bought the rc boat of david last week, and this week started on sorting the body for a paint job
the original paint wasn't to my taste, and also had a sort of cracked finish on the paint (not the fibreglass), so decided to fill the cracks in the paint with filler primer, and then was going to sand down, looked great


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left it a few minutes to dry out, and got this again


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which must be what happened to the original paint. but how can i stop this happening again? don't know what the original paint was, and although i haven't asked him, i think it was like this before david got it.

you need barcoat or to strip it back totally. The paint underneath is not compatible and is soaking the thinners up from the new paint making it shrink. You can get barcoat in aerosol or by the litre. Ensure the new paint hardens before repainting

ah nice one where will i get barcoat? can it be bought from somewhere like halfords?
if i was to use cellulose thinners, i think it would ruin the fibreglass? what about nitromors? will that affect fibreglass? i'd prefer to strip it all back really

I'd be wary, I've had this happen on a real boat, and it was because the first layer of paint didn't like the fibreglass resin. Even with a barcoat over it, the cracks eventually spread through (then it peels off).
Sand back to bare fibreglass, then use a paint that you know is compatible (can take a while for the cracks to show through).

agree the only real way is a full strip back Sanding is the best way but laborious, I would still apply barcoat either way, you can buy this from some motor factors so I think Halfords will supply it

i originally started with sanding back the original pint, but its VERY hard, i tried 60 grit paper, and it made little difference, so thats why i tried filling the cracks rather than sanding

looks like there is wax or silicone from the origanal mold on it and the paint wont stick ,if your near cumbernauld pop into rods bodyshop telford place and we will have a look for you i have used nitromors myself but you need to be very carefull you dont melt the gell coat.

strip it down totally.

and ensure you clean it properly.

dave