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i got problems with me grp gel cracking off to find voids to the matting underneath its realy getting me down
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When mounting the rear arches I accidentally shone a flashlight through one, and saw lots of bubbles in the gel coat, too...
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Shabby workmanship from the laminator and not excusable
Lost a lot of money with my GRP work and boat moldings because the laminators taking short cuts and had similar type rejects...
These faults usually happens when the operator tries to laminates 2 or more layers at one go causing the bottom layer to be left partly dry, or to thick CSM grade as a surface layer against the gel. Most commonly caused by not rolling out the wet laminate out with ribbed rollers and using brushes only.
Depends how you want to have it fixed. If you want a gelcoat finish there is one way and if you are to paint the parts another way. But first, take a 10mm round bar and round off the one end smoothly but pointy (about 150mm long). Start tapping away over the complete surface of the molding you have and as soon as you find another bubble(s) it will sound hollow or the gelcoat will crack away. When you are sure their are no hidden bubbles, take a sharp object and start peeling the gelcoat off until you get to a solidly bounded gel again.
Be warned, some of these bubble gelcoat will peel away to quite a large area although it did not sound hollow when tapped.
When you are done removing all the loose gel coat, time to repair.
If you are going to paint: Mix some micro balloon spheres (or "kulu" powder) into some general purpose laminating resin until you have a nice textured paste much like the viscosity of toothpaste. Clean all the areas to be fixed with acetone or styrene. Take a flat scraper and fill the holes but make sure you apply plenty pressure for a good bond. Fill until damage area is slightly higher than the surface - dont forget to add MEKP
(hardener) to the mix and mix small quantities at a time to limit waste should it gels on you whilst busy.
When done, sand down. I prefer 120# grit dry AbraMat - aluminum oxide - sanding strips which I stick onto a flat plank (handle on) with velcro backing fitted to roughen excess filler off. Then start with 320# grit water sand paper and finish down till 1000# grit.
Prime and paint with 2K or similar 2 pack paints.
If you want gelcoat finish; Preparation much the same as above and fill the holes partly with filler to leave little space for gelcoat if it is deep - if the area is shallow, apply gelcoat directly to area. Do not apply gelcoat thicker say than 2mm because although it will cure, styrene is trapped and will over time evaporate to the surface causing discoloration and the common cracks found in older grp parts which is a direct result of to thick a gelcoat.
BUT, gelcoat is un-waxed and need some liquid wax to be added for it to cure.
If you do not have liquid wax, dont panic. Apply the gelcoat
(remember the hardener) straight out of the tin so it sits a bit higher than the surface. Cover the gelcoat with a piece of wide (40 - 50mm) Cellotape or brown box tape. The purpose of this is the same as the liquid wax - to remove oxygen from the gelcoat to be able to harden. If you have PVA mold release (red stuff), just smear some of that over the gelcoat for the same result and when the gel is cured, simply wash off the PVA with water.
Sand down. If you still have some spots and hollows after gel is sanded smooth, simply repeat the step but remember to clean the area with acetone or styrene before applying more gelcoat or filler.
My only problem with gelcoat repair is the fact that the areas will be visible if the colour matching of the gel is not 110%...
Hope this will help
