PJ, what you surmise is one way to do this. you can make a 3D representation of the wing, as a solid. You can then slice it at angles in a manner similar to Bob Hunts lost foam jig. rotate the sliced representations to view them perpendicuilar.

Or,

There are airfoil programs that will loft the ribs in several truss layouts.

I personally use Compufoil Pro, and it will do that and more, once I used the program enough to do it. The ribs produced are true and fit perfectly.

PJ  I have built many I/Beam wings both ways and there is no difference in the flying from one model to the other. I/Beams do not have a constant airfoil like a sheeted wing as the covering pulls down some between the ribs. I can't see how geodetic would have any effect on a D/Tube wing. Lost foam is more correct if you think it is that important.
Ed

.....With Geodetic wing construction the wing ribs are angled in and out - Like pidgeon toed.

When designing these ribs - has the angled curve been taken into consideration that it will change not only the camber of the airfoil but the overall length and dimensions ( height exculded ) ?

If you take a standard shape rib - and angle in to any degree - you will change the shape of the airfoil from the front on perspective.....

PJ, it is very time consuming and pretty tricky to loft the correct sections for a geodetic wing manually.  That is what computer programs, lost-foam construction are for, and why the Swallow, posted in the other thread, sanded the whole wing out of an eggcrate of balsa rectangles.  The sanding block method is a very low tech way to get a very high tech result.

As far as overall shape of the wing, any dips and ridges caused by the rib angles is pretty much irrelevant.  The low speed airfoil studies started by Prof. Mike Selig at the University of Illinois Urbana/Champaign(UCIC) showed that small variations in shape only affected the very peak performance of airfoils.  So if you are building a high performance sail plane, or an electric powered plane expected to fly for days off of solar cells there is a measurable effect.  Stunt planes never get into that flight regime, and it is nearly impossible to get the required accuracy of the airfoil using the construction techniques we use.  Think about trying to build a stunt wing with the whole outer surface within .002 inches of the designed shape.  Can't be done with balsa wood, silkspan, and dope.

An I-beam wing might actually be better than a D-tube in this respect.  It has only two spanwise edges in the airfoil.  Smooth and sleek.  Somewhere on the web(I've lost the bookmarks) there is a picture showing what happens to the airflow over a D-tube wing with capstrips- if the end of the D is right near the highpoint of the wing the edge there and the sag in the covering between the ribs can cause significant changes in the airflow with increased drag and not good changes in the lift and drag.  The location of an edge or tubulator like the back edge of the D can disrupt the airflow at least moderately, sometimes good and sometimes bad.  That is why free flighters use turbulator strips on their wings and why laminar wings have to be built with extremely smooth leading edges.  An I-beam wing has one turbulator way up front at the back of the leading edge, which is in the area where tubulators usually do the most good.  The rest of the airfoil is a perfectly smooth curve so the whole setup is pretty much ideal from a lift/drag perspective.

Wow.

Perhaps I was reading into it more than what I thought .

I did say at the start of the thread :

" Id love someone to tell me Im wrong - and perhaps I am "

It was a mental excersise - Thanks HOward