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wozza
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Jess8bit (11/06/2013)
Yeah, the tiny bubbles I see are stuck to the tows. Sorry if I get you wrong but, what you're suggesting is to clean the cured gel coat layer with any degreaser to avoid the sanding dust from sticking to it (because I did sand the gel coat to flatten it), before laying down the first carbon cloth ? I did not get the clear coat part of your word though (ashamed I am). Only sand the GC50 where you have any drips/blobs. And even then be very gentle using 1200's. Trust me the "orange peel" finish you get when you spray it into the mould is OK to Infuse over. When you sand it you are more likely to leave dust etc in there which will ruin the finished part. Trust me on this one 
Carbon Copies Ltd
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Jess8bit
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It's crystal clear now
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carboncactus
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No sorry, I was talking about your first part, the one you didn't use GC50 on.
Degrease it and watch how the degreaser acts on the surface, if the white specs disappear temporarily, clear coat the part 3-4 times, sanding in between and your part will be spot on. If you imagine being a tiny bug on the surface of your part, it would look like this:
_________ _________ ________
\ / \ / <------ Laminate with pinholes
If you sand it down, you will effectively taper the edges of those pinholes, making it easier for lacquer to fill them, but it does take a few coats to bury them, and you have to sand down in between coats. Imagine you have a road full of 2 foot deep potholes. You lay down a layer of tarmac and you fill the holes a bit, but you also make the rest of the road higher. You have to scrape that tarmac off, and repeat until the holes are filled.
As for your second part, the pinholes are covered, they look like this:
______________________________
______________________________ <------GC50
\ / \ / <------ Laminate
They are both the same, the only difference is the gelcoat.
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Jess8bit
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Group: Forum Members
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Visits: 566
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Yeah, the tiny bubbles I see are stuck to the tows. Sorry if I get you wrong but, what you're suggesting is to clean the cured gel coat layer with any degreaser to avoid the sanding dust from sticking to it (because I did sand the gel coat to flatten it), before laying down the first carbon cloth ? I did not get the clear coat part of your word though (ashamed I am).
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carboncactus
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Test your pump by plugging it straight to your gauge. Yea, the bubbles are there because they are pinholes on the carbon, behind the gelcoat. If you look closely at the part, you'll see those "bubbles" are in the intersections of the tows, typically where pinholes form. Remember the gelcoat is hard before you infuse, so the pinholes are the same ones you had on the first part, they are just covered, which makes them bubbles, if that makes sense. Have you tried panel wiping your first part? The dust that has filled those pinholes is epoxy dust, which is actually transparent. If you panel wipe it, the specs should temporarily disappear, as the dust is wetted by the degreaser. If it does disappear, you can clear coat the part a few times, sanding in between and eventually you'll build up to a nice piece.
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Jess8bit
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carboncactus (10/06/2013)
Have you tested your vacuum pump to see if it pulls a bar?I don't suspect the pump itself, but for being 100% sure, how can perform such a test ? And did you do a drop test? yep. Always. and more than 15mn. I can't really tell from the photos, but I think the only difference between the first and second part is the gelcoat. yeah it's difficult to see on the photos. I think you just had a pinhole issue. When you sanded, you filled the pinholes with epoxy dust on the first part. Same has happened the second time but the gelcoat is covering it. I think those bubbles are pinholes covered by the gelcoat. no no, the "bubbles" you see on the last part are here before any sanding action.
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Jess8bit
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yeah, I can only imagnie. thanks for sharing  (@ warren)
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carboncactus
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Have you tested your vacuum pump to see if it pulls a bar? And did you do a drop test? I can't really tell from the photos, but I think the only difference between the first and second part is the gelcoat. I think you just had a pinhole issue. When you sanded, you filled the pinholes with epoxy dust on the first part. Same has happened the second time but the gelcoat is covering it. I think those bubbles are pinholes covered by the gelcoat.
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wozza
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Ha Ha trust me I have learnt the hard way 
Carbon Copies Ltd
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Jess8bit
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But why can't I find this by myself ?? Oh, I know, because YOU're the boss !  I'll try this for the next part.
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