The Insight G1 has relatively flush door handles but still does not represent the optimum aerodynamic design.
The Tesla Model S has a 0.24 drag coefficient (cf G1's 0.25). There are a variety of significant reasons for this but one small area that intrigued me was their door handle design:
As the video shows it is a completely flush low drag design. I was after a similar aero door handle for the Insight but without the weight and mechanical complexity found in the Model S.
By filling in the void in the door handle area this better obtains the ideal smooth surface for the air to flow over without creating a lossy recirculating zone. However this would not allow the door to be opened in the conventional manner. A compromise is to have an insert that blocks off the majority of the void but allows a single finger to open the door (the car's AL door can easily be opened with 1 finger).
Process that was used:
1) Make 2 patterns (one for each side) using GFRP and filler (using the door as a mould - covered with silver foil and wax to prevent sticking to door)
2) With the cleaned up pattern make 2 moulds per side (top; back & front) - hence 4 moulds in total
3) Use the moulds to make CFRP parts that are then glued together
4) Filler gaps, paint and lacquer
5) Fit to car with 3M's VHB double sided sticky tape
6) Show Wife how to open the doors with a single finger
Weight 25g each