Creating Cross Sections

See if your local library has any books on drafting. Many of those books covered methods of measuring cross sections from planform and profile views.  The methods may not work on complex enough surfaces, however.  For some aircraft you may need to find 3 (or more) view drawings.  Sometimes you can sweet-talk mfgs to give you such drawings. The newer the aircraft the more difficult it is to find scale drawings.  And, unfortunately, not as many folks model choppers, so that makes it harder than ever.  There are a few companies that supply scale drawings for RC modelers, but again, not as many RCers build choppers as fixed wing.  I think one of the biggies in that business is a company called Bob's Documentation or something similar.  While at the library, check for a mag called "Model Airplane News."  The company usually has ads in that mag.  Chances of them having an S-3 variant of any sort are slim, but if you find their web site it may not be that hard to check.

Find a photo or drawing of the view you want. I make my own drawing of the subject by using the photo or drawing views and drawing lines across and down the picture. Then use a clean piece of drafting paper with the same line pattern only 2 or 3 times larger. (1" equals 3" as an example). Carefully draw your project in the larger boxes corresponding to the approximate  position of the lines in the smaller box. No drafting skills required. Just an eye for crossing the pattern lines with your hand drawn line.

Dimensions depend on size of pciture you start with. Easy way to do it.

The same process can be used to make an accurate wheelbase for a car.

Jack

The drafting knowledge comes because it is very hard to find views that show a pure undistorted cross section.  In order to take quartering views and derive depth from them, one needs to know some discriptive geometry tricks.  Also pictures tend to show true perspective, not isometric perspective.