This part has a couple small dry areas on the surface where the epoxy resin didn’t penetrate. I need some proven tricks for repairing this. I can make another part but I still want to try and fix this for practice.
There’s not much you can do other than apply some resin and then sand it back. There are some ‘tricks’ you can try to reduce the amount of sanding you have to do like applying release film or flashbreaker tape to flatten out the resin, but this can take a bit of practice and make it more work if you get it wrong.
My preferred method is to just apply some resin to the dry area making sure that it is slightly proud of the surrounding area, and let it cure. Once cured, treat it like a run in clear coat and use a really fine 2k body filler like Evercoat Easysand. Apply it all around the patched area, making sure to feather it out finely at the edges. This then protects the surrounding area as you sand with a block, so that you only touch the high spots and don’t dig any low spots or into the fibres in the surrounding areas. Start off with something like 240 or 320, and move through the grades as you get closer to flatting off. You should be aiming to finish with 1200 or 1500 just as you remove all the body filler. Once the body filler is gone, you know the area is flat and you can simply polish it back up. Here is a good video demonstrating the technique:
Thanks Hanaldo. I hadn’t thought about the risk of sanding through the surrounding area. One thing I am worried about is air getting trapped in the repair area. I thought about placing some release film over the fresh resin which only allows air to pass through, not resin. Am I just paranoid?
No, not paranoid, it’s a very real possibility and in actual fact quite likely. But I don’t think you will find a film that let’s air out but not resin, not like what you are thinking of.
Really the easiest solution for me has been to simply fill the area, then ‘tease’ out any trapped air with a pin or scalpel. This generally works pretty well, it isn’t often I end up with air in a finished component.
Thanks, that’s a good video. I’ll give it a try.
I found that these dry areas were caused by the spray adhesive holding the CF fabric so tight against the mold that it prevented resin from getting between the fabric and the mold. I’ve switched to using Duratec Sunshield as an IMC and the results are amazing.