ORIGINAL: UStik
DC-3 had NACA 2215 airfoil at root and 2206 at tip. A quick check with [link=http://www.mh-aerotools.de/airfoils/javafoil.htm]JavaFoil[/link] shows the former being very docile (stall-wise) while the latter is nasty, at least at model Re numbers.
That might have been a problem even in full scale, considering the wing sweep giving additional pitch up when stalling the tips first. (And the normal down pitching moment of the airfoil is reduced at stall.) Had the original DC-3 wing washout or did they simply fly at high aoa only with flaps down? Both would work but it's still speculation. Someone here who knows the facts?
We used to have a utility C-47 at a place where I worked. I just now got off the phone with an old co-worker who was one of the company test pilots and flew our C-47 regularly. In answer to my question about stall characteristics, here is what he told me:
The airplane buffets very heavily as the stall is approached. In addition to the tail buffet, there is some pitch nodding. He said he did not recall pressing deeper into the stall because of the severe buffet. Also, his recollection was that he had satisfactory roll control at all times.
So there is our answer to why the full scale airplane has so many loyal admirers and such a good operating history. Apparently the buffet warns the pilot away from further increasing AOA and he never gets into trouble. As far as operating with the flaps down, the lift coefficient is increased with no further increase in AOA. I rode in our C-47 many, many times and don't the pilot ever doing a 3-point landing. Now I know why.
I agree with the other posters that any savvy modeler would look at the DC-3 wing and shudder. It has all the elements necessary to cause a nasty tip stall wing taper, thickness taper and leading edge sweep. Maybe if we could feel stall buffet in our transmitter sticks we could stay out of trouble too!
The only option that we have with our models is to carefully limit elevator travel such that we never quite get to the stall point. That's basically what the full scale plot is doing.
Dick