Help- Fiberglass Foul Up!

[robo1]

I need some good advice regarding a bad situation.

Last week I put what I hoped was almost the finishing coat on some repairs to my sailboat (3 dinnerplate sized holes and one approximatel 8" x 36"). I used boatyard resin and hardener with West System microbubble. The 3 smaller of the 4 patches have kicked. The last, which is on the bottom of the hull is firm, but not sandable. I can still make a dent in it with my fingernail.

I know my errors are twofold. 1. I mixed in some microbubbles before putting in all the hardener. 2. I did not add enough hardener.

I am now about 7 days out from this repair. Some people have said I need to completely grind this off. (I'm not sure this is even possible, I am afraid I'd just whip it into a melted mess). Others have suggested that I expose it to sunlight or heat it up with a heater. Note the 2nd and third patches kicked around day #4. The deepest patches were probably 3/16 thick. I had multiple layers of fiberglass under this.

I would appreciate the sage advice of this forum.

Thanks,
Robo 1

[Gary Baigent]

In my experience there is no escape - get some scrapers and chisels and rip it off, mate. Power grinders will just clog. Next time check your hardener amounts. Sorry to be so boring.

[BHOFM]

I would have some concern about the spots that took four
days to set??

It will be easier to fix now than later!

[PAR]

Robo, there isn't any short cut, unfortunately. Additional time may permit a sort of cure, but the resin/hardener matrix isn't right and can't be relied on to be waterproof or have any real strength. There's no way to fix this without removing all of the bad batches.

Scrape, sand or other wise remove the screwed up resin. Grind back to good 'glass and try again.

Always mix resin and hardener first, get a good, complete mix, then add fillers.

The batches that did get hard, can you dent them with the corner of a screw driver, by pressing hard? If you can, then it's no good. Polyester and epoxy will not dent when properly mixed and cured. What was the general temperature when you mixed and applied the goo? I'm assuming your in the Philadelphia area, which means if done relatively recently (this summer), the ambient temperatures would have been sufficient enough to cure epoxy or polyester.

When in doubt, grind it out . . . You don't want to have to worry about this further from shore then you can swim back to.

[robo1]

I am overwhelmed by world opinion (from Florida to New Zealand). I'll stop waiting and whining and get out the scrapers and strip it down. Par- regarding temperature, we have had a bunch of warm days which should have done the job.

My one concern is whether you can get a super hard surface if you properly use these microbubble fillers. I like the idea of having a medium like frosting or peanut butter to nicely smooth in the low areas, but I want it to be strong. Do you need to add more resin to compensate for the additional filler material?

Thanks again y'all.

Robo

[PAR]

A fairing filler has the have a few requirements for it to be effective and perform it's task. It should be a light weight material, because you'll smear lots of it all over the place. It has to be easy to sand or you'll make a career out of fairing up the hull. It should be lower in density then the substrate you're putting it on, so it sands away before the substrate does. Low cost would be nice.

This is why micro balloons (and other "bulking agents") are used. There are a couple of different types of balloons: Microballoons, which are microscopic spheres of quartz (a white glass) and phenolic spheres, which are plastic.

By adding silica to the mixture (typically to prevent sagging) you can get the consistency you desire. Generally you want your fairing coatings to sand easily and worry about "hardening up" the surface with additional coatings with other things, like graphite powder. Phenolic spheres have good compression strength. I usually mix in a little talc to smooth out the mixture (make it extra creamy).

Adding fillers to resin actually increases the amount of goo you have, so you don't need extra resin. You add filler material to resin, until the desired consistency is reached. If you add more resin, then you're just thinning out the filler and it'll go from peanut butter to ketchup.