Removing old antifoul

[Spankerwrap]

I need to remove two to three old coats of old antifouling and cannot afford to have it done professionally. Has anyone any advice on the "least worst "way of doing it e.g. electric sander, wet and dry, scraper, chemical remover etc.
Also, should there be an anode attached to the prop shaft as there does appear to be one.

Many thanks.

 

[JeremyF]

Funny how one decent weekend in March causes a flurry of activity on all matters antifoul!

Suggestion for manual antifoul removal is to use a scraper with 2 1/2" blade. This manual approach lets you feel how much pressure you are applying. You can get them from any DIY shop, they are the shape of a gemmy bar. Change the blade after every 4 hours. This way you shouldn't score the gel coat too often.

Jeremy Flynn

www.yacht-goldeneye.co.uk
New pics 11.02.02

 

[claymore]

And...

Wear a mask and goggles, rubber gloves and keep it wet to avoid dust.
There are nitromors types of products which might help soften it - they don't cost the earth and might make a particularly horrible job a bit easier.

 

[vyv_cox]

We used a scraper that attaches to a vacuum cleaner. The hardened blades stay active for a good while, we did a Sadler 34 on two blades. All the removed stuff goes into the vacuum. It's physically rather hard work but cleaner, safer and probably faster than all the DIY alternatives. Wife and I did the whole hull in a weekend, not full time as our ancient muscles didn't like the non-stop effort.

Sanding it off is a terrible job. Just smoothing off the final scraping leftovers has taken longer than the scraping. You wouldn't need to do this unless Gelshielding.

 

[Chris_Stannard]

Why take it off unless you are racing and trying to save every ounce. If you use a scraper youare almost certain to end up with scratches/scores on the gelcoat which need filling. Rub it down well with wet and dry and antifoul it. If you know the makers of the old antifoul so much the better but most are compatible. The dust mask etc are a good idea and you need the long sleeved rubber gloves avoe your overalls to stop the water going down your sleeves.

I always fit a shaft anode in addition to my main cruising anode, its closer to the prop and always seems to have taken a hammering when I come to replace it.

Chris Stannard

 

[Sirus]

Dont mess about with scrapers the best thing is a sharp wood chisel so much easier,just make sure it is kept sharp with no knicks in it.

 

[extravert]

I am taking all my antifoul off this year, back to the gel coat. The old stuff is 3 years worth thick, and the base layer bonding is failing, causing full thickness chunks to fall off. Sanding was no good, as there didn't seem to be an end to the weak stuff. Being a racer, there's only one option - take it all off and start again.

I am using chemical stripper, but (asuming it's a GRP hull) don't use Nitromors, it's not suitable and will damage your gel coat. If you are using a chemical stripper, use one specially for GRP. I tried a few types, none is as effective as conventional strippers like Nitromors, but the one I found best is International Interstrip. It's not like using normal stripper though. It doesn't bubble up the paint, rather it just re-liquifies it, leaving a nasty gooey mess than can be almost spooned off, and then finally cleaned off with a solvent. Even with only 4 coats it takes me 2 to 3 goes to get it all off. One tip if you are going to use it, it liquifies the old paint, then leaving only a few minutes to get it off. It will soon re-dry again, and then becomes even harder to get off.

On my X99 10m hull (and low volume/wetted surface area for 10m as well) it is going to take 5 man days and 10 litres to do it, excluding rudder and fin keel, which will be done next year. It's about £10 a litre.

If you are going to do it chemically, it's expensive in time and materials, really messy, and the chemicals are none too pleasant. On the upside, the final finish looks as good as the day it came out of the mould.

 

[vyv_cox]

My experience is that after four or five years the antifouling is spalling off in parts, has had a few knocks and generally looks a mess. I don't think that successive coats can be applied indefinitely.

What the charter fleets do is to rub down with a nylon pan scourer as soon as the boat comes out, keeping it wet all the time. There are now special coarse versions of the same sort of scourer specifically for this job. Doing it this way gets the vast majority off and leaves a good finish for next year's coats. Keep hosing down to avoid drying out. Definitely a job for all those people you gave a day out to in the season.

Old antifouling is very friable and comes off extremely easily with a scraper. I didn't find that using a chisel or paint scraper was at all effective, a shave-hook might work well but the stripped paint will go everywhere. The purpose built device got good reports from YM and we found it to be pretty good. I do agree about the scratches, I ground the corners off the blades and that helped, but we will need a certain amount of repair filler.

 

[quaelgeist2]

One generous application of Dilunet (left on over night against advice from the print on manual) and a power wash on the next day - done.
Worst case - a second serving...
Con: environmentally it's not the thing to do given that Dilunet like all other chemical removers is highly caustic/toxic.
Wear protective gear and make sure the next boat doesn't get flying parts when washing off.
No problems for gelcoat or 'normal' hull paint.

chris

Some semi-professional service providers should be able to make you a reasonable offer for blasting of the old stuff - that's the real alternative

 

[Guest]

I took about 20 years of the stuff of my Centaur when I decided that the hull needed epoxying. I got her ladyship to help and she was close to leaving me because I started the job!!!

My anti fouling was absolutely rock hard and about 1.5 to 2mm thick. Sharp chisels were ok but I recommend an electric scraper. Mine is Bosch and was about £70 8 years ago. Got from B&Q. I could get 1/2" strips off with it. About 1 sq yard (meter) per day.

I also used a compressed air needle gun that I hired complete with small compressor from a hire shop. You need to be careful but it certainly breaks up thick antifoul. You just have to scrape it afterwards. The needle gun is great for cast Iron keels that have gone rusty and have flaking paint.

Don't envy you once you start it took me all winter. The boat next to me had very flakey antifoul and he did his whole boat with a wallpaper scaper in less than a day!!!.

 

[Guest]

What is, where does one find, and how much does it cost, how much does one need of this 'Dilunet'? It sounds from your comments, to be wonderful.

 

[castaway]

I had this discison on my 'new' 36ft hull with loads of old hard AF.. in the end had it slurry blasted off and worked the week end as over time to pay for it...... Lots easier and no toxic poisoning. Seriouly cant understand why people still apply hard AF to sailing boat hulls. For years now I have only used Soft stuff and pressure wash it off at the end of the season. New coat goes on in the spring and never ever had any build up.

Nick

 

[gunnarsilins]

Dilunet??? What exactly...

...is that?
Will try to find its Swedish equivalent!

 

[ccscott49]

Just as an aside, I use an old sponge mop thingy, one of those flat jobbies, with the handle to wring them out. I wire very coarse scotchbrite pads all over it and use that wet for preperation purposes, its brilliant! I have used stainless mpot scourers aswell, just as good, still wired to the old sponge mop! Keep it wet!

 

[quaelgeist2]

mmmhhh just read my own posting again, not precisely wonderful, but maybe we can agree on powerful

For removal of several layers of hard + soft antifouling on a 25ft boat in two rounds I needed two containers of about 2l each - at a price of about GBP 30-35 per container.

I bought it in Kent, but have seen it also on London and numerous other places in Europe.

Can't find a link to it anywhere on the web - sorry.

chris

 

[PeterGibbs]

Re: Old antifoul - a contrarian\'s view.

I find the attention given to a smooth antifouled finish almost a metaphore for the typical sailing season - starting with excessive attention to matters having little impact on the season's enjoyment, and ending with scant regard to the vitals, such as changing engine oil to the manufacturer's recommendations (a potentially much more insidious sin!)

Isn't the practical approach to antifouling to assess what areas of the hull are seriously unstable and just remove that much with the least effort? (a Scarsten-type scraper with filed over edges mounted on a 2 foot handle is best for me)What is the value of getting back to the hull? What is the point of stripping off stable antifoul on the grounds that "it's x sesason's old" and needs replacing"? We cannot expect the paint companies to assit these decisions becasue it's their profits we are slinging on the deck and splashing in our hair!

For cruisers let's face it, the difference in boat speed from a few rough antifoul patches well below the water line is not measurable. You cannot prevent slime deep under the hull so why bother with more than one roller coat there? Most fouling takes places at or near the waterline, and this is where I apply the paint liberally.

So may I suggest we invest more effort on important matters and less on polluting the environment needlessly?

PWG

 

[ccscott49]

Re: Old antifoul - a contrarian\'s view.

I wholeheartedly agree, the serious racing crowd polish the bottom of their boats anyway (burnish) I just get it slapped on and back in the water, in fact last time in Dartmouth, I did a side at a time on the scrubbing grid, two tides, back on the mooring! Thats a 57' boat, two of us, pressure washed, quick scrape and sand here and there, 25 litres of antifoul with roller and bootopping with brush props polished and black leaded, all done and 22 pounds for two days use of the grid! I installed a echopilot sounder transducer at the same time! Still good after two years, one season in the meddy, Jotun non stop! simple!

 

[Miker]

Re: Old antifoul - a contrarian\'s view.

Nice to read of a quick and cheerful appoach to antifouling. I, too, just scrape off the loose stuff and slap some primer over where necessary. The first year I did this I was surprised to see that the antifoul was still in place when the boat was taken out at the end of the season. It seems to me that the ravages of the winter on the hard strip off more antifoul than a summer in the water. The underside is starting to look like the surface of the moon but I am putting off removing all the old antifoul for another year.

 

[ccscott49]

Re: Old antifoul - a contrarian\'s view.

Mine is beggining to look a bit bumpy, but what the hell, when I get somewhere they can blast it all off, or somewhere with very cheap labour, it will stay like that, I might be losing 1/2 knot, or using 0.05 litres an hour more diesel, big deal!

 

[MedMan]

I too have used the Vacuum Scraper. It is an excellent, and cheap product. Details on http://www.gelplane.co.uk/

Good luck,

David