I agree they seem to be about lift and parachute deployment, but they also seem to be constrained in length.
If I can get 100% boat-tail in three feet, would the trailing vortexes feed into reattachment on top of the tail?
I'm starting to picture the vortexes, which I always associated with large spirals trailing along behind the car, being more about an inch-thick sheet of air that is tripping over the edge of the drip rail and creating a flattened oval spiral shape that eventually normalizes to counter-rotating circles far behind the car.
Doe the center-lines of the vortexes stay the width of the B-pillar apart, or are they pulled into the tapering wake? Maybe the outer limit of the vortex moves straight back, and the center moves down and in?
The current design would have a curved tube lower frame with coroplast/aluminum underbody, two curved laminated redwood panels that meet at 45°, and a black fabric tonneau cover that slips over the top of the engine lid and snaps to the redwood panels. This would weigh nothing, and serve as foundation for experiments with V-shaped Tropfenwagen backlights or vortex sucking air intakes.
I'll work on a picture.
EDIT: As promised. I took the liberty of pencilling in Coanda nozzles that would be fed by a plenum ducted from the engine cooling air.
