I continue to be blown away by the large positive effect of the Zig-Zag tape. I have now had a chance to drive the Matrix at speed in the rain. The air flows right over the side windows completely scrubbing them of water droplets. All you can see is little water drops the size of pin heads being blown to the back of the car. The wind noise continues to be dramatically reduced too. Even if there are no positive mpg results that makes it worth while.
Next project is rear wheel skirts. I have decided to make them out of 8 ounce fiberglass cloth and polyester resin. I prepared a piece of two inch thick blue Styrofoam to be used as a mold. It cuts easily with a knife and 100 grit sand paper in a palm sander cleans up the edges fast. I then covered it with aluminum foil. If not covered the polyester resin will eat away the Styrofoam destroying everything. It worked really well until I decided to unmold it, which was easy. However the skirt warped with several ripples in it. I guess I took it off before it completely cured. I will likely remold it and apply a couple of layers of polyester resin and then some Bondo to smooth it out.
Here it is remolded.
Having learned my lesson on the first one I will not unmold the second skirt until I have painted it. I have applied the fiberglass and 3 layers of polyester resin and have a very good smooth outside surface. After it cures completely I will paint it and then unmold it and if necessary reinforce from the back.
It looks much better, even professional!