Hull pitting exposed after blasting - best remedy?

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arcbennett

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After 15 years of using eroding antifouling, there were several areas that had flaked off. As I'm planning to now convert to Coppercoat, it seemed time to bite the bullet.
I used a contractor to blast off the old antifouling. My hull is now fully cleaned off, but I have several areas (especially aft and on the rudder) that are quite severely pitted.
I need to keep costs down, but at the same time do not want to do a half job.
Any suggestions as to how to best treat the pitting? And how many coats of epoxy primer(?) to apply thereafter?
 
I imagine the holes are very small: maybe 2-4mm across. Because of their shape these are difficult to fill properly. Easiest solution is to gently grind out to a shallower profile, then fill with epoxy and microballoons. For grinding, a Dremel with a suitable tool, or battery drill with counter-sink bit works fine.

As to primer: I'm not sure you'll strictly need any: Coppercoat sticks fine to keyed gelcoat, although if the hull is good and dry you might want to consider applying an epoxy barrier coat. Talk to AMC (the Coppercoat people): they're happy to help.
 
I have just had my boat Coppercoated. After blasting they went over the hull in meticulous detail and filled every pinhole with epoxy filler and sanded that off so the whole hull was completely smooth. They didn't coat the keel as they said it didn't last on old cast iron or the p bracket which was pitted.
 
When you say severly pitted, is the fiberglass exposed or has the gel coat disintegrated. Do the pitted areas smell? That will be an indication of osmosis.

If osmosis is the cause then you will need to treat (wash/steam) the affected areas to remove the salts. Once clean and fully dry (according to a test meter) you can then laminate the area using an epoxy and seal with a new gel coat.

If the gel coat has broken down then once dry you should be able to use an epoxy filler to fill the voids.

Once you have reached the stage for antifouling, I would advise against Coppercoat. The reason is it is quite expensive and if you do get any further problems it is money down the drain. Personally I would suggest applying 3 coats of Gelshield, not the 5+ International recommend, and then 2 coats of hard antifouling followed by 2 of self polishing.
 
Concerto's points are well-made if the pitting is as he describes. However, if it's simply small pits as I described earlier (essentially just exposed air-bubbles in the gelcoat, which are commonplace), then they can be disregarded.
 
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I filled any imperfections / holes with marine epoxy filler and sanded the whole hull to remove any traces of the previous coating.
I then applied 2x solvent free epoxy and 5x Coppercoat. The epoxy was thick and covers imperfections, less so the Coppercoat.
 
Thank you very much for all your most helpful replies. Concerto, I do not believe I have osmosis; there is no indication of gel coat disintegration or any sign of a smell. My symptoms are more as macd describes. Looking back to my original post, its not the pits themselves that are severe, but more the number of them. So I suspect they fall into the category of exposed air bubbles in the gel coat. I do have one or two nicks in the hull, so these will obviously have to be filled. But most of the pits are no more than 1mm across, if that.

fastjedi, can you tell me the name of the epoxy filler you used, and indeed the epoxy?
 
Slightly off topic. We have been considering CC (and have a new motivated distributor in Oz) but its almost unknown here. Consequently there are few with any hands on experience.

You talk of 'blasting' - do you refer to soda blasting, or something else? And if something else, what? What sort of costs are incurred in the UK - for whatever sized yacht you have? And how long does the blasting take?

Reading between the lines I understand your issues are subsequent cold and damp, ours might be at the other extreme, too hot!

We have a 38' cat, I think it might have the same wetted 'surface area' as a 45' AWB.

Jonathan
 
MoodySabre said:
I have just had my boat Coppercoated. After blasting they went over the hull in meticulous detail and filled every pinhole with epoxy filler and sanded that off so the whole hull was completely smooth. They didn't coat the keel as they said it didn't last on old cast iron or the p bracket which was pitted.
Click to expand...

Grateful if you could expand the detail a bit, does this mean that you still have to use traditional AF on the iron keel?
 
J Neeves said:
Slightly off topic. We have been considering CC (and have a new motivated distributor in Oz) but its almost unknown here. Consequently there are few with any hands on experience.

You talk of 'blasting' - do you refer to soda blasting, or something else? And if something else, what? What sort of costs are incurred in the UK - for whatever sized yacht you have? And how long does the blasting take?

Reading between the lines I understand your issues are subsequent cold and damp, ours might be at the other extreme, too hot!

We have a 38' cat, I think it might have the same wetted 'surface area' as a 45' AWB.

Jonathan
Click to expand...

Mine was sand blasted, all done in one day. Cost was about £550 for 31'. Then hand finished to totally clean gelcoat and then all the pinholes filled will expoy filler. The boat was in a heated shed. I imagine that applying CC when it is too hot and in sun could be a problem. Not one we have here!
 
I helped Coppercoat a friends boat. He had it sand blasted to clean off all the old anti foul down to clean gel coat which took about a day including putting heavy plastic sheeting all round the boat to catch the sand during the blasting. Then a team of five of us (4 painting, 1 mixing) applied the Coppercoat which took us about a day. It works out that put four coats on, using all the Coppercoat recommended for the size of boat. He had an encapsulated keel, so that got done a well. Can't clearly remember costs but I think the blasting was about €800 or so for a 36 foot boat.
 
MoodySabre said:
I have just had my boat Coppercoated. After blasting they went over the hull in meticulous detail and filled every pinhole with epoxy filler and sanded that off so the whole hull was completely smooth. They didn't coat the keel as they said it didn't last on old cast iron or the p bracket which was pitted.
Click to expand...

Mmmm ... we did our S31 in 2010/11. The keel has 2x Corro Tech + 2x ME100 + 4x CC. I am repairing a patch about 2" sq adjacent to the hull/ keel joint this winter. Otherwise perfect.
 
macd said:
I imagine the holes are very small: maybe 2-4mm across. Because of their shape these are difficult to fill properly. Easiest solution is to gently grind out to a shallower profile, then fill with epoxy and microballoons. For grinding, a Dremel with a suitable tool, or battery drill with counter-sink bit works fine.

As to primer: I'm not sure you'll strictly need any: Coppercoat sticks fine to keyed gelcoat, although if the hull is good and dry you might want to consider applying an epoxy barrier coat. Talk to AMC (the Coppercoat people): they're happy to help.
Click to expand...

Did my hull last year, opened up every small hole with a dremel, then coated them with a solvent free epoxy and then filled them with epoxy, then had another 3 coats of epoxy applied before coppercoating the hull. All done on the recommendation of my surveyor.
 
longjohnsilver said:
Did my hull last year, opened up every small hole with a dremel, then coated them with a solvent free epoxy and then filled them with epoxy, then had another 3 coats of epoxy applied before coppercoating the hull. All done on the recommendation of my surveyor.
Click to expand...

AMC advised me that additional epoxy coatings under the coppercoat was not necessary. I asked about the pin holes & they said that the gel coat was only there for Aesthetic reasons & i should just put the copper coat straight on.
having done this I began to have concerns that perhaps I should have applied a couple of coats of epoxy, but when the coppercoat failed - miserably- I did another treatment of coppercoat so I now have double the layers
As for the keel - this worked OK although where i grounded rather badly the coppercoat has gone from a large patch. I also touch bottom in the marina & the coppercoat did not work on the bottom of the keel so I antifould the bottom 18 inches with an erodable antifoul paint which I can replace in 3 hours. I often push through mud to get into the marina so one could not expect the coppercoat to survive this

As for cost ( my boat is a 31 ft fin keel)- if the first lot had worked it would have cost £ 1050-00 being £250-00 for the sandblast £ 690-00 for the coppercoat & the rest being for the yard adjusting props, plus rollers etc
this is miles cheaper than ordinary antifoul paint. 2 tins of Blakes ocean performer cost £ 190-00 each year so 5 years & cash back with no labour ( which used to make me ill & take just over a week to sand & apply the paint

Unfortunately the copper coat first time did not work so i applied another lot. If that does not work ( signs so far is that it does) it is still easier for me to get the boat lifted & jet washed mid season ( I get lifted for the winter as well) so I keep a clean hull without the constant migraine attacks sanding the hull caused me

I had lots of pin holes in the gel coat & to fill them all would have taken ages. However, the coppercoat has filled them & so now only a very small area ( less than 1 ft2, shows any sign they were there
 
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As well as my cruiser I have a squib which sits on a mooring rather than the marina
that is coated in Copper Tec
Our club has several squibs coated in coppercoat but my squib seems to out perform the copper coated ones
We all have to lift every 4 weeks for jet washing but my squib would last 5 weeks for the same condition & there is a slight difference
My crew, who helped with my cruiser, is very meticulous with things like this so it may be the care he took over applying it as opposed to the professionals that did the other squibs
but it certainly is better
That being said none of the squibs fared very well with build up of slime this year -- River Blackwater
One using the electronic system did not work at all although that may have been an installation problem. He had a solar cell fixed to the cover to power the transducers & had to dry sail most of the season
 
All good stuff and thanks to those who quoted costs.

One of the factors quoted by CC, or AMC, is that you save on AF costs but it is still necessary to slip to change anodes, treat the prop(s) (plural in my case) and to check hull fittings for growth and then blockage. It is also necessary to clean the water intakes on the sail drive(s). I appreciate many, or some, in the UK dry store their yachts for the winter (so they are lifted anyway) but there are still lots kept on swing mooring or in marinas and who, if they were using CC, would still need to slip for the inevitable maintenance. Slipping costs are not cheap - and that cost is fixed (whether you use conventional AF or CC) and most, with CC, mention that they need a lift and a power wash anyway.

I am sorely tempted, but not because of the cost as I have the nasty feeling that it might be an illusion - but not having to wield a roller is enticing.

So how do the costs really stack up.

Jonathan
 
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