Top and bottom cleaning

Yngmar

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Planning the upcoming liftout and associated tasks. One of them being the complete removal of all fouling and old antifouling prior to applying Coppercoat. This being my first big boat, I understand the general idea of scraping and sanding the bottom down to the gelcoat, but am somewhat fuzzy on the details (apart from the Coppercoat application, which is well documented).

I've scored a random orbital sander at a recent sale, and have an assortment of discs, but expect to be using rather a lot of them - which grits should I go for to clear the bottom, getting off the old antifouling without getting off too much of the gelcoat underneath? And how many discs should I stock up (40 ft monohull). Prior to sanding, I assume there'll be some scraping (there's blue antifoul on there, probably quite a few layers thereof). Any recommended scraping tools or techniques? Is paint stripper worthwhile/needed?

I'm aware of the slurry blasting option, although if I can stomach two weeks of grinding (rough guess - am I far off?), I'd rather put in the work than the money.

Then there's the topsides. They're white with a blue cove stripe. Generally the gelcoat is fine apart from a few small spots to fill, but a bit chalky and dull. How do I get them gleaming again - will a polish do or should I sand them with some very fine grit first (preferably without mucking up and having to repaint the cove stripe)?

Thanks for any advice!
 

pvb

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It's not a good idea to dry-sand antifouling;the dust is harmful to you and others.

For the topsides, you could try polish on a section before deciding whether you need to apply some sort of cutting compound instead. I used to get good results on old gelcoat with 2 applications of Meguiars Polish, followed by 2 applications of Meguiars Wax. Both products are very easy to apply by hand and polish off by hand.
 

Tranona

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Forget removing antifouling yourself in preparation for Coppercoating. Have it blasted as this will get the surface properly prepared for epoxy coating prior to Coppercoat. Preparation and careful application is key to success in the process. Ask The manufacturer for recommendations for a blaster to do the job for you in your area.
 

Giblets

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As the OP is in a marina (and assume that's where the boat will be ashore) it might be worth checking that the use of sanders is permitted. I'd be rather upset if the boat nextdoor on the hard covered ours with a/f dust!
 

Daydream believer

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I used a local firm ( as used by the marina for odd jobs)who sandblasted the hull leaving a relatively small amount of antifoul in patches. This took 1 day to remove. What did take another full day was the 50mm strip they left at waterline. This was so thick i ended up chipping it with a hammer
The cost of my 31 ft boat was £ 200-00 cash so quite honestly i could not see the point of poncing about trying to remove it myself
Some say one should use soda blasting but there was nothing wrong with the work i had done.. I was present when it was done and watched to ensure the chap was gentle with the boat. He was . I also wanted to be on hand to get a primer on the keel within an hour or two so that rusting was kept to a minimum. In heindsight i should have put on more primer layers on the keel but otherwise it went ok. Copper coat say that there is no need to worry about the gel coat but if you are worried then put on a couple of coats of gell paint prior to copper coating.
However, i have just spent half an hour scrubbing below the water line to remove weed because the coppercoat itself is not a good antifoul, apart from the fact it does not need re applying every year, just jetwash at end of season plus a mid season jetwash and that is a bonus
 
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Daydream believer

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As for dry samding - before copper coating i dry sanded with 60 grit every year removing a third each year. I had an article published in pbo describing how it was done.
I fitted a sander so it pivoted by putting bolts into the sander handle holes an fitting a "y" shaped. piece of metal on the end of a 50x50mm timber 3.9 m long.(2 bits of bat strap from travis perkins)
At the centre of balance of this set up i put an adjustable line with a hook to the boats gunwale
By pushing down on the end of the pole the sander is forced up under the hull. Being 3.9metres away dust is not a problem. It saves trying to hold a sander up above your head to remove the anti foul and it is easy to just lean down on the pole moving ot about to cover an area
 

Yngmar

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To clarify a few things:

I don't want to sand off the layers of antifouling, I want to scrape them off, then sand whatever patches are left after that until the hull is clean. Thus my question about scrapers and stripping liquids.

I would obviously wear a suitable get-up, filter mask, goggles, disposable overall.

I've talked to the boatyard and they're okay with sanding as long as it's under cover, so I was thinking I'd tape some polythene sheeting all around the hull, creating a curtain (heat may be a problem, but I'm counting on English weather there). That should keep the dust in and away from other boats and unprotected lungs.

I've considered blasting, but this seemed rather pricey for a 40 footer (I remember something like £500-600). I've just asked for a quote in case it isn't. Recommendations welcome - the boat is in Brighton.
 

Bobc

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My advice would be...don't bother.

If you're going to coppercoat, get it slurry blasted. If not, just slap new on and go sailing.
 

Tranona

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I've considered blasting, but this seemed rather pricey for a 40 footer (I remember something like £500-600). I've just asked for a quote in case it isn't. Recommendations welcome - the boat is in Brighton.

After the first week of trying to strip it off yourself and still not finished you might come to the conclusion that blasting is a bargain! all done and cleaned up rady for first coat in an afternoon. Try Symblast for a quote.
 

Yngmar

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After the first week of trying to strip it off yourself and still not finished you might come to the conclusion that blasting is a bargain! all done and cleaned up rady for first coat in an afternoon. Try Symblast for a quote.

I've asked them and they quoted me something fairly outrageous (well beyond a grand, plus VAT). Plus, they're no longer Symblast and this all sounds a bit dodgy:

Due to recent restructuring of the company (Our accountant woman completely screwed the whole lot up) we are now named Southern Blast Ltd, the change will have no effect on work carried out previously and all warrantee work will be honoured, (the fact is there isn’t any warrantee work). My company carries on exactly as it has for the past 16 years-providing a high quality service at reasonable costs as it always has. Needless to say we now have a very competent accountant! Thanks to all our customers and suppliers support over the last 6 months and prior 4 months of total hell.
Paul Hockey-Director


After that quote, I'm even more motivated to strip it myself instead.
 

Capt. Clueless

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A god awful job I was not looking forward to, but got masks, goggles and gloves and firstly got stuck in with a good quality scraper. This went a good way through all the older antifoul that had been applied with no good previous preparation. I then systematically went over it with an orbital sander and did it it DRY! There was no one about although it is in a boatyard, and I was suitably covered, except my arms.(Walking through the streets of woodbridge on a Sunday with blue arms does attract some looks)!
Once I was satisfied I had done a suitable prep, I then applied 2 coats of International antifoul primer, before applying two coats of dark blue antifoul. Flamin horrible job, but I was happy that I had done the best I could with what I consider to be very expensive materials.
 

Tranona

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What was Paul quoting for? Was it just blasting or preparing for Coppercoat with a primer? He charged me £350 to do a 26' boat, just removing the antifouling.

DIY Coppercoating has a mixed reputation, particularly if done in the open, partly because of the difficulty in preparing the hull and keel and partly controlling the conditions for application. Personally, not sure I would do an existing boat myself and as you might have seen I had my new boat done professionally under cover immediately after it left the factory. Took 10 days from start to fully cured.

Clearly there are advantages in the product, but even doing yourself it is an expensive process and when I did my research it seemed to point towards professional application being more successful.
 

JumbleDuck

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I don't want to sand off the layers of antifouling, I want to scrape them off, then sand whatever patches are left after that until the hull is clean. Thus my question about scrapers and stripping liquids.

I stripped my Hunter 490 back to the gel coat below the waterline this spring. It was a bloody awful job and I never want to do it again. I started with Removal 620, which is what they now recommend for GRP and it was pretty useless, so I swapped to Removall 220 which is now supposed to be for brick and steel but which they used to sell for GRP. That worked OK, ish, but I ended up removing the final layer, which I suspect was two-pack, with a hot air gun and a 1" chisel. It was at least five full days' worth of work, spread out a bit.

At some point I'll probably take the accumulated antifouling of years off the 26-footer, which looks a bit like Barbara Cartland's face in places. When I say "I'll take it off" I mean "I will pay someone to blast it off". At the moment, though, it costs me around fifty quid a year in paint and equipment, and the boat is pressure-washed when she comes out for the winter, so Coppercoat doesn't make any financial sense at all.
 

AndrewL

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I had a go at wet scraping many years of old anti-foul. I had read on the forum about how hard, nasty and unrewarding it would be, but didn't fully believe it until I tried. 22 foot boat and 2 full days days got about half done and I stopped saying to myself "I'll do the rest next year". (I stopped at a symmetrical point).

I was just attempting to cleanup a bit before new anti-foul. If I had to get a perfect surface for coppercoat or epoxy I would definitely pay to get it blasted off.
 

Yngmar

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Boat was lifted around noon today and I started scraping right away. Half a day later:

scrapscrapescrapescrapescrapescrapescrapescrapescrapescrapescrapescrapescrapescrapescrapescrape.JPG


Went better than expected after all the dire warnings here. The Bahco 665 two-handed scraper is an absolute must. I've ground off the edges (tough on the grinder, the tungsten carbide blades are really hard). If I had only a putty knife, I would've cried and called the blasting guys within an hour. At this rate I guess a few days more and I'll be ready to sand. Scraping works much better when wet, so I kept hosing the part I was working on down when it got dry. That also prevents the dust, as the stuff comes off with a satisfying slurp rather than go airborne. I wore a disposable coverall with hood, mask, goggles and gloves. Ended up with blue clothing and arms anyways, despite doing the correct removal procedure for chemical weapon contaminated protective clothing :)

For the dry sanding bit I plan to tape polythene sheeting all around the topsides.

If I did this for a living I'd worry about looking like one of those bodybuilders with gorilla like upper bodies and tiny legs.
 

Yngmar

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Do drop by, with this sort of work, any distractions that allow me to lower my arms for a little while are most welcome ;-) I'm near the center of the boatyard - the boat with no rudder (it's around here somewhere).

More than halfway scraped now. Took the afternoon to take a saw and chisel to the seized rudder bearing ball. That was tricky, because the sawblade ran hot, melted the plastic which then gunked up the teeth until finally the saw battery I've neglected to charge ran out.
 
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Capt. Clueless

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For me, that is the only way to go. I also used a quality scraper instead of a poundland effort. I then used an orbital sander for dry sanding. (mask, goggles & gloves).Well done, all it needs is some effort without clearing your bank acct.
 
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