Hand lay up in an open silicone mold

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#1

Hello everyone,
this is my first post, first excuse me for typos and mistakes, cause english is not my native language, so i’ll try to stay short and clear as possible :slight_smile:

Ii’m trying to replicate the plate in the picture.

The object length is about 4 inches (20 cm) and it has some undercuts. I’ve made a silicone mold, but cause my totally inexperience with epoxy resin i’m facing some difficults:

  • if i use dry fabric (light carbon twill) in the mold, then wetting out it with epoxy resin, when demolding there are usually a lot of bubbles or bridging in the corners.

  • if i try to start with a gelcoat layer, the gelcoat run down and simply don’t stick in the upper corners (i’m using a 2:1 clear epoxy gelcoat).

  • the only set up that’s working require that i mix the gelcoat, wait for 30 minutes, then when it starts to gel paint it quickly inside the mold, using a spatula to limit the bubbles. Then apply the dry fabric and start the wet lay up.

I’ve seen a video where the gel coat applied to a silicone mold stay firm, but mine is running everywhere, letting a lot of dry areas.

Any one could provide some advice on a correct workflow laminating in a silicone mold?

Thanks,
Alessio

#2

Silicon is a demoulding agent by nature.

Which type of gel coat are you using ? I would try to reduce the “fresh resin” time as much as posible. Just don’t let it drain or get opened.
Try to low its temperature, in order to reduce its viscosity?

I´ve had problems with my epoxy clear gel coat and everything got corrected when changing into vinil ester clear gel coat. MUch better. Short gel time. Good thixotropy

Maybe if using PVA as reléase agent it could act as a barrier between silicon and gel coat, avoiding problems ?

Maybe a combination of them ?

#3

Thank you!

I’ll try to airbrush a layer of PVA.

I forgot to mention that the objects have just aesthetic value, so weight and resistance are not a priority, but i’d like to obtain a nice lens effect over the fibers.

#4

What gelcoat are you using?

#5

I bought the gelcoat from an italian seller, it’s unbranded.

It’s epoxy based, clear, 2:1 mixing ratio, all two components are gel, pot life 30 minutes.