Bottom Blasting

[David M]

Originally Posted by Cheechako

Some people call Interlux 2000 etc a barrier coat. It is nothing like the real thing :, Epoxy resin. 2 coats of real resin works for most people. I've often wondered if paint stripper doesnt soak into the very pourous gel coat....?

Interlux 2000 and 3000 are epoxies. In my experience they are excellent.

2000 is super tough. I use it on the hull and on the after deck with a non-skid. I drag anchors and other heavy metal things across the deck with very minimal damage to the paint. No other coating holds up like this.

[Fiberglass1Inc]

The manufacturer does indeed approve AwlFair below the waterline. And if properly mixed it may be OK. But I've seen multiple failures. Personally, I would prefer to make my own filler using WEST or Systems 3 with 80/20 cabosil/3Mglass bubbles. In theory, as long as whatever you use is mixed accurately, and as long as adequate (12 mils) barrier coat is applied over the fillers, it shouldn't much matter.

[David M]

I would consider putting the fillers over the barrier coat. This way if the filler fails you still maintain the moisture barrier coat

[Ziggy]

Originally Posted by David M

I would consider putting the fillers over the barrier coat. This way if the filler fails you still maintain the moisture barrier coat

Interprotect 2000 needs to be coated with antifouling while still tacky. If you apply fairing over IP2000 but before the antifouling, you're likely to miss this time window.

[David M]

Or you can sand Interlux 2000 before applying bottom coat.

You are right in that a chemical bond is always better than a physical bond.

[Fiberglass1Inc]

You probably would not want to put the barrier coat on before the fillers. The normal procedure is to "prime" the indentation with plain unfilled epoxy before applying any filler. This primer coat soaks into the raw glass and gives root to the fillers. Mixed properly and applied to a dry surface, it just doesn't fail. The Interprotect is too thick to soak into the glass and you would lose this advantage.

[AtlanticGreenPro]

Just a word of advice... anytime you have a boat media blasted... as in soda blasting, sandblasting or even wet abrasive blasted you really have to use some type of epoxy barrier coat on the gel-coat to seal it before applying your ablative paint.

I've seen way to many boats that were dry sandblasted and then the customer decide to apply ONLY ablative paint over the freshly blasted gel-coat.

The problem is gel-coat absorbs moisture as much as no one wants to admit... freshly sandblasted gel-coat has a tendency to get little micro pinholes which most of the time you can't see unless you look real hard.

Half the boats we wet abrasive blast... we also do the bottom painting and on those boats we either put 4 coats of Interlux 2000E of 2 coats of SeaHawk Tuff-Stuff epoxy barrier coat.

More of our customers are moving to SeaHawk Tuff-Stuff because 2 coats of SeaHawk Tuff-Stuff equals 4 coats of Interlux 2000E which saves a lot of time and money.

Here's a video we shot this week of a badly blistered boat that was sandblasted maybe 10 years ago and then had only ablative paint put over the gel-coat without a barrier coat.
Badly Blistered Gel-coat caused by Sandblasting and no barrier coat
blisteredbottom - YouTube
Had the boat owner done it right and barrier coated the boat there would have never been any blisters.

This is what a healthy gel-coat should look like during wet abrasive blasting
cleanbottom - YouTube