Just trying to find out if there's any reason why you cannot do a hand layup in a silicone mould (in this case epoxy / carbon fibre).

All I tend to see in searches are silicone moulds being used to cast solid resins or plasters.

Silicone would be the perfect material to make a mould from the object I want to duplicate (although, there are no complex curves or fine details)  and ideally I would use the mould to make both a plaster 'buck' for vac forming and also do a carbon fibre hand layup.

I agree that it may be problematic but there are so many different hardness and types of silicone that you could probably make it work.  Do you need the silicone to mold in undercuts?  If not then an epoxy tooling dough might be worth a look.  I have hand laid up into silicone before but with polyester and mat over gelcoat - it was messy but worked well to mold complex textures that you couldn't tool any other way.  The mat and polyester conforms easily - and of course cosmetics weren't an issue - so you may have a harder time with carbon/epoxy that you want to clear!

Thanks Chris. I think what I will do is go ahead and make a silicone mould and then cast something sturdy to work from because I want to preserve the original as it's a one-off item.  I can cast in some material, maybe something like Alumilite, using the silicone mould, that I can use to make an epoxy mould from or experiment with vac forming.

This is the object I am casting, it's a custom made rc helicopter canopy, made in carbon fibre - I suspect using a vac infusion process. So I want to keep it in pristine condition and make a couple copies in other materials as well as one in carbon fibre. (the one with the green stickers is the original and the other one is my first foray into carbon skinning.