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MarkMK
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Hi all A couple of recently infused parts have demoulded with small dry areas of crazing on the part surface. I'd sprayed GC50 into the mould first, left overnight and infused the next morning.In both cases full vac was achieved and drop-tested for 30 mins before infusion All other aspects of the process were adhered to carefully. If there was anything amiss I'd have expected to see any blemishes to appear below the outer gelcoat surface so was puzzled by the surface imperfections Could it perhaps mean that I need to apply the gelcoat a little more thickly, as I'm usually concious of not spraying too much and creating sags or uneveness that might affect the appearance of the cured fabric.
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ajb100
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Are the parts de moulding easily? Is the crazing happening during removal? Alternatively, is it happening in exactly the same spot each time?
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Hanaldo
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Could you quickly just clarify what you mean by crazing? I have heard people use crazing and alligatoring to describe the same problem, and to me they are different problems. So just to be sure what you are referring to, could you please just describe the issue or better yet post a picture? In the meantime, I'm pretty sure you are talking about what I call crazing, which is hairline cracks in the gelcoat? This is always due to stress and movement, but can be caused by a number of things. I think ajb100 is on the same wavelength as me here, as this sounds like a potential mould sticking issue. The one time I got crazing in my in-mould coating was because I had applied a bit too much pressure buffing off the residue of my release agent, buffing off a lot of the release agent. So when I demoulded, the part didn't stick bad enough to destroy the mould, but the coating on the part was very badly cracked from the stress of demoulding. Otherwise, is your laminate stiff enough? A very thin and flexible part could result in the gelcoat cracking from the movement, though I am inclined to doubt this possibility.
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Warren (Staff)
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If you can take a photo we shall try and work out what is going on. Actual cracking would tend to indicate too much flexing when you demould, literally breaking the gelcoat. Alligatoring could be a number of issues.
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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MarkMK
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Hopefully the attached pic will provide a bit more insight. I'm guessing it's what's commonly referred to as alligatoring? The demould was easy, but I did have to hold the part in the mould to remove some of the peel-ply in strips, as the part had freed itself before all of it was stripped away. Not certain if some movement during demould could have caused the defects but ift feels odd that the damage has only followed the lines of the fabric matrix if so? Additionally, I did use acetone to partly activate the coating in certain areas to help with positioning the fabric. Not caused me an issue previously, but could over-use of it degrade the coating to this extent? If this is a risk then perhaps I'd be better off just using the Aerofix 3 for help in positioning. I know the debate's been had in other posts already, but I've found it doesn't leave any residue, even without using an in-mould coating, just so long as you finely mist it from distance onto the fabric and allow it a little time to settle before positioning.. Early attempts spraying direct to tbe mould caused problems and when i'd gone a bit heavy with it in places. . Anyhow, all input on current issue much appreciated Mark
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ChrisR
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It looks like dry spots from the infusion rather than a surface problem
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MarkMK
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I agree, it does, but the imperfections have also broken the outer gelcoat when previously I'd only ever witnessed this appearing underneath (which is worse as you can't get to them in order to try and rectify). The part wasn't overly large and ambient temps have been around 20° of late. I've also been careful to leave the resin feed open for 15 seconds or so following closure of the vac line.
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Jacopo Carbonio
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This also happened to me when I closed the entrance of the resin and after too much time the vacuum line, because the vacuum has sucked too much resin..so usually I wait the resin arrives in outlet pipe (vacuum tube) and so I close the line of the resin and after a very little time the vacuum line, to prevent the resin to be sucked from the gaps of the tube or of the spiral. You can try, or describe better how you did your work, no problems for the spray glue if you don't use too much
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MarkMK
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I can understand it had I been shutting off the resin feed prior to the vacuum line, as you explained, but I have been allowing the resin to continue flowing for a while after closing the vacuum which I hoped would help guard against possible dry areas. Thanks anyway 
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Warren (Staff)
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The picture looks like there are actual voids there not alligatoring.
The voids are right through the gelcoat.
We dont recommend spraying acetone onto the gc50 so its possible that eat through the gel leaving voids to trap air.
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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