Bottom Blisters

[jackryan]

I looked at a 32' Grand Banks trawler today and she was in great shape, but when that boat was hauled out for the bottom inspection, there were tons of blisters--maybe 800 to 1000 blisters total. Most were the size of a quarter with some the size of a silver dollar and a few that were tennis ball size. I guess there are 4 options.

1) Spend the summer grinding and repairing blisters. (Not gonna happen)
2) Have the yard peel and barrier coat the bottom. (Probably very expensive$$$)
3) Ignore them and just use the boat as is. (Least expensive route, but going to have major resale issues-possible delimitation issues)
4) Keep looking for another boat.

Anyone have a ball park guess as to what it would cost to peel and barrier coat a boat this size. Would it be insane to buy the boat and use as is-the current owner said the blisters have been there for years and not caused any issues for him.

Open to any input/suggestions regarding blisters

Thanks,

JR

[Carl]

-the current owner said the blisters have been there for years and not caused any issues for him.

JR

You are reluctant to buy and if you do, I have a feeling this "non-issue" will affect the asking price. That kinda sounds like an issue to me.


Aside from selling, looks and performance (trawler...not alot of performance to lose), blisters allow water to penetrate further into the glass, which can cause blisters to form further in or worse delamination, that's a problem. I'd address at least the larger ones, and see how deep and far they reach. The problem is, doing a few every now and then without barrier coating, you'll see more. If you barrier coat, it's a hell of a job to be re-doing...even in spots.

I am one of those people who if I did not address the problem, it would grow into a larger issue. I know plenty of people who take the other road with a very clear head. A friend of mine decided to buy a boat even though the surveyor told him the entire side hull of the boat pegged his moisture meter, with an estimated 15k to repair. His plan was to buy and run the boat as is, then sell it in a couple of years. It "was" his plan, someone decided to buy without a survey handing over the deposit before him. Todays market is a bit wonky with people jumping on boats, that may not hold out when time to sell. Again, others would find buyers, maybe even making money, me...I'd get stuck.

Good luck, Grand Banks, a great boat!

[Sriver43]

Seems like the cost of the professional repair should reduce the purchase price proportionately at the very least. Seems like one of those things where it either needs to get fully fixed ASAP or buy a different boat… best of luck with it those are great boats!

[jackryan]

Got a couple of estimates and waiting on a couple. The first one was $57,000 to sand and repair the 100 largest blisters. The price included leaving the boat on the hard for months to allow it to dry out. Got another one for a peel and barrier coat for $15,000 but that didn't include the yard fee to leave it on the hard to dry, so probably more like $20,000, $25,000. Those are some big # for an old boat. My two biggest concerns are: Delamination and running into the same objections that I currently have when it comes to selling the boat. My brother has a mid 70's Hinckley that went through the peel and barrier coat due to delimitation from blisters. The blisters will eventually come back even with the peel and barrier coat.

JR

[Amberjack]

Jack, I went through that process a couple years ago with Amberjack. It wound up costing about $25,000 and took 6 months. Various "experts" told me the blisters weren't significant or deep and to ignore them but they bugged me and were only going to get worse. By the way, boats dry from the outside and the inside. The boat will need to be opened up during the process.

If you buy this boat and have the bottom done you can feel confident in the history of that boat. You could buy a different used boat with a clean looking bottom this year and have an unhappy surprise at the next haulout.

[Yannis]

JR,

Is this the only boat being sold? Aren't there any other boats you can buy?
Unless you are somehow attached to this very boat, I suggest you start distancing yourself from it, or in other words, run.
As for whether any boat can have similar issues that you will simply find out at the next haul out, thats not necessarily true, as you can prevent a lot of grief with a good survey.
Considering a boat that already has a minimum of 25K in improvements, with no guaranteed results as others here say, is not what I would call a wise choice, at least for me.

[Tony Meola]

Jack

Grinding is the tough way to go. To open them up, sandblasting will do it. Do you want to or have time to take on some of the work. Then from experience, I can tell you will spend days seeking out and filling every little pin hole the sand blasting made when it opened up a multitude of sins.

Once that is all done, then it comes down to the barrier coat. When we did our boat way back in 1986, they recommended 5 coats of barrier paint. Now the issue was you could not do three one day and two the next. That would have required sanding between that last dried coat and the next one. Luckily at the time we had people who fished with us a lot so we gathered five of us, and put on 5 coats in 8 hours, then had to have the yard lift the boat and shift it enough to the areas that were blocked off by the supports.

It has held up until this day.

Why did we do it, well my father wanted to get rid of the built-up paint and we had a couple of small blisters. We also found a crack in the gel coat on the center line at the stern. The sand blasting opened up that crack.

The boat you are looking at sounds like it is in worse shape.

If they blasted the bottom and you filled in the voids and then they barrier coated it, might be a financially acceptable option. But then there always is another boat that hopefully does not have that problem.

[jackryan]

Thanks for the insight and advice. I found a guy in the Chesapeake Bay area that specializes in bottom peels and thats all he does. He said he would peel the bottom back to dry laminate, then re laminate, followed by several barrier coats. He said the job would take around 65 gallons of resin. It would cost between $20,000 and $25,000 depending on the price of the resin. This option would only make sense if I were able to negotiate the cost of the work into the price. The other issue is that the boat is on the gulf coast and it would be expensive to transport to the Chesapeake Bay.

I have been thinking about a trawler, in addition to my 31 for a while. I was interested in this one because it was relatively close to home and it is a very clean well taken care of boat--except for the blisters. Not sure this is true, but several boat yard guys said that blistering issues are much more common and severe down south due to higher water temperatures. They also said that boats up north are out of the water in the winter which helps reduce blisters.

JR

[Carl]

Having the boat out of the water half the time should reduce the amount of blisters. Not ever putting boat in the water I would expect would further reduce the blisters.

This kind of reminds me of a sales guy selling me a pair of boots. If you want these to last longer, buy another pair and alternate wearing them to allow the leather to relax.

I couldn’t tell if he was joking or serious, but I didn’t buy another pair.

Sounds like an awful lot of work to rip it all off n re-glass. What kind of support comes along with that job?

[Stephan]

Not ever putting boat in the water I would expect would further reduce the blisters.

I'm sorry to hear that this otherwise great candidate has blisters.
I remember some years back Tillotson-Pearson did research where they found that warmer water and fresh(er) water had higher incidence of osmosis on their test panels.
I feel (subjective) that there is a difference between gelcoat blisters and moisture that gets into the laminate. Perhaps picking a few would be informative?
A dear friend had a Grand Banks which he did the loop on, many happy days for he and his wife. However this works out I'm confident it will be for the best.
Good luck,
Stephan

[Tony Meola]

Jack

I believe Interlux has always claimed that blistering was more common in warmer waters. It also seems that in some cases it has to do with the layup of the boat. It has been somewhat of an issue on the older Bertrams, however there are those out there with no problem and when they were built the resins were not blister resistant, like they are today.

I have seen videos of peeling the gel coat, but it was always my understanding that they did not remove any green glass so the only thing that was needed was fairing and barrier coat. Is all that resin for fairing or are they coating the bottom with it>

From what I have seen in the Marinas I have been in, the boats are sandblasted then allowed to dry and then barrier coat. Not sure what the peeling does for the job outside of expanding it.

Based on the following from Boat US it sounds like the hull is saturated. I would take a pass on the boat unless you want to take on a big job.

Fiberglass blisters occur because water passes through the gelcoat.

Water soluble chemicals inside the laminate exert an osmotic pull on water outside, and some water molecules find a way through the gelcoat. As more water is attracted into the enclosed space, internal pressure builds. The water molecules aren't squirted back out the way they came in because they have combined with the attracting chemicals into a solution with a larger molecular structure. Instead, the pressure pushes the covering gelcoat into a dome — a blister.

There has been a great deal of hysteria about blisters, but the reality is that the number of boats that develop serious blister problems is extremely small. An occasional blister or two is not a serious problem, any more than is an occasional gouge in the hull. Some boats seem to exhibit a greater propensity to blister, presumably due to the chemical components used and/or the lay-up schedule, but all boats are at some risk. Surveys suggest that about one boat in four develops blisters.

Repair Materials

Effecting the repair of a few hull blisters requires an appropriate quantity of epoxy resin and hardener. Do not use polyester resin for blister repairs; you need the stronger adhesion and better water impermeability epoxy provides.

You also need a filler to thicken the epoxy into a putty. Select colloidal silica. Never use microballoons or any other hollow or absorbent (talc, for example) fairing compound to fill blisters.

A quart of acetone, a box of TSP (trisodium phosphate), a few acid brushes, and a 36-grit sanding disk completes your supply list. If the blisters penetrate the laminate, you may also need a yard of 6 to 10 ounce fiberglass cloth.

Minor Blistering

The first step in minor-blister repair is opening the blister to let it drain. Pop the dome with a chisel, screwdriver, or rotary tool. Be sure you are wearing eye protection; pressure inside a hull blister can be double that of a bottle of champagne, and the fluid that blasts out when you pop it is acid.


Load a disk grinder with your 36-grit disk and grind the open blister into a shallow depression. The rule of thumb is that the depression should be 20 times as wide as it is deep, and it should only be as deep as required to remove any damaged laminate beneath the gelcoat.

Use a plastic mallet or the handle of a screwdriver to tap the hull all around the blister. Sound laminate will give a sharp report. A dull or flat sound anywhere indicates additional delamination, meaning that the blister is larger than you thought. Increase the circumference (not the depth) of the depression until the laminate all around it is sound.


Flush the open blister with water, then scrub it squeaky clean with a solution of hot water (if available) and TSP 7mdash; about a quarter cup of TSP to a gallon of water. Rinse thoroughly, then allow the blister to dry for at least 48 hours, longer if practical. If you dry-store your boat for the winter, grind and scrub blisters at haulout but don't fill them until launch time.

Filling

Just before filling, scrub each depression briskly with a clean rag dampened with acetone.

Mix a small quantity of epoxy (one pump) and paint this unthickened resin into the cavity. Wet out the entire surface of the depression. Use an acid brush to apply the epoxy and give this application 20 or 30 minutes to begin to kick. For shallow blisters, prepare a small amount of fresh epoxy (one or two pumps) and thicken it to peanut butter consistency with colloidal silica. Fill the depression completely with this mix, using a squeegee to compress and fair the filler. Silica-thickened epoxy is difficult to sand, so take extra time to fair the epoxy as well as possible while it is wet.


Deep blisters require the replacement of the damaged glass fabric. Cut a disk of fiberglass cloth to match the diameter the depression, then cut several more, each a little smaller than the last. Use only fiberglass cloth. Chopped strand mat (CSM) can be held together with a binder that is incompatible with epoxy, so never use mat with epoxy resin unless you know it is specifically intended for epoxy use.

Wet the bottom of the cavity with epoxy and lay in the largest disk of cloth. Wet out the cloth with resin until it is transparent, then lay in the next, slightly smaller disk. This counterintuitive schedule of large to small maximizes the area of the secondary bond, the adhesion of the new cloth to the old laminate. Wet out the second layer, using the end of the brush to tamp the disks and compress them together. Continue adding disks and saturating them with resin until the repair is even with the surrounding surface. Curing epoxy generates heat, so if your repair requires more than 5 layers of cloth, you will need to pause after 4 or 5 to allow the epoxy to kick and the heat to dissipate before continuing.

Whether you have filled the cavity with glass disks or epoxy putty, allow the filler to kick. When the epoxy is no longer fluid, but still tacky, paint the repair and an inch or so beyond with at least two coats of unthickened epoxy, letting each coat kick before applying the next.

Let the repair cure for 24 hours, then scrub it with water and an abrasive pad (like Scotchbrite) to remove the waxy film on the surface of the epoxy. Fair the repair with a sanding block and you are finished.

Gelcoat should never be applied over epoxy. Since the repair will be covered with bottom paint, there is no need for a gelcoat surface anyway. Don't use gelcoat in blister repair.

Boat Pox

Boat pox is a much more serious condition, related to the occasional blister like acne to the occasional pimple. If the bottom of your boat is covered with blisters, filling them won't cure the problem. Pox is a systemic condition indicating that the hull is saturated. The actions necessary to remedy boat pox require specialized equipment and expertise.

[jackryan]

Tony,

Sorry, I've been on vacation and just getting around to seeing this.

Wow, thats the most exhaustive explanation of blisters and how to deal with them. I did not buy the boat. I did find a guy in Maryland that is an expert in this sort of thing and its all he does. He seems to think it is repairable, and would cost in the $20,000 to $25,000 range to repair. The big problem is that the boat is 1700+ miles from Maryland and the owner is not willing to come down much on the price. I'll keep looking, but highly appreciate all of the insight!

JR

[Carl]

In the words of Garth Brooks, thank god for unanswered prayers. Letting that kind of project boat slip out of your grasp sounds like a blessing in disguise.

[Tony Meola]

Jack

Another will show up. The only issue is that if one has the problem, I am sure others of that era also have the problem.