Thoughts on Blisters

Hi TF People!

Everyone in Sandy's path stay safe. (not the question)

What are your thoughts on blisters? We know we have some. It's one of the reasons we haul and paint yearly. When we surveyed originally the bottom was very bumpy and the surveryor said that it would need doing eventually. PO hadn't painted the bottom in the 4 years he owned the boat. Since our yearly paint jobs, the bottom has improved quite a bit.

We're hauled at a new yard, and of course the yard manager wants to talk about our bottom. We're going tomorrow to see her and see if it really looks any worse than it has in the past couple of years. (Tom was in a little bit of a hurry when he delivered her there, and didn't make a point of taking notice other than the previous paint didn't look so bad)

The full peel is out of the question financially. But what about sandblasting back to gelcoat and an epoxy barrier coat? What are your thoughts on that job. Is it worth it? Does it fix the problems or is it just a stop gap on the road to the a peel?

Thanks ya'll!!

From what I have been told about blisters, there are blisters and there are blisters. They are often more cosmetic than actually detrimental. So you need to determine if the ones on your boat are potentially structurally debilitating or are simply annoying.

Blisters can be treated on an individual basis as opposed to having the whole hull peeled and barrier-coated. I believe Eric Henning has done this on the hull of his Willard.

One factor is how long do you anticipate owning the boat and what affect will the blisters you have have on the resale value if you anticipate getting a different boat in the not-too-distant future? It may be smarter to take a bit of a hit in the selling price of the boat instead of forking out the major bucks to do a proper peel and barrier job, a cost you might not recoup in the selling price of the boat.

And make sure what you're seeing really are blisters. Sometimes it's just little bubbles under the paint. The giveaway I was taught is to "pop" them with a fingernail and if you finger smells like resin/acetone/etc it's a blister. If it doesn't it's not an actual fiberglass blister. If they're big, however, they're not likely to be paint bubbles.

There is a lot of information on the web about fixing blisters. I've never done it nor have we had to do it on our boat to date. What I have gathered, however, is that the key to a successful fix, be it an individual blister or the whole hull, is to get everything absolutely dry. A co-worker had a major blister problem on his 1980s vintage Bayliner Trophy. The boat had to sit in a heated building for a couple of months as I recall before it was totally dried out.

If you own a Uniflite built from 1972 to 1977 you may have a blister issue. Otherwise it's a scam.

av8r said:

If you own a Uniflite built from 1972 to 1977 you may have a blister issue. Otherwise it's a scam.

Click to expand...

Because..........? (Not preparing to argue the point, just curious as to why you feel this way.)

The common thought is

It's commonly believed that those Uniflights could have blisters that can penetrate the hull. This is thought to be due to the fire resistant resin Uniflights used in those years. I think blisters are for the most part cosmetic and repairable one at a time at your convenience. I don't think months of drying out are needed or stripping the hull for that matter. A die grinder and epoxy filler after a couple of days are all that are needed.

While I never saw the co-worker's Trophy out of the water, from what he told me the entire bottom was covered with major big blisters. Bayliner picked up about half the tab for the repair which involved a thorough drying out of the hull after the gelcoat had been ground off and then a new layer (or layers) of fiberglass applied plus (IIRC) new gelcoat plus a barrier of some sort.

The boat was laid up during the winter for this and as I recall it was done at a Bayliner facility although I may be misremembering that part. But Bayliner was very much involved in the fix.

I understood that the issue with Uniflite's from the early 80's was they constructed the hulls using long strips of glass matt that drew water the length of the hull via a capillary action, there was, I believe, a class action against the company.

Bess, if your boat is on the hard at the moment I would recommend that you down load David Pascoe's article 'Blisters Again,The Wonderful World of Hull Blistering and Other Interesting Scams', sorry i don't have a hyperlink.

Amongst other bits of information, he tells you how to determine what type of blisters your boat has, all you need is a knife.As Marin said there are blisters and there are blisters.

The considered opinion is that blisters will not sink your boat(not usually) nor will they weaken the structural integrity of the vessel. They will affect resale and give you a bit of extra work on your annual antifoul.(grinder & epoxy)

One thing I have learned is that it is better to have an older boat with blisters than a newer one. Apparently, once the boat has been in the water for a few years what you see is what you get, with a newer boat you are not sure how bad it will get before you get to that stabilisation stage. Also, if your boat has never had blisters it is very unlikely to develop them as the boat ages.

To give you some comfort, here are some pic's of our IG at her recent antifoul showing before and after shotsof her blister issues.(taken just before my brother -in- law fell off the gantry and broke his leg, could have been worse he had finished the antifouling by then)

Boat Hull Blisters: Blisters Again?

It is a well written article Andy

Besslb said:

Hi TF People!

Everyone in Sandy's path stay safe. (not the question)

What are your thoughts on blisters? We know we have some. It's one of the reasons we haul and paint yearly. When we surveyed originally the bottom was very bumpy and the surveryor said that it would need doing eventually. PO hadn't painted the bottom in the 4 years he owned the boat. Since our yearly paint jobs, the bottom has improved quite a bit.

The blisters are still there. Painting over only hides them.

We're hauled at a new yard, and of course the yard manager wants to talk about our bottom. We're going tomorrow to see her and see if it really looks any worse than it has in the past couple of years. (Tom was in a little bit of a hurry when he delivered her there, and didn't make a point of taking notice other than the previous paint didn't look so bad)

The full peel is out of the question financially. But what about sandblasting back to gel-coat and an epoxy barrier coat? What are your thoughts on that job. Is it worth it? Does it fix the problems or is it just a stop gap on the road to the a peel?

Unless you have localized blisters, the only way to correctly fix the problem is to peel, dry, repair/rebuild and then the barrier coat. There are different methods to get there; air dry vs heat/vacuum or peel vs grind vs sandblast, etc.

Or you can forget about it. I know, easier said than done. In mostly cases though blisters are not a structural issue.

Click to expand...

The picture was taken last month just before the gel-coat came off. We had blisters. This is our second blister job on as many boats. One thing about blisters and how to deal with them is everyone has an opinion and some people have two.

Few people actually know the possibilities unless they have done this and studied the subject....

A bit more than what the surveror thought....

Och

That may be the worst I've seen. I suspect there is is more to this than just blisters.

Sand blast a fiberglass boat.

Sand blasting will really leave a porous surface after it takes the gel coat off.

I don't think it is a good idea.

Perhaps if something like soda blasting or crushed walnut shell were used.
That would be interesting to know.
SD

Besslb said:

Hi TF People!

Everyone in Sandy's path stay safe. (not the question)

The full peel is out of the question financially. But what about sandblasting back to gelcoat and an epoxy barrier coat? What are your thoughts on that job. Is it worth it? Does it fix the problems or is it just a stop gap on the road to the a peel?

Thanks ya'll!!

Click to expand...

After fixing individual blisters for several years we barrier coated my brothers boat about five years ago. Note that blisters begin to recede immediatley upon haulout so you won't get an accurate assessment if the boat has been on the hard for several days...even after a few hours.

Brother's boat was in warm water location for about 15 years, then moved to Great Lakes. Yard wanted to peel the bottom. We elected to first remove bottom paint to get a good look at the gel coat. Blasting was rejected because it would have messed up the surface too much to get a good visual. 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.

When we got the bottom paint off we could see discolored spots where blisters were forming, even if the surface was not raised. Anything suspect was ground out with a Dremel. There was no evidence that the entire bottom needed a peel...none. The hull was allowed to dry in heated winter storage for eight months. In the Spring we repaired large spots with mat and epoxy...small (pimple sized) ones with a thickened epoxy paste.

Interlux barrier coat was followed by a coat of red non-ablative bottom paint (guide coat), and then two coats of black ablative. We wanted a bottom paint that would not lose anti-fouling properties when hauled (many of them do). Note that the first coat of bottom paint must be applied while the last coat of epoxy is still "thumb-print" tacky or a chemical bond will not be achieved. This is important because epoxy cures hard and slick, so relying only on the mechanical bond is taking a risk (ask me how I know).

A note about Great Lakes boats....since they are in the water for a limited amount of time each year, and they dry out on the hard each winter...many boats with a blister prone bottom will not exhibit syptoms. Put them in a warm water environment for extended periods and the problem will pop up.

This job took two of us a total of about two weeks. The yard had estimated $12,000 at the time. Materials cost us about $3000. Finally, we are huge fans of MAS (no bush) epoxy. Why anyone would deal with a blushing epoxy in this day and age is baffling.

Besslb said:

Hi TF People!

Everyone in Sandy's path stay safe. (not the question)

What are your thoughts on blisters? We know we have some. It's one of the reasons we haul and paint yearly. When we surveyed originally the bottom was very bumpy and the surveryor said that it would need doing eventually. PO hadn't painted the bottom in the 4 years he owned the boat. Since our yearly paint jobs, the bottom has improved quite a bit.

We're hauled at a new yard, and of course the yard manager wants to talk about our bottom. We're going tomorrow to see her and see if it really looks any worse than it has in the past couple of years. (Tom was in a little bit of a hurry when he delivered her there, and didn't make a point of taking notice other than the previous paint didn't look so bad)

The full peel is out of the question financially. But what about sandblasting back to gelcoat and an epoxy barrier coat? What are your thoughts on that job. Is it worth it? Does it fix the problems or is it just a stop gap on the road to the a peel?

Thanks ya'll!!

Click to expand...

As Marin stated, make sure you determine if they are bottom paint blisters or actually in the gel-coat and fiberglass. Most likely it's just cosmetic.... be careful that you aren't chasing a phantom problem.

Blisters are for newbies...

The old timers have to deal with hydrolysis and dry laminates that is the bane of these poorly made Far East trawlers from the 70's and 80's..

Seriously...your boat can be a hit or miss situation...but you just don't know the extent of the problem without coring or grinding deep.

Taking off the paint and barrier coating over gel coat can be an expensive mistake if you really have a severe blister or hydrolysis problem.....as they will just return with a vengeance.

Many boats can have severe hydrolysis without blisters...usually ones where the gel was so bad that water passes freely in and out of the laminates without enough pressure building to cause a blister.

Since our yearly paint jobs, the bottom has improved quite a bit.

What is you prep work like if you do a bottom job every year?

Do you just power wash and paint or have you removed the old bottom paint down to the jell coat?

It could tell you a lot if you really take the anti foul off and see what Lays beneath.

Then again I just read what Psneedl wrote so perhaps not.

sd

My 88 FHB trawler has blisters. Mine are in the 1 to several dime sized blisters per sq ft range. I had the same surveyor check out my boat that had done it for the pervoius owner 4 years earlier. They had not changed that he could notice. we left them alone for now and possibly forever. The crusty old guy that ran the boat yard recomended the following if i wanted to do something about them:
Immediately on haul out use a large diameter drill bit that is the size of the blister and has a stop on it that lets it penetrate about 1/4+ inch and drill into each blister to get it out. Then strip the bottom of all paint using chemical stripper. Drill grind out any more that are identified. Fill each the holes/grindoutds with filled epoxt. Sand smooth. Coat the bottom with 2 layers of epoxy barrier. Bottom paint and splash. He said on a old boat like mine i should have a 95% chance of no more blisters beacuse anything that wanted to blister should have already.

Third-Reef said:

The crusty old guy that ran the boat yard recomended the following if i wanted to do something about them:
Immediately on haul out use a large diameter drill bit that is the size of the blister and has a stop on it that lets it penetrate about 1/4+ inch and drill into each blister to get it out. Then strip the bottom of all paint using chemical stripper. Drill grind out any more that are identified. Fill each the holes/grindoutds with filled epoxt. Sand smooth. Coat the bottom with 2 layers of epoxy barrier. Bottom paint and splash. He said on a old boat like mine i should have a 95% chance of no more blisters beacuse anything that wanted to blister should have already.

Click to expand...

Similar to approach we took for brother's boat, except that we filled larger divots with a buildup of fiberglass cutouts and epoxy. Larger blisters are best removed with a Dremel and sanding drum. We also let the hull dry prior to barrier coat so as not to seal in lingering moisture. We inspect every year immediately after haulout. Not a single blister in four years.

skipperdude said:

What is you prep work like if you do a bottom job every year?

Do you just power wash and paint or have you removed the old bottom paint down to the jell coat?

sd

Click to expand...

We would powerwash, acid wash and do a decent job sanding and feathering in of flaking paint, getting a smooth-ish surface to paint on. Then three coats.

So. we went to take a look. And while we do have some big blisters, several of which have already been ground out, the biggest issue that we want to deal with is the 26 years of caked up paint.

So, looking at this from a different angle....is there any reason to "not" sandblast all of that old - thick - layers and layers of paint off, get 2 coats of barrier epoxy and start with new paint? Having the biggest blisters ground out while they're visible.

Since our next boat is most likely several years down the road, is there a valid reason to not do this now while she's already out of the water? We're thinking that it will make the future bottom jobs a much easier task.

My biggest disappointment is missing the Fall gunkholing.

Amazing how little boaters, surveyors and even many NA's really know or understand about hydrolysis, blisters and dry laminates....

Pop a few, grind a bit and add epoxy...a recipe for disaster....

Besslb said:

We would powerwash, acid wash and do a decent job sanding and feathering in of flaking paint, getting a smooth-ish surface to paint on. Then three coats.

So. we went to take a look. And while we do have some big blisters, several of which have already been ground out, the biggest issue that we want to deal with is the 26 years of caked up paint.

So, looking at this from a different angle....is there any reason to "not" sandblast all of that old - thick - layers and layers of paint off, get 2 coats of barrier epoxy and start with new paint? Having the biggest blisters ground out while they're visible.

Since our next boat is most likely several years down the road, is there a valid reason to not do this now while she's already out of the water? We're thinking that it will make the future bottom jobs a much easier task.

My biggest disappointment is missing the Fall gunkholing.

Click to expand...

Professional soda blast to remove the built up a/f is a good start, old a/f needs removal after years of build up.
You`ll need some kind of sealer undercoat before new a/f.
But first, repair the blisters of any consequence you can see, or you are just painting over defects, as the PO did with my boat after soda blast. Blisters are best seen just after hauling while the surface is still wet.
Blisters should be ground out until the area ceases to ooze liquid and stays dry. Apply local heat periodically to draw moisture out. Leaving the ground areas for months to dry is optimal,but not always possible.
As suggested by others, the ground areas,which should be a saucer like shape achieved by using an appropriate dished grinding tool on an angle grinder ,can be filled with concentric gradually enlarging circles of mat,with epoxy,filling the defect back to smooth.You could use filler on small blisters, but not large ones.
To my mind the problem would need to be very widespread to remove the entire gelcoat, I think you would then be committed to letting the hull dry out over an extended period before epoxy restoration.Yours does not sound so bad. Good luck. BruceK

Without removing ALL the gel coat...your hull might take years to dry out. GEL COAT IS USELESS ONCE IT HAS BEEN COMPROMISED OR THE HULL LAMINATES ARE WET.

Might as well get rid of it at that point...and start fresh...otherwise you are just covering wet laminates and spending money for nothing and actually making the situation worse.

psneeld said:

Without removing ALL the gel coat...your hull might take years to dry out. GEL COAT IS USELESS ONCE IT HAS BEEN COMPROMISED OR THE HULL LAMINATES ARE WET.

Might as well get rid of it at that point...and start fresh...otherwise you are just covering wet laminates and spending money for nothing and actually making the situation worse.

Click to expand...

Sounds like you're assuming that blisters automatically equate to compromised laminates throughout the boat. That was absolutely not the case on the boat we repaired. We could easily see where the mush in an individual blister ended and perfectly solid structure began. Big difference between a rash like that shown in your photos and individual localized blisters. The hull we repaired was quite dry on a moisture meter....not that I place much stock in that little gizmo.

Does anyone know of a boat sunk by blisters?
12 years ago I had a surveyor warn me of the impending danger of blisters, indicating the boat would probably sink if I didn't take it to the yard he recommended for a full gel-coat peel. The broker said it had already had a life-time guarantee peel, only the owner couldn't find the paperwork and the yard had gone out of business, oh well.
I had 3 bottom jobs done and started moving the boat between fresh water and salt water every year on a trailer. The "blisters" never changed. There are a few, just like the surveyor said, but they are still the same size. The boat still floats.
Terredo worms sink wood boats, but I think it takes rock to sink a fiberglass boat.

Besslb said:

... the biggest issue that we want to deal with is the 26 years of caked up paint.

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Just curious--- what kind of paint has been used on the bottom of your boat all this time? Ablative (sloughing) or hard?

Ok kiddies... Here is the story and the pictures.

We drove down today to get a 1st person look at her bottom. When we pulled up we were both most surprised by how much work had already been done. Apparently, they had started to grind out the blisters without having been authorized to do so. Once the yard owner saw what was going on, he stopped it and has said he'll fix what was done. Anyway, it's worse than I thought, but not as bad as it could be. The worst is mostly around the bow.

The big thing is that there is a large amount of thick and flaking paint. Years and years of it can be just popped off with your finger nail. Grab a flat scraper and you can turn a 1" spot into a spot more than a foot across with ease. To us, removing that mess is the highest priority. And from what I am told, media-blasting it to remove it will open many, or most, of the blisters.

Therefore, we are leaning toward going ahead and getting the whole job done. I will let Bess explain more of the arguments for and against. We saw a few boats in the yard that were in various stages of the same-ish job and the results look very, very good.

There are more details than just this, but we spent 8 hours in the car today and I am tired of thinking about this. All of your opinions are read and we take them in and discuss them. We want to make a good decision, but in the end, it will be OUR decision based on what WE need to do. Skinny Dippin' is 26 years old and is probably reaching the golden years. We plan to keep her for a few more years in hopes of PERHAPS finding a boat with a few less compromises based now on our new experiences. Still, nothing is certain.

Thanks for all your help... Bess may continue this later. Me? I have a few more Dark-n-Stormy's to drink.

So here are my photography-challenged pics:


P1010982 by GonzoF1, on Flickr


P1010985 by GonzoF1, on Flickr


P1010970 by GonzoF1, on Flickr


P1010971 by GonzoF1, on Flickr


P1010976 by GonzoF1, on Flickr


P1010977 by GonzoF1, on Flickr


P1010978 by GonzoF1, on Flickr


P1010972 by GonzoF1, on Flickr

Marin said:

Just curious--- what kind of paint has been used on the bottom of your boat all this time? Ablative (sloughing) or hard?

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Cheap CPP ablative. We figured if we were hauling yearly, we'd use the cheap stuff.

I'm surprised ablative paint built up that much since it goes away as the boat moves through the water. We've been using ablative paint (Petit Ultima SR until this year) since we bought the boat 14 years ago and the buildup is minimal. In fact if we let the paint go too long we start seeing the blue hard paint that was on the bottom when we bought the boat.

Marin said:

I'm surprised ablative paint built up that much since it goes away as the boat moves through the water. We've been using ablative paint (Petit Ultima SR until this year) since we bought the boat 14 years ago and the buildup is minimal. In fact if we let the paint go too long we start seeing the blue hard paint that was on the bottom when we bought the boat.

Click to expand...

We have the same build up and issues as Tom and Bess and really need to being it down to gel coat and start over. So yes it happens. Luckily we have no blisters but the many layers of crappy paint make it hard for new paint to stick and a new bottom doesn't last long. We're on the second new bottom in two years and really need to suck it up and spend the money to take it down and start over.

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.