Datcom_1-1
so, lets begin the very first datcom lesson, by analyzing a wing planform. Just wing, without fuselage and tails. Let the wing, say, Wing-1, be as described in the figure below (click figure to enlarge):
The wing, as shown above, is a simple straight tapered wing, swept back, with some dihedral. The wing section is simply a naca 2412 airfoil.
Those geometrical parameters should be inputted to datcom using a dat file named specifically as for005.dat. This dat file should b
e in the same folder as the datcom.exe console. It is actually a good idea to make a specific folder for each analysis, maybe like the figure on the left.So lets begin our work by creating a text file using notepad (wordpad or even ms word is also ok). Open a notepad file (obviously the name will be untitled first). Then lets use the first line by typing our analysis title, beginning with a control command CASEID, as follows (you may use your own title, but should always use the CASEID). The title in the example is "MyFirstDATCOM_Wing_1", as follows:
Next line, we define the dimension we want to use in our analysis, using the control command DIM, followed by the chosen dimension. In this case, lets use metric dimension, represented by M, as shown in the figure before. FYI, the DIM control command could define other dimension units like FT, CM, or IN. More information about DIM, click here.
Now, before we start some more complicated stuff, lets save our file first for005.dat file. We can easily do this by writing the .dat extension in the file name column, as shown below.
Next we move on for our first namelist, WGPLNF, the wing planform. A namelist defined as a group of variables that contain values of a aircraft part parameters. So, the WGPLNF namelist is a group of variable that define a geometrical values of a wing planform. Wing planform here refer to the top projection of a wing. Observe again our Wing-1 above.
What values do we need to declare to define the geometrical shape of wing-1? Right, we should declare the span, the root chord, the tip chord, sweep angle, twist angle, and dihedral angle. In datcom, we should also declare the wing type, which for our wing-1, its a simple 'straight tapered' wing planform, with a dihedral and lets assume the twist angle is zero.
So to declare the wing planfor
m, we use the WGPLNF namelist, followed with the variables, enclosed with two dollar sign ($), as shown in the figure on the left.I am sure you can figure out what the variables meant. However, I'll give you hints as follows:
TYPE = type of the wing (1 - Straight Tapered Wing, 2 -; Cranked Wing, 3- Double Delta Wing), explained later as the lesson goes
CHRDR = Root Chord Length
CHRDTP = Tip Chord Length
SSPN = Semi Span Length (Semi!)
SSPNE = Exposed (not covered by the fuselage) Semi Span Length (here, its the same as SSPN, explained later)
CHSTAT = Chord station where we measure our swept angle, here, we take the leading edge = 0. Commonly one use the 0.25, quarter of the chords
SAVSI = Swept Angle (positive backward)
DHDADI = Dihedral Angle
TWISTA = Twist Angle
The variables name is mandatory, you cannot name them other way. The variables I use in the example is the standard for a wing. There are few other variables existed in the WGPLNF namelist, which you could find here.
Notice in the previous figure, I wrote the namelist and variables, not in the first column of the window. It is on purpose. The fact is, Datcom requires the control command (CASEID, DIM) being written starting from the first column, the namelist (WGPLNF, preceeded by $) start from the second column, and the variables start from the third and beyond. Another rule is that you must input the values of each variables using at least one decimal. If you forget to put a decimal, (format *.*), your datcom file would not run. And one more thing, another rule, always put a comma after the value, except maybe for the last variables value in a namelist, which you could simply end the value with dollar sign ($). Along with this explanation, many rules in writing the for005.dat file will emerge. For the complete writing rules, see here.
