Talk Composites - The Forum for Advanced Composites

Worm holes appearing in my gelcoat

http://www.talkcomposites.com/Topic2839.aspx

By Caden - 9/13/2012 12:56:26 PM

Hey guys, this is my first post. I have been making a set of moulds to make a carbon fibre wing skin. I started with cutting my pattern out of high density blue foam. I then coated it with a couple layers of coating epoxy with a few scoops of microbeads thrown in to make it thicker and sandable. After sanding it down to a nice smooth finish, I cleaned the surface with the Easy-Lease mold cleaner. I then applying several coats of Easy-Lease release agent (letting it dry for about 15 mins between coats). I then went ahead and applied the gelcoat for the uni-mould process. I put a second coat on after letting the first dry for a few hours. I then let it cure over night. The next morning these wrinkles appeared in the gelcoat right in the middle of the surface. I figured they were only on the exterior. I then proceeded with the coupling coat followed by the reinforcement. The next day when I pried the pattern out there were these worm holes where the wrinkles had been in the gelcoat. They appear to be air pockets but when I put the gelcoat down (both times) the was a generous even coat. I've been following the recomended ratios for the catalyst so I'm right stumped to figure out what I did wrong. I tried a second go using the same process but with waitng a little longer between the steps but I got the same wrinkles in the gelcoat again. Can you help me?
By andygtt - 8/13/2013 9:58:32 PM

I've had a few instances of the gel wrinkling in this way... In my case I'm almost certain it's when the paint on the buck isn't good quality and reacts.

Must say I've not used 2 layers of gel coat on any of my moulds as I've been worried about the second coat attacking the first and it's hard to judge when it's cured enough.... Is it better to leave it a couple of days and then key it up?

On a side not, I have made some very successful moulds in a single day... Most significant is my front clip that I needed to use at 8pm (meaning demould deadline of 6pm) and had a delay of material deliver meaning I couldn't start the final section till midday... I increased the catalyst a large amount to make it go quickly and fortunately it came out good rather than being ruined.