Originally Posted by Don Boyd
I was planning to replace the roof vent on my 1989 b190 and noticed lots of small hair line cracks in the roofs gelcoat. I have seen gel coat on ebay and wondered if anyone has tried this type of repair on their van. I only plan on the very top because I see no damage to the sides, front or back. It appears that you just need to clean and lightly scuff roof before applying a few coats of gel coat. I can use any advice you might have on this subject. Thanks, Don
So called spider cracks can appear for couple of reasons. One, the layer of gel coat was applied too thick. This happens more often in the inside corners where it is difficult to spray gel coat evenly because of deflection from two or more angles causes heavy application on inside of the corner.
If that was a reason for spider cracks, scuffing that area and applying the second coat will only worsen the condition as the gel coat has no linear strength. It is much as the egg shell, it is fragile and only a dressing for fiberglass.
Spider cracks can also develop from flexing of the surface to which gel coat is applied. Unless you stabilize the area and eliminate the flex no gel coat repair will be successful. There is a quite a bit involved in gel coat repair. The old cracked gel coat must be removed down to fiberglass tapering the edges of the repaired area. You must very accurately add 2% Of MEKP [hardener] by weight to the mix. You must thin it with Styrene or Acetone to a spray-able consistency. You must add dryer agent to gel coat, or the surface of the newly repaired area will never dry up enough to sand, compound or polish the surface.
Take my advice and leave it to the pro and you will be glad you did. In my life I have designed, repaired and build many boats in 42 years. Thanks, "Boatdoc"