antifouling falls off - need advice

[gjgm]

I am not sure there is an issue at all.
If this is what the hull looked like after you have been zooming along at a few knots, and lifted, then yes, something is amiss.
If this is what it looked like after someone went mad with a pressure washer, then,especially if eroding antifoul, I am not surprised that AF got blasted off.
Tho, dont think OP has returned,has he?

 

[mjcp]

My boat was epoxied mid 90s and on the whole, the class has very few osmatic issues.

When I bought it, there was unknown antifoul and it was flaking off in places too, typically in hard to sand areas, under/behind the keel, under the cockpit / near the rudder etc. (hard to sand as they are above the sander's head rather than angles etc!)

I used a 150mm RA sander (and dust extraction) to knock back. (Went a bit deep in places, so needed to "re-epoxy" one or two areas) In the areas where there was flakes - sanded back to sound and then local re-epoxy treatment.

Then the whole hull (now knocked back and local epoxy) was given 2 x coats of fresh high build epoxy and then a tie-coat compatible with the new CuPro (SML paints) antifoul. Lastly, 2x final coast of CuPro on top of all. Full epoxy and tie coat might have been overkill, but I want a simple life in the future!

A year later and no AF flakes and minimal growth. slime removed easily with gentle jet wash and light cloth clean.


Local High build epoxy over the old (over) sanded base treatments. A 2nd full layer went over this and then lightly knocked back again to give a good surface for the top coats.

1st coat of AF over the tie coat.


After (~ 1 year later, 700 nm this season)

 

[Chiara’s slave]

That’s a lovely bottom you have. I’m in a boatyard right now, not many as good as that. Including a Contessa 32 that really fancies herself on the race course. I’ve just copped a feel, it’s got a finish like cellulite

 

[The Q]

As others say, just remove old anti fouling, then it needs painting with the correct primer for new antifouling ,using that primers instructions for surface preparation. No need to remove epoxy.

 

[Caer Urfa]

Sand blasting any boat is not cheap so almost all people who have their boat hull sandblasted back to the original gel coat then its all wiped down with International thinners no 7
Then continue with 4/5 coats of International Gelshield 200 epoxy primer (for protection of GRP against osmosis) which is applied in two different colors Grey & Green to ensure each coat is fully covered,then a prima coat (say primocon) then 2 x coats of anti-foul
So how is it we see the white gel coat hull in your picture ??
Sorry me thinks the whoever coated with antifoul did not apply it correctly or maybe not in the correct conditions
The fourth picture show at lift out after 3 year just slime and just jet washed the hull off, only thing to touch up was the boot topping