Small blister question

[GenesisCaptain]

Hey everyone. We just hauled and power washed our 78 Catalina 27 which is new to us this season. good news is the hull is in excellent shape for being on a mooring the last 2 years. The only issue besides needing a light sanding and a few coats of bottom paint were a few small blisters ranging in size from a quarter to an eraser head. They felt hard and sounded solid when tapped lightly with a resin hammer. The yard owner didn't think it was a major issue. Just grind them past the gelcoat, fare out with epoxy, barrier coat, and paint. A few questions:

1. Since they are so small, how long should I let them dry once I open them up?

2. Do I need to apply glass or should a good epoxy like West Systems with faring compound do the trick?

3. How many coats of barrier paint should I apply, what kind should I use, does it come in quarts?

Thanks for any input!

[paulk]

A week's drying wouldn't hurt, but might be more than you actually need for stuff this small. Epoxy fairing compound would be the stuff to use. Polyester resin doesn't "stick" as well, especially in small spots like what you have. Two barrier coats should do nicely - two-part epoxy stuff. You could probably make do with a pint.

[sailingdog]

Did you open any of them? Did they have any liquid in them?? If not, then they're not osmotic, they're voids... If they were dry, then you can grind them a bit, coat with epoxy and then fill with thickened epoxy and then paint.

Whether you need to add fiberglass has to do with how deep the blisters are. If the blisters are just below the gelcoat, then you probably don't need to add any fiberglass. I wouldn't use West Systems epoxy. System 3, MAS, and the epoxy from Progressive Epoxy Polymers in NY are equally good and far less likely to blush.

If you want to barrier coat them, use Interprotect 2000E, and use four coats or so. It does come in quart-sized packages. IMHO, it really isn't necessary, since epoxy is water impermeable. But, you might want to just use one coat to act as a primer to help the bottom paint stick to the repaired areas. If you're doing this, remember to "hot coat" the bottom paint to the Interprotect 2000E.

[GenesisCaptain]

Thanks Paul, comfirms what I was going to do. I'm no stranger to bottom repair but have never had to deal with blisters before. Good opportunity to break out the Dremel. Thanks again.

Thanks dog, I've got a MAS system as well, I'll use that. What's hot coat mean? That's a new one on me??

[sailingdog]

Basically, that means you apply the bottom paint to the epoxy before the epoxy is fully cured. This will give the paint a much stronger bond to the barrier coat than if you let the barrier coat cure completely.

To "hot coat" the bottom paint should be applied when the epoxy is at the stage where it takes a fingerprint impression but isn't sticky.

Originally Posted by GenesisCaptain

Thanks Paul, comfirms what I was going to do. I'm no stranger to bottom repair but have never had to deal with blisters before. Good opportunity to break out the Dremel. Thanks again.

Thanks dog, I've got a MAS system as well, I'll use that. What's hot coat mean? That's a new one on me??

[sailingfool]

Dry the blisters until ... well they are dry. To see if they are dry, blow some chalk dust on them, see if it changes color.

[donlofland]

FYI-if you do decided to barrier coat, 2 gallons of Interlux 2000 provided for 4 coats...

[donlofland]

Oooops-on my Catalina 27, that is...