You dont need cad to produce the ribs.Use Paint.net to select the airfoil at the root,copy it,and place it at the cross section line of the base chord on the overhead wing view.Do the same for the tip airfoil,and place it at the tip of the wing transect.In the drawing I provided,there are 13 stations from tip to base root airfoil.Increase the size of the canvas on one side to allow you to copy each wing transect from the overhead wing view to the side of the drawing,spaced to allow copying of the airfoil.Now you have 13 horizontal lines,each getting progressively larger,until the base rib.Select rectangular select,and copy the largest airfoil,using control-C,and sequentially ,paste using control-V and scale it to the appropriate line transect length,before continuing to insert the airfoil using control V.Ultimately,you end up with the 13 airfoils of the ribs,on the side of your drawing,correctly scaled.If you plan ahead,you would draw in lightening holes,and the base chord line,before you copy,and paste.You can then take it to the printer,and ask to print the whole drawing,based on any dimension you provide as a reference.