Scratchbuilding pt.12: Two-Dimensional Curved Structures

Introduction

Apologies, this is going to be a lot of preamble – but if you want a shorter read, jump down a couple of pages to where most of the pictures are :)

In general, I don’t even try to “restore” polycarbonate bodies or parts – they’re often too damaged, badly cut out by previous owners, badly masked and badly painted (sometimes with the wrong sort of paint), or more usually some combination of the above.

I know that it’s theoretically possible to bridge cracks or holes (on the inside) with reinforced tape, mesh or Shoe Goo, you can use filler on the outside, and prime with Tamiya PS paint before moving on to acrylics – but I’ve never had anything special enough to warrant doing so.

Replacement - with a less damaged example, new old stock from back in the day, a re-release body, or reproduction item from the likes of Penguin Customs or Team Blue Groove, or one of those options for a body issued on the same chassis is so much more practical.

 

However, I have tried stripping paint from decent polycarbonate bodies. The options I’ve tried include De-Solv-It Graffiti Remover brush on gel (out of production for a long time, supposedly polycarbonate safe but caused much clouding when I used it), strong caustic soda (aka lye – use eye protection; I had great results but others have reported cracking & complete body failure), and very careful scraping/wet & dry abrasive paper (which can take forever).

There are also several things I haven’t tried: Tamiya “Polycarbonate Body Cleaner” (40ml, anywhere from £1.69 to £9.99) and Carson “Paint Killer”. By repute both work very well but so slowly they are only useful on small areas. Further options include Tamiya “Paint Remover” (typically £16.99 for 250ml, stated as being polycarbonate safe but causes much cracking according to some reports), Nitro Fuel (apparently very effective, but can cause weakness that may take a long time to show up), and brake fluid (report seem to indicate either complete success or total destruction).

I’ve felt increasingly priced out of the RC restoration market (especially with the Covid-19 premium), so when I saw a 1980s vintage TMS (Trade Model Supplies) polycarbonate Rough Rider body being sold at a decent “Buy It Now” price on eBay, I jumped at the chance, anticipating that I’d be able to do something with it.

When it arrived it was obvious I’d been guilty of some wishful thinking – it had been very badly cut out, there were a lot of stress cracks at corners where the cuts met at 90 degrees, extra holes, and several areas of clouding and even full thickness crazing where someone had tried to strip the paint off before. Furthermore, I had hoped the paint would be old, barely bonded brush paint that I could take off in large flakes - but was in fact what I believe to be very well bonded Tamiya PS-4 Blue.

jr lexan strip 001Inside, before

The question is then, can you remove very well bonded on paint from a polycarbonate body in a safe way, at a rate that makes it worthwhile?

 

The Product

By repute, Autosmart TARDIS (tar dissolver) is another option to remove polycarbonate that works very well. As I already had a bottle of the Detailed Online equivalent (“Tar & Glue Remover”, available from £5.99 upwards from https://detailedonline.co.uk/collections/decontamination/products/tar-glue-remover?variant=7566439317559) I thought I’d have a go with that.

 jr lexan strip 002Tar & Glue Remover

The Process

Initially I started by decanting a little of the Tar & Glue remover into an empty 10ml Tamiya glass paint jar, and applied the Tar & Glue Remover to a small area with cotton buds. After 3 passes - and 3 cotton buds – and with much rubbing, I’d cleared an area about 25mm (1”) square that still needed a few spots picking off.

jr lexan strip 003Before

 

jr lexan strip 004Pass 1 jr lexan strip 005Pass 2 jr lexan strip 006Pass 3

Things needed to go a lot faster to make it a practical proposition. Remembering that any scratches on the inside of a polycarbonate body (other than the window & light areas) are invisible after painting, I used quite an aggressive grit wet & dry paper to rough up the painted surface before proceeding.

This allowed the Tar & Glue Remover to penetrate deeper, with the paint peeling off in strips in places. For the same number of cotton buds, and the same amount of time & effort, I was able to strip a 120mm (4”) by 50mm (2”).

jr lexan strip 007Pre scuffing

 

Nb: Way back when Tamiya’s “PC” range of brush on/airbrush paints didn’t stick anywhere near as well as their “modern” PS spray paints, “keying” the inside of polycarbonate bodies was often recommended.

After quite a lot more work, the body showed some areas of scratching and the damage from previous attempts to strip it was also more apparent. I “keyed” the whole inside (minus the window areas) before respraying.
After polishing the outside with Novus scratch remover (both “heavy” and “light”) and two attempts at decaling, I think it’s quite presentable – and a bit of (somewhat rare) RC history that was otherwise only fit for the bin has been saved.

jr lexan strip 008Completed jr lexan strip 009Repainted

 

Conclusion

I’m going to rate the Detailed Online “Tar & Glue Remover” as 6 out 6, despite this not being it’s intended use. It’s very effective using the right technique, and although it’s a bit whiff, it’s not so stinky that you can’t use it indoors.

Any long-term effects have yet to be seen, but several weeks after I’ve used it, there’s no signs of any detrimental effects to the polycarbonate.

 

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Written by TB member Jonny Retro

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