Antifouling and Epoxy Question

timmygobang

timmygobang

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Hi there,

I could do with a bit of advice. I became the owner of dare I say it, a lovely 'long keel' boat last year (LK boats seem quite topical recently...)

The survey reported that the hull had various layers of epoxy paint which have various levels of adhesion. Several small sections of antifoul came away with the paint (though this could be primer). On a couple of spots all the coatings came away, AF and epoxy revealing the gel coat.

The surveyors recommendation said consideration should be given to removing all the coatings of epoxy and start again, checking moisture levels on the gel coat. (this was marked as Items of maintenance or requiring further investigation/cosmetic defects)

It sounds like an incredibly expensive process to remove everything back to the gel coat and start again, and I know surveyors tend to err on the side of caution sometimes.

My question is this, if i get a company to blast clean the antifouling off, can I patch up the exposed areas of gel coat with new epoxy (after preparing the area properly). I'm guessing the blast cleaning would expose any areas where the epoxy hasn't adhered to.

What would you do? Take a chance and patch it up? or start again?

Few pics http://www.flickr.com/photos/77037314@N07/sets/72157632857034317/

Cheers

Tim
 
I would say it's your private bottom, unless you show it off publicly for some reason only you will know it's patchy. Up to you I'd say.
IMHO all depends what is the condition of the hull, is there any sign of osmosis, old repairs that suggest it's prone to it, etc.

Some of those old boats were made with good resin and had no osmosis problems, so epoxy is not necessary. Painting with it only gives problems itself, as you see. If this is the case repainting those places is not necessary also.
So check, ask opinion on the boats this type. If they are known for osmosis then better to touch up the areas with new paints.

Blast, powerwash, maybe some scrub to remove what's not sticking - you will see how much falls off. The rest will possibly stay there so may be painted over with antifoul. Will some fall off till next time - at least saves you the scrubbing... :)
Will there be much area exposed then your decision. Personally I'd not paint with epoxy then, just antifouling, so not to mess the situation further now; after few years you will know better what's going on. In the future indeed taking all down to gelcoat may be good idea so the less paints on - the easier it will be...

If not much falls off, just some smaller patches - then not much work, touch up, and for small but deeper repairs you may use some epoxy putty, may be simpler.

What did surveyor say about the long keel itself - seeping rust down there, BTW?

PS - but in case you decide to put some epoxy on, first dry the hull! On wet hull it's nonsense.
 
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timmygobang said:
The surveyors recommendation said consideration should be given to...checking moisture levels on the gel coat.
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Are you saying the surveyor didn't do this? It's normal for the surveyor to remove small patches of AF (and, sometimes, any barrier coat) to take moisture readings at various sample points along the hull. Indeed, I'd expect it on any survey of a GRP boat.

Before you can properly decide on the best course of action, I'd suggest you need such readings. Low or normal readings would, at least, be some reassurance. That said, even high readings are not necessarily indicative of a major problem.
 
Thanks for the replies.

Rossynant - Maybe I've not understood why boats have a epoxy layer on top of the gel coat. I thought the epoxy layer was to protect the gel coat from water ingress. I don't mind having a patchy bottom :) I just thought perhaps it was bad to apply antifoul directly to the gel coat.

As to the keel, he said a bit of rust is normal, and as a recommendation I should clean the cast iron back to bare metal along the joint, and then apply coats of primer and apply a bead of sealant along the joint. This sounds pretty

macd said:
Are you saying the surveyor didn't do this? It's normal for the surveyor to remove small patches of AF (and, sometimes, any barrier coat) to take moisture readings at various sample points along the hull. Indeed, I'd expect it on any survey of a GRP boat.

Before you can properly decide on the best course of action, I'd suggest you need such readings. Low or normal readings would, at least, be some reassurance. That said, even high readings are not necessarily indicative of a major problem.
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Macd - No he did do moisture readings, what he's saying that if all the epoxy was removed, to then do more moisture readings on the gel coat that was previously hidden by epoxy.

I've just spoken to a company that will remove the AF for £400 + vat by blasting it.
 
timmygobang said:
I've just spoken to a company that will remove the AF for £400 + vat by blasting it.
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Depending on the size of the boat and quality of contractor, that sounds like a good deal. I'd suggest you check out their reputation first if possible. The usual blasting method for removing AF is wet blasting/slurry blasting, which is far less aggressive than dry blasting. It also gives an excellent 'key' for the application of subsequent coatings.

If your keel has anything other than light surface rusting or is confined to small areas, the only effective method of getting back to bare metal is (dry) sand blasting. Grinding it off could take until Xmas. It might be a big bonus for you if the same blasting company can do both jobs in the same visit. Once blasted, the keel needs a coat of epoxy primer immediately.
 
macd said:
If your keel has anything other than light surface rusting or is confined to small areas, the only effective method of getting back to bare metal is (dry) sand blasting. Grinding it off could take until Xmas. It might be a big bonus for you if the same blasting company can do both jobs in the same visit. Once blasted, the keel needs a coat of epoxy primer immediately.
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Yikes - immediately? I am about to follow the same path, and was told by the stripping co they would paint the keel with Fertan for later epoxy coating. I was hoping I could leave it for a while until the temperature has risen enough to safely apply the epoxy.
 
timmygobang said:
Rossynant - Maybe I've not understood why boats have a epoxy layer on top of the gel coat. I thought the epoxy layer was to protect the gel coat from water ingress. I don't mind having a patchy bottom :) I just thought perhaps it was bad to apply antifoul directly to the gel coat.

As to the keel, he said a bit of rust is normal, and as a recommendation I should clean the cast iron back to bare metal along the joint, and then apply coats of primer and apply a bead of sealant along the joint. This sounds pretty
Macd - No he did do moisture readings, what he's saying that if all the epoxy was removed, to then do more moisture readings on the gel coat that was previously hidden by epoxy.
I've just spoken to a company that will remove the AF for £400 + vat by blasting it.
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Not a painfull cost then :) Naturally epoxy is for protection, not that I much believe in it. Also have such patches of epoxy getting off, though just a few very small, probably from impact or scratches, as generally it holds; made just over 10 years back but there was no osmosis problem then, after 30 years. Just the whole boat had a good painting done. In my case bilges are a watertank, GRP there will never be dry, so where is the point? :D
Of course antifouling may be applied to gelcoat directly. But epoxy should be put on hull dried first (in UK weather that is impossible, only in heated shed) and not much sense to put it on old gelcoat which may be failing itself...
 
RadiumRob said:
Yikes - immediately? I am about to follow the same path, and was told by the stripping co they would paint the keel with Fertan for later epoxy coating. I was hoping I could leave it for a while until the temperature has risen enough to safely apply the epoxy.
Click to expand...
Consult the paint instructions, there are various 'systems' for steel protection. Some primers are just a bit of etch with zinc chromate or such to be put on, but are meant to be painted over right away; but there are some more like paint, that can be left. Had railing on my balcony painted in two layers of primer paint, standing 3 years before final coats, just a few speck of rust appeared where covering probably had voids.
Remember though that primer also has requirements for application, as temperature and humidity...
I will not speculate what to use in UK, that rainy weather could rust anything.
 
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Sound advice so far. I'd want to know how far moisture has made it in the laminate. If not at all, I'd be very rellaxed. If it has penetrated a substantial amount I would be reducing my offer or walking away.

The keel is a different matter. For various reasons I asked the National Physics Laboratory to weigh a keel to the nearest gram. They would only agree to do it if it was delivered at a high enough temperature to ensure that it would not fall below 100C before the weighing was achieved. Obviusly I asked why, and was told that by the time it was cooled to ambient, it would absorb 1% of its' mass of water.

So expecting anything to to bond to the surface when totally dry is the preferred condition, is optimistic.
 
Thanks for all the replies, very much appreciated.

So my plan is to avoid hull blasting at the moment, I dont think the keel looks to bad and as the gel coat is only visible in a couple of places. I'm thinking of just applying a underwater primer on the exposed gel coat, then a fresh coat of anti foul.

One last question :) if the previous owner put a layer of anti foul and 3 months later I wanted to give it another coat, could I just apply another coat without sanding first. I think he may have just given it one coat. Th3 surface looks pretty smooth to me.
 
One last question :) if the previous owner put a layer of anti foul and 3 months later I wanted to give it another coat, could I just apply another coat without sanding first. I think he may have just given it one coat. Th3 surface looks pretty smooth to me
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All that is normally necessary when overcoating sound antifouling with the same or a compatible product is to clean and rinse with water.

See the maufacturer's data sheet for the product you are using for full details.
 
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