Sanding CF parts

Hi All
I was doing a little sanding on a new fin and sanded deep enough for the waste to turn black(sanded into the CF). Should I be putting on another coat of epoxy to seal it or??

Hi Don,

I do this with rudders using 200 gsm carbon layer, wet sanding until to I have perfectly smooth & get all minor bumps & hollows out, when waste water turns black use this as indicator to apply another coat clear varnish.

Cheers Alan

Hi Don,

Sanding Woven style finishes can leave you with pinholes. Uni directional finishes are usually better.
It is good practice to re- seal the carbon after it has been sanded, but not a requirement.
Just be aware that epoxy resin is not UV stabilised and will yellow in sunlight. This is the main reason for applying the varnish.
My preferred is 2 pack polyurethane such as ‘International’ Perfection or a 2k clear laquer for cars.

Cheers, Jim

If the carbon fiber is well wetted out with resin, as it should be anyway, then it is no problem at all. I do it all the time. The carbon itself is very chemically stable and will not break down. If the fiber is not well wetted it could wick in water. A light application of resin, preferably thinned with maybe 5:1 resin to alcohol would seal it. Get the epoxy to a near watery consistency with a little 90% rubbing alcohol or other preferred solvent. The 80% has too much water in it and will not allow the epoxy to cure properly. Put the thinned resin on the part that needs sealing, wait a minute for it to soak in, and then wipe it off with a paper towel. But again, you probably do not need to.