I recently built a fairing out of coroplast for a tricycle as a school project to test efficiency and the effect of aerodynamics. The data I collected was taken at a fairly low speed where the margin of error showed that there was no significant difference between fairing vs no fairing. However, I think this would probably affect more at higher speeds, although more data is needed to determine that. This fairing is fairly cheap, light, and easy to build and very visible to cars on the same road.
If I was to redo this, I would make it less tall so that there was no extraneous space and I would make it more aerodynamic with a shorter ceiling. I would also work on making individual fairings for the wheels.
Step 1: Build the Frame Base
To build this frame use out of 1/2 inch conduit pipe, and a few aluminum flat bars. Aluminum is lighter but much more expensive than conduit. To build the frame, use a pipe bender or a foot to bend a half circle 3 feet wide at the center, and then bend each end towards each other but not touching. Then attach separate pieces to the ends using pipe connectors so that the entire base is six feet long. You should have an ice cream cone shaped base for the fairing that is about 3 feet wide at its widest point and 6 feet long.
Step 2: Finish the Frame
Next, bend a 10 foot length of conduit so it has a straight back and curves into about a 75 degree angle. This is piece A as shown in the picture.
After that piece is bent, take one more length and bend that into a upside down U shape. This will go in the center and hold up the previously made piece and is piece B. This piece should be about 4 feet tall and curve with about 3 feet between each pole.
Connect these pieces using conduit connectors and small bolts. B should be 1/3 lengthwise down the base, so closer to the front or big part of the ice cream cone, and A should be right down the width-wise center. They should be bolted at the top where they connect.
For added support, repeat with step B and make a smaller version for the end. I used Aluminum flat bar for this, but conduit would also work. make it as tall as it must be to intersect with A.
Step 3: Put on Coroplast
The next step is to attach the Coroplast onto the frame. I used zip ties to hold pieces together onto the frame. I also duct taped the seams so that there would be less change between the different heights of the coroplast. Also shown is painter's cloth attached as a windshield, this wasn't used in the final product because you can't actually really see through it. Coroplast can be found at most Home Depot or Lowe's stores, but you will need multiple pieces put together to cover the whole area and curve the pieces enough.
Step 4: Place the Windshield
Now that the coroplast is all placed on the frame, get a piece of clear vinyl, plexiglass, or polyurethane sheet. This can be however big as you want or can afford, but remember that it is heavy and relatively expensive. This is difficult to drill through, so I attached it by curving it slightly around the front of the frame and wedging it between Coroplast pieces. Then I duct taped the corners, and it has held fairly well.
Step 5: Put the Fairing on the Tricycle
To attach the fairing, I used an aluminum rib, duct tape, and zip ties. The rib could be U bolted for added stability, but I just duct taped it to the center under the tricycle steering wheel. Then cut a slit in either side of the fairing at the height needed for keeping it off the ground, and simply stuck each end of the rib in the fairing. This held up the front of the fairing. In the back, I zip tied the base to the place where you would normally put a basket. This held the back down.