Trouble with gelcoat

Randy · #1 02-03-2009, 11:37 PM

This looks like trouble here. Hope I can get some expert advice.
My intent was to remove bottom paint prep hull and re-apply barrier coat and an epoxy paint. I took off about 5 layers of bottom paint with a chemical stripper then began sanding. I uncovered what looks like tons of small blister. I'm unsure because they where filled with paint and had no moisture. Is there any other reason for this type damage to old gelcoat? Can I just fair the holes or does every one need sanding/ground down? Thanks for help.

Ed · #2 02-04-2009, 01:40 AM

If you don't see any signs of moisture, spider cracking or delamination, I would probably give it a good cleaning, let dry and then put 3-4 coats of epoxy barrier coat on it. The barrier coat is pretty thick stuff and will fill in many imperfections.

stoney · #3 02-04-2009, 09:19 AM

I had the same issue on my 1973 23ft. I filled the bigger ones with quickfair. 4 coats of epoxy sealer 2 coats of paint and 8 months in the water no issues. Buy your barrier coat in two different colors so you can see the coverage.
http://i15.photobucket.com/albums/a3...HIPPING012.jpg

Islandtrader · #4 02-04-2009, 10:18 AM

Does this look familiar?

Same problem on the 21...just voids in the lay up. Since I was not going to bottom paint I filled all the voids and now in the process of fairing.

The quick fair works well.

3rdday · #5 02-04-2009, 11:22 AM

It might be a combination of voids in the layup + osmotic blistering I see them on my 21 also if there is a higher concentration at & below the waterline those may be both, and if they exist above but more sparse those may be voids in the layup- Fiberglass was very new to the public/commercial when the 21s were built so I am sure there was a learning curve. In any case a good barrier coat is important.

muddywater · #6 02-04-2009, 12:05 PM

I have been using Quikfair. Do I need to put some kind of coating over that before I gel coat? I will not be adding a barrier coat because people down here generally do not keep their boats in the water.

Randy · #7 02-04-2009, 09:14 PM

Islandtrader
Looks identical. Got my order of quick fair in and going at it when the temps warm a bit. What's the deepest void can you fill with quick fair? Was planning on using Awlgrip 545 as a barrier. Reading a lot of threads here, it looks like a common barrier. Anything better?

Caymanboy · #8 02-04-2009, 10:09 PM

You can't use an epoxy coating then apply gelcoat over, just can mix epoxy and polyester, for the same reason 545 is not good below the waterline. If you are going to use an epoxy filler then stay with an epoxy barrier coat, say Interprotect 2000, if you are going to gelcoat it, then yse a polyester filler, but that won't stop any water intrusion. Hope this helps.

3rdday · #9 02-04-2009, 10:29 PM

Caymanboy is correct. Uncured expoxy will bond to cured polyester, however uncured polyester will not bond to cured epoxy well. Caymanboy is also saying that polyester absorbs water, that's why polyester gelcoats require a barrier coat.

Caymanboy · #10 02-04-2009, 11:00 PM

Ifin it was me, I would use the Interlux underwater epoxy filler,, sand it, it sands well, apply two coats interprotect 2000, is the boat going to live in the water it's whole life? If it is I would put three coats interprotect, if it is just a w/e splash, I would consider not doing it at all.just fill with epoxy and bottom paint it, As said before polyester fillers absorb water. Thanks 3rdday, you know your stuff.