Weather Spotter Rear wheel skirts
How to make a wheel skirt
To make one, start by looking at the shape of the car body before and after the wheel wheel. This is the shape you want to match. Also look to see how far out past the wheel wheel you tire sticks. You will need to have the side skirt bow out to accommodate this space (plus a little gap to make sue they do not rub).
Next make and attach brackets to hold the bottom brace on. I used angle brackets bought from the local hardware store. I screwed them into the plastic (rear) into the metal lip (top) and epoxied the front one on.
Next take your paper template and cut out your wheel skirt. I used some galvanized sheet steel I had. Others have used colorplast. If using sheet metal, mark along the template but cut about half an inch further out. Bend in along the marked line. This forms a rolled edge which adds strength and removes the sharp edge. pound the bent material flat (picture shows it just bent up, not hammered over yet).
I attached my wheel skirt with flat head screws (to the brace) and used self tapping sheet metal screws to attach to the brackets. Nodice that for the top I used a hinge in place of a bracket, this allows for easier access to the air valve on the tire.
Reattach and test your results!
Test methods and results
steady state MPG Matrix wheel skirt testing Testing conditions: Warmed up car by driving 15 miles before testing Flat road was two miles long (one mile was the test distance). Measurements with done with a scan gauge. Tested in this order B, A, B2, A2 B= with both wheel skirts on A= normal no skirt Winds 5-8 N, NE
I speed up the car to 55MPH (speed limit) and engaged cruse control (same setting for duration of testing). At my start point I hit reset on the ScanGauge's trip function. AT the end point (1 mile) I wrote down the trip average MPG. I turned around and ran the test from end to start. Each set (example "A") includes 6 runs south and 6 runs north at a mile per run.
I would like to toss out my first set of "B" data because I found that the drive train does not warm up until 30+ miles have been driven. The data above contains all the data I gathered.
Data summery: with wheel skirts I had a 1 to 1.5 % improvement in MPG.
For more info and picts take a look at my thread: 
--WeatherSpotter-9828 10:16, 18 August 2010 (EDT)