Method for making 3D shapes (used to make a bike fairing)

Step 3 Cut the master pattern and the crescents

In order to cut the crescent shapes properly, you need to make a ruler out of cardboard that has just the right shape on it. I've developed an excel spreadsheet that helps you calculate what you need: you just use the Chord Length and Chord Height values along with a ruler to go ahead and plot the curve shape you need on your cardboard.
Once you've made it, you can use this cardboard cutout to transfer the shape you've drawn to the plastic sheet. You will find that most plastic comes with a protective film coating both sides: I recommend leaving this on as long as possible, which usually means stripping off the inside for gluing and the outside when you are done with the finished shape.
Transfer the shape to the plastic, then get a stout pair of aircraft tin snips. You will find that this piece of the project is by far the worst, it is very annoying to have to cut the shapes out (but hang in there!). You can also try using power shears, scroll saws, etc. Cut the shapes out, one (or two) for each segment on the fairing.


At this point, you should also cut out the baffles that will brace the shapes while you're gluing. The shape that I decided on for my fairing is a wide shape that will allow me to test out my side wind safe vehicle (detailed in another instructable). So I decided on a shape that if you cut it in half along the longest axis looks like an elongated stop sign (octagon) with 10.5" sides on the smaller sides. The total length of the fairing was to be 100".