Removing old anti-foul

[Chiara’s slave]

We should have outsourced, took weeks of misery to get back to gel, or rather epoxy. Looked like a couple of smurfs at the club summer ball?

 

[Wansworth]

We should have outsourced, took weeks of misery to get back to gel, or rather epoxy. Looked like a couple of smurfs at the club summer ball?

And your long term health?

 

[srm]

Advice please.
The anti-foul on my Leisure 18 is looking a bit rough, with some chipping off.
How aggressive can you be without damaging the underlying gel coat or fibreglass?
I don't need to remove it all but just get it to a smoothish finish prior to re-antifouling it.

You will probably find all you need to know, and some that you don't, by reading through this recent thread:

Removing a ‘fair few’ layers of antifoul with orbital sander?

Only you can decide if the job is worth doing either by hand or paying for soda or dry ice blasting.

 

[David_cepi]

Short of removing the lot, it depends on what method you use. When mine was several years old it started flaking in places due to poor adhesion to the original a/f. I just used a scraper and got the loose stuff off. I then used a sander to feather the edges before painting the patches with primer, resanding by hand and adding more primer and a/f, leaving a smooth surface. I found a rotary sander the easiest and quickest way of feathering off with a coarse disc, which sounds alarming but can be quite gentle. After a few years of this I came to my senses and had the lot taken off by a pro.

Do the sandpaper gets easily blocked when removing palative a/f? Is there a trick when sanding a/f?

Thanks.

 

[ChromeDome]

Do the sandpaper gets easily blocked when removing palative a/f? Is there a trick when sanding a/f?

Thanks.

3M Blue Net Disc Roll and similar meshed products are less prone to block. Several types around - mesh is the key word to search for

 

[srm]

Do the sandpaper gets easily blocked when removing palative a/f? Is there a trick when sanding a/f?

Thanks.

Whatever you use ensure it can be used wet, and use lots of water to wash the dust away as it is designed to be toxic. Its not a good idea to get antifoul dust near your eyes, nose or mouth.

 

[Fantasie 19]

Got the same job this winter and based on responses here previously I have a sanding pole and a long roll of coarse sanding mesh ready for the job.. plenty of water, wet it down soft and then just rub until it's smooth.. have a bucket of water to dip the head in from time to time as well

 

[johnalison]

Whatever you use ensure it can be used wet, and use lots of water to wash the dust away as it is designed to be toxic. Its not a good idea to get antifoul dust near your eyes, nose or mouth.

Although true, I only ever sanded small areas around the edges to feather them, which I found impossible to do by hand.

 

[[70521]]

Advice please.
The anti-foul on my Leisure 18 is looking a bit rough, with some chipping off.
How aggressive can you be without damaging the underlying gel coat or fibreglass?
I don't need to remove it all but just get it to a smoothish finish prior to re-antifouling it.

Having done a complete scrape back to GRP by hand, I strongly advise getting somebody in to do the job by either blasting or dry ice.

My current boat was professionally blasted back and copper coated. The 1 knot increase in average speed has been a joy.

 

[Aquanaught]

Having done a complete scrape back to GRP by hand, I strongly advise getting somebody in to do the job by either blasting or dry ice.

My current boat was professionally blasted back and copper coated. The 1 knot increase in average speed has been a joy.

Sandy,
Any recommendation for blasting and copper coating (Plymouth area) - I'm thinking of having this done on my boat in coming season.

 

[ChromeDome]

In another thread not too long ago I mentioned dry ice blasting.

Boat Jobs You Don't want to do Again

 

[srm]

Any recommendation for blasting and copper coating (Plymouth area)

I had my boat soda blasted at a yard in Plymouth but that was back in 2009. Pleasant guy who traveled around the yards in the area so it should not be difficult to find someone now if you ask at the boatyards. I applied the epoxy and Coppercoat myself after tenting the hull with tarps.

Soda blasting only removed soft coatings, I had to remove an old epoxy base coat with a random orbital sander.

 

[Spirit (of Glenans)]

Do the sandpaper gets easily blocked when removing palative a/f? Is there a trick when sanding a/f?

Thanks.

You'll be using Wetordry sandpaper. The paint dust washes out.

 

[Spirit (of Glenans)]

Short of removing the lot, it depends on what method you use. When mine was several years old it started flaking in places due to poor adhesion to the original a/f. I just used a scraper and got the loose stuff off. I then used a sander to feather the edges before painting the patches with primer, resanding by hand and adding more primer and a/f, leaving a smooth surface. I found a rotary sander the easiest and quickest way of feathering off with a coarse disc, which sounds alarming but can be quite gentle. After a few years of this I came to my senses and had the lot taken off by a pro.

For the sake of both your own health and that of the environment, and so as not to get blue dust all over neighbouring boats, you should only abraded anti fouling with wet-sanding media.

 

[penberth3]

For the sake of both your own health and that of the environment, and so as not to get blue dust all over neighbouring boats, you should only abraded anti fouling with wet-sanding media.

Interested how you deal with the wet residue, with regard to health and environment?

 

[Spirit (of Glenans)]

Interested how you deal with the wet residue, with regard to health and environment?

I empty the bucket down the drain at hardstanding where the boats are powerwashed on liftout.

 

[eddystone]

There is a state known as stable rust which forms a protective layer over the unconverted metal underneath. Bearing in mind rust, so long as it remains attached, is heavier than cast iron blasting back to bare metal every year might affect your ballast ratio ?

 

[[70521]]

Sandy,
Any recommendation for blasting and copper coating (Plymouth area) - I'm thinking of having this done on my boat in coming season.

Contact Mylor Yacht Harbour.

 

[PeterWright]

The PBO one is to remove it all. Why don't they do an article to tell you how to do patching job and then go sailing, Patching is fine for cruising. I find that if you do little each year it is easy to keep on top on it. JohnAlison's method works well.
David MH

Didn't you read to the end of JohnAlison's post and learn what he did when he "came to his senses"?

Get a grit blaster, experienced in blasting grp hulls, to come and take the lot off. If you want to get a good price, find a few mates with boats on the same site and get him to come and do them all in one day. Consult with the site owner about requirements for collection and disposal of the debris, whether you use a grit blaster or sanding discs.

Peter.

 

[PeterWright]

There is a state known as stable rust which forms a protective layer over the unconverted metal underneath. Bearing in mind rust, so long as it remains attached, is heavier than cast iron blasting back to bare metal every year might affect your ballast ratio ?

I beg to disagree.

Rust formed on cast iron is even more porous than the iron it was made from and will allow the salt water access to the uncorroded iron for the rust to grow. Protective corrosive layers are in the world of austenitic stainless steel. While the rust will be heavier than the iron it came from (each Fe atom has acquired some H and O atoms) it will also occupy about 8 times the volume of the iron it was formed from so even if each rust molecule is double the weight of the iron it was formed from, it will be about one quarter the density increasing its bouyancy. The whole assessment is destroyed by the fact that some of the rust formed will stay in the sea, no longer attached to the keel.

I agree that blasting back to metal every year is a fool's game. Do it once, wash thoroughly with fresh water using a pressure washer to get as much as practical of the salt out of the pores of the slightly porous cast iron, give it another quick blast over to remove the light rusting from the wash then prime with at least 3 coats of a rust and damp tolerant epoxy primer. You can then coppercoat with confidence that it will not fall off the keel.

We did this with our 1989 built Moody 11 years ago, and it's still holding up. The finish remains fair and is a major improvement on the cratered state when we bought her. When the Coppercoat stops working, we will have that cleaned off and replaced without disturbjng the epoxy primer.

Peter.