how exactly do you trim carbon fibre before it cures? i know it can be done for a super fine edge but when exactly is the best time during curing to do this. for example in the carbon mods video regarding the skinning of a wing mirror, could the excess carbon at the back (thats got resin on it) be sliced through with a scalpel?

Hi,

In the skinning process (the Carbon Mods video with the wing mirror in) there are only two points where a scalpel would be effective, they are:

1. When you've first put the carbon down onto the basecoat
In this case you would stick the carbon down to the basecoat and then allow the basecoat to cure fully. Once it's fully cured there is no danger that the scalpelling off of the carbon will disrupt the carbon or pull it away from the body of the part. You can trim any overhanging carbon from all around the edge of the part. Doing this will reduce the amount of heavy-going trimming that you would have if you left the fabric overhanging and then wet it with resin in later stages.

2. When the carbon has been wet out with resin and the resin has cured to uts 'B' stage.
In this case, you can still get scalpel through the carbon when it's been wet out with the first coat of epoxy, providing that the resin hasn't fully cured. There's not really any advantage in doing the scalpelling at this point in the skinning process because you could just have done it before you put the resin on instead (as above) but there are occasions in normal laminating (not skinning) where you might want to cut through reinforcement/resin before it fully cures.

I hope this helps,

Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

thanks Matt thats given me something to think about.