Pin holes in gel coat

Nick_H

Nick_H

Well-Known Member
Joined
20 Apr 2004
Messages
7,660
www.ybw-boatsforsale.com
As I needed to epoxy coat the hull of the Windy due to some grounding scratches, and anyway all the old anti-fouling was flaking off, I organised the Antifoul Removal Company to blast the hull on Friday, they use the Farrow system.

They did the job, I watched them the whole time and they appeared to be skilled in the process, and did not excessively blast any of the hull as far as I could tell. None the less, when they'd finished I had two problems. Firstly, the gel coat on the transom was so thin, that there were patches of GRP exposed, and secondly I found loads of pin holes in other areas of the gel coat. I was concerned, but decided the remedial action for both problems would be to epoxy the hull, so decided to Coppercoat it, which involves four coats of epoxy.

On Sunday, after two warm and breezy days to dry out the hull after the shotblasting, I opened up some of the holes with the tip of a stanley knife, and there was no trace of moisture, so I proceeded with the Coppercoat.

Suprisingly though, I couldn't get the coppercoat to fill the holes, i'd gloop loads of the thick mixture across the holes, they would appear to fill, then re-appear again. I thought maybe the second coat would do it, but even after all four coats, lots of the holes are still evident /forums/images/graemlins/frown.gif

Does this mean it's only a matter of time until I get osmosis? I've decided it's going back in the water on Friday as planned, and i'll probably have to lift it at the end of the summer and get it looked at properly. My gut feel is that it's a gel coat problem, rather than a blasting problem, but i'm no expert.

Any opinions?
 
I think what you are getting is chalking because og the blasting job
your mistake from here I would say that u did not fill the pinholes with epoxy filler or gel coat
you still can do this by sanding the copper coat where the pinholes are showing and fill them with epoxy or gel, many would tell u under the waterline epoxy is better
normally in 1 hour epoxy is solid as a rock
 
[ QUOTE ]
Does this mean it's only a matter of time until I get osmosis?

[/ QUOTE ]

I don't believe this changes anything - I suspect the pin holes were there as part of the production process - I've seen these before and even noticed them on my own boat where the hull has been polished back.

Also, to my knowledge gelcoat is porous anyway, which is one part of the equation in why osmosis can occur in the first place.

Therefore, this doesn't mean you'll get osmosis. Although it's likely that you would anyway at some point in the boats life, no matter what you do with it.

Hope that helps put your mind at rest.

Cheers,
Paul
 
Have you got me on ignore /forums/images/graemlins/confused.gif

Copy here of what I keep posting
<span style="color:red"> A few years ago at lift out a friend had his 1987 Fairline corniche at the side of my 1988 corniche.
He wanted me to join him for a slurry blast of 'gentle soda'.
I wasn't keen even when offered a two for one deal and declined.
My mate went ahead and I saw the damage the following weekend

Whole hull was riddled with small holes in the gel coat.
The whole boat had to be filled and epoxy coated.
At some stage a section of 1 ft by 2 ft on my bow had also been blasted.
It is unclear if
they started on the wrong boat.
they hit it by accident
they wanted to see if my hull would also be wrecked
they thought it was such a good job I would want mine done


My 'test' section was also covered with pin prick holes that I needed to fill.
I was pleased a small section had been tested as it confirmed to me that GRP shouldn't be grit blasted unless it needs an osmosis treatment.
A friend was then kind enough to clean my hull with an electric chisel, the old antifoul came off and left beautiful white shiny gelcoat with no visible signs of weakness.
It is clear that older boats have naturally occurring bubble holes deep within the gel coat that are created during the mixing. These bubbles are fine and will not cause a problem unless the Gel coat is over polished with compound, over sanded or slurry/grit blasted.

The slurry blast had not made the holes but it had exposed voids that had been water tight for 15 years (moisture reading were very good).

The grass under the treated boat has still not grown back and turned into a bog for a while.

From my experience I would only have a slurry blast on a modern boat that had used a vacuum technique to mix the gel coat and so reduce the amount of bubbles.

If you read the professional sites they warn about this in a round about way " leaves a nice key finish ready for filling and epoxy coating " shouldnt the surface be ready for AF Primer ?
</span>

Pin holes are naturally occurring in gel coat.
Traditional methods of mixing can not avoid bubbles in the gel.
The gel coat will be thick enough so the bubbles will never let water in unless you blast the hull and take away some of the gel coat as slurry/sand/grit/washing soda and now you have added farrow system too which I believe is the soda blast.

Some manufactures are claiming that a new method of mixing can reduce the bubbles, the idea is to mix the gel in a vacuum and so reduce the air bubbles. Bayliner use this vacuum method and they do appear to have reduced the problems but there will be holes in the hull if some one sand blasts it !

Your copper coat treatment should solve the problem but if they didnt warn you then in my opinion they have damaged your boat hull and they should pay.

They state that the blast leaves the hull ready for 'coatings' , they mean epoxy coatings, if you asked for your hull to be cleaned ready for new antifoul then they have clearly exceeded your request and caused damage.
I would be annoyed /forums/images/graemlins/mad.gif
edit
Sorry Nick , I just re read, are you saying there are now pin holes in the copper coat ?

That would encourage premature osmosis if left unchecked.
I would be trying to recover off the sand blasters for taking too much gel off, I presume you asked and paid for old antifoul to be taken off , did they warn that some or 30-40% of the gel would be lost ?
Sounds like they took 100% off at the stern which can not be right.
 
Coppercoat isn't far off the consistency of a filler, and it's epoxy, so it seemed to me it would do the same job. On balance, I probably should have used an epoxy filler.

Just to add, the holes are tiny, about 1mm across, so I really though a more liquid epoxy would be better at getting into the holes.
 
I did vaguely remember your post, but this is a 2004 boat, and your post related to older boats. I always planned to use either an epoxy coat prior to anti-foul, or to use Coppercoat, so I did want the sanded finish you get with blasting, to get the best adhesion.
 
I am not even sure your Princess will have been vacuum mixed, I doubt it, it is only the cheaper end of the market that do, its a way of cutting down the amount of materials used.

Your insurance policy may include accidental damage and as long as there is not an added clause to the effect 'cleaning process' is excluded then you may be able to hand the fight to them, if they do pay for the inspection lift and repairs they would then try to recover off the sand blasters.
If your insurers will not pay under the accidental section and lets face it it is a little thin then perhaps you have a legal expenses section on your policy , a threat of action against the sand blasters may encourage them to cough up ?

Sand blasting is fine as long as the client knows what to expect and a sand blasted finish is well beyond a quick paint over, although I think you have been unlucky that your copper coat hasnt covered it up.
 
out of interest, how much does a farrow system blast cost?
I guess you are getting air trapped in the pinholes, rather than them being filled by the coppercoat. Maybe one of those barrier coats recommended bwtween different a/fouls would be thin enough to fill the holes?
Maybe c/coat have an answer.. they must have come across this before?
 
I had similar when ours was blasted. I had the Gelcoat man pop down & fill them. He was saying that it's not uncommon, and nothing to worry about. Epoxying was the other option, which you've done, so hopefully no worries.
 
[ QUOTE ]
I am not even sure your Princess

[/ QUOTE ]

It's a Windy
 
to be 100% sure I would do as I say, filling with Epoxy is always better to gel as this is less water solubile to gel wheter Polyster or Isphotalic
the first Princess to be vacuum bagged is the new V78 hull no.1
Princess said that all V78 would be built this way and then by time move production in this way to all its range
is normal to have Pinholes and chalking with blasting...
osmosis can occur more easily with this but then depends on the type of resin Windy uses and where and how it uses this
 
My gut feeling is that it is a gelcoat prob too. Couple of references on the interweb HERE and HERE
You've just bought this boat, haven't you? I think that the Windy dealer should take a look at the hull and you should get a surveyor in to give an independent opinion. Is there any hull warranty left? Some builders give 5 or 7 years. Even if it is out of warranty, you might get Windy to contribute to a repair if it is necessary. I had minor osmotic blistering on an Azimut beyond it's hull warranty period and Azimut repaired it at their cost and extended the hull warranty. Windy is supposed to be high quality product and, if there is a problem, they should stand by their product in the same way
 
[ QUOTE ]
this is a 2004 boat

[/ QUOTE ]Geez, that hurts!
A 2004 Windy with grp exposed on the transom, I'd have cried...
 
Trying to pick up a few points:

Cost for farrow system was £450. I took some video and was going to post a link, but I think its too high resolution and was taking ages to load on photobucket.

Yes, I think the reason the holes wont fill is that air is trapped in them, so all i'm managing to do is create a film over the entrance to the hole, which opens up again as the paint dries. Not sure i'd have any more success with filler?

I'll check out the hull warranty, and I agree that if it is manufacturing faults, i'd expect Windy to cover at least some of the cost if repairs are needed.

The thin gelcoat on the transom is really dissapointing. There's no way the blasting company have removed that much gelcoat, it was obviously just very thin to start with.
 
[ QUOTE ]
.

Yes, I think the reason the holes wont fill is that air is trapped in them, so all i'm managing to do is create a film over the entrance to the hole, which opens up again as the paint dries. Not sure i'd have any more success with filler?

.

[/ QUOTE ]

Not trying to be pedantic but the reason the holes keep comming......

Copper coat does not dry it cures. As it cures it heats up, as it heats up the air trapped in the holes heats up, expands and the pressure pops the bubble and leaves a hole.

You could preheat the hull before painting which will suck the copper coat in as it cures but not sure how easy it would be heating that amount of hull.

or you use filler and try to squash out the air in the holes as you fill.
there will still be air in the holes but the filler has more body and strength to withstand the heated air popping (filler still heats as it cures).

In my opinion sand blasting is totally inappropriate and it is being marketed in an inappropriate manner, someone needs to stop them.
 
I did mine last week too. It seems the boat had been previously blasted, and rather roughly. I had a number of (dry) pinholes. So I filled them all and sanded the hull, did 3 coats of epoxy, sanded it again, then did the 4 coats of coppercoat. It looks good but I am exhausted. If you've done the coppercoat its too late to fill the pin holes, but as you say the coppercoat should make it nicely waterproof. I think the pinholes occur on all hand laid hulls.
 
[ QUOTE ]
I think the pinholes occur on all hand laid hulls.

[/ QUOTE ]

And vacuum mixed ones but hopefully to a lesser extent.

The amount of time that goes into rectifying the damage from shot blasting amazes me, it would be more cost effective to take the antifoul off with an electric chisel, doesn't take so long.
 
Ever wish you hadn't started something?

Just had a call from the A Glaze people to say the polythene sheeting we put up to protect the coppercoat from the rain has fallen off, and loads of the coppercoat has washed off, back to bare GRP in places /forums/images/graemlins/frown.gif

I've had to delay the lift in so we can try and sort it next weekend. Next problem is that Coppercoat is not supposed to be allowed to fully cure before the next coat is applied, so we may have adhesion problems.

I suppose it will at least give me time to try and sort out the pin hole issue before it goes back in.
 
I suggest to you that this is good news.
they clearly suggest the surface after sand blasting is ready for coatings which it clearly isnt in your case.

They have to have left powder on the gel and in the pin holes that has stopped your 'coating' from sticking.

You have a very strong case for handing the problem to them.

You paid them to get your boat ready to paint.
You have ended up with a major repair job.
 
The problem is not adhesion to the hull. The Coppercoat is a water based epoxy, and needs to be protected from rain for 48 hours after application, until it's fully cured. Being a bit of a dipstick, I didn't read the instructions properly until I got home, so not realising this I had only put a token rain shield around the hull to protect it from any light showers expected during the Sunday evening, thinking it would be pretty much cured within a couple of hours.

It then rained heavily during the day on Monday, and the wind picked up, so it seems the token rain screen fell off, and the rain washed off the uncured coppercoat. Think of it like painting a wall with water based emulsion, then hosing it down before it's dry. It's my own fault for not reading the instructions, cos I'm a bloke and reading instructions is for girls.

I do then have a second problem, that the coppercoat that has remained will now cure fully before I can get to the boat again, and it's not reccomeded to paint new coppercoat, onto cured coppercoat. I'm probably going to have to sand it all down first.
 
You must log in or register to reply here.

Share this page

Top