I wonder, maybe a stupide question but, do the CF parts we buy have received a lacquer coat on top of the gel coat ?

It depends on what you want and/or what the part's purpose is. It also depends how good you are at producing. For ultimate strength and lightness, especially for purely structural parts or racecar parts, people will just leave it as it is out of the mould.

If it is to be cosmetic, people may make it resin rich out of the mould, also leading to a nice surface, more difficult as imperfections may occur. Others apply a gelcoat to the mould and then reinforcement.

Another method is using an in-mould-coating, it is a PU 2 component paint that goes into the mould and provides the surface layer. The mould should be polished (it should always be to provide best finish regardless).

You are asking about varnish, you should not use varnish but rather an automotive clear coat (or any color) which is usually PU based and 2 component. This will protect the part against UV damage.

cheers

As far as I know epoxy has little in the way of UV protection when exposed to a lot of direct sunlight such as in car hoods. You can spot the garbage carbon hoods from china that yellow in their first year on your car. Some of them I hear are polyester which is even worse.

You might consider this method.

If I know the part will see alot of sunlight I spray 2 part automotive clear (with high UV protection)in the mold and wait over night for that to cure. I then do my infusion.

My thinking behind this is, I know I will clear the part anyway so I will need to scuff the part when it comes out of the mold. I would then risk sanding into the carbon because it is so close to the surface. Seeing that I already have sprayed clear in the mold the scuff is only on the clear layer.

If you want absolutely show quality shine like hot rods have, you must flat wet sand the clear and then go the polish route.

At first I was afraid that the clear would not bond well to the epoxy that came next. I did tests and the two become one. The application is just backwards, instead of clearing the epoxy you are epoxying the clear! 

Hope this may help with your decision on what to do.

Fred

I wouldn't have thought of clearing the mould, fearing it sticks to the mould surface and the fact it might not bind.

I always clearcoat my parts to protect them from UV.  I'd never considered clear coating the mold though.  Thats a great idea!  My prefered apraoch has been to avoid using gel coats as I find I cant get a perfectly even coat so you see the odd bit of unevenness.  I make my molding, clean it and clear it.  Always worked OK for me.

Thank you  for sharing FLD 

high solids automotive paint would be best, as it has high UV protection in it already. but they are made to cross link with their respective brand's base coat( the color in base coat/clear coat systems), so they may eventually peel. be sure to carefully abrade the surface, i suggest a gray scotch brite pad and
something like comet household cleaner. it is a dry powder and is for scrubbing(with water added) bathtubs and sink basins and will take the gloss off and not expose the carbon fibers themselves. plus side is it cleans the parts very good but you must be crazy with the final clean. comet leaves a chalky haze when dry so be very sure you get the surface totally clean.

CarbonFiberCreations