Positioning carbon with spray glue


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Damien
Damien
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Hi,

So here  are my issues...probably standard, so I am sure there is a solution.

I have made moulds, pretty standard (mould gel coat layer over a waxed part, then glassfiber...standard). Then I wax the mould, so far so good. Now the mould is a bit complex with many folds and I am using 200 g/m2 carbon cloth...Initially I was using epoxy and let it harden a little bit to fold the carbon so that it would hold in place...it was always a bit of a mess...so I moved to the spray glue. Sounded like a good and easy way for a non pro looking to make parts that look good and are solid, though they don't have to be the best in the world either...I do this, then use epoxy, vacuum, and it all goes well...
 It worked ok, but I am not sure I do this well. Indeed, when I sand a bit the carbon part, I see small white spots (not due to the dust of the sanding, these are under the epoxy)...so I thought that maybe when using the spray glue on dry carbon fabric leads to some micro bubbles being trapped...could that be ?

The thing is that I am using 3 layers of carbon...and what I did was put the first layer with the spray, and then the 2 others, also with the spray...all dry. And then I put my epoxy everywhere, hoping that it will penetrate fine everywhere as well. Is that supposed to work or spraying all layers is not a good idea ? Shall just spray the first layer and then just go with epoxy ? But that would make the same problems as the first layer...on all corners, bends and folds, I cannot keep the carbon fabric in place.

Or is it OK to dry glue all the layers ? My microbubbles would come from something else ? Epoxy being too cold (working in my garage) ? Epoxy not sufficient vacuumed to debubble it prior to applying it ? To be honest, I found the use of the spray for all layers pretty handy, allowing to make something quite clean...but I am wondering if it's a good idea or if it makes it challenging to get the resin everywhere and no microbubbles, even with vacuum,

Thank s for your help !


MarkMK
MarkMK
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It's difficult to comment on the particular spray tack that you're using and it's compatibility with the resin also, but it does just sound like you're experiencing surface air entrapment in the part. The white appearance is likely just the sanded material trapping itself in the tiny holes that are appearing when you sand the surface

If your mould has quite a few corners and bends to it, then it would be a challenge to achieve a totally perfect cosmetic finish, even with the use of vacuum but, I imagine, that doing the lay-up by hand will make this challenge all the more difficult. Even with spray tack application and the most careful application of the resin, you're never going to get close consolidation of the fabric into tight corners, with these areas being resin-rich and, most likely, holding onto trapped air as well.

Allowing the resin to de-gas for a while prior to wetting the fabric will help, but the process of applying it will always introduce some additional air to the part. Working in a warm environment will help, as would ensuring that the part cures in an environment of 20 degrees, at least. Applying some gentle heat via a heat gun after laminating will also help to relieve some of the trapped air, but to get perfect results on such a mould it does sound like you may need to think about investing in a pump to, at least, vacuum bag the part after hand laying the fabric

Edited 6 Years Ago by MarkMK
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