Blistering

Prairie Schooner

Jeff & Donna, E35-3 purchased 7/21
Ksmt bottom 2024_3-27 6003.jpg
One of this year’s projects is stripping the bottom to the original surface (gel coat?). I’m scraping off what must be at least two decades of bottom paint in most places. This photo shows the tools I’m finding most useful.
Ksmt bottom 2024_3-22 5954 sm.jpg

There isn’t a Master Thread on bottom painting or repair as of this writing. This thread seemed to have a wider variety of perspectives so I thought it would be a good place to leave some breadcrumbs. These are the posts I’ve found helpful:

- https://www.interlux.com/en/us/paint-guide/BW058-how-to-fully-repaint-grp-frp
- https://www.interlux.com/en/us/paint-guide/BW057-how-to-fully-repaint-bare-grp-frp





After reading all this, and more, the plan is to sand the rest down, patch any dings/scratches with filled epoxy, fair the keel, apply barrier coat (2-4 coats), then bottom paint. I used Total Boat Total Protect over the transducer and strut work and that seems to have held up well, so that’s what we’ll use for barrier coat. For bottom paint we picked up Micron CSC, black. We’re doing the rudder in white again.

Ambience.
Ksmt bottom 2024_3-22 5956 sm.jpg
 

Prairie Schooner

Jeff & Donna, E35-3 purchased 7/21
Fortunately I haven’t come across any medium or big blisters. There are a multitude of small blisters, around 1/8” in diameter. Also fortunate, they all seem to be dry.



Ksmt boot strp 2024_3-19 5938.jpg

This leads me to believe the white stripe is gelcoat.

My Question is about the white boot stripe. I’d like to be as minimally invasive with it as possible. I’m thinking of just filling any popped blisters with white gel coat and lightly sanding. Is there any reason not to do that? Would you recommend something else? Below the waterline I’ll patch with filled epoxy.

(We’ll consider raising the boot stripe at some point, but for now I just want to get the bottom back to good, original condition.)

Thanks,
Jeff
 

PANorth

Member II
I’m thinking of just filling any popped blisters with white gel coat and lightly sanding. Is there any reason not to do that? Would you recommend something else? Below the waterline I’ll patch with filled epoxy.
Among the abundance of blisters we repaired over the past couple of years were old repairs of small blisters. It appears that these were filled as you propose. Water had penetrated around many of these. Of course I cannot vouch for methods as it was long before I owned the boat. Perhaps flaring the edges is important.

As an update on our work: We used CopperCoat as "bottom paint". The system, as we applied it, includes two layers of barrier coat (supplied by CopperCoat) and four layers of CopperCoat. The boat has been in the water since November. Repair of a leaking fuel tank kept us from sailing through the PNW winter. But we are refilling the tank today after an epoxy repair and hope to sail in the next couple of weeks for the first time since owning the boat. Yeah!

Below is a picture of the pit corrosion in the tank. There was a clear distinction between the area with corrosion and clean metal. We coated all areas with corrosion with two layers of epoxy. It was all within reach of the port. I'm not a weight lifter so I could fit my arm into the port. We will report on all of this as we put it to use.

IMG_8228.jpeg
 

peaman

Sustaining Member
What a challenging project, to strip the entire bottom. On a 41 foot boat near me, the owner has spent 10 days or more so far, 5-6 hours per day, over the course of a few weeks, with an orbital sander attached to a shop vac, as he works back to a specific prior coat, sometimes lying on his back on a bench as he works around the keel. And then yesterday, the 40 footer next to him had a polyethylene skirt clamped to a plastic sheet ground cover, with a truck bearing signage "Billings Media Blasting" parked alongside, while the crew was rigging hoses to the tent formed under the boat. About 4 hours later (and reportedly $5000), the truck crew was finished blasting ground walnut shells at the bottom, right to the layer requested by the owner.

I hope your project is completed swiftly and to great satisfaction.
 

Prairie Schooner

Jeff & Donna, E35-3 purchased 7/21
What a challenging project, to strip the entire bottom. On a 41 foot boat near me, the owner has spent 10 days or more so far, 5-6 hours per day, over the course of a few weeks, with an orbital sander attached to a shop vac, as he works back to a specific prior coat, sometimes lying on his back on a bench as he works around the keel. And then yesterday, the 40 footer next to him had a polyethylene skirt clamped to a plastic sheet ground cover, with a truck bearing signage "Billings Media Blasting" parked alongside, while the crew was rigging hoses to the tent formed under the boat. About 4 hours later (and reportedly $5000), the truck crew was finished blasting ground walnut shells at the bottom, right to the layer requested by the owner.

I hope your project is completed swiftly and to great satisfaction.
Thanks Steven.
I've done a fair amount of bottom sanding on friends' boats. I think the scraping is a lot faster. I'm only good for a couple hours at a time, though. We put in a few days last fall and I've been heading to the yard off and on since February. It was cold and blowing stink today so I worked inside the boat. Donna kept suggesting the blasting, but I told her I'd rather spend the money on a spinnaker pole. We'll see if that math works out.
 

Prairie Schooner

Jeff & Donna, E35-3 purchased 7/21
Among the abundance of blisters we repaired over the past couple of years were old repairs of small blisters. It appears that these were filled as you propose. Water had penetrated around many of these. Of course I cannot vouch for methods as it was long before I owned the boat. Perhaps flaring the edges is important.

As an update on our work: We used CopperCoat as "bottom paint". The system, as we applied it, includes two layers of barrier coat (supplied by CopperCoat) and four layers of CopperCoat. The boat has been in the water since November. Repair of a leaking fuel tank kept us from sailing through the PNW winter. But we are refilling the tank today after an epoxy repair and hope to sail in the next couple of weeks for the first time since owning the boat. Yeah!

Below is a picture of the pit corrosion in the tank. There was a clear distinction between the area with corrosion and clean metal. We coated all areas with corrosion with two layers of epoxy. It was all within reach of the port. I'm not a weight lifter so I could fit my arm into the port. We will report on all of this as we put it to use.

View attachment 49603
Thanks for the feedback, Phil and Amanda.
When you get more info on the tank repair, it would be a great help to the collective wisdom here to document it in a thread. I've been using this one:
- https://ericsonyachts.org/ie/threads/e35-3-replacing-fuel-tank.17731/#post-156979

Jeff
 

Pete the Cat

Sustaining Member
View attachment 49598
One of this year’s projects is stripping the bottom to the original surface (gel coat?). I’m scraping off what must be at least two decades of bottom paint in most places. This photo shows the tools I’m finding most useful.
View attachment 49599

There isn’t a Master Thread on bottom painting or repair as of this writing. This thread seemed to have a wider variety of perspectives so I thought it would be a good place to leave some breadcrumbs. These are the posts I’ve found helpful:

- https://www.interlux.com/en/us/paint-guide/BW058-how-to-fully-repaint-grp-frp
- https://www.interlux.com/en/us/paint-guide/BW057-how-to-fully-repaint-bare-grp-frp





After reading all this, and more, the plan is to sand the rest down, patch any dings/scratches with filled epoxy, fair the keel, apply barrier coat (2-4 coats), then bottom paint. I used Total Boat Total Protect over the transducer and strut work and that seems to have held up well, so that’s what we’ll use for barrier coat. For bottom paint we picked up Micron CSC, black. We’re doing the rudder in white again.

Ambience.
View attachment 49600
I would suggest caution with the idea of a barrier coat unless you are going to strip all the gelcoat off and recover with glass. The problem is that your moisture (and this is true of most blisters I have seen) are between the gelcoat and the fiberglass substrate. Unless you give your boat a long period in the hot sun to totally dry, I think you might end up hatching more blisters with the barrier coat (see my experience, read on). I agree with your general approach, but I would not put a barrier coat over gelcoat that has already shown a penchant for bubbling. I pointed out earlier in this thread, I bought a boat that had had a bottom job where a very expensive yard had put a barrier coat over some damp gelcoat and hatched 10,000 blisters. I peeled all the gelcoat off the bottom (Swan and Nautor never put gelcoat on the bottom in the first place because it actually serves no purpose other than to make a cheap smooth surface to paint. I have some blisters on my current Ericson that I will look at when I haul, but unless I think they are attacking the glass beneath (something I have not seen in the yards I have been in), I will likely do nothing.
 

PANorth

Member II
unless I think they are attacking the glass beneath (something I have not seen in the yards I have been in), I will likely do nothing.
How will you know unless you dig into the blister? We had blisters that had multiple layers of delamination of the fiberglass. We kept going until we hit fiberglass that looked and sounded (tapped) solid. Even then, as described in one of the threads linked above, moisture bubbled up in a few spots when we heated it to apply the first epoxy.
 

Pete the Cat

Sustaining Member
How will you know unless you dig into the blister? We had blisters that had multiple layers of delamination of the fiberglass. We kept going until we hit fiberglass that looked and sounded (tapped) solid. Even then, as described in one of the threads linked above, moisture bubbled up in a few spots when we heated it to apply the first epoxy.
What I thought I saw were many small blisters. I would probably open ones that were larger that a quarter or 50 cent piece. If you had multiple layers of laminate affected on even one of them I would be concerned about the integrity of the layup. I think blisters are more of a symptom than a cause of delamination. But that is just an opinion. The blister problems in the 80s (Valiant, Uniflite) were about a fire retardant mixed in the resin. I believe this started lots of folks believing the gelcoat blisters were an indication of some similar laminate problem in other production boats. I think most boatyards have cooled their blister frenzy. But that is not to say delamination could not happen. Some of the Ericsons were said to oil can and that flexing could cause delamination. As could a resin starved layup that gets worked a bit. I have not seen any boats sink from blisters or localized delamination. Having been a victim of over reaction to the blister crazes of the 80s, I am probably on the other end of the spectrum these days.
 

Prairie Schooner

Jeff & Donna, E35-3 purchased 7/21
I would suggest caution with the idea of a barrier coat unless you are going to strip all the gelcoat off and recover with glass. The problem is that your moisture (and this is true of most blisters I have seen) are between the gelcoat and the fiberglass substrate. Unless you give your boat a long period in the hot sun to totally dry, I think you might end up hatching more blisters with the barrier coat (see my experience, read on). I agree with your general approach, but I would not put a barrier coat over gelcoat that has already shown a penchant for bubbling. I pointed out earlier in this thread, I bought a boat that had had a bottom job where a very expensive yard had put a barrier coat over some damp gelcoat and hatched 10,000 blisters. I peeled all the gelcoat off the bottom (Swan and Nautor never put gelcoat on the bottom in the first place because it actually serves no purpose other than to make a cheap smooth surface to paint. I have some blisters on my current Ericson that I will look at when I haul, but unless I think they are attacking the glass beneath (something I have not seen in the yards I have been in), I will likely do nothing.
Thanks Ray. It's really appealing to be able to cut out the expense and time of barrier coat. I'd just assumed it was standard procedure. I might call Total Boat and see what they say, fully aware they have a vested interest in selling the stuff. It's complicated by an unusually wet spring here, tho the boat has been out of the water since September. I'm continuing to watch responses here before we decide.
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
Thanks Ray. It's really appealing to be able to cut out the expense and time of barrier coat. I'd just assumed it was standard procedure. I might call Total Boat and see what they say, fully aware they have a vested interest in selling the stuff. It's complicated by an unusually wet spring here, tho the boat has been out of the water since September. I'm continuing to watch responses here before we decide.
If you decide to apply a barrier coat, it might be helpful to put a tarp around the hull (taped in place to minimize air escaping) and add an industrial heater for a few days to further dry out the hull. You should be able to rent one at an equipment rental shop.
Frank
 

Prairie Schooner

Jeff & Donna, E35-3 purchased 7/21
After much vacillating, we’re going to barrier coat the bottom before we bottom paint. What tipped the scale was a chance re-connection with a past acquaintance. He is an industrial chemist with a long career who has spent the last several decades working for a marine resin company. He’s also a former boat owner. I’m leaving the names out in case I’m misrepresenting what he said.

According to him, gel coat formulas from the 70’s - 80’s weren’t dialed in yet. They are porous. Water will get in. This is causing the blisters. He recommended three layers of barrier coat. So, even though it’s costing extra boat buck$$ and time, we’re doing that.

For the white boot stripe, I used a small brush and filled each popped bubble with white barrier coat. Very tedious. Once sanded down, we’ll cover the entire stripe with white barrier coat.
Ksmt bottom bs 2024_4-26 sm.jpg

Ksmt bottom bs 2024_5-5 sm.jpg

The keel was stripped to bare metal and barrier coated. The seam joint was filled with Thixo flexible epoxy.* Then it was faired with TB epoxy fairing compound, and will be covered with barrier coat.
Ksmt bottom 2024_4-23a sm.jpg

Ksmt bottom 2024_5-2a sm.jpg
*If you buy Thixo, definitely get an extra thrust caulk gun. My regular gun required way too much hand pressure and still only pumped a trickle. The 'SolidWork Professional Caulk Gun with Ergonomic Steel Handle, for 10 oz Cartridge, Adjustable 24:1 Thrust Ratio' worked well for me. Also, Total Boat doesn’t sell extra nozzles, but the West Six-10 static mixing nozzles fit, if the two TB supplies isn't enough.
 

Prairie Schooner

Jeff & Donna, E35-3 purchased 7/21
I very much appreciate everyone who's shared their experience. It's all valid. There are so many variables. After weighing it all, we're taking this route in the great boat ownership experiment. One thing we're not able to do is make a tent and dry the hull out further. We've had rain at least once a week all spring. That may come back to bite us in the transom. But, the boat has been on land since September. Not being immersed is a big thing, I think. I'll report on how it all works out.

Ksmt bottom 2024_5-6 a sm.jpg
We'd left some patches of thin old bottom paint since Micron CSC could go over that. The new plan meant we had to take off anything thick enough to still be ablative. What is left only amounts to what I consider 'staining'. The gray patch is where I rebedded the strut. We paint the rudder white and will give that the full strip treatment another year.
Ksmt bottom 2024_5-6 b sm.jpg
Today is painting day.
 

Pete the Cat

Sustaining Member
I very much appreciate everyone who's shared their experience. It's all valid. There are so many variables. After weighing it all, we're taking this route in the great boat ownership experiment. One thing we're not able to do is make a tent and dry the hull out further. We've had rain at least once a week all spring. That may come back to bite us in the transom. But, the boat has been on land since September. Not being immersed is a big thing, I think. I'll report on how it all works out.

View attachment 49957
We'd left some patches of thin old bottom paint since Micron CSC could go over that. The new plan meant we had to take off anything thick enough to still be ablative. What is left only amounts to what I consider 'staining'. The gray patch is where I rebedded the strut. We paint the rudder white and will give that the full strip treatment another year.
View attachment 49958
Today is painting day.
I am sure you have everything timed correctly. The guys at my yard have a particular timing of barrier coats and generally want to put the first actual bottom coat on ASAP per the directions so that it binds with the barrier coat. Every different layer on the bottom creates a possibility for small, probably only esthetic, blisters. While I disagree with your consultant: I worked in boatyards in the 70s and 80s and I really question the question about the gelcoat formulas changing, but he is right to say that it is very porous (so why would you put some thing "impenetrable" over something porous?) but West Systems guys were blaming gelcoat guys, the gelcoat guys were blaming the glassmen and West Systems folks (they had the big guns back then) and boatyards were blaming both and boatowners were paying the bills. There was a period where everyone decided that all the blister moisture was coming from inside the boat! There are opinion everywhere and mine is just one. I think you will be fine with what you are doing if you have the hull reasonably dry. Looks like you have done a good prep job and being out of the water as long as you have is a real plus for avoiding problems I have seen.
 
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