Curious Bottom

[Scott T-Bird]

After 11 years owning this boat, this is my first opportunity to actually refinish the bottom. We had her sand-blasted to remove the layers of very rough and tenacious bottom paint of unknown origin. I thought there might be some hidden surprises but I don't really know what to make of the results. Thousands of tiny chips have broken from the gel-coat surface to expose a red-colored layer underneath. The chips are very consistent, just 1/8" to 1/4" diameter and about 50 mils deep.
I would think they are blisters, but there is no weeping liquid.
Other boats next to ours which were sand-blasted do not have this condition. Could it be that the paint adhered so tenaciously that removal caused the chips? Why the red color? It looks like gelcoat or paint but I can't figure out why there is a colored layer underneath? My bottom paint was red. I assume the lead keel had a gelcoat layer over it which came off, hence the white residue left over in a few locations. It has a few rough surfaces which I would guess should be faired.
My plan is to barrier coat with an epoxy paint before applying ablative. I assume that I should fair the entire surface smooth in the spring.
I've not asked the contractor about this yet, as we first saw it yesterday. Any thoughts?

 

[Rick Webb]

Lightning Strike?

 

[DougM]

I would suggest that the red color that you are seeing is the Fiberglas resin used when the hull was constructed. The pock marks are small gel coat blisters that have popped open.

Worst case scenario is that the bottom will need to be stripped and re-gelcoated. I'm not certain that barrier coating will solve the problem in the long run. That's just my opinion.

 

[Gunni]

That is curious. Looks like you have a red gelcoat hull, and a previously applied barrier-coat that has chipped away, or is possibly blistered. A moisture meter can tell you if the laminate is wet. I would expect some large blisters if the laminate was wet. Don't barrier coat until you have it sorted. Let it stay open this winter.

 

[Jackdaw]

Are you SURE you are down to gelcoat? That looks like paint over a red barrier.

 

[Scott T-Bird]

Are you SURE you are down to gelcoat? That looks like paint over a red barrier.

That's a good question. Honestly, I have the same thought and I can't tell. The boot stripe is paint over gelcoat. If the layer is a white barrier coat, it should seem raised from the boot stripe but it doesn't seem that way to me. How thick should the gelcoat be? I wondered if the laminate has a reddish color. Many of the areas are more of a gray color. The red color isn't consistent.
This boat spent the 1st 10 years or so of it's life in Texas where I'd bet it was in the water all the time. It spent the next 10 years in Sea Bright (NJ), so it was on blocks for winters (probably). The last 11 years have been on land over the winter for about 6 months each year. The paint layers were multiple and very rough for as long as we had her. There was no ablative that was wearing off during the time we've had her.
There is no way I am stripping and re-gelcoating. The boat doesn't have enough value for that extreme. I'll definitely evaluate at the end of winter and I'll be looking for signs that it is weeping moisture, but right now, it seems very dry.
Attached is a curious picture that I took before sand blasting. Those white spots of gelcoat seemed odd to me. When I used an awl to scratch them, nothing weeped out, it just cracked the surface, like I was chipping dry gelcoat.

 

[Scott T-Bird]

Here's another close up which definitely shows red under the surface. But many areas are gray, too. This photo just happens to be on the edge (left side) of an area which appears to have some stress failure, such as a strike just below waterline. But there are no others signs of weakness, otherwise. The paint that was on the surface actually looked like it sagged, so there was a hint that the stress marks were there. If the red is actually the surface of laminate, it appears that gelcoat blisters went no deeper than the surface of the laminate. I think I read that in this case, the chips should be tiny, as I find that they are.
Assuming that the laminate is dry, and I can test with a moisture meter. My intention is to fair the surface with epoxy and paint. If the boat lives another 20 years, in the same imperfect condition as I came to own her, she will be doing well.

 

[Gunni]

Laminate resin can be reddish in color:

 

[Scott T-Bird]

Thanks for that picture ... I think that may explain it. I'll be watching for moisture. It won't hurt to let her dry out good and long if the moisture meter tells me it needs to dry. I'm certainly not going to turn this into a peeling project.

 

[Rick D]

Your plan makes good sense to me. Fairing with epoxy and then barrier coating. My yard suggested 3-6 months drying before barrier coating since they don't want to have any moisture in the hull. So, you should be in perfect shape to do that before launch. IMHO, with the usual disclaimers

 

[Ilanortho]

Looks like instances where automotive paint is applied and there is silicone residue on the surface and it fails to adhere in nicely circled areas (is it called "fisheyes"?). I have seen that happen and it looks exactly like your picture. Ilan

 

[Scott T-Bird]

Looks like instances where automotive paint is applied and there is silicone residue on the surface and it fails to adhere in nicely circled areas (is it called "fisheyes"?). I have seen that happen and it looks exactly like your picture. Ilan

Yes, that is what I think as well. I don't know the history, but there were 2 thick coats and I always thought the second could also be a barrier coat. The fish eye shows through the first layer. I wonder if the previous owner just painted another barrier coat over the 1st coat just to cover it up. The second layer came off in slabs with a scraper when we first owned her, but other areas adhered tenaciously and could never be scraped off or scrubbed off with a brush as I removed algae in the water.

 

[CloudDiver]

This is a text book example of 'micro-blisters' (my word for it), where the water molecules have only permeated the outer gelcoat but not gotten into the laminate, that's why they remain so small and easily blown away by sand blasting.
Why the red? That is gelcoat that was the last color layer sprayed into the mold. Before the boot stripe was painted over was it red gel-coat anyway? My C-22 has a blue boot stripe and cove stripe, but under all of the white gelcoat of the boat is the same blue underneath before you hit laminate, even under the tan non-skid. This is because the white gelcoat is sprayed into the female mold first with the stripes taped off, tan on the nonskid parts of the deck mold... then they spray the entire thing down with blue after the masking is removed. The color makes the stripes where it was masked but over the entire interior it's better to visualized the wet-out as they lay in the laminate.
You made the right choice having it sand blasted, that saved you hours of agonizing sanding. Let her sit for winter and when the weather is fair use the Interlux Water-Tite epoxy filler. the bigger 8oz can is the best deal and a little goes a long way to fill all those tiny holes. Its just easier to mix at a 1 to 1 ratio, the SBO store price is hard to beat. Put a full 2 gallons of Interprotect 2000 barrier coat and your antifoul of choice.

 

[weinie]

epoxy, barrier coat, and paint. It'll last 20 years at least.

 

[All U Get]

Just had ours done this summer. We had each pock mark ground out, let dry, then filled (I think polyester). Then barrier coat was applied and three coats of bottom paint.

All U Get

 

[woodster]

Take a side grinder and grind a spot on the edge of the disk and see if you have layered color down in any deeper and you will know what's going on

 

[capta]

Polyester mites!

 

[woodster]

polyester powder post beetle maybe

 

[CloudDiver]

Do NOT use polyester filler or resin!

 

[Scott T-Bird]

Thanks all! I figured on epoxy filler. Our yard uses all interlux products, so CloudDiver's formula appears to be the best bet. I looked carefully for larger blisters but did not see anything that appears to penetrate the laminate. I'm happy with the way the hull-to-keel joint looks. The lead looks a little scaly on one side of the keel (as the photo shows). I wonder if that is a defect in forming the lead as I wouldn't expect a corrosion problem. I figured on grinding some of the gouges smooth and filling with epoxy to fair it all out. The lead has a number stamped on it in the upper-front corner on the port side. I wonder what the number represents? I forgot to write it down for future reference ... perhaps next time I'm there.
Actually, one of my photos captured the number L2253.