If a man must be obsessed by something, a boat is as good as anything, perhaps better than most E.B. White
5/4/2008
12:35 PM
What are Blisters and How do They Form
Technically speaking, blisters are the symptom of a condition that is known as hydrolysis of the laminate. Hydrolysis is the chemical process of decomposition of a material and the addition of water (Webster's). When used in reference to the polyester resin it is the breaking of the bond of the resin. In layman's terms, it's simply the decomposition of uncured resin.
As you will see, not all bottoms with hydrolysis damage have blisters, but all bottoms with blisters have some degree of hydrolysis.
All boats of polyester fiberglass resin design and manufacturer soak up water. I've heard that a boat may soak up to 20% of its original weight in water. What happens is when water penetrates the gelkote, the glass fibers assist by acting as capillarys to transport the water into the laminate. Once inside, the water goes into chemical solution with the resin in the gelkote and laminate.
So how do the blisters form? Blisters form when the flow of water into the laminate is greater than the flow of hydrolysis fluid back out. The acidic solution, under pressure, that is produced by hydrolysis cannot escape back out through the gelcoat and a blister begins to form. Over time, they grow larger and slowly start delaminating the outer layers of laminate. Smaller blisters will combine with others to form larger blisters and the process continues.
One of the most asked questions is "Why do some older boats blister and others do not? What we find is those older gelkotes are porous. Water flowing in is equal to the acidic solution flowing out. The gelkote is much like a sponge. The result may be underlying hydrolysis but no blisters.
So why are blisters and hydrolysis a problem? First, it is unsightly and may slow the boat in the water. But more importantly, if hydrolysis goes unchecked structural delamination can occur. Nothing will scare away a potential buyer faster than blisters.
The affects of hydrolysis on the resin may be quite serious. The hydrolysis process can soften, weaken and remove the resin from the laminate. Strength of the hull is reduced.
You might ask how long might it take for the deterioration to become a structural concern? No one really knows yet; fiberglass boat building has not been around long enough to determine that.
So we now know that any boat with blisters has a hydrolysis problem to some degree; however a boat without blisters may have a problem but doesn't show it. So what can you do to evaluate the hull for hydrolysis?
Identify the size and frequency of blisters. Blister diameter is often associated with the depth of the blister and thus a rough gauge of the depth of the hydrolysis. Bigger blisters usually mean bigger problems.
Look for cracks, crazing and pin holes. These may be letting lots of water into the laminate and accelerating hydrolysis.
Look for sediment piles inside the hull. These typically indicate active hydrolysis, even though there may be no blisters
Take moisture meter readings both inside and outside.
Drill or grind into the laminate to determine the extent of laminate damage.
REPAIR OPTIONS:
There are some differences with owners as to the best way to repair blisters and hydrolysis.
Some owners choose to do nothing. Maybe not the best choice, but we all tend to postpone it as long as we think we can get away with it.
On the simplest level, I have simply popped blisters and filled them with epoxy. Some owners have tackled the entire boat blister problem this way and proudly claimed they have solved their problem. Of course, this completely ignores the problem of water continuing to get in to the laminate and causing even more blisters and hydrolysis.
And finally, the most complete repair is the removal of the gel coat and replacing it with a impervious barrier coat.
LAMINATE REPAIRS
Perhaps the only successful method to date of repairing a blistered boat hull is by peeling the gelcoat and any damaged laminate from the boat. Some have tried sandblasting the hull but it's a hit and miss attempt at best requiring a very skilled blaster. The best you can hope for is an uneven, wavey hull when complete.
To begin the repair the boat is hauled, washed and the blocked on stands.
Once the amount of laminate to be removed has been established, the removal process begins. A tool that has become commonly called a Peeler is used. It cuts the gelcoat and laminate off like a hand-held electric planer. It can be adjusted to remove only to the depth of a single coat of bottom paint if need be. The hull is left quite smooth, requiring only minimal sanding and fairing.
The cutting tool is a much cleaner operation in comparison with grinding or sandblasting, both for the boat and the environment.
Once the gel coat and any damaged laminates have been removed, its time to dry out the boat. We now need to remove as much water from the boat's hull as possible before making our repairs. This does not suggest that we will get all of the water out ( I doubt this is possible anyway), but to remove as much as practical.
We've chosen this time of year as this is the dryest season in Florida with the lowest humidity. The boat's hull will be measured initially with a moisture meter to give us some baseline reading. She will then sit for days, weeks, months "draining" water from her hull until we have obtained the lowest moisture readings possible on her hull. She'll be monitored weekly. We've talked about building a tent over her to speed up the drying but the yard says that they have had less than satisfactory results with this method.
After the hull has dried, it will be time to re laminate any areas that were found to have hydrolysed laminates. Woven glass cloth will be used with epoxy.
BARRIER COATING
Following removal of hydrolyzed material, drying of the hull and replacement of glass as necessary, a barrier coat is applied. Epoxy resins are by far the best water-proofing materials to date for boat use. Although they have much higher costs, they have been the preferred resin for many successful repair jobs.
As a barrier coat, six rolled coats will be applied to arrive at a thickness of about .030". Once faired, two coats of anti fouling paint completes the repair.
So there you have it. If you find just the right boat that has some blisters, you now know what they are and how they got there. You also know what options are available to repair.
References:
BLISTERS & LAMINATE HYDROLYSIS by Craig Bumgarner, Updated April 9th, 2003
Yesterday, the Patricia Ann came out of the water as planned. The bottom did not look as bad as we had expected. We had delayed a new bottom job knowing we were going to repair the blisters. We got 27 months out of the antifoulant paint; it was time however.
We have the boat at Tiger Point Marina and Boatworks in Fernandina Beach, Florida. This yard is in Northeast Florida just north of Jacksonville. Other than just being good folks to be around, they offer some of the least expensive services anywhere; even a do-it-yourself yard is available.
The operation is managed by owner, Bill Kavanaugh. He has a great group of skilled technicians on site. You can contact the yard at 904/277-2720
The physical gelcoat removal is being completed by Tom Musto, owner of Boat Savers, Gel Coat Removal.
A pressure wash got the scum off so we could see details.
Once she was "clean", you could see the blisters on her hull.
You can see many in these photos. Most of the blisters were
not larger than a dime. But in the long run, its better to deal
with the problem sooner than later; the blister problem will
never get better.
This was the worst area found where some delamination was occuring on starboard side. This will have to be hand-ground out and then re-glassed with new fibercloth and epoxy resin. The area is about 15 inches long. No blisters were found here but hydrolysis was at work from within.
You can see the blisters in this photo. A few of them were weeping but not badly. Now something to think about, this is a slow repair process, the boat has to dry out to be able to replace the epoxy barrier coat. If you can't allow the time, don't even consider this or you will be wasting your money
Here is a photo of the "peeler", the hand-held device to remove the gelcoat. The cutter head rotates to strip the gelcoat, a small amount of glass chop and any remaining paint at about 1/64 of an inch. The device is attached to a large shop-vac eliminating any significant environmental concerns.
Tom is shown using the "peeler", taking about a 6 inch swath off per pass. Notice Tom is protecting himself with the use of an airline respirator and hearing protection. The "peeler" is very loud!
After about 10 minutes, we are making progress. The white area is gelcoat not removed by"peeler" where the mold had an indentation during layup at the factory and the gelcoat was thicker.
Three hours of work, about 1/2 done. The blue areas not removed by the "peeler" will be removed by grinding.
So what happens next?
Tom will be back in two weeks where he will finish the grinding, The boat will have begun drying by then. He'll them pressure wash it again.
Mosture readings will be taken at that point.
8/30/2008
3:50 PM
Sanding the Bottom
Week 12 - 84 days
On Thursday work progressed on our trawler's blister project; it was time for step 3, sanding the bottom.
A protective tent of sorts was again built around the boat to protect other boats and people from the flying resin dust that would be generated.
A 6 inch sanding disk of 36 grit was used to sand the entire bottom to a smooth finish, and yes, it is very smooth.
The next step will be to fill the bottom. In this step, epoxy resin will be mixed with cabosil to a peanut butter consistency and them trowelled onto the hull. This will begin next Tuesday.
You see a photo of me hosing the hull with water; here is why.
When Tom completed his sanding, he found trace elements of moisture just beneath the surface; the sanding released it from the resin.
Although its normal for this to occur, washing daily removes the remaining contaminants allowing the hull to completely dry by next Tuesday.
9/2/2008
3:00 PM
Week 13
Filling the Bottom
Tom was here right on time and after a few brief showers got to work.
Tom mixed up a mixture of epoxy resin and 410 microlight filler, mixing it into a peanut butter like consistency.
After rolling clear epoxy resin onto the hull and allowing it to become tacky, Tom troweled the mixture onto the hull filling small voids as he went.
On Wednesday Step 5, Tom was back at work, even with the threat of the Tropical Storm Hanna.
Tom again faired the epoxy to a smooth surface with 60 grit paper.
Its now time for the barrier coats.
6/30/2008
6:45AM
On Friday, Tom was back at the Patricia Ann, this time to finish up the peeling of her hull. There were a few spots that he could not get to with the peeler so he had to use a smaller rotary grinder. I suppose he was there about 4 hours. I couldn't talk to him as he was inside the enclosure.
The enclosure is used to control the dust.
In addition, moisture readings were also taken before the hull was pressure washed.
We are now beginning the 4th week of drying and the moisture content is dropping, some 15-20% below the original readings in some places. I am trying not to get too excited as you can't rush the process. I am still anticipating her being on the hill until at least mid August.
Stay tuned.
Here are the steps of repairing blisters and applying a barrier coat.
Strip the Bottom. This must be done to expose the affected lamnate
Dry the Bottom.
This was begun last week, June 11th to be exact. Moisture readings have been taken all over the hull bottom and the results written on the hull with a Magic Marker. Those are % moisture you are seeing. She obviously had a lot of water in her. During this step, readings will be taken each week followed by a pressure wash to help neutralize the acids and open up and tiny pin holes. We expect/hope this to be complete on or about August 15th.
Sanding of the Bottom
After the hull is dry, the entire hull will be sanded with 36 grit sandpaper. This ought to be fun...:)
Filling the Bottom
Upon completion of sanding, the bottom pin hole voids will be filled by applying a coat of clear epoxy resin. While the resin is still tacky, a mixture of epoxy and cabosil will be spread over the entire bottom. Cabosil is a filler which gives the epoxy a consistency of peanut butter. The small amount of glass work on the starboard side will be done in this step.
Fairing the Bottom
The entire bottom will be faired (sanded ) using 60 grit sandpaper to duplicate the original hull shape.
Barrier Coat Application
5 coats of Interlux 2000E epoxy barrier coat will be rolled on; additional filling will be done as necessary.
Bottom Paint
2 coats of bottom paint will be applied.
Well there you have it. The complete process is laborious but will produce a better vessel than before. Tom has stripped over 1000 boats in his 10 years in the business; he tells me the Patricia Ann is in real good shape with minor blister issues.
So what does it cost to have this work done? I am paying $169.00 a foot to have the bottom peeled and the epoxy applied. New bottom paint is not included. You could apply the bottom paint yourself at Tiger Point saving yourself even more money.
So, if you are buying a boat and she has blisters or if your current boat has them, you now have a bit more information as to what to do, and how much it will cost you. If I am helping you buy a boat, I'd suggest we negotiate the cost of a repair in the purchase price.
9/8/2008
2:30PM
Barrier Coating
Today we began the final step in the barrier coating of the hull.
We chose to use the Sea Hawk brand of epoxy and it's easy to use and provides a thicker coating than does the Interlux. Three coats will be applied to the hull by hand roller, allowing three hours drying between coats.
Here is the port side with one coat of barrier coating. Looks pretty good huh? Now for some of you that may be thinking about what we'll do about the areas where she's resting on the blocks and jackstands, we'll move the boat and coat them when we have completed the rest.
Three coats of barrier coats have been applied; next we'll move the boat so the remaining spots under the jacks and blocks can be reached.
After than, two coats of bottom paint and we're all done.
It's been 92 days for the duration of this project. If you choose to undertake a blister project, just remember, you can't rush it.
Mike
9/21/2008
6:15AM\\
New Bottom Paint
Since the last posting, we completed the final epoxy barrier coats on the spots where the jack stands and blocks were. We then had to overcoat those posts with bottom paint too. In the midst of all this activity, I repainted the dark blue boot stripe on her as well.
Well the day finally arrived, Friday September 19, 2008. It was time to splash the Patricia Ann. It had been 102 days since she had seen the water.
Now keep in mind, that storing a boat out of the water for this long will be cause for concern. Why? The systems have not been used and an idle boat will usually not work as planned.
The launch was made and I had David, the yards Master Mechanic on board with me to inspect his below the waterline work for leaks; there were new sanitation hoses, a new Electra Scan, the rudders had been dropped, and the trim tabs had been removed. No leaks found!
A quick run to our "new" slip was made without trouble; the good looking Swedish twins performed their best as usual. But as expected, we had problems; the aft AC will not work, there was a cracked water main in the forward stateroom and the freezer will not power up. Go figure?
The girl was absolutely filthy, everywhere. So yesterday I repaired the water leak and began cleaning her up.
Today, we'll complete the cleaning. Tomorrow I'll address the AC and freezer issue.
If you are searching for your first boat you've very likely heard about blisters. Most boaters with in-the-water boats are aware of them. But what are they, how do they form and most importantly, what do you do about them...if anything? I've been involved with 5 surveys since the first of the year and every time a boat was hauled from the water, blisters are the fear from the prospective buyer. You have no need of panicking, however, the issue is easily managed.
My trawler, the Patricia Ann has had a number of tiny blisters on her hull for some years and I've known about it. I've just watched them and evaluated them each time I pulled her out of the water. I've finally decided to tackle the problem. Next Monday, 5/12/2008, she will be pulled from the water to begin the task of removing the existing blisters, drying of her hull and applying a epoxy barrier coat, and finally new bottom paint.
To help you better understand the cause and what to do about it when you are searching for and evaluating your next boat, I'm going to chronicle my project with descriptions and photos. It's my intention that you will have a much better understanding of the issue when your surveyor says, "this boat you wish to buy has blisters".
