Antifoul removal by scraper

[bobgarrett]

I am wondering whether it is safe/practical to remove layers of erodable antifoul with a simple scraper - like that used to remove paint from glass window edges. Could this damage the grp?
I had the idea when I saw a boat in a yard which looked like it had been stripped this way and recalled seeing a surveyor scrap the antifoul away in exactly this way to see and test the surface below.
What does the team think?

 

[Avocet]

That's how I normally get rid of mine. Goggles / gloves and a mask are a good idea. It's often easier taking several years' worth off in one go bcause the greater thickness makes it brittle. It's pretty hard work mind! I use a Sandvik scraper with replaceable carbide blades. Sharp blades and holding it at the right angle are the key. Also worth trying to grind the corners of the blades (if you can find anything hard enough!) to a gentle radius to stop them digging into the gelcoat.

 

[alahol2]

I did mine this way but you need something stiffer than a normal paint scraper. A 1.5" chisel (with rounded off corners) is what I used. Hard work but you get there in the end.

 

[mainmarine]

I use a Bosch power scraper, I removed all my antifouling earlier this year with one, before sanding and applying epoxy coating, precautions as above. For easiest removal, you need to keep the blade edge at the correct angle with a file or use replacement blades.

 

[Dipper]

I stripped my 26 ft yacht using a Hamilton heavy duty scraper bought from B&Q (now £6.48). Mine came with two reversible blades which was enough for my boat.

The Sandvik is supposed to be the best but it is quite expensive.

Avocet's advice is spot on. Wear a mask and goggles and grind the corners of the blade off otherwise it digs into the gel coat. Once you have got through to the hull, if you get the technique right you can catch the edge of the old antifoul and with one movement 'judder' all the layers off in one go. It's easier to do than explain! Use two hands - one on the handle and one pressing on the blade. I also placed a dust sheet below the area being scraped so I could collect all the scrapings which I put in an old antifouling tin and took to the paint section of the local dump.

 

[lw395]

A cheap 1" chisel sometimes works well. Take the corners off to avoid scratching the gel coat/epoxy.
A carbide tipped scraper is also good. Harris do one, avail in screwfix. There is a posh one with a vacuum cleaner attachment in the yachtmags.

Best to have a variety of tools, as what works best varies. Let the a/f dry out completely so it crazes for easiest removal where its thick.

Alternatively, wet and dry, wet is quite effective while the a/f is still damp.

 

[ghostlymoron]

I need to do this as well but I am wary of damaging the epoxy coating. Does the team think that this is likely?

 

[Lakesailor]

If you've ever tried rubbing down epoxy you'll know it's as hard as nails.
I have both the Sandvick type scaper and use old chisels. I find the pressure required to use the fancy scraper tiring. The old chisels work a treat. Keep them sharpish on a grindstone and as others have said round off the sharp corners. If you have three or four under the boat as you are working it saves popping out to sharpen them.
I've done erodable antifouls and also multiple layers of hard antifouling using this method.

 

[Deleted member 36384]

Anti Foul Removal - Sanding By Hand

At the end of last season I sanded by hand a 41' hull with 3/4 keel. It took a day. In the morning I sanded with about 80 grit dry wrapped around a sanding block - I use and old style cork block. Screwfix (online) supplied the roll of sand paper. I kept changing the pad at the first sign of wear. I washed the hull and had lunch to let it dry. I then sanded it again with a finer grit, about 120, not sure. Washed the hull again and came back the following weekend to prime and paint.

In some places the sanding was through to the gell coat but in most places the old anti fouling was just heavily cut back. At the time I thought about removing it all but decided a layer of prepared old anti foul that has adhered well to the hull was a good base to apply the new anti foul onto.

Next time I will sand with wet and dry used wet. The dust got everywhere. I used a disposable cover-all and dust mask. I ended up having to tape off the wrists and replace the dust mask every 15 minutes. It was hard work, more a good workout than knackering as my stamina is set for office work!

I tried the scraper and while it worked I thought that I could sand faster and achieve a good surface with sand paper. I also tried International's anti foul paint stripper on the rudder. A messy, slow job which would have required a few applications and would have been expensive. It did work though.

I considered having the hull dry ice blasted for various reasons but was quoted around £1500, so I didn't bother. I'll keep this for the year I decide to paint the whole hull and copper bot below the waterline. Until then its old sanded layers for me.

Its lasted well this season so far.

 

[alahol2]

... The dust got everywhere. ...

I bet your neighbouring boatowners absolutely loved you

 

[paulrae]

Removing Old Antifoul

I spent last winter removing all of the antifoul from my new (to me) boat. The most effective tool was a cheapo (Parkside, I think) equivalent of the Bosch power scraper that I obtained from Ebay for £15. It was painfully slow, but didn't damage the gelcoat, other in a few small locations when my concentration waned and I took a little chip.

I also used the hand scraper with the hard blade. It was very easy to damage the gelcoat with that. I reckon that's what one of the previous owners had done, as there's a small area of hull with lots of little nicks.

Alternatively, there are folks on the forum who strongly recommend a slurry blast system. I'd be very keen to investigate that route if/when I need to do it again.

For doing it yourself I'd strongly recommend the power scraper and lots of patience.

Good luck.

 

[samwise]

This all sounds like a lot of hard work to me. Unless you need to get all the antifoul off, then the one day rub down proposed in an earlie post is probably the easier option. Faced with the need to get the hull of our boat right back to the epoxy, I went the chemical route. We used Removall stripper and it worked a treat.
Unlike the International stuff and things like Nitromors , it is much more enviro friendly. You can choose to apply by brush or spray. You then leave it for eight to 12 hours ( depending upon temperature) and then set to with the scraper. By that time the a/f is softened and the job is like peeling wet wallpaper. Have a look at the Cirrus Systems website and if you have any queries, call them, they are very helpful. It will cost more than straight scraping but in my view a lot less hassle and effort

 

[Ruffles]

I was quoted £400 to grit blast a 31' fin keel boat. This included cleaning and an anti flash coating the iron keel. Note that if grit blasted you do not need to sand to key the primer. This is quite a lot of work in itself. I've seen GF hulls after they had cleaned them and it really does produce a perfect surface for painting.

I elected to use a power scraper and a couple of weekends. In retrospect I should have spent the £400. The paint itself must of cost me £250!

Remember, whether you scrape or blast the hull you will have to apply a primer afterwards. This is not cheap in itself!

 

[Deleted member 36384]

I bet your neighbouring boatowners absolutely loved you

They didn't know because I washed it all down and off their boats where it was present. I didn't love my neighbour because he jet washed his hull and sprayed it all over my mast lying along side. It took quite a while to get off the mast and the lines are still stained in some places.