Shops are shut so can't ask them yet. I made up a mould today and it didn't go very well. All my other parts have gone well but this particular one hasn't. It is a door skin and Ill do my best to outline what Ive done:
part prepped, release waxed, PVA coated (about a day and a half of drying given). Then I put Gel Coat on, at 2% by weight ratio as per the instructions. It got one thick coat, so about 2mm worth. This then sat for about 4 hours, it took just over two hours to be touch dry.
started laminating and I noticed underneath that it was starting to seperate from the part and wrinkle up in a couple of places. Not much you can do at that stage so I carried on and finished the laminating.
The temperature at the time was about 22 degrees, much warmer than the previous parts Ive done.
I can't see what Ive done wrong, the main different has been the temperature but I would have thought that 22 deg would still be in a workable range.
Its not the end of the world, I can just put a skim of bog over the wrinkles and fix the mould that way but Id love to know what caused it to wrinkle up.
newtec1,
Apr 5, 8:52am
Any humidity around. ?
morrisman1,
Apr 5, 8:55am
it wasn't significantly humid.
rob_man,
Apr 5, 11:42am
If you brush gelcoat you really need to double coat it, even if it's cured well some bits will be too thin to withstand the styrene attack from the resin and will fry up. You'll notice the alligator effect follows the brush marks as a rule. Also, four hours might be a little too soon.
neville48,
Apr 5, 12:11pm
Dead right, you have thin spots in your gelcoat and the resin has been a bit slow going off so has more time to attack the thin spots during cross linking of particles between gelcoat to resin so you get alligator. If you are using PVA release off the mould just fill them with bog or rub of as high spots from the product.
flancrest,
Apr 5, 12:18pm
Totally agree with 4 & 5. Thin Gelcoat. Always back up when brushing.
morrisman1,
Apr 5, 8:27pm
cheers guys, I thought I had it ok, but mustn't have. Will keep that in mind on the next part.
spottie,
Apr 7, 10:01am
As already stated gelcoat was probably to thin. Need to be 20 thou thick for a proper cure (0.5 mm). You can get a styrene inhibited cure in the low spots like in the bottom of a well so standing a mould up to let the styrene out works. Another possibility is that your catalyst is to old. Lots of other variables will do the same thing but the first one to look at is the thickness as stated. Cheers.
morrisman1,
Apr 7, 10:12am
Catalyst is about a year old. i have since more on order so will see how that goes.
spottie,
Mar 25, 3:50am
Fresh catalyst is best, and there are different types that give different gell times but the cure time should be similar. Gelcoat should be sprayed with a less reactive catalyst that cuts down the porosity from the released oxygen from the chemical reaction than the catalyst that is used for laminating resins. But most people don't bother and use just the one type across the board. We use 4 different types according to the application.
Since the public registrations are closed, you must have an invite from a current member to be able to register and post in this thread.
Have an account? Login here.