Removal of old antifoul

[Freebee]

We have a 50 year old grp hull with many layers of antifouling that need to come off I imagine some of the older layers maybe quite toxic..what's the best way of removing them..???

 

[duncan99210]

If you're truely set on removing them, then the best method is to pay someone to grit/slurry blast the hull. Not cheap but the only other methods of removal involve a lot of backbreaking labour....

Scraping is probably the most effective method after blasting. Get hold of a two handled scraper and some spare blades and settle down to some serious hard graft. You can't really dry sand the hull as the resultant dust is both somewhat toxic and very messy. You could surround the hull with some plastic sheeting before sanding but you'd need serious breathing protection.

All that said, unless you're thinking of going racing I'd be tempted to do as I have done with my Hurley 18: remove the loose stuff with a scraper and then apply fresh paint and go sailing.

 

[davidej]

And don't waste your time and money on paint-stripper. Plenty of threads on how useless it is for this purpose.

 

[jeanpaulcopie]

Unless I had signs of possible osmosis, then I wouldn't bother to remove the old antifouling! If you have to, then the cheap way is the scraper, and the best is soda blasting! But what I would do is to scrape off what seems to be falling off, then dry sand all the rough edges wearing a simple mask, put a coat or two of barrier paint (ie. International PRIMOCON) and finish with two coats of self polishing antifouling. For the barrier paint and antifouling, best to keep to the same make.

 

[lpdsn]

And don't waste your time and money on paint-stripper. Plenty of threads on how useless it is for this purpose.

It's a little less useless if you cover it with cling film or tin foil after applying it. Don't leave it like that more than a couple of days though.

 

[crispyone]

I recently took a few layers of old antifouling off a Bonwitco hull. I used Owatrol Marine Strip covered with cling film, and most of the stuff came off with 2 applications. Some really hard thick spots that were left came off easily with a hot air gun and a wooden spatula.

 

[James_Calvert]

I recently took a few layers of old antifouling off a Bonwitco hull. I used Owatrol Marine Strip covered with cling film, and most of the stuff came off with 2 applications. Some really hard thick spots that were left came off easily with a hot air gun and a wooden spatula.

Bet you turned it upside down first!

 

[crispyone]

no, you lose the bet, the boat is on the trailer and is converted to a cabin cruiser, so no chance of that. I only decided to remove the A/F when I converted to electric power and needed to make the boat as slippery as possible. I also added a home made 'sugar scoop' to negate the effects of the flat immersed transom. The Bonwitco was designed for early planing with only moderate power, while I am using it as a river cruiser.

The hull was the old single-skinned variety of Bonwitco hulls, so I guess the antifouling has been added in layers since the 1980's.

 

[H35]

A 50 year old boat has seen some layers of antifouling on. After a MAJOR work over two years ago, with paint stripper, lye, scraping, sanding and so on for 3 weeks, on my "only" 40 year old boat.... I am entitled to an opinion: HIRE SOMEONE TO BLAST IT!!!
-And when you're there - down to a stripped hull, put some layers of epoxy primer on.

 

[James_Calvert]

Re the Bonwitco, as a teenager we had a early open single skinned one, a 450, built in 1968. Looked lovely with varnished gunwales and thwarts. Easy to turn over for cleaning/ antifouling, only weighed 150lbs.

 

[crispyone]

then mine must be earlier than 1980's cos it's also a single skin 450. However the manufacturer's website claims it weighs 190kg, which sounds about right.

when I acquired it in 2015 the gunwales were partially rotted. I fixed that and used the timber from the main and forward thwarts (40mm mahogany) to construct a foredeck. As you say, when varnished (I epoxy coated first, then epifanes UV proof) it looks a treat.

 

[davidej]

It's a little less useless if you cover it with cling film or tin foil after applying it. Don't leave it like that more than a couple of days though.

Have you tried that often quoted tip?

I have -incredibly messy as the stripper is squeezed out by the film, and almost impossible single handed.

And in the end, it still didn't do much. It would only take off 4-or 4 layers at a time so multiple applications required.

Ergo, either a scraper of get it blasted

 

[johnalison]

It depends on how much you value your leisure time, and sanity, but blasting is certainly easier. I have heard it suggested that newspaper works quite well as an alternative to cling film.

 

[Capt Popeye]

Humm on the H&S front; do you require permission from the Yard, Marina or Club if not on your own premises ?
as all Yards, Marinas and Clubs that I have visited now have their H&S rules, especially with Anti fouling removal, dispose of the Garments and Tools that you use, certainly do not take them off site to contaminate elsewhere.

 

[JumbleDuck]

And don't waste your time and money on paint-stripper. Plenty of threads on how useless it is for this purpose.

I have found Removall paintstripper to work very well on both soft and hard antifoul.

 

[crispyone]

Have you tried that often quoted tip?

I have -incredibly messy as the stripper is squeezed out by the film, and almost impossible single handed.

And in the end, it still didn't do much. It would only take off 4-or 4 layers at a time so multiple applications required.

Ergo, either a scraper of get it blasted

blimey, it ain't that difficult; the clingfilm is only to stop the jelly drying out, it doesn't need to be applied so thick that it 'squeezes out'.