Gel Coat Blisters

[talbot]

I have just initiated a topic that will run for six months, even if I'm the only contributor, because that's how long this disaster will take.

I flipped the boat on its trailer in September and moved it into the garage to do "a little work" on the hull. Here's what "a little work" seems to involve:
--September-October: Mark a hundred or so gel coat blisters on the hull. Grind each one down to the glass. At the base of each blister is a white spot where the glass is rotten. Cut it away. Wash the hull to challenge the remaining gel-coat and reveal any remaining blisters. (I started with the idea, "God, don't let me find any blisters." Now it's blister Pokémon: Gotta Catch 'Em All.
--October: Palm sand the entire hull. Challenge the gel coat. Grind any new blisters. Sand. Wash.
--November: Keep drying the hull. According to Interlux, it takes a minimum of 3 months.
--December: Seal the hull with epoxy. $200. ca-ching. Wait two weeks.
--Early January: Sand. Build up the really bad areas with new resin and fabric. Wait two weeks.
--Mid January: Fill all the divots with putty. $60. ca-ching. Wait two weeks
--February: Fair the hull (i.e., Sand. Sand. Sand. Sand. Sand.)
--Early March: Barrier-coat the hull. $220. ca-ching. Paint the same weekend with bottom paint. $200. ca-ching. Wait two weeks.
--Mid March: Paint the topsides. $150, ca-ching. Wait two weeks. Pay the moorage fee. $500. ca-ching
--April 1: Turn the boat right side up. Put it in the water. Ignore the fact that I just spent (including all the sand paper and solvent) about $1,000 on the hull of a boat that cost me $900 to start with.
Or don't ignore it. I just got laid off from my job, so I may try to figure the cost into the sale price of the boat. Watch this space.

[K.C. Walker]

Talbot, I'm sorry to hear about your blister outbreak.

I went through a similar renovation after finishing the inside of the hull with my "core project" four years ago. The good news is, after I did all the work, I have had no further evidence of blisters. It is amazing, when I really started looking, how many of them showed up.

[talbot]

Thanks. Nice to hear of a successful resolution.

[Interim]

I have a similar quandry. A small leak on the centerline of my hull, about halfway between the mast and the stem. Estimates from two different shops run about $1,000 on a boat I paid $1500 for.

I want this fixed, so I am toying with the idea of learning the fine art of fiberglass repair. I'll have to cut a new inspection port inside the cuddy, so that plus the fiberglass will run me less than $100. What I don't know is whether I can apply gel coat, and if so, what tools will I need.

Jump in, right?

--john

[talbot]

My suggestion:
Step 1 Investigation: Stick a small digital camera into your cockpit inspection ports and snap a picture forward. See if you can estimate whether your leak is covered by any structure inside.

What I found in repairing a collision hole in my hull was that the sharp V of the hull foward of the mast is bridged with a fiberglass box (presumably to keep the water pressure from compressing the hull.) I could not directly apply glass and resin to the inside of the hole. I had to do everything from the outside. I had good access to the underside of the cuddy, but that didn't help, because the area I needed to work on was covered up.

Step 2a: Access Inside: If you think you can access the damaged area from the inside, cut an inspection port opening into the cuddy floor.

There are stringers under the cuddy floor that you don't want to sever. Use your digital photos to help you place your cut between the stringers. Don't forget that the inspection port will need a margin for accepting its own attachment screws. I would use the largest port you can fit into the space, at least 6". DO NOT mount the inspection port yet.

Step 2b: Access Outside: If you can't reach the damaged area from inside, skip the inspection port.

There is a way to cut open the hull and insert backing from the outside, but let's say the damage doesn't require that much reinforcement. In that case, just sand the gelcoat off around the damaged area, all the way to solid glass and resin. Once you are there, you will be able to assess from discolored fiberglass whether the damage is really a hairline crack or more extensive. If it's more extensive, you use a technique akin to drywall repair. Email me.

Step 3: Reinforce.
Whether working from inside the hull or on the outside, you pretty much follow the directions on the epoxy. (And use epoxy, not polyester). Three layers of wetted 6oz fabric (not mat), each overlapping the one below, should bring the surface back close to the level of the surrounding gel coat. If you are working inside the hull, do the same thing. There is sanding and decontaminating of the surface involved, but again, follow the directions for the epoxy you are using. I use Interlux. Others on this forum use West System. I have also used EverCoat, but I think the Interlux and West are better.

Step 4a Finish Inside
If you are able to do the repair from the inside, just install the inspection port ring and cover plate, and you're done. No one will ever see the repair, so the only criterion is that it is sound.

Step 4a Finish outside

If you had to cut into the finish, this is the step you were worrying about, with good reason. I have never been able to do a good job matching gel coat. There is a reason why they want $1,000 for the professional repair. When I win the lottery, I will ever after pay other people to do my boat repairs. I'll be in the clubhouse, at the bar. Until then, there are lots of how-to videos and manuals on the web. Follow the instructions. Don't get mad. Remember you can always paint if it doesn't work out.

I am using epoxy putty to fair the hull around my repairs. I sanded it even and then will seal with epoxy primer and epoxy bottom paint. If you want to try refinishing the gel coat over epoxy, you have to let the epoxy thoroughly cure and then scrub off all the amine blush (I think with TSP; check the gel-coat instructions). Then you sand it and remove the dust with solvent (acetone or special epoxy wash). Then you mix the gelcoat color to match. Or, in my case, to not match. Ever. No matter how many times I try. As with the epoxy resin, just follow the directions for the polyester gel coat resin.

That pretty much exhausts my knowledge. Others with more skill or patience may have better ideas.

--Talbot

[GreenLake]

Amine blush yields to soapy water, so TSP should be fine.

There are epoxies out there that are marketed as amine blush free (for example System Three's silvertip).

There are other epoxies that are marketed expressly for the purpose of being finished with gel coat (for example System Three's SB-112).

Different hull colors are more sensitive to precise color matching than others. And some areas are more visible than others

My boat didn't have blisters, but it had a gelcoat that was entirely cracked with tiny spider lines all over. Just the hull, not the deck. A PO had attempted to paint over this mess, but the cracks, while now sealed, were "printing through". Getting all the cracks ground out to where it would have been possible to make a gel-coat repair did not appear even feasible.

After sanding off the failing paint job and opening most of the cracks with a chisel, the hull was in a similar state as talbot's post blister removal moon-scape, except the gouges were shallower than his craters.

Some people actually re-gelcoat a boat. Don't know whether this treatment usually applies to decks only or includes the hull (but for bigger boats too). But they may be set-up to spray the stuff. I didn't think this was feasible, so I went with a paint that's compatible with the way I sail the boat (dry), pretty much going through the same series of prep steps talbot described.

Now, if you have structural issues, I'm all for doing structural repairs and getting the boat back into a state where you can sail it (optics be damned). Epoxy and exposed glass will need to be covered, of course. I've used pre-tinted gelcoat repair kits for motor boats occasionally. Not a great match, but close enough for below the water line.

[Interim]

I'm not worried about matching the color. If that part of the hull is showing, I've got other problems. Mostly I'm tired of taking in 5 gallons in a four hour sail.

Greenlake, you mentioned spider cracks on the deck. I have those in a couple spots, like around the chainplates for the shrouds. I have convinced myself they are just in the paint and not in the fiberglass because there is no flex in the surface with the pressure I can apply by hand.

Am I kidding myself? I'd hate to have the mast go over in a good wind.

--jf

[Interim]

Perhaps this is a naive question, but do I need to flip the hull to do the repair? Are the Epoxy and Gelcoat gravity sensitive? How-to videos make it seam that this can be done upside down. It might mean thinner coats or more sanding, but that seems easier than trying to roll the boat.

--john

[GreenLake]

Gelcoat is not a flexible as the fiberglass. So, spider cracks around stress points can be expected. But, I believe they do not necessarily have to be symptoms of any real damage.

The various generations of DS have slightly different ways of attaching shrouds. Different designs have different failure scenarios, but an absence or flex in the fiberglass would be a good sing, I suppose.

About taking on water: when fairing and repainting my hull I found a soft spot the size of a dime below the water line. I can't be sure, but it might have been a puncture hole "fixed" with caulk and then overpainted by the PO. Hate to think of the scenario if that "repair" had ever failed. In the event, when I found it, I could push the "plug" out with my little finger...

[GreenLake]

Perhaps this is a naive question, but do I need to flip the hull to do the repair? Are the Epoxy and Gelcoat gravity sensitive? How-to videos make it seam that this can be done upside down. It might mean thinner coats or more sanding, but that seems easier than trying to roll the boat.

Gelcoat needs to have air excluded to cure. (Unless it has wax mixed in). There are these stiff foils that are used for overhead. If they haven't gone the way of film with everything going digital, they make a great cover for gelcoat while its curing. You will be left with a smooth surface that conforms to the adjacent hull, so will have less final sanding.

That takes care of any gravity issues.

For epoxy you can use the same thing, except you don't really want it flush with the hull (unless you end up painting it). So you may need to sand away a bit to make room for a layer of gel coat.

[Baysailer]

Talbot,

Just saw this post and went through a similar experience. Buccaneer sailboat that had many small blisters. I didn't go to the extremes you plan to but it still took a while. I flipped the hull onto some saw horses so I was working at bench level. Used whatever means I could to break the blisters and carve them out to clean fiberglass. A can opener was my main tool of choice. I can still close my eyes and see all the poc marks on the hull. Cleaned it out with some acetone and let it sit for a month or so to totally dry it out, here procrastination pays. Made up some goop with epoxy and filler, filled all the holes as level as I could to reduce the sanding. Sanded/faired the hull then painted using west marine paint. It was cheap but premixed and went on easy and came out OK. It's been a few years and it's held up well with no returns on the blisters. The paint does need touch ups when I get emabarassed by its appearance but its easy and cheap.

[talbot]

Interim asked about flipping the boat. Not absolutely necessary, but it is much easier to work on. Because I'm in a cool climate, I put mine back on the trailer upside down, so I could roll it into the garage. It's in the 20's this week, so work (not to mention drying) would be totally stopped if the boat were outside.

Another thing is that all sorts of repair/enhancement procedures are possible or easier with the boat inverted. Many of these have been discussed on the forum. They include:
--reinforcing the coaming for oarlocks.
--reinforcing the coaming for moving the jib leads off the CB trunk.
--reinforcing the cuddy floor (actually, anything on the underside of the floor).
--anything on the underside of the deck, like reinforcing the control line cleats or mooring cleats.
--reinforcing the lip to support the chainplates.
--working on the CB trunk.
--repairing damaged or failing hull/deck connection.
etc. etc.

Flipping is a hassle if you don't have a wide flat lawn or a convenient support for a hoist. I have two really obnoxious intrusive-species sweet gum trees that are only alive today because taking them out would remove my derrick for lifting the boat. If I can ever figure a way to get my boat up to the back lawn (a terrace about 8 feet above the front yard), those leaf-farters are FIREWOOD.

[GreenLake]

We've had several threads on flipping the boat. There are many clever methods and then there's the "three strong guys" (or in a crunch two strong guys and a teen). Go read the old threads or the three of you figure it out.

Good luck!

[Interim]

I will look for those. Thanks. One thing I have plenty of is lawn.

But I also have cold (Nebraska), so I may have to pick my moment.

Thanks.

--john

[talbot]

Some of you asked for photos of the gel coat repair. I consider these dirty pictures.
The first one shows the hull with blisters sanded, just before the first sealer coat.

Gel coat blister repair

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There are actually several repair procedures under way at the same time here:
--gel coat repair
--repair of collision damage to keel under the bow
--repair of delamination and rot in transom
--repair of hull/deck joint.

In photo 1 the stripped transom appears at the bottom. The fairing compound smudged on the surface covers the holes used to inject low-viscosity epoxy. Also in photo 1, the after corner of the coaming shows the area where the open-to-the-water gap between hull and deck was filled and glassed in.

Photo 2 shows the procedure to repair through hull damage when you can't access the inside of the hull. A semi-stiff sheet of class is pushed through the opening. Once inside, it expands. Then epoxy putty is injected in on top of it, and the patch is pulled up against the inside of the hull with nylon threads (attached prior to insertion).

Hull patch

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Photo 3 shows the repaired keel area prior to fairing. The patch in picture 2 had been sanded and faired, and the whole forward part of the keel has been reinforced with 3 layers of 6oz glass and epoxy.

Gel coat blister repair

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