Why barrier coat?

[Drinky Crow]

It only traps water in the laminate.

Or do you wait, dehumidify, and trust a moisture meter?

After soda blasting the old bottom paint off I found just one blister. Ground out revealing wetness, poked w/awl and applied acetone.

Going back in within the month. Plan is to prime, antifoul and launch.

[catsketcher]

I am not sure about your situation, but if you are new to yachts -

- polyester resins are not totally watertight - so after years of immersion water molecules can make their way through the gel coat and into voids. This can lead to blistering. Not all polyester boats get blisters - it sounds as though byours hasn't although they do tend to take a few days or a week or so to grow after you haul the boat out.
- epoxies are waterproof. So epoxy coating an old polyester laminate is a good thing if you want to avoid osmosis later on. But you do need to ensure the laminate is dry.
- It is possible to do things - like heating and vacuum bagging to get water out of laminates faster.

So epoxy barrier coating is great over a nice dry laminate.

cheers

Phil

[s/v Jedi]

Wash and scrub that spot daily for a while, pressure washing is good too. Look for a wet line before washing… if visible, it needs deeper grinding.

Then dry it. For a small spot you can help with daily heat gun treatment (no too hot…). You can test dryness by taping a piece of transparant plastic over the spot and checking for condensation the next day.

When it is dry, first brush some neat epoxy on to wet it out, then add colloidal silica filler and fill where it was grinded. After cure, sand, incl. into surrounding antifouling. Instead of regular primer, use TotalProtect or InterProtect 2000 etc. barrier coat and do a couple coats using fingerprint test for timing. Finish with a fingerprint test and first coat of antifouling (so hot coat it for chemical bond).

Now sand again and do the whole antifouling or just a larger spot when the rest is still okay.

[coopec43]

s/v Jedi

Your Sundeer 64 is aluminum from memory? I'm impressed with your knowledge of fiberglass yachts. Have you owned one (or more) previously?

I have a problem with Helen's barrier coat, I gave the hull three coats of barrier coat then 3(?) coats of black Altex No 5 anti fouling. Then I noticed the barrier coat was cracking on the starboard side of the keel. I quickly realized the hot afternoon sun was heating up the black anti-fouling on the keel to a point where the barrier coat couldn't handle it and started to crack.

Before I launched her I sanded off the anti-fouling, epoxied glass cloth over the cracking then 3 coats of barrier coat and then the anti fouling. When I hauled her out it was obvious that I hadn't completely covered the cracks. (an area of about 2 feet X 3 inches. When I haul her out next I plan to dry her out then sand the anti fouling, epoxy/glass, X3 barrier coat and anti-fouling.

Do you think that is a reasonable approach?

[CarlF]

It all depends on the resin and how well it was handled during layup. The quality of resins went up and down over the years. They were especially problematic after the oil price increases of the Arab embargo. Most better builders would test each new drum of resin to see how quickly it “kicked”. A good layup took a lot of “chemistry” expertise.

Some boats built with polyester resin never have a blister problem. A 40+ year old boat that’s been in the water that doesn’t have a lot of blisters isn’t going to suddenly develop lots of them now. The blisters are usually just a few and shallow. They can just be sanded and filled. For these boats, barrier coat isn’t worth the money.

[rslifkin]

Originally Posted by CarlF

It all depends on the resin and how well it was handled during layup. The quality of resins went up and down over the years. They were especially problematic after the oil price increases of the Arab embargo. Most better builders would test each new drum of resin to see how quickly it “kicked”. A good layup took a lot of “chemistry” expertise.

Some boats built with polyester resin never have a blister problem. A 40+ year old boat that’s been in the water that doesn’t have a lot of blisters isn’t going to suddenly develop lots of them now. The blisters are usually just a few and shallow. They can just be sanded and filled. For these boats, barrier coat isn’t worth the money.

Agreed, susceptibility to blisters varies significantly between boats. It depends both on the resins used and also the construction methods, etc. used. Some builders did a better job of avoiding blisters than others, and some had issues only in certain time periods when they had resin issues (like Uniflite with the fire retardant resins).

Originally Posted by coopec43

Your Sundeer 64 is aluminum from memory? I'm impressed with your knowledge of fiberglass yachts. Have you owned one (or more) previously?

I'm pretty sure the Sundeer series were all fiberglass. I don't think the Dashews did too much with aluminum until they started building the FPBs.

[s/v Jedi]

Yes, after original Sundeer in aluminum, all the series production was done in fiberglass with Vinylester resin.

I have not seen the barrier coat cracking because of heat… butI have seen foam cored rudders having the foam melt away when covered with black antifouling so consider everything possible.

Yes, some extra glass before barrier coat and antifouling sounds good. I would start grinding at these cracks to see how deep they are and flare it out to create space for the fiberglass to keep it all flush.

[Bowdrie]

Fiberglass boat builders took two big hits in the early '70s.
1, The OPEC nations skyrocketed the oil prices, that drove the price of resin thru the roof.
2, The EPA clamped down on the amount of Styrene that could be used in the resin.
Fiberglass used a binder that the Styrene would dissolve, and allow the resin to obtain a good bond to the individual glass strands.
So, builders did everything to reduce the amount of resin they were using.
The results were "dry lay-ups", less resin used, and the resin used had less Styrene to dissolve the binders.
This was a major cause of blistering as time/age went on, billions of fibers that had microscopic channels for water to pass thru the laminates where the binders had never been dissolved.
It's always been under-reported, but a lot of blistering came from boats that sat at a dock in cold water with heaters going in them.
With raw fiberglass surfaces under the floorboards that were damp from bilge water and condensation, but at the same time significantly warmer than outside water, the osmotic pressure would drive the inside moisture thru the unprotected laminate until it hit the gel coat, where it formed a blister.
I've seen that many times here in the PNW.
The boat sits in its boathouse/dock for 8 months with heat inside and the floorboards lifted-up.

[Fore and Aft]

DrinkyCrow a few coats of epoxy undercoat never hurt, personally I would be leaving it to the last week before you do the painting. Give that hull a chance to dry out. Make sure you take a few photos as it is a good selling point being able to prove the hull has been recently stripped and painted again.
SVJedi foam and black paint usually don't mix and its one of my go to areas on boats that have black paint around windows.
I have surveyed some boats and you can literally see a line below the waterline where one worker has taken care and rolled/laid the fiberglass properly. Then the next area of the hull is blistered and looks awful.
Coopec 43 did you put a barrier coat like Vinyguard 88 between the epoxy and antifoul? Drinky Crow I have seen this paint blister on a really wet hull that was facing the sun.
Cheers

[Benz]

Originally Posted by coopec43

s/v Jedi

Your Sundeer 64 is aluminum from memory? I'm impressed with your knowledge of fiberglass yachts. Have you owned one (or more) previously?

I have a problem with Helen's barrier coat, I gave the hull three coats of barrier coat then 3(?) coats of black Altex No 5 anti fouling. Then I noticed the barrier coat was cracking on the starboard side of the keel. I quickly realized the hot afternoon sun was heating up the black anti-fouling on the keel to a point where the barrier coat couldn't handle it and started to crack.

Before I launched her I sanded off the anti-fouling, epoxied glass cloth over the cracking then 3 coats of barrier coat and then the anti fouling. When I hauled her out it was obvious that I hadn't completely covered the cracks. (an area of about 2 feet X 3 inches. When I haul her out next I plan to dry her out then sand the anti fouling, epoxy/glass, X3 barrier coat and anti-fouling.

Do you think that is a reasonable approach?

Depending on the resin you used, you may not need barrier coat at all. If you used Vinylester, you'll be fine without. If you used the cheapest polyester laminating resin, you may still be fine for some years without barrier. Knowing the hassles of barrier coat, I'm trusting to my vinylester to not osmote.

[coopec43]

Originally Posted by s/v Jedi

Yes, after original Sundeer in aluminum, all the series production was done in fiberglass with Vinylester resin.

I have not seen the barrier coat cracking because of heat… butI have seen foam cored rudders having the foam melt away when covered with black antifouling so consider everything possible.

Yes, some extra glass before barrier coat and antifouling sounds good. I would start grinding at these cracks to see how deep they are and flare it out to create space for the fiberglass to keep it all flush.

The cracks are only hairline cracks.


Next time I have it on the hard I could give the hull a couple of days to dry (in the summer heat), sand off the anti- fouling, epoxy/glass the area, x3 coats of barrier coat then ant-foul.

[catsketcher]

Originally Posted by coopec43

s/v Jedi


I have a problem with Helen's barrier coat, I gave the hull three coats of barrier coat then 3(?) coats of black Altex No 5 anti fouling. Then I noticed the barrier coat was cracking on the starboard side of the keel. I quickly realized the hot afternoon sun was heating up the black anti-fouling on the keel to a point where the barrier coat couldn't handle it and started to crack.

I am not sure what is happening here - epoxy doesn't tend to crack from heat - it just softens and then hardens up again when cooled. I guess the barrier coat is not straight epoxy. I don't get why you need to glass over a crack in an epoxy barrier coat. I would fill and leave it at that. I have done a mono barrier coat and just used straight WEST 105 epoxy before using epoxy high build primer. I would not glass if either layer had cracks - but I have never seen epoxy crack from heat.

Maybe the epoxy cracked from thermal expansion of the lead keel. But epoxy usually softens when heated and this is what we do to raise epoxies heat distrotion temperature and improve meachnical properties.

cheers

Phil

[Drinky Crow]

So I'm about to slather this stuff... https://fibertek.ca/collections/epox...ducts/quikfair ...all over a divot under the bow and low spots just aft leading edge keel stubby approx. parallel to forward keel bolt. Find diagram this page...
https://www.cc27association.com/vchange.html
Got a buncha' smaller voids/pits on stubby.
Any reason why I wouldn't use excess fairing compound to also fill those?
Should I coat all fairing compound applied with neat epoxy?

[catsketcher]

Gday Drinky

I have not played around that much with polyester monos - I have done repairs and stuff on my family boats. My experience for 30 years has been with epoxy boats.

That being said - I almost always coat fairing compound with neat epoxy. One reason is that you can stop sanding with 80-120 grit instead of needing to go to 180. Also your high build primer will just be absorbed into the cured fairing compund if it is not sealed with neat epoxy - it just goes in so you need more coats anyway. And fairing compound is not totally waterproof (supposedly) so you want to seal it.

In essence - seal all fairing compound with neat epoxy before coating with high build primer. You can roll multiple coats of epoxy on in one day - as it gels roll another epoxy layer on - when it hardens enough to make a thumprint or a fingernail print but not rock hard (then you have to sand it). Do the same for the next coat of epoxy when you are putting the high build on - as soon as it goes hard enough for the thumbprint roll on the primer - much less sanding then and you can get a few coats on in one day with better inter coat adhesion.

[Fore and Aft]

Drinky Crow I love pre-mixed epoxy fairing compounds they are so easy to use. The one you are using must have some really fast hardener if you can machine sand, it in four hours. I also use the straight epoxy, then epoxy paint and finally a tie coat like Vinyguard 88 in one day to save sanding.
Cheers