In the olden days the word 'dope' meant something totally different than it does today.
Planes were made from wood with the trailing edge being a steel wire ran through the end of the ribs. The frame was then covered in cloth and painted with dope. The dope stuck the cloth to the ribs and spars and tightened the cloth like a hot iron does to
monokote leaving little scallops on the back edges of wings where the wire was bowed due to tension as the dope shrinks the cloth.
Covering with dope.
Trailing edge with steel wire.
Of all the planes of that era,
perhaps the most famous is the Fokker DR1. These photos clearly show the scallops left as the dope tightens the fabric on the frame. The dope NEVER stops tightening the cloth. If not properly maintained, it can eventually pull the airframe apart. Modern dope is plasticized to slow this effect but still tightens and shrinks the canvas covering over the years.
Here you can see
a Blue Max from the rear.
Eventually they stopped using the wire and the scallops went away. Having a wood trailing edge would seem to me to make for a more rigid and effective flight control surface but that's just me speculatin'.
I think the scallops on the back of the Mini Scout are an homage to the pioneers who flew these insanely flammable airplanes in the pursuit of testing the limits of human ingenuity and courage.
