About Airfoil Plotting
How you choose the airfoil you want to plot is up to you. I have
enough experience building flying models that I can usually pick a good
airfoil by looking at it without knowing much about it. Unless an
airfoil is radical, some things will clue you in to its performance, such as
the maximum thickness of the airfoil, where the maximum thickness falls,
reflex, camber and leading edge shape.
If the application is
critical, then I go to one of the popular online forums, such as
Universe, and present my design specifications and questions. I always get good
feedback - sometimes more than I can digest or understand. But I end
up with some good choices of airfoils.
Once you know what airfoil you want to plot, it is time to get busy.
One thing to note is that there are several computer programs that will do
all this for you - many of them are shareware or freeware. Plotting an
airfoil is much faster using a computer if you understand the program.
Some programs are designed to create wing ribs and will print a ready-to-use
I still manually plot my airfoils because it only
takes me about 10 minutes to do it and my printer never works. A computer program can print an airfoil more accurately than I can draw it.
Which brings up the next point - accuracy. Is it important? Yes
and no. Yes, you should try to draw as accurately as possible, but in
the end, you probably will not have the exact airfoil you plotted anyway.
If you manually plot the airfoil, then your drawing will be slightly
inaccurate to begin with. Even a printer is not 100% accurate. Cutting and sanding the ribs introduces more
inaccuracies. The sheeting may or may not be the exact thickness you
accounted for - especially after sanding it. Finally, you apply a
When everything is said and done, you will have a close approximation of the
airfoil you chose, but it will not be exact. Just be as accurate as you
can in each step and do not sweat it too much. Your plane will fly