Thoughts on Blisters

While I've no concern with blisters, I do about rust.

Nice pics Gonzo, I`m having a deja vue moment just seeing them. Naughty of the Yard to start without authority( you are only liable for work done at your request),but seems it helped clarify the issue.
Although my boat had been soda stripped( not very well,and not repaired) before I bought(we renegotiated price post survey), we repaired all apparent blisters individually, as described. The hull was still rough and uneven after the osmosis work and we (ourselves) did the major dry sand back, pre painting with a vinyl and then a/f. Good effect on the boat but not on us(cough/splutter);we regretted not doing a soda strip first. Without intruding on your decisions,food for thought.Result was a nice smooth faster hull. Best of luck with it. BruceK

Well, at least removing a bunch of excess layers of paint is a relatively simple and inexpensive (more so if you do it yourself) process compared to a hull peel, repair, re-gel coat, and barrier coat.

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Once the gel-coat comes off and the repairs are done, you do not re-gel-coat. The barrier coat is the replacement.

BruceK said:

Result was a nice smooth faster hull. Best of luck with it. BruceK

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So, how much did you gain? 1/2 knot? A whole knot?

The sandblasting, blister repair, barrier coat and paint is just....(cough cough) $3500.00. As opposed to a full peel at 8-10k. I think we'll go for it. The two boats that we saw at the yard that were done this way looked great! really great. I think that not only will the money be well spent for our own maintenance, but when it is time to sell her, it can only help. Maybe not in price, but perhaps in a quicker sale.

My experience

I went through the same thing you're going through when I bought my boat. The surveyor showed me several dime to quarter sized blisters which he wrote up as being mostly on the starboard side.

When I hauled the boat 6 months later I found 150 blisters pretty much equally spaced between starboard and port. I did the internet research thing and ended up calling West Systems. They have a pretty good site explaining how to do with this.

I ground out each blister with a grinder. You know it's a blister when yucky fluid comes out. I filled each with West Systems Six/10 epoxy, an easy way that automatically pre mixes the 2 part epoxy. I did not dry the area, rather I just ground out the area until I got to dry fiberglass. Filling the ground out area is like putting a plug in the cavity and I was concerned that the plugs would fall out under use. That never happened. I had to fill each ground out area twice to get it to fair with the hull using 60 grit paper between fills to ensure a tight bond between fills.

I also considered soda blasting, but decided against it due primarily to cost. The blaster did some test areas on the boat as shown in the second pix. I covered that area with a thin coat of Six/10.

Almost 2 years later I've had no problems and the hull looks good. I won't know for sure if the blisters have returned or I've gotten more until I pull the boat again, of course.

This was a messy time consuming job, but not really difficult or expensive. If you can hire a grunt to help you, it doesn't really take much experience or knowledge, the job will of course go much quicker. I had to experiment with the grinder and type of grinding material, but once I got that part figured out, the job went pretty fast.

I'll estimate the total cost to be under 1.5 boat bucs inc the paint & haul out, but I did all the work.

Besslb said:

...The sandblasting, blister repair, barrier coat and paint is just....(cough cough) $3500.00. As opposed to a full peel at 8-10k. I think we'll go for it. The two boats that we saw at the yard that were done this way looked...

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I don't think the price sounds bad considering all that is to done. And an other plus is you no longer have to haul every year.

timjet said:

I also considered soda blasting, but decided against it due primarily to cost. The blaster did some test areas on the boat as shown in the second pix. I covered that area with a thin coat of Six/10.

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Excellent...someone with hands on experience with blasting. Were you able to clearly distinguish blisters after the area was media blasted, or had those blistered spots already been ground out before the blasting? Did the blasting open any blisters? It apparently was deep enough to disrupt the contour of the bottom if you had to fair it with putty? Also I wonder if the factory used a poly or vinylester resin? Thanks...very helpful photos and info.

I did a full peel, post cure with the Hot-Vac system, and relaminate. That was about $25k 10 years ago.

skidgear said:

Excellent...someone with hands on experience with blasting. Were you able to clearly distinguish blisters after the area was media blasted, or had those blistered spots already been ground out before the blasting? Did the blasting open any blisters? It apparently was deep enough to disrupt the contour of the bottom if you had to fair it with putty? Also I wonder if the factory used a poly or vinylester resin? Thanks...very helpful photos and info.

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As I recall the blisters were already ground out. The soda blasting as I remember does nothing to fix blisters, it just removes all the paint and gelcoat so that when you put the barrier coat on, nothing is between the barrier coat and the fiberglass hull. The blisters must be ground out either before or after the soda blasting, however I would check with the soda blaster before I dealt with the blisters. The idea here being that blisters won't form under the barrier coat.

The soda blasting removes a thin layer, you should not need any filling after the soda blasting, except of course for the ground out blisters. After the soda blasting is complete and you've filled and faired all the blisters, you will need to apply a barrier coat, which is just a thin coat of 2 part epoxy. It will of course need to be sanded smooth, and that will be a job.

Soda blasting and the application and sanding of the barrier coat adds greatly to the cost and work involved. That's why I chose to skip it. Time will tell if that was a wise decision.

Tim,

I was trying to determine from the second photo if the blaster only took off the paint and stopped before ripping off the entire gel coat. That appears to be the case, although it's difficult to tell for sure. The reason I ask has to do with determinihg the best method for removing paint only. I would never remove the entire gel coat for a barrier coat job unless I determined there was a massive blister problem or delam issue. If the majority of the gel coat is solid, fix the blisters and put the barrier coat over the existing gel coat. But again, it's crucial to be able to identify blisters in the gel coat after the paint is stripped (and it's impossible to identify the extent of the problem without removing bottom paint). If blasting erases all the telltales, then chemical strip might be a better approach (for a barrier coat over existing gel coat). Also, I believe most yards would use the peeling machines to remove an entire gelcoat.

Greetings,
I had occasion to have a peel and re-do job on a vessel. Overall, two layers were removed with specific areas ground out deeper. Extensive blisters with some in the 4" range. I DID look into the Hot-Vac" system but decided not to go that route. The yard then proceeded to give the stripped hull a pressure wash about every two weeks for the first while to totally remove the liquid blister residue. The hull was allowed to dry and two new layers of glass were applied with appropriate materials. Barrier coats and AF were applied and after a haul recently (5 years after the fact) no deterioration or blisters were visible.
Cost about $15K for a 42' hull. Was it necessary or needed? Did I WASTE the $$? I'm good with what I did.

Larry M said:

Once the gel-coat comes off and the repairs are done, you do not re-gel-coat. The barrier coat is the replacement.

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I wasn't sure about that part. Thanks for the clarification.

skidgear said:

Tim,

I was trying to determine from the second photo if the blaster only took off the paint and stopped before ripping off the entire gel coat. That appears to be the case, although it's difficult to tell for sure. The reason I ask has to do with determinihg the best method for removing paint only. I would never remove the entire gel coat for a barrier coat job unless I determined there was a massive blister problem or delam issue. If the majority of the gel coat is solid, fix the blisters and put the barrier coat over the existing gel coat. But again, it's crucial to be able to identify blisters in the gel coat after the paint is stripped (and it's impossible to identify the extent of the problem without removing bottom paint). If blasting erases all the telltales, then chemical strip might be a better approach (for a barrier coat over existing gel coat). Also, I believe most yards would use the peeling machines to remove an entire gelcoat.

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In 2004, we hired a contractor to sandblast off 20 plus years of hard bottom paint. All the surveys said we had "minor" gel-coat blisters. The idea was to remove all the paint and the gel-coat in local areas. With sandblasting, heat is generated from the friction. The heat raised blisters that we didn't know we had, lots of them and some were deep. After the sand blasting our next next step was to peel the hull and start repairs. We spent $1,100 on the sandblaster to find out we had a serious blister issue. And peeling the hull is not an exact science. How deep do you peel? After the gel-coat, what you take off you have to put back. Do you only go so deep then spot repair the blisters? As it turned out, 3 years later and after $10,000 spent on the blister repair, we had blisters again.

I believe this is the method that Keith had done. We considered this option before we sandblasted/peeled the hull in 2004. We probably should have done nothing or spent the big bucks on this process. Hotvac Boat Hull Drying, Osmosis Treatment, Osmocure

If you do a web search on the topic of blisters on fiberglass boats, you will get as many opinions as articles on the subject. Everything from "ignore them" to "strip the gelcoat, let the hull dry for two years, then replace the gelcoat".

About the best you can do is read the atricles, try to figure who knows what he is talking about, and who doesn't, then apply the information to your own boat and situation.

RT Firefly said:

Was it necessary or needed? Did I WASTE the $$? I'm good with what I did.

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I think in the end, after hearing everyone's opinions and weighing all of the options, RTF is dead on. As long as we're good with the $$ spent, it's not a waste of money.

Thanks everyone for sharing your thoughts and experiences!

Besslb said:

I think in the end, after hearing everyone's opinions and weighing all of the options, RT is dead on. As long as we're good with the $$ spent, it's not a waste of money.

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I've met people who put more into a complete ding/scratch/chip repair and complete paint job on the their boat that cost more than the boat was worth. While logic and common sense suggests that this was a big waste of money, it wasn't to them because for their own reasons it was important to them to bring the boat up to the standard they wanted it to have. So in their eyes it was money well spent, and in the end, that's the only opinion that matters.

...The yard then proceeded to give the stripped hull a pressure wash about every two weeks for the first while to totally remove the liquid blister residue. The hull was allowed to dry...

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We are doing a blister job now. The 25 years of hard bottom painting was chemically stripped then the gel coat ground off. I have opened and enlarged every blister I can find. Twice per day I wash the bottom with pressure fresh water to aid in the drying and to remove any of the blister residue as RT had done. This seems to be a very important step and one we didn't do in 2004. I am just now filling by first wetting out each area with unthickened epoxy then going back with in an hour and filling with thickened epoxy. After all the blisters are repaired/filled/fared, 3 coats of barrier coat, primer and then paint. Will it work, I hope so.

skidgear said:

......We sanded off 15 years of bottom paint. Would use chemical strip in retrospect. Sanding is a nasty, dangerous job...dust results in vomiting and nose bleeds if not wearing a mask and nasty earaches if not wearing ear plugs........

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Worse, it could result in long term conditions that might not surface for many years. And if you bring the clothing into the house or even your car, you could endanger the health of family members. There are some pretty nasty things in boat bottom paint.

Removing bottom paint is the type of thing I'm willing to pay someone else to do.

rwidman said:

Removing bottom paint is the type of thing I'm willing to pay someone else to do.

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ME TOO!! I'm also willing to pay the yard kid for waxing the hull. I tried to do it. $600.00 is very much worth it.

Larry M said:

We are doing a blister job now. The 25 years of hard bottom painting was chemically stripped then the gel coat ground off. I have opened and enlarged every blister I can find. Twice per day I wash the bottom with pressure fresh water to aid in the drying and to remove any of the blister residue as RT had done. This seems to be a very important step and one we didn't do in 2004. I am just now filling by first wetting out each area with unthickened epoxy then going back with in an hour and filling with thickened epoxy. After all the blisters are repaired/filled/fared, 3 coats of barrier coat, primer and then paint. Will it work, I hope so.

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Not clear how pressure washing helps it dry out. We swabbed every divot with alcohol to clean up the blister residue...multiple times during the process. Think I read that in the West Systems material.

Regarding primer, the Interlux techies told me that if the first layer of bottom paint is applied while the last coat of epoxy is still tacky, then there is no need for primer...the epoxy and the paint will chemically bond. And if you let that epoxy fully cure, there's a good chance anything you apply next will fall off anyway (personal experience speaking). Then you get to blow off whatever remains of the bottom paint with a pressure washer (works well for ablative), and clean up what's still stuck with a sander or media blasting. Whatever, the cured epoxy should be scuffed and Scotchbrite won't cut it. Then apply one more tack coat of epoxy and apply the bottom paint as it should have been done in the first place. We ended up with four coats of epoxy, wasted two coats of bottom paint (actually we let it fall off for two years before fixing it), and gained a whole lot of aggravation. I share our screw up for the benefit of do-it-yourselfers everywhere....and boat yards for that matter.

rwidman said:

Removing bottom paint is the type of thing I'm willing to pay someone else to do.

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Or do it chemically, which is relatively benign if you protect your skin and don't swallow it.

Greetings,
I would rather rebuild each head three times during a month long taco and bean-fest than work on the bottom. Almost worth mortgaging a first born male child to acquire to funds to have someone else do it. But let me tell you how I REALLY feel about bottom work.......

Besslb said:

So, how much did you gain? 1/2 knot? A whole knot?

The sandblasting, blister repair, barrier coat and paint is just....(cough cough) $3500.00. As opposed to a full peel at 8-10k. I think we'll go for it. The two boats that we saw at the yard that were done this way looked great! really great. I think that not only will the money be well spent for our own maintenance, but when it is time to sell her, it can only help. Maybe not in price, but perhaps in a quicker sale.

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On Sydney prices $3.5K sounds cheap. The soda blast we did not do would have been $2.3K.
Don`t knock a well faired hull. It was faster,maybe half a knot,over the usual gain from fresh a/f. We stripped thick old flaky lifting a/f on a sailboat I raced, it went from uncompetitive to competitive.It`s a bonus, you already see the need for the work. Osmosis is so common, selling with a treated hull, (verifiable on survey),is a plus. We started pre purchase survey told the osmosis had been fixed, it had not, that and other things cost the seller $20K in renegotiation (and almost cost him the sale). BruceK

skidgear said:

...Not clear how pressure washing helps it dry out. ..

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The moisture in the hull is not fresh water. By rinsing with fresh water (after the gel-coat is off), I am speeding up the drying process by getting rid of the water soluble contaminates. I compare it to swimming in salt water and with no fresh water rinse. You'll eventually get dry but you will also have residue left behind.

Skidgear,
I think you're right, the soda blasting just took off the paint not the underlying gelcoat. Those areas in the pix that were soda blasted were just a demo of what could be done. There were some blisters in those demo areas that were ground out and filled. I then used a 2 part epoxy and using a trawl (sp?) spread a thin layer over the blasted areas.

A light sanding of the bottom uncovered most of the blisters. Since a blister forms a small dimple in the bottom paint, sanding with 60 grit paper quickly removes the bottom paint covering the dimple exposing the gel coat underneath. What you see is a bunch of white dots all over the hull where the blisters are.

Going to the extent of peeling and for the most part installing a new layer of gel coat is beyond the means of most owners, I would think. Perhaps the cost and labor to do this would bring into question whether the boat is really worth the cost.

None of the blisters on my boat were structural, the largest being the size of a half dollar, and not many that size. I dealt with the blisters because the boat was hauled to fix a rudder issue. Next time I haul, I'm not sure I'll deal with the blisters, if I have any.

If you think you have a problem..read up on the latest from the industry (have to search quite a bit)...I would link them to you but after finishing my bottom they got deleted.

Also search fiberglass tank/piping articles on hydrolysis and blistering...very informative.

Much that has been posted here is NOT what the most experienced in the marine field concur with. The prevailing thought is smattered about but only a little in every post...I wouldn't dare call it the truth but it's what makes sense to me from over a year's indepth research on it involving daily searching/reading plus dozens of interviews and phone calls.

Don't be sold a "fix" until you know the source of the problem. Small areas of the gelcoat need to be removed and determined whether there are excessive voids or poor wet out of the skin out mat. If there is, the usual "fix" isn't going to work.---David H. Pascoe

Interesting read if you're not in a hurry.

psneeld said:

If you think you have a problem..read up on the latest from the industry (have to search quite a bit)...I would link them to you but after finishing my bottom they got deleted.

Also search fiberglass tank/piping articles on hydrolysis and blistering...very informative.

Much that has been posted here is NOT what the most experienced in the marine field concur with. The prevailing thought is smattered about but only a little in every post...I wouldn't dare call it the truth but it's what makes sense to me from over a year's indepth research on it involving daily searching/reading plus dozens of interviews and phone calls.

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I understand your expertise, however, there is more to it than us just finding the solution that you feel is right (seeing that you have not offered it up and just tell us to go find it), it's that we trust a) the majority decision from others that have had the same experience and b) the opinion of the experts in the yard.

There are some systems I need to become an expert on because I will be doing regular repairs on them and there are others that I do not. That doesn't mean I go into it blindly, but it does mean that I have a little faith in the chosen experts.

We have weighed our options. This boat does not need to last another 30 years, nor do I believe that any solution is permanent. We have a rough looking bottom and need to clean it up. For many years, grinding out and filling with resin has proven to be an adequate solution. I think that by now, if there were widespread issues, the industry would not still be offering it. This is the right solution at the right price for us.

I appreciate your input, Scott.

Tom-

GonzoF1 said:

I understand your expertise, however, there is more to it than us just finding the solution that you feel is right (seeing that you have not offered it up and just tell us to go find it), it's that we trust a) the majority decision from others that have had the same experience and b) the opinion of the experts in the yard.

There are some systems I need to become an expert on because I will be doing regular repairs on them and there are others that I do not. That doesn't mean I go into it blindly, but it does mean that I have a little faith in the chosen experts.

We have weighed our options. This boat does not need to last another 30 years, nor do I believe that any solution is permanent. We have a rough looking bottom and need to clean it up. For many years, grinding out and filling with resin has proven to be an adequate solution. I think that by now, if there were widespread issues, the industry would not still be offering it. This is the right solution at the right price for us.

I appreciate your input, Scott.

Tom-

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Without seeing your boat...I wouldn't dare give a final opinion...the several times I've posted drails of my findings/solution WITH LINKS of other professional inputs...I've been overposted so bad by the "don't worry, be happy" and the "fill them blisters and just go sailing" types that the details just get lost...

I learned a long time ago if you want someones input you can really relate to....you PM them...keeps the internet hecklers at bay....