what are these spots in my gelcoat?

[naturewaterboy]

I have some small (most are about 1mm) diameter round "holes" in my gelcoat, all on the sides of the boat, at or below the waterline. I stripped the bottom paint off the hull, sanded a little with 80 grit and found these all around the boat. They seem to be more on one side of the boat than the other. They are not very deep - they don't seem to go thru to the glass - maybe 1/2 mm deep or less. Any ideas what they are, and are they a problem? :?:

[ondarvr]

How did you strip the bottom paint off?

[mark775]

Imperfections/ foreign matter in the gelcoat that you sanded "a little" through. One of the spots (green) looks to be the color of PVA (polyvinyl alcohol) used as a parting agent. The blue, I don't know. I believe that the builders were a little sloppy but also that you were too aggressive sanding.

[naturewaterboy]

On the sides, I just sanded with a 6" Festool DA sander in the rotary mode. It doesn't sand in a pure, rotary pattern like a grinder does, it wiggles around a little. I'll look closer at the color of the spots. The blue is probably bottom paint.

[ondarvr]

They most likely scraped barnacles off the hull and then bottom painted it, they can take chunks of gel coat off.

[Boatpride]

Once barnacles take hold, they bore through the gelcoat into the fiberglass - if unchecked. They get more and more secured. So when its time to remove them, then as Ondarvr suggests the gelcoat comes away in chunks.

If you would like to read a post on fixing gelcoat follow this link

Gelcoat Repair (http://boatpride.com/fiberglass-boat-repair-and-sailboat-painting/gelcoat-repair.html)

Hope that helps!

[naturewaterboy]

I am repairing the bottom with epoxy resin, so I'll fill these with some epoxy, as it is all going to get painted with Interlux 2000E barrier coat and then a bottom paint - probably Petitt Vivid Eco. Thanks for the answers - the holes probably are from barnacles, as the bottom paint was pretty well gone when I bought the boat, and it had a lot of hard growth on it.

[mikereed100]

Possibly styrene that was incompletely mixed with the gelcoat?

Mike

[mastcolin]

Bubbles in the spray-on gelcoat?

They were closed till you sanded?

Fill them with epoxy, paint.

Have you checked the hull for moisture content? Not that it can necessarily mean anything but if it is very high and you put on the epoxy system you may encourage osmosis later in life.

ps so the holes maybe the gelcoat osmostically breaking down for the reason given previous - pva, stryrene, bad mix, too much catalyst

[naturewaterboy]

I haven't checked the hull for moisture, but it has been sitting on land for 5 years, and I've had a tarp rigged up for shade over the boat for the last two. It also keeps most rain off the boat.

[Herman]

OK, so we have:

-barnacles
-unmixed styrene
-bubbles in gelcoat (less likely)

I would like to add:
-unmixed drops of peroxide in gelcoat. (malfunctioning spray equipment).

That can also be the cause. However, both unmixed styrene, mek or peroxide, or bubbles, are likely to cause problems on the surface directly after demoulding, so at least should have been taken care of by the manufacturer.

Luckily solving this problem is not difficult nor expensive.

[Wynand N]

contamination is my guess and it looks suspiciously like some moisture was present in the compressor/pipes when spraying the gelcoat.

Funny, we sprayed some epoxy paint this week on the deck of a 6 meter daysailor with the same symptoms - left small patches of pin holes holes at places on the primer that will not cover.
Found out the guys did not drain the compressor for a couple of days and after doing so, the problem disappeared.

[Herman]

Forgot about moisture indeed.

On all your machines, have a moisture trap installed, and get the one that drains automatically.

When spraying with a spraygun, have a moisture trap (and pressure regulator) as close to the gun as practical.

[ondarvr]

They don't look like water or catalyst drops, Water leaves round pits, catalyst will leave soft spots that will deform the surface. These look like chunks that were removed from something sticking to the surface.

[naturewaterboy]

It probably is attack from marine organisms - probably barnacles - as the bottom paint pretty well gone in around the waterline when I bought it. Thanks to everyone for your ideas.

[duktig102]

itself the best answer is just add salt water, I am confusing Gelcoat the car filler 1:4, to fill these shortages, I invite you to http://laminat-repair.co.uk/

[tunnels]

Re: WARNING!!! Polyestermites

Posted By: Sam McFadden
Date: Friday, 11 August 2000, at 11:52 a.m.

In Response To: Re: WARNING!!! Polyestermites (James Cameron)

Sail magazine did an excellent expose of polyestermites back in the late 70's. Unfortunately, I think the polyester lobby in Washington has worked to suppress knowledge of this insidious infestation. Alarmingly, there is recent evidence of a mutation that allows common polyestermites to digest epoxy...

: Several times you have indicated that you would be using polyester resin as a
: finish coat. I thought someone would have warned you about polyestermites
: by now, but it hasn't happened, so I thought I had better do it. I know
: they are really bad in Florida.

: It's not really surprising that there has been no warning, as polyestermites
: are a really sneaky little critter, and most people have never seen one
: and don't know anything about them. They look just like the polyester they
: are eating, so unless you have some way to detect them, you could be
: looking at what appears to be a really nice finish and it would be
: polyestermites busy munching away.

: The problem is, when they run out of polyester to eat, they leave, taking
: your beautiful finish with them. That's why you don't see polyester suits
: much any more. Some guy would be walking down the street in a well
: tailored polyester suit and the polyestermites would eat the last of the
: polyester, then leave, and the guy is standing there in his skivies,
: unless he was wearing polyester skivies....well, you get the picture. It
: was embarrasing, and there were a lot of complaints, but no solution to
: the problem was ever found, so polyester suits just kind of died out.

: Fortunately for you, you have used epoxy to build your boat. If you had used
: polyester throughout, you could go out one day and pick up your boat to go
: paddling and end up with an arm load of disconnected strips.
: Polyestermites don't eat epoxy. It gives them really bad gas and tends to
: give them away.

: Detecting them can be a really vexing problem. If I were you, and going to
: use a clear finish, I would mix a couple of small batches with some bright
: colored dye in them, maybe dayglo yellow and dayglo orange. Then I would
: sprinkle little spots of these colors all over the boat. That way, when
: you check your boat, if the colored spots are moving, then you know you
: have polyestermites and you can get the exterminator in to get rid of
: them. You also might check with your local surf board place to see how
: they handle the problem.

: I thought you ought to be warned. Hope this helps. Good paddling

: James :P

[Itchy&Scratchy]

Judging by the blue streaks around those bubbles in the surrounding gel in those photos , it looks like the gel has been sanded too thin or applied too thinly when being moulded.
If it is the sanding then the gel has been sanded away too much resulting in opening up of the the bubbles in the laminate.
Itchy

[Herman]

Oh yes, polyester mites. I have bad memory about them.

The point is, your polyester gets eaten. OK, I can live with that. I have a garden full of plants, and they get eaten as well (only they grow back). But don't stop reading, it gets interesting.

I once heard to get rid of the mites, you could scare them away by wiping with a mixture of acetone and styrene. And so I did. And I wished I never did that. What happens is that indeed polyester mites do not like the mixture, but no-one told me that wiping the boat with this mixture makes the mites very upset, and make them crawl up into my face and on top of my head, eating my hair! They got up about halfway, when I got the luck that my wife came by, and warned me. So hastily I dipped my head into a bucket full of acetone / styrene. Which luckily stopped the mites.

so there I am, front head bold, sides and rear still with hair....

And I will tell you: If you see all the guys in Washington, they are mostly bold or with little hair. They were all boat people, and did the same as I did, but all of them were so ashamed, they conspired together, and organised this huge cover-up. Thay is why no-one knows about it! Conspiracy!

Now I also understand why I have seen boats transported to Area 51...