortex. If
one has a construction (consisting of min. 1 wing) to be present, then the
entry 'DXF-Export' in the menu 'File' becomes enabled. If one clicks on this
entry, a new window appears.
Construction drawings can be provided in a variety of ways.
1) The classic real 3-side view:
In doing so the object is drawn in such a way, as one would see it from above,
in front and from the side. From this design one can take all necessary data,
which are required for making the model. For clarity sometimes also sectional
views of the object are added, in order to make certain parts better visible.
2) The 3D (three-dimensional) construction:
In this technique distinctive points (corner points, points of outline) are
stored with three-dimensional coordinates in the computer. Thus a solid model
is available. One can regard the model from all sides, therefore the coordinates
are turned simply around one point in the virtual room. The turn can take place
around any axis X, Y or Z. Since all model determining points are present,
easily the 2D-view and cross-sections can be derived from the 3D-construction.
3) Typical model-making model plan view:
In model-making usually one builds in sections and the model-maker often does
not have the knowledge of a mechanical engineer. Therefore a slightly different
drawing technique became generally accepted here. Wings and tail units are
drawn flat, thus one has the possibility to tack the components (like ribs,
longerons, leading and trailing edges) directly on the model plan and to stick
them together. 3-dimensional design features (dihedral, twist etc.) are drawn
in additionally 3-side views e.g. the wing in the front view, in order to make
a dihedral visible. If one would draw only the classical 3-side views, then one
would have problems to build e.g. a V-tail unit, since one could hardly
determine the exact position if the ribs.
In the left side of the window, one can finds four areas with check-boxes.
Select the check-boxes with the desired options for the DXF output. When using
only a 2D-CAD program, it makes no sense to select a 3D output.
In the top right all surfaces are listed which are part of the construction.
Unwanted surfaces can be deselected. On the right side of the window one finds
the following option.
1) Units for output:
The DXF format uses dimensionless units. FLZ_Vortex uses the unit 'meter'. If
the target CAD-system is set to inch, 1 m in FLZ_Vortex will change to 1 in.
One has to know the unit which one uses in ones CAD-System. AutoCAD and
AutoSketch are typically set to mm. In this case one selects the unit
'Millimetre [mm] Factor 1000' and 1.000 m in FLZ_Vortex will become 1000.000 mm
in the DXF-file.
2) Number of Airfoil Coordinates:
Airfoils are drawn in a traverse; there is a quantity of coordinates, which are
connected with straight lines. The number of coordinates determines the
refinement of the airfoil outline. Avoid to enter 1000 by all means, the time
for generating the DXF-file increases enormously and the size of the file
becomes gigantic. As a general rule 50 – 100 coordinates are sufficient.
3) Font size:
If the check-boxes for rib lettering are selected,
an appropriate text output into the DXF-file occurs. Into the input field 'Font
size [m]' a suitable value in m can be entered.
4) Interpolated airfoils:
The wings in FLZ_Vortex are built segmentally. Every segment has an airfoil on
each border (edge) and a segment width. If one would like to build a ribbed
wing, then one needs further interpolated airfoils between the segment edge
airfoils. Select the check-box 'Generate interpolated airfoils' and enter
maximal rib spacing into the input field 'max. Spacing of Ribs [m]'.
Interpolated airfoils according to the entered resolution will be written into
the DXF-file.
5) Save DXF-File
Click the button 'Save DXF-File As...' to
generate the DXF-file and save with the file name entered in the Save File dialogue.
The following pictures show some screen-shots of different CAD-programs in
which the DXF-files generated by FLZ_Vortex were imported.
3D in AutoCAD
2D classic real 3-side view
2D model-making model plan view
2D Rib list