Do I have this Right?

[hriehl1]

1968 Hinterhoeller HR28
I had my bottom soda-blasted before winter to remove untold layers of paint from the prior owner. It is down to gelcoat on 95% of the surface area. This spring I need to get it ready for launch. I plan the following sequence.
1. Orbital sand entire bottom with 80 Grit
2. Wash, rinse, wash, rinse
3. Fair as needed with thickened epoxy
4. Wash, rinse, wash, rinse
5. Roll 2 coats of West System epoxy for a barrier coat
6. Wash, rinse, wash, rinse
7. Bottom Paint

My question is that Interlux sells a barrier coat product... it is really anything different from other quality epoxy products? And would 2 rolled coats of epoxy be sufficient?

Thanks... Hank

[Paulus]

Common practice is to put 5 or more (some say 7) coats of barrier, but that is to prevent blisters from developing on more modern, new-age gelcoat. Your hull is aged (like mine) and if it has none to date, I would not wast time and money building to the recommended mills on the cans... Two coats of Interlux barrier coat , as I have on my 1970 Mariner will provide for a sound base for a few coats of ablative.

[Figment]

Omit steps 2-6.
Splash and sail.

(yes, a search of this forum will reveal that I once did 2-6 and more, but that doesn't make it "right")

[CharlieJ]

Common practice is to put 5 or more (some say 7) coats of barrier, but that is to prevent blisters from developing on more modern, new-age gelcoat. Your hull is aged (like mine) and if it has none to date, I would not wast time and money building to the recommended mills on the cans... Two coats of Interlux barrier coat , as I have on my 1970 Mariner will provide for a sound base for a few coats of ablative.

Yeah, well- my 1961 Meridian had zero blisters too- after being in the Great Lakes it's whole life. Then I brought it to Texas, restored it and launched. Next haul-out- Blister city!!!

I'd highly recommend the barrier coat. I first used WEST, which did pretty good. They make an additive just for that by the way. Next haul out, we had a very few new blisters, which were probably old ones we missed first go around coated with 4 coasts Interprotect.

I''d do the barrier coats if it were me. And I don't think two coats is enough.

[Hirilondë]

I have read numerous posts over the years and talked with numerous professionals at work regarding blistering, osmosis, moisture and related bottom concerns. The one thing I have found is that almost no one agrees on anything. Do people think that the barrier coats prevent moisture from getting into the composite (glass/resin)? Or do they think it just creates a more stable base on which to build (bottom paint)? What confuses me the most is that few people ever discuss what they are trying to accomplish, just the method they claim is superior. If the reasoning for barrier coat is to keep moisture out then one must also consider what to do about the moisture already there before coating. Some say the problem is salt that is absorbed into the composite that has to be removed after stripping/sanding but before barrier coat. They claim an extensive rinsing and drying process to draw it out before applying anything is necessary. So many things I have heard over the years seem logical yet no single theory and method are considered the industry standard for a quality repair.

I don't have any answers. I don't mean to confuse hriehl1 or the issue at hand, but we may be in fact discussing several different problems in one topic as if they were all the same.

[hriehl1]

My situation is as follows... I've been in frequent touch with the prior owner who has no reason to mislead me because he donated the boat and I then bought it at auction. He has demonstrated truthfullness time and again and his family has owned the boat since 1969. It has always been sailed in Mass-NH-Maine.

So, this boat has never shown any blister symptoms. It has now been out of the water for 4 seasons so it totally dried-out. I had the hull soda-blasted in October and will sand down to original gelcoat so my ownership begins with a known bottom condition. Nothing scarey was exposed though I do have some hull-keel joint fairing to attend to.

I could just bottom paint and splash. But this boat is sitting in my driveway so if a barrier coat is advised, now is the time and place to do it. I was planning on 2 (or more) coats of epoxy. My understanding is that coating, when overcoated with ablative bottom paint, presents a far less porous surface than gelcoat covered with paint; hence reducing the likelihood of any absorbtion.

I am talking myself into this... though Hirilonde's observations that no one agrees WHY barrier coats are advised gives me some pause.

[Paulus]

If I were in your situation, I would buy two gallons of two part barrier paint and apply until gone - giving some extra to high wear areas - then bottom paint and splash.

If for no other reason than peace of mind.

[Hirilondë]

I can't imagine that barrier coat will hurt. The real question is whether it helps. Some say that barrier coat is simply a means of making money by the manufacturers. I find this easy to believe, but can offer no proof this is the case. That is serves no real purpose as you can't keep moisture out when the boat sits in the water 4-10 months a year and that the moisture isn't really an issue for paints except LPUs. LPUs should never be used below the water line anyway, and they (the manufacturers) tell you this.

As your boat has been in salt water all it's life I would suggest several rinsings with fresh water followed by a day or so of drying out. If in fact salt can be removed this should do it. You can wipe off the surface after it has dried and see if you find any salt. Then I would use a couple coats of some kind of primer (epoxy, barrier coat, specialty primer, whatever) as recommended by the manufacturer of your bottom paint of choice. As much as I hate to fall for the manufacturer tactics to get me to buy something I don't need I have to agree with Paulus here. You are at a point now where you really want to get this right and like I said above, I don't think it can hurt to seal your bottom with something.

This is one of those topics where I claim no one knows for sure what is best. The whole point of my previous post was to say that.

[mitiempo]

A day or so of drying out will not do much - a few months might. Any moisture in the hull took months/years to be absorbed and will not be leaving quickly. If you only wait a few days all you are doing besides adding to the manufacturer's of the barrier coating product is sealing the moisture in.

If there are not any (or very few) blisters after the last 44 years it is unlikely it will start now. As I recall blisters were not real prevalent before the early 70's.

[Hirilondë]

A day or so of drying out will not do much - a few months might.

When rinsing you are not saturating the hulll. It is just to help absorb any salt in the hull, near the surface and help to remove it. A day or 2 is more than is needed for this rinsing to dry. Any contaminant will compromise the bond of paints and this rinsing is just a way to help reduce one. This day or so of drying between rinses has nothing to do with lowering the moisture content of a saturated hull.

[mitiempo]

I understand, but a barrier coat on a hull with the moisture content of years afloat is false economy I think if you are not going to dry the hull as thoroughly as possible. That takes time. As I said, if the hull has not had blisters in its long life they are not likely to occur now, barrier coat or not.

[earlylight]

Hank said the boat has been out of the water for 4 seasons drying out

[mitiempo]

I missed that.

Hank

Has the boat had any blisters?

[hriehl1]

The boat has never had blisters and has been on the hard for 3+ years. I've washed and rinsed the hull after the soda-blast 3 months ago a couple times. That sucker is as clean and dry as it'll ever be.

The way I see it, 3 or 4 coats of epoxy rolled onto a 28-footer is one long day for wife and me... as someone said, it is worth it for (at least) peace of mind and maybe (though I'll never know) it'll save some blisters.

I'm gonna do it... I will start another thread in the materials section with some follow-up questions.

Continued thanks from a newbie.... Hank