Cutting out is the part people rush, and it is the part everyone sees. A shell with clean arches and holes in the right place looks professional before a drop of paint goes on. Do it while the shell is still clear: you can see the chassis through it, and there is no paint to scratch.
The tools
- Curved scissors for wheel arches and any line that bends. The curve lets the blades follow the arch without the tips digging in.
- Straight scissors for long runs along the sills and bumpers.
- A body reamer for post holes and aerial holes. It is a tapered cutter that makes a round hole exactly the size you stop at.
- A sharp hobby knife for scoring straight lines and tight corners.
- Fine sandpaper (400 to 600 grit) or a sanding drum to finish the edges.
All of them are on the scissors and reamers shelf.
Cutting the outline
- Find the cut line
Almost every shell has a faint moulded line showing where to cut. Run a fine marker along it on the outside film if it is hard to see. No line? Sit the shell on the car and mark where it clears the chassis and bumpers.
- Rough cut first
Take off the bulk of the waste a centimetre outside the line. The shell is much easier to handle once the flange has gone, and the final cut is then a thin strip that curls away from the blades.
- Cut the long lines
Use straight scissors with long, smooth strokes and do not close the blades fully at the end of each cut; that is what leaves little nicks. For a dead straight edge, score the line lightly with a knife and a steel rule, then flex the plastic along the score until it snaps clean.
- Cut the arches
Curved scissors, with the curve pointing the way the arch bends. Start from the bottom edge and cut up and round in one movement if you can. Arches too tight for scissors can be scored with a knife or cut with a reamer or sanding drum.
- Finish the edges
Run fine sandpaper along every cut edge. It removes the sharp lip and any small steps, and a smooth edge is much less likely to start a crack.
You do not need to cut right through polycarbonate with a knife. One or two light passes are enough; bend the plastic away from the score and it parts along the line. Straight edges, vents and window openings all come out cleaner this way than with scissors.
Marking and reaming the post holes
- Set the body height
With the car on its wheels, hold the shell over the chassis so the arches sit evenly round the tyres. Compress the suspension and turn the steering to check the tyres do not touch. Note which hole on each body post gives that height.
- Mark the posts
Because the shell is clear, you can look straight down and put a marker dot over the centre of each post. Body post hole markers make it foolproof: they sit on the posts and leave a mark, or hold a magnet against the shell, exactly on centre.
- Ream from the inside out
Push the reamer point through the dot and turn it with light pressure. Stop early and test on the post; it should slide on without play. A hole that is too big lets the shell rattle and wears quickly.
- Aerial and other holes
Do these now too, along with any cut-outs for a nitro engine head, fuel filler or exhaust.
Do the front pair first and fit the shell on them before marking the rear. A shell that is 3mm off centre looks wrong from every angle, and holes cannot be moved.
After paint: mounting hardware
Once the shell is painted, it is held down by body clips through the posts. Pull-tab clips are easier with cold fingers. Drift and scale builders often swap to magnetic mounts, which leave no holes or posts showing.
Making the shell last
Cracks start at stress points: post holes, the front corners and the arch edges. Before the first run, stick reinforcement tape on the inside around each hole and along the nose. Many racers add a thin layer of flexible adhesive over the tape. It adds a few grams and a lot of life.
Shell cut and fitted? Next is masking, or go straight to painting.