About 1950. The drag bag was a canvas oblong about 10 x 6 x6 inches which hung down underneath at the back end of the dinghy with a 4 inch aperture to allow it to fill with water. The idea, I suppose it was to act a bit like a weighted keel but because it hindered moving through the water (we made hand paddles out of plywood) we cut them off.
KimH