Painting RC car bodies, focusing on polycarbonate shells. The main differences, compared to ABS shells, are that the body is painted from the inside, and the order you should paint the various shades in a multicolour scheme is reversed, i.e. paint the dark colours first, then move on to the light colours. The other difference is that you can’t use conventional automotive type paints – they just won’t stick. Lexan vs Polycarbonate Polycarbonate is the generic term; Lexan, although generally thought to be the best, is just one of many trade names for it Paint Types Tamiya “PS” aerosols. Absolutely the best in terms of adhesion and coverage. The small cans seem poor value, but seem to go a long way – there’s usually enough to spray one average car. Cutting Out Check the body for “extras” – sometimes wings/splitters will be on the same forming, wing end plates are often “hidden” in the wheelarch “void”. Most polycarbonate bodies now come with a protective film on the outside. Because this is removed after painting, you can mark edges to be cut, using a superfine permanent marker, without fear of damaging the surface. Trim the flat bit off the bottom of the vacu-form with a craft knife – it just gets in the way. Cut off unwanted parts. Use small curved scissors (Lexan scissors) & nail scissors, others advocate lightly scoring with a craft knife & folding/snapping off. Shape the wheelarches – you can sand them by hand, but a Dremel with a sanding drum is faster – be gentle though, and be sure to finish with wet & dry paper, making sure any burrs of melted plastic are removed. Finish flat edges with wet & dry on a block. Use 240 grit for any major aberrations, 400 grit, then 600 to finish. Round the cut edges very slightly, the edges should not feel sharp. Holes If the shell needs any hole’s drilling (for mirrors, wings, antenna tube, etc), carefully drill those now, using a block of wood to support the body. Use a larger drill bit to take off any burrs. Body post holes can be tackled slightly differently – for a start you need to be VERY careful about where the holes are. Shells are marked (with a dimple) for their intended chassis – but when you are fitting a shell to a different chassis, they will probably be in the wrong place. Remember the adage “measure twice, cut once” – you need to take this to extremes and measure many, many times, making sure the body is sitting correctly side to side, and front to back, before you commit to making the holes. To Sand or Not? In the past, sanding (or rather, keying) the inside of the shell to promote adhesion of the paint was recommended Washing It is recommended to wash the inside of the shell, to remove any particles left from cutting & sanding the edges of the body, any fingerprints you might have out on, and any mould release agent used in manufacture. I’d suggest using regular dish washing liquid & lots of warm water, and using a lint free cloth to speed drying. Window Masks A lot of shells come with precut masking for the inside of the windows, if yours does, then mark the outline of the windows on the outside to help you position the masks correctly on the inside. If you apply the masks wet, then you will need to allow a couple of days before painting for them to dry off completely – otherwise paint (especially water based ones) will get sucked in. If your shell didn’t come with masks, consider making your own from self-adhesive vinyl (rather than using masking tape) Masking It is advised you put small bits of masking tape on the outside of any holes previously drilled in the shell even if there is a protective film on the outside. If you’ll be painting your shell in a single colour then that’s all you need to do before painting – however if using 2 or more colours – this requires masking. Work out where the line(s) between the colours needs to go – use masking tape to get the line right, then marked on the outside with a fine permanent marker. Remember that dark colours need to be painted first, using masking tape for the edge, and paper for the rest of the area. Use brown Kraft paper as it’s a lot more reliable than newsprint. It is advised to tape over the wheelarches on the outside – sealing the areas to be painted later avoids having to clean off any spray drift later. Spraying With decent paint you should be able to do it in two coats - firstly a light one – which doesn’t need to be perfect and, after appropriate curing time, a heavier second coat. As long as the colour looks dense enough when you’re looking down on the shell (i.e. not holding it up to the light), then it’s good enough. Once you’re happy with the paint & have allowed enough time for it to cure, you can carefully remove the masking – but NOT the window or hole masks. Spray the second colour in the same way as the first: light coat, drying time, heavy coat, drying time. Final Unmasking Remove the window masks by carefully picking at one corner with a craft knife until there’s enough free to grab with your fingers, and carefully peel the mask off at an extreme angle. The protective film on the outside can be removed in a similar manner.