thousands of bottom blisters

[double u]

I am only too happy to piss off Corrosion Eng!

[double u]

“Maybe it's a little bit of knowledge is dangerous.“
Which “knowledge“? “Epoxy catalyst“?
I am increasingly irked by people writing their wild-assed assumptions as the gospel truth.

[rbk]

Originally Posted by double u

I am only too happy to piss off Corrosion Eng!

I’m beginning to think it’s not even a person but rather some program that notices key words like “marine” + “issue” “problem” and spits out a flyer for the magic fix all box, cause there seems to be zero thought put into the posts but just a predetermined statement.

[timeout2]

Ran into the same issue with my 1985 boat. Belt sanded the bottom. Then used a power washer to pop off many of the blisters. Then went over each square inch and hand lifted any still present. I did not find any evidence of osmotic blistering or moisture penetration.

I ground out any blister where there was evidence of going thru to mat. Used West system to fair whole hull. Sanded again. Faired again. Sanded again.
Once fair I used West system for 2 barrier coats. (sanded each coat)
Finished with 2 coats bottom paint.

Just hauled boat last week, zero problems.

Extremely time consuming and laborious process but hull was in dire need of repair. Mostly cosmetic but too many places where mat was showing.

Probably a result of very poor quality control during initial layup. Poor mixing of catalyst, high humidity during cure, poor wetting of mat, but reason is moot. It needed repair and I did not want to invest 20K in a peel.

[Little Song]

Hi.

Are you really sure it is not osmosis?...

Sorry for asking, I know it is an unfriendly diagnosis.

Ask a pro. It might prevent a structural hull damage, if corrected on time.

Cheers.

[Disailor]

assuming the boat was in salt water there will be salt in the moisture inside the blister. Air drying merely evaporates the water leaving the salt behind which over time will absorb moisture from the air = never drying. My 33' Morgan OI had blisters in every 1 sq foot of bottom (1000nds).

In 2010 I opened every one (some quite deep, nearly all wet), flushed with water to remove salt, alcohol wash to dry (alcohol mixes with water & removes water as it evaporates), epoxy fairing, 4 coats of 2000e . Never had another.

Good info here: http://www.yachtsurvey.com/blisters.htm

[rchildress]

Go watch Patrick Childress Sailing on Youtube. He has been dealing with the bottom of his boat now for more than 6 months in Africa. He will have one specifically on blisters soon, but there are many that show the state of the boat, and how he took all the pain to off himself etc.

[Peter O]

I feel for you having gone through the same issues recently.

While your boat is old, I understand your motivation wanting to stop the deterioration of your hull which in the end is the most important part of your boat or all your other investments in the vessel are almost worthless.

When sanding after 24 hrs you will highlight all blisters very well because they emerge as white spots in the bottom paint. Judging by the photo you have some blisters that are deeper than the gel coat. I would grind those out making a shallow crater with a small 4 1/2” angle grinder with some like a diablo 40 grid flap disk. You will know when you have removed enough materials that nothing is wet or separated anymore.

You did not state if your hull was cited below the waterline. If it is, you want to grind out all small cracks and holes and you may potentially have to replace some core. But if it is solid glass, you won’t have to be as concerned.

I would agree with prior posters to remove all bottom paint as the barrier coat will not stick well long term on the ablative paint.

As far as the little blisters do, I struggled with sanding those as there where lots of tiny gel coat pieces that were lose. I ended up getting the whole boat blasted because the time and cost for sanding disks was significant too. The blasting took care of removing all the lose pieces to I had a solid substrate to built up the hull again.

As you suggest, I would allow significant drying time after you opened up all the blisters. I let it sit from September until the following summer. A moisture meter helps a lot and may also help you locate areas where the core has gotten wet, if the hull is cored.

As far as materials go, I built up the deeper craters with epoxy and fiberglass matting. Vinyl ester might actually be better and more compatible with your hull. If you use West System you have to make sure you rough up the surfaces to remove the blush. Mass Epoxy worked better because the epoxy shrinks and it’s difficult to sand the low spots. Also, it takes several applications to built up the craters and in the last applications, I used fillers, first the harder kind and last the fairing filler for easier sanding.
The built up process worked better than I expected. The hull went from looking like a drive by shooting in Iraq to looking nice and smooth in the end.

I used 7 layers of barrier coat.and some of the tiny holes only started filling after 5 layers.
It is very important that you apply one layer of bottom coat immediately after the last layer of barrier coat while the barrier coat is still a little sticky. Once the barrier coat is dry the bottom paint will no longer stick.
Good luck!

[Coast Wanderer]

We have just gone through this with our 1990 Cooper Yachts Prowler.

We saw a few blister during a haul out, but we wanted to make sure they were treated and investigated, before repainting the bottom.

It turned out that we also had thousands of very small blisters, after the paint was sandblasted off. Our fiberglass guy meticulously circled each one and later ground each blister out. None of them were more than about 1/16" deep, but they all had some of that lovely smelling liquid that forms when this happens.

The main thing is to make sure that you get ALL the moisture out of them and let the hull dry out. We used heaters under the boat inside a shop, to make this happen over a few months. Once the blisters had been ground out, fully dried and filled with filler, we applied 6 coast of epoxy primer and 7 coats of bottom paint, with the first coat being a light color, so we could see when it is time to repaint.

If I ever buy a brand new fiberglass boat, I think I would immediately have the hull painted with epoxy primer, then with whatever other paint. Fiberglass is not impermeable to water so it's probably only a matter of time and conditions until water works through the gelcoat. Some boats are famous for blistering, while others are not, yet can still suffer this annoying fate.

The kicker that started all this was the surveyor we hired, who saw a few blisters and recommended to our insurance company that they should be fixed immediately. That was a huge PITA for us and everyone else we spoke with about it said that the surveyor should have said we should just keep an eye on them at annual haul outs. The surveyor even stated that he didn't know much about blisters, so he basically copied and pasted a chapter about them from an online post, that went into how they are to be repaired and what you have to wear to protect yourself, etc. Seems to me that someone who says they "don't know much about blisters" should simply refer us to an expert, rather than trying to pass himself off as an expert.

Anyway, we got it all done and while it was out, we made damn sure that the next surveyor would see a solid, safe, compliant and reliable boat, that any insurance company would not mind covering.

Good luck to any and all who have had this particular pleasure..

[sailorladd]

This is osmosis, which all fiberglass boats suffer from, as the gelcoat is not totally water proof, and salt water will osmote through it and into the fiberglass...

I usually grind off the bubbles until the moisture, as you saw, is exposed, and allow this to dry out, usually takes a day or so... you could help it by wiping acetone or some similar agent to speed up the drying and to clear out the holes..

Once these are dry I would use a decent epoxy resin and paint the entire bottom at least twice to create an impenetrable barrier to the sea water, and depending on the type of epoxy you use, you would need no further coats of paint other than the two coats of antifouling you would normally use...

in some cases the epoxy coat might need to be primed for the antifouling, but I have found that if I do a coat of antifoul the day after the epoxy cures, you should be fine to apply the first coat of antifoul, and then as soon as that coat is touch dry, apply a second coat (always advisable) and then when that coat is dry, launch the boat shortly after that or as soon as you are able.

Make sure the epoxy coat cures properly, and check that you have covered all the blister holes, in some cases the holes may be quite large, in which case you need to make a paste with epoxy and microballoons or similar filler and putty knife them closed... good luck

[lestersails]

[QUOTE=Georgiamarie;3007288]Here is an article on Hull Blisters:
Blisters? No Problem!



As I stood waiting I scanned the boats in the anchorage. One sail boat looked awfully familiar. I borrowed a dinghy and went in for a closer look. I rowed around the boat and eventually could not stop myself from being rude and climbed on board. I checked her over pretty carefully and concluded she was in pretty good shape and obviously ready and trimmed to take her owners on the next leg of their voyage.

Wow - this seems wildly inappropriate to me. And I wouldn't change my opinion even if he was certain it used to be his boat. It is not his boat now and unless he was performing a rescue function - he should not board that boat.

[lestersails]

Sorry on my last post - i deleted the end quote of the quote function. The quote should end at "voyage". If a moderator wants to delete that posting (and then this one as well), I can try again.
Apologies all

[Bawlmer]

I had the same thing happen when I hauled out in 2015. The yard wanted to charge me 14K to peel and seal the bottom. I passed. I let the boat sit over the winter and it all went away. In the Spring I sanded and applied new bottom paint and it was fine.

[Poche]

If the boat has low value I would just paint the bottom in the spring and use it. Maybe address large blisters if there are any.
Does anyone know of a boat falling apart from small blistering?
They are ugly or might slow a boat down by a fraction but that's all I have heard.

[David Mathis]

The blisters indicate moisture getting through the gelcoat and causing a separation of the outer fiberglass layers of the hull. The boat will not heal itself by letting it dry. You have a good start by sanding but a device is available to strip the gellcoat from the hull. The device looks like an electric plane. With extensive blisters covering most of the hull, one of these tools could save hours of labor. After stripping the gellcoat, let the boat dry for a couple of months or until a moisture meter indicates most of the water has evaporated. Now it's time for epoxy, barrier coat, and paint. It's too bad the manufacturers can't (or won't - damaged boats get replaced with new ones) either mix a barrier material with the gellcoat or just barrier coat and paint the areas below the waterline.