Hey all,

I have been using EG160 tooling gel coat for my moulds backed up with carbon fibre and EL160 for items being made with ooa prepreg.

On a couple of occasions after the first attempt at making a part and after the heat cycle I have noticed hairline cracking in the gelcoat (see attached picture).

Note: I have only ever seen this after the heat cycle and releasing the part. Before the heat cycle everything is fine. 

Any ideas?

I would check the thickness of your gel and also stability of the mould.  If the gel is too thick and/or the mould moves quite a bit during curing etc then it could cause issues.

Also I see a bit of print, perhaps check you leave it long enough to cure before demoulding as that can cause print as well as making it harder to demould, which may make cracks that become visible later in the cure cycle.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Sounds like it should be plenty stiff. Perhaps too thick gel or demoulding too soon? 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant