antifouling falls off - need advice

[oldsalt83]

Mates, I need your advise...

Two ears ago my hull was sandblasted up to gel, and 5 coats of epoxy primer was applied before AF. The boat was in water for 2 years without any problems with antifouling.

Now, after lift out and cleaning the boat with pressure cleaner, the hull looks like on a picture - there are many places where antifouling fall off.

Marina guys propose sandblasting again and apply new primer + antifouling, and insist that there is no other good option. I don't like the idea to sand out my 5 layers of epoxy primer, which was quite expensive job to apply.
Is it really no other way to apply new AF on existing epoxy primer?

 

[potentillaCO32]

I would just scuff the epoxy primer where exposed with 180 grit by hand and slap another coat of AF on.

 

[Chiara’s slave]

I would just scuff the epoxy primer where exposed with 180 grit by hand and slap another coat of AF on.

I’d chemically strip the remaining antifoul, wash, then abrade with 240 grit paper, normal antifoul primer then antifoul of choice. That epoxy primer isn’t a good link coat clearly. It needs an interim primer.

 

[dansaskip]

Yes as already said it needs (needed) a good primer over the epoxy before antifouling

 

[Refueler]

Looking at picture ... I cannot see any ridge round the exposed areas - so forgive me if wrong - but its 'eroded' away in patches ... not fallen off.

Even so - I would expect a yard who did the work 2 yrs ago - to have used correct primer for the AF used.

Personally - I would generally abrade the whole ... incl the white gel ... apply primer to the white areas then abrade lightly to remove any ridges ... then AF the whole lot .... I don't see need to strip hull back again ...

TBH - my 1973 25ft Motor sailer has only ever had AF put over top of old .. even when patches showed when she was in Salt Water (UK) .. I just removed the ridges ..

 

[Chiara’s slave]

Looking at picture ... I cannot see any ridge round the exposed areas - so forgive me if wrong - but its 'eroded' away in patches ... not fallen off.

Even so - I would expect a yard who did the work 2 yrs ago - to have used correct primer for the AF used.

Personally - I would generally abrade the whole ... incl the white gel ... apply primer to the white areas then abrade lightly to remove any ridges ... then AF the whole lot .... I don't see need to strip hull back again ...

TBH - my 1973 25ft Motor sailer has only ever had AF put over top of old .. even when patches showed when she was in Salt Water (UK) .. I just removed the ridges ..

You’re probably right for a cruiser. Most people here have probably gathered I’m obsessional about bottoms. I like them lovely, smooth and blemish free.

 

[potentillaCO32]

You’re probably right for a cruiser. Most people here have probably gathered I’m obsessional about bottoms. I like them lovely, smooth and blemish free.

That's why i like copppercoat. One jetwash and it is back to a racing finish.

Ps. There is a dragonfly on the hard here in la trinite

 

[Rhylsailer99]

When I scraped mine back to gelcoat I did 3 coats of 2 pack primer then 2 coats of single pack primer. The antifoul stuck really well to thw single pack primer. Could applying antifoul to 2 pack primer be too much of a shiny finish so it does not stick so good.

 

[vyv_cox]

The instructions for Gelshield 200 were that before the final coat had cured, still tacky, a coat of hard antifouling should be applied. I think in your case a light abrade with maybe 180 or 320 papers would be sufficient for hard antifouling to adhere. You can then apply eroding a/f as required.

 

[Minerva]

You’re probably right for a cruiser. Most people here have probably gathered I’m obsessional about bottoms. I like them lovely, smooth and blemish free.

I’m sure we all do, but the OP is asking about boats.

 

[Fr J Hackett]

You’re probably right for a cruiser. Most people here have probably gathered I’m obsessional about bottoms. I like them lovely, smooth and blemish free.

Don't we all

 

[Chiara’s slave]

Don't we all

You gentlemen of the Cloth are meant to be above such smutty allusions.

In my experience, just abrading epoxy coating is not sufficient to get a good key. Abrade it and prime it. And make sure to get your old antifouling smooth in following years, or you end up with that awful lunar surface effect. And everyone with a decent underwater finish will piss past you.

 

[sigma38dave]

As above, I’d 180 grit sand the boat, coat of Primocon primer and new anti foil.

Save yourself a lot of unnecessary aggro or ££’s getting all the paint off again.

If this doesn’t work you’re only a can of primer worse off and can look at the possibility of another bottom job.

I know racers tend to obsess over this bottom prep, in reality one bad tack, tactical decision or not writing the course down correctly is where races are won or lost, not a tiny bit of paint imperfection on the bottom.

 

[Chiara’s slave]

As above, I’d 180 grit sand the boat, coat of Primocon primer and new anti foil.

Save yourself a lot of unnecessary aggro or ££’s getting all the paint off again.

If this doesn’t work you’re only a can of primer worse off and can look at the possibility of another bottom job.

I know racers tend to obsess over this bottom prep, in reality one bad tack, tactical decision or not writing the course down correctly is where races are won or lost, not a tiny bit of paint imperfection on the bottom.

I disagree about bottom finish. If you are 1/100 of a knot slower than your competitors, that is 3 boat lengths per hour in our class. Races are frequently decided by far less than that. Why would you not pursue perfection?

 

[sigma38dave]

I disagree about bottom finish. If you are 1/100 of a knot slower than your competitors, that is 3 boat lengths per hour in our class. Races are frequently decided by far less than that. Why would you not pursue perfection?

The racing on the Medway isn’t exactly Olympic standard but take your point in highly competitive one design racing with an abundance of world class talent competing for the chocolates there’s a case to be argued for a smooth bottom.

Back in the real world people will be moaning about their ratings and blaming the crew!

 

[Chiara’s slave]

The racing on the Medway isn’t exactly Olympic standard but take your point in highly competitive one design racing with an abundance of world class talent competing for the chocolates there’s a case to be argued for a smooth bottom.

Back in the real world people will be moaning about their ratings and blaming the crew!

My skipper blames the crew even when we’re winning

 

[Mark-1]

I had exactly this problem. Epoxy sticks to everything, but nothing sticks to epoxy. One year I tried properly priming it and it made little difference. After that I just painted AF straight on and accepted bits would fall off.

I was on a drying mooring so hard AF was a possibility for me and that stuck very well in comparison.

So I can't help, but I can commiserate!

 

[Chiara’s slave]

I had exactly this problem. Epoxy sticks to everything, but nothing sticks to epoxy. One year I tried properly priming it and it made little difference. After that I just painted AF straight on and accepted bits would fall off.

I was on a drying mooring so hard AF was a possibility for me and that stuck very well in comparison.

So I can't help, but I can commiserate!

My day boat is epoxy sheathed, primed and hard AF. The AF does not fall off. I’d like to say we don’t take the ground, but sadly that happens sometimes…

 

[grafozz]

Mates, I need your advise...

Two ears ago my hull was sandblasted up to gel, and 5 coats of epoxy primer was applied before AF. The boat was in water for 2 years without any problems with antifouling.

Now, after lift out and cleaning the boat with pressure cleaner, the hull looks like on a picture - there are many places where antifouling fall off.

Marina guys propose sandblasting again and apply new primer + antifouling, and insist that there is no other good option. I don't like the idea to sand out my 5 layers of epoxy primer, which was quite expensive job to apply.
Is it really no other way to apply new AF on existing epoxy primer?

I had Copperbot on my boat from new and after the years sailed by it became less and less effective . I finally gave up scrubbing the bottoms at anchor and applied a local antifoul straight on top of the Copperbot . It gets 2 coats every spring and works well .

 

[PeterV]

I’m baffled that nothing sticks to epoxy. Last year I put 4 layers of epoxy on my underwater surfaces, followed by one coat of primer, then 2 coats of eroding antifoul. I’ve just sanded down in preparation for a new coat of antifoul and I’ve removed the remains of the second coat of antifoul, none of the first coat or the primer has fallen off.