some approaches and techniques I have found useful in building a Canary Derby car…
Determine what position the driver is going assume in the car (head first not allowed). Have the driver assume that position and measure total height, width and length. Having the driver do that on a long bit of cardboard or paper allows you to scribble down the stats right on what you will be using as a template.
Now decide on shape, starting with plan view, that will enclose the measurements you just made. There are a couple of things to remember in this layout process:
1. reducing frontal area reduces drag
2. a fair curve is a fast curve (fair means smooth curve transitions)
Strike a centreline down the length of the cardboard/paper template. Lay out the measurements from that centreline, but only do one half, as if car was sliced longways down middle. Then draw the plan shape on one half. You can use a long bit of 1 x 2 wood as a batten to spring a nice curve.
You then can fold along the centreline and cut out the template to make a symmetrical pattern. A plan view outline of the car.
An elevation view follows more or less the same procedure. But here you have to decide how much of the driver will be sticking out of the car, will there be a canopy etc? Just remember that reducing frontal area will reduce aerodynamic drag (its a mantra I will repeat often). Also consider hand placement for steering, knee and foot room, and ingress/egress.
The plan view template is useful even if you are making up a welded tube type car. It allows you to experiment with the placement of axles, steering gear, back rests, ballast points etc. For me its more “real” than using Autocad or Solidworks or even hand draughting. You can make cut outs of component profiles and place them on the template, have the driver on it, move positions, see what works and what doesn’t (interference issues do arise) before cutting building materials.