Starting from scratch - how do I antifoul?

[Otter]

The boat has been out of the water for the last 5 months and the hull cleaned off with a strong pressure washer. This has taken patches of the hull back to antifoul that must be 10 years old, other parts to gelcoat and most to last years antifoul. The surface isn't silky smooth by any means so as she is going to be in the water now for the next 3 years, I thought I might start the antifoul from scratch by sanding back, priming and then 2 coats.

Questions -

Is it worth it, will I get a much smoother surface?

What grade of paper should I use - can I use an electric sander or must it be by hand?

Do I need to use primer, or can I antifoul straight onto sanded gelcoat?

Should I just polish what's there to get a reasonable surface and put 2 coats of a/f on?


When it's done, 'Muddy Paws' will be in a half tide marina in mud on the East Coast.

Thanks for your help.

 

[Talbot]

dont sand unles you are dealing with a really small area - the a/f is really toxic so face mask and full cover up is essential.

You have the time so a slow scrape back to bare gel coat is worthwhile. A sandvik scraper is good (tungsten blade) The gel coat should be abraded not polished fore the paint to adhere, and most new antifouling has a limited life before immersion in water. If you have scraped back, you should be able to paint a/f directly to the gelcoat. However if the boat is going to dry out for 3 years and be scraped clean, you might also consider an epoxy coating first.

 

[Otter]

Sorry, may have misled you, the boat is going back in the water for 3 years without coming out again except for a scrub off and new a/f; must work on my grammar

 

[Bodach na mara]

As Talbot says DON'T sand antifouling. It is nasty stuff if you inhale or ingest it.
I suggest complete removal of the old stuff. This can be done using chemical stripper such as Dilunet gel or you may get away with a dry scrape using a decent hook scraper (Skarsten or similar.) I got away with a dry scrape but my old stuff was very thick and poorly bonded. In either case, use protective clothing (gloves and overalls + hat) and ALWAYS wear a mouth mask and goggles.

Once the hull is clean, check for scrapes and gouges and fill with a filler such as International Watertite (an epoxy I think.) It is worth putting on a coat of epoxy tar after this. The final stage before the antifouling itself is a coat of antifouling primer (which seems to be a sort of aluminium-bearing paint) as it seems to get the antifouling to stick better to the hull.

 

[Talbot]

Dooooh