Carbon frame chip repair?

Assuming it's just a scrape the main thing is that it's waterproof to stop more serious damage.

I'd use a two-part epoxy or car body filler. UV damage shouldn't be a massive issue underneath, but paint over any minor scuffs too

Water can get into the carbon fibre which is not a good thing. I tend to fill chips in with clear nail varnish, you could do several coats and give it a sand and coat of paint.

I'd get a stick on downtube protector or some helicopter tape to the underside of the down tube, or there are plenty of kits online from basic ones (cheaper) to full custom ones (expensive).

some helicopter tape

I put some on the downtube, but didn't have enough for the bottom of the BB shell area. Sods bloody law! Thanks for the tips.

Easy Composites do a carbon repair compound in black, bit thicker than an epoxy resin and ideal for dinks and gouges