Blisters, yet again...

mvweebles said:

Question on repair: I don't see recommendations to epoxy laminate a thin skin of fiberglass mat over the peeled hull. I've seen this being done and would think it would be far superior to paint-on Interlux 2000 alone. Would it be preferable to add a layer of epoxy mat?
Peter

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You're right, Peter. They did not mention adding any layers of mat. I will ask them further about this. Obviously, they would have to do it if any delamination were found. If adding mat helps increase the liklihood of long-term success, then it's something I would want to do, despite the incremental cost.

ScottC said:

...do you know if anti-fouling paint could be expected to protect the epoxy from UV damage?

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I would check with the experts on the Interlux technical hot line.

rslifkin said:

For the 2 color route, I'd personally use a hard paint for the first layer, then a compatible ablative over that.

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Thanks for adding this....exactly what I did. If I remember correctly, Interlux had/has a table discussing compatibility, although I called their tech line to
double check. As for the paint over epoxy cure times, my spouse and I got the ablative over the hard paint layer applied within cure windows.

ScottC
Your vessel has a composite rather than solid FRP hull as best I recall. Best to insure that whoever does the remediation can demonstrate requisite type experience. A decade or so ago Keith (RIP) posted on TF the steps for his composite hull KK 42 to cure a similar issue. Along with hands on comments and PMs from PSN, Commodave and others you've got some good TF advice.

I compliment you on the steadfast approach you're taking. During these COVID times getting work done at faraway "locked down" yards is a challenge for several of us.

sunchaser said:

ScottC
Your vessel has a composite rather than solid FRP hull as best I recall. Best to insure that whoever does the remediation can demonstrate requisite type experience. A decade or so ago Keith (RIP) posted on TF the steps for his composite hull KK 42 to cure a similar issue. Along with hands on comments and PMs from PSN, Commodave and others you've got some good TF advice.

I compliment you on the steadfast approach you're taking. During these COVID times getting work done at faraway "locked down" yards is a challenge for several of us.

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Thank you, sunchaser.

The dealer documentation I have refers to: "polyester resin laminate using injection technology". Not sure if this is the same as the "composite" you're referring to or different??

ScottC said:

You're right, Peter. They did not mention adding any layers of mat. I will ask them further about this. Obviously, they would have to do it if any delamination were found. If adding mat helps increase the liklihood of long-term success, then it's something I would want to do, despite the incremental cost.

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PSNEELD mentions it in one of his earlier posts. In the hands of skilled workmen, fiberglass work isn't too difficult. I would think the prep would be done already, would just be a few days to apply the skin and some minor fairing.

Good luck -

Peter

Fiberglass work isn’t rocket science but it is hard work if you are working upside down on the bottom. People that do it DIY can get really good results, experts may get a slightly better job mostly because they know more tricks of the trade than DIYers. If I were younger and didn’t have back and shoulder problems I would have no hesitation on doing it. But not anymore. I did do a blister job back about 20 years ago. It was tough work, especially in Arizona where it was 110, but not technically difficult. I would follow, to the letter, the directions and advice from the paint manufacturer. We did a whole bottom blister job and painted the entire boat with 2 part polyurethane paint using the roll and tip method. It came out beautifully. We followed the directions as closely as possible.

I had a wonder. Greenlines are pretty light boats. I'm guessing the idea is that with a hybrid drive it takes less energy to push a light boat than a heavy boat. So because of this the construction may be more sophisticated than the usual. I'm guessing that the hull is cored and also possibly the laminates on either side of the core are thin. This might effect what you end up doing after peeling the hull. If much laminate is removed you'll need to put it back. Also again because the boat is designed to be efficient bottom fairness and finish might be an issue. Smooth, fair hulls are easier to push than rough unfair hulls. So you could potentially be looking at adding back laminate and then refairing the hull. A wise choice would be to get a knowledgeable marine surveyor involved.

Been there

I peeled bottom, filled and faired. Forget gel coat. Not needed. Next sanded. Then 8 coats Interlux barrier coat alternating colors white and grey to ensure coverage. Then bottom paint. To avoid a hard edge where the epoxy meets the gelcoat above the waterline, mask tape the gelcoat. Then with each subsequent epoxy coat move the masking tape down an inch. Mine has been good for 12 years and counting. 8 coats may be overkill but you don't want to do it twice.

Rthomas said:

I peeled bottom, filled and faired. Forget gel coat. Not needed. Next sanded. Then 8 coats Interlux barrier coat alternating colors white and grey to ensure coverage. Then bottom paint. To avoid a hard edge where the epoxy meets the gelcoat above the waterline, mask tape the gelcoat. Then with each subsequent epoxy coat move the masking tape down an inch. Mine has been good for 12 years and counting. 8 coats may be overkill but you don't want to do it twice.

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+1, I agree. We had a previous boat soda blasted down to gel coat. Fixed some minor blistering. Then put on 6 coats of Interlux 2000 Interprotect. If you are doing the barrier coat, some will say only 2 coats or so, but why not make sure and do it right. The small incremental cost isn’t much. Getting ready to paint is most of the work, adding some extra coats is easy.

Greenline those are nice boats. My understanding is that the issue is caused by to much solvent when the hull is built. Another issue is the final gelcoat layer with a bit more solvent so they can get a better finish. Sure it will look nice but likely not for long. But you have ALREADY GROUND IT OFF ONCE AND IT REOCCURED....
If you have had her dry docked for a year in a warm environment it should be ready.

Best wishes

As I have posted before, stick with the advicecfrom white papers and yards with experience....

Most individual experiences are just that....

The fact that the boat has been in indoor dry storage for a year is a plus when considering a project like this. A lot of drying has already occurred.

I'd get the bottom paint removed. I don't see the need to remove the gel down to the laminate. Just grind out the blisters and fill with epoxy putty. It is more work to remove the gel and probably not necessary. Once you get the bottom smooth, apply multiple layers of an epoxy barrier coat (we use interprotect 2000), then bottom paint.

The big advantage here is that the hull has been drying for a year.

If you go look at the boat now, you may find that the blisters have reduced in size due to drying.

While the old gel may still be hygroscopic, it won't really matter if it is sealed with epoxy.

There is no barrier coat where 2 coats will do. Read the directions on the can. Each product has a different number of coats needed.

PMF1984 said:

There is no barrier coat where 2 coats will do. Read the directions on the can. Each product has a different number of coats needed.

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I agree. Putting the Interprotect on is the easy part of the job and relatively cheap too. Just make sure you put at least the minimum number of coats on and do it according to the time schedule so you are adding coats before the previous coat has dried completely so you get a chemical bond between the coats. Usually they want it thumb print dry, dry enough so paint doesn’t come off on your finger but still wet enough to leave a thumb print in the paint.

Thanks go to everyone who took the time to contribute thoughts, experiences and recommendations!

My next steps are:
1) Still more research
2) Possibly a bottom-focused survey
3) Perhaps an additional offer or two to compare with the offer I have from the factory.
4) Have the work performed (Corona permitting)
5) Continue to enjoy the boat (Corona permitting)

I will eventually come back here to let everyone know the rest of the story...

I think it is essential that the gel coat be peeled. In my case there were many large voids that could not be seen or adressed without removal of the gel. It is not much more work, if any, than removing just the paint. It comes out failrly smooth so little sanding is needed. Again no need to reapply the gel coat.

Update:

After much research, discussion with the factory and with a nearby Greenline dealer, I have decided to take my boat to the dealer to have this situation addressed during the coming winter.
The dealer is very knowledgeable about this situation (which seems to affect only some of the very early Greenlines) and has had experience applying this solution to multiple Greenline hulls. I am advised that the defect is in the gelcoat itself and that in all previous cases, the affected hulls had very low humidity levels underneath. I am inclined to believe this, since popping the small blisters produces only clear fluid. No black ooze or the like which would suggest serious hydrolysis.

It has been a difficult and agonizing decision, but I have decided to go with what the Greenline dealer recommends will work, based on their experience. It does not involve a full gelcoat peel (which seems to be the consensus approach recommended by the august posters in this forum) but rather sandblasting the gelcoat, while not removing it entirely.
Then:

• 3 coats of MAP yachting IM409 EpoxyGuard
• 1 full treatment with Awlflair (or similar)
• 2 Coats of Inernational Interprotect High Performance Epoxy Primer (I’m thinking of requesting the color red)
• 2 Coats of Hempel Hard Racing Antifouling (extra slippery for fast boats…and I guess for slow electric boats). The antifouling color will be grey
• 5 years warranty

If I get 5 years down the road and learn that it really should have been a peel job, etc., etc. I will cross that bridge when I get to it. Having a solution NOW that is likely to be good for a least 5 years is more important to me than having a solution that might last a lifetime, but under current conditions is not practically obtainable for me (Pandemic, me not being local to where the work is being done, further extended interruption of a long-planned Mediterranean journey, language issues, etc.). And, while the work I’m about to authorize is not cheap, it will not be a financial disaster for me if I someday find it needs to be done all over again with a full peel.

I will try to keep this thread updated with my experience on this over the coming years, in case it can be of any benefit to other early Greenline owners.

This an interesting recipe and I'll be interested to hear how it performs over time. I have not heard of the IM 409. One of the generally accepted recipes at the yards here in San Diego for blister prevention is Interprotect 2000 after repair/fairing, the Interprotect asks for six coats, followed by your choice of primer and antifoul.

sbman said:

This an interesting recipe and I'll be interested to hear how it performs over time. I have not heard of the IM 409. One of the generally accepted recipes at the yards here in San Diego for blister prevention is Interprotect 2000 after repair/fairing, the Interprotect asks for six coats, followed by your choice of primer and antifoul.

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IP 2000 good stuff I have used it on a fresh from the factory Searay just for extra protection and have never had issues. A couple of others I made repairs then IP 2000 without further issues. Good stuff

I have use the Interprotect system, 6 coats, on multiple boats and have never had any blisters afterwards. Good luck.

If all the areas going to blister have and the blast media takes the tops off and opens them up, that might work. But have they? If the blasting removes the outer gelcoat, and if the blistering is not deeper, that might work. But...
I think this work is not under warranty, you are paying. Are they warranting the repair?

sbman said:

This an interesting recipe and I'll be interested to hear how it performs over time. I have not heard of the IM 409. One of the generally accepted recipes at the yards here in San Diego for blister prevention is Interprotect 2000 after repair/fairing, the Interprotect asks for six coats, followed by your choice of primer and antifoul.

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IM409 is a product by Map Yachting. A French company that specializes in marine and aeronautic finishes.


https://www.map-yachting.com/home/

BruceK said:

Are they warranting the repair?

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5 years.