Epoxy resin to help waterproof the wetted area?

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Bought a '78 26' S2 for experience prior to a larger boat for world cruising.

The bottom has a couple dozen blisters, probably due to the factory using polyester resin instead of epoxy resin until sometime in the 80's. Only the outermost layer of fiberglass was affected by the blisters.

The blisters are slowly shrinking in this desert environ. The boat has been out of the water for a month now. I don't know of the boat ever leaving the water for a long period in the past. It was either on the SF Bay or Delta.

Bought two gallons of Pettit Trinidad paint which should be extremely good at over $300/gallon retail.

Would applying a gallon of epoxy resin prior to the paint help prevent blisters? Or would it take 2-3 gallons to make a difference?

I plan to sell in two years by the way. Not going to get my money back. Mostly just want to do a good job. Don't have the time to do the "perfect" job.

[UNCIVILIZED]

Most folks use 3-5 coats+ of epoxy barrier coat, which is purpose designed for the job. And formulated to work well with the bottom paint they're using. For example Defender.com Search Results: barrier coat
And the paint manufacturers have tables which will tell you how much coverage you'll typically get from a gallon.


Though I've often wondered if using regular epoxy resin would work, so it'd be worth talking to the resin manufacturer to ask them. The biggest catch that I can think of is to ensure to aggressively remove the amine blush prior to applying anything overtop of the cured resin. As if you don't, the subsequently applied paint will come off. And with some resins it can take quite a while for it to fully cure (days, & sometimes even a week or more). Which, the amine blush can't fully be removed until this happens.


I once had to re-do some deck paint due to it's peeling off because of this. Even though I didn't put any primer on overtop of the epoxy for a good 10 days after I'd applied the resin, & the ambient temp's were plenty warm enough to cure things.

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Originally Posted by UNCIVILIZED

Most folks use 3-5 coats+ of epoxy barrier coat, which is purpose designed for the job. And formulated to work well with the bottom paint they're using. For example Defender.com Search Results: barrier coat
And the paint manufacturers have tables which will tell you how much coverage you'll typically get from a gallon.


Though I've often wondered if using regular epoxy resin would work, so it'd be worth talking to the resin manufacturer to ask them. The biggest catch that I can think of is to ensure to aggressively remove the amine blush prior to applying anything overtop of the cured resin. As if you don't, the subsequently applied paint will come off. And with some resins it can take quite a while for it to fully cure (days, & sometimes even a week or more). Which, the amine blush can't fully be removed until this happens.


I once had to re-do some deck paint due to it's peeling off because of this. Even though I didn't put any primer on overtop of the epoxy for a good 10 days after I'd applied the resin, & the ambient temp's were plenty warm enough to cure things.

Thanks for that helpful information. Looks like Total Boat Epoxy Barrier Coat and Tuff Stuff Marine Epoxy are similar products.

It would clearly costs plenty to have a boat yard properly refinish an old bottom. Costs plenty to do it yourself...

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FWIW....for science......the original owner used epoxy resin when he turned the 2' shoal keel into a 3' deep keel while adding 800 pounds of ballast.

There are no blisters on the keel where the epoxy resin was used. System 3 epoxy resin was used. There are a few smallish blisters on the rudder. The hull has some larger blisters, a couple that were almost 1/2 dollar in size. Though they are rapidly shrinking in this mountainous desert environ.

[UNCIVILIZED]

Note that their shrinking doesn't automatically mean that they shouldn't be further investigated, & or, repaired. Since the fluid that caused them is still in there somewhere. And it sometimes is but a symptom of other issues. Some of them being significant ones.

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Originally Posted by UNCIVILIZED

Note that their shrinking doesn't automatically mean that they shouldn't be further investigated, & or, repaired. Since the fluid that caused them is still in there somewhere. And it sometimes is but a symptom of other issues. Some of them being significant ones.

Yes indeed. I sanded them so I can still find them if/when they disappear.

One definitely needs to let the fluids dry out before applying epoxy resins that will never let them out. I'll have to open them up when air drying doesn't work. Then refill the material that was removed. Thinking fiberglass would be the best for that. May use strands....not sure. I think strands would provide the smoothest finished product.

Four gallons of epoxy primer should make the bottom reasonably water tight. After proper prepping of course. It did pretty well for almost 40 years of frequently questionable maintenance.

I thought I was being real lazy while sitting here. Actually letting the bottom dry out was/is about the best thing I could do without a commercial dryer.