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Old 24-07-2010, 04:09   #1
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Cleaning the Hull without Removing Antifouling

A relative newby to this buiness....we hauled our Bavaria 36 out at the end of the southern summer in April, cleaned and sanded the hull. Then applied two coats of ablative antifoul. 'Sweet As' has been in the water over winter and I intend to haul her our for a clean and anode inspection in spring. What is the best approach with repsect to cleaning the wet part of the hull when we haul her out? It will no doubt be tempting to give it a clean with a pressure cleaner - will this also wash the antifouling off? I really don't want to have to antifoul again until after summer.

John
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Old 24-07-2010, 04:16   #2
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The pressure wash will remove the antifouling.
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Old 24-07-2010, 04:40   #3
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Thanks Panaseaya, I suspected that would be the case. So does one just live with a grubby looking hull until the antifouling needs reapplication?
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Old 24-07-2010, 04:53   #4
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I agree with Panaseaya. Only hard non-ablative antifouling can withstand a pressure wash.

Don't know if you haul out for close to nothing but every 6 months sounds a bit overdone. We are at the moment in the SE Caribbean where the fouling is extreme due to watertemp and organisms from the Amazone. We put on 3 layer of Jotun antifouling last november. We use a plastic scraper with round edges and we remove growth and inspect zincs using our snorkel gear.

I guess we'll haul again next november and like last year will be thinking seriously about putting on hard antifouling, like coppercoat. I hate it when you put on the soft stuff for over 200 dollars a gallon and start to scrape it off after a few months.

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Old 24-07-2010, 06:20   #5
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A pressure wash will NOT remove ablative antifoul. You wish it was that easy. Just have the operator do enough to get rid of the growth - like a meter away. If the growth doesn't just fall away you need new antifoul anyway. Or use a garden hose and a soft cotton cloth - like a diaper.
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Old 24-07-2010, 06:28   #6
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A pressure wash will NOT remove ablative antifoul. You wish it was that easy. Just have the operator do enough to get rid of the growth - like a meter away. If the growth doesn't just fall away you need new antifoul anyway. Or use a garden hose and a soft cotton cloth - like a diaper.
Whatever you do, do it as soon as the boat is hauled, before it dries. Let that stuff sit a day or two and you'll need a chisel to get it off.

I would think a hose and running water and one of the plastic abrasive pads would do it. Or a plastic scraper as suggested above. Or both.
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Old 24-07-2010, 07:01   #7
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I would think a hose and running water and one of the plastic abrasive pads would do it. Or a plastic scraper as suggested above. Or both.
Those sounds harsh, And go against the manufacturer's instructions on the paint's I've used: Pettit and Interlux.

If hard stuff doesn't just fall away you paint is done, gone, toast. Simply recoat. No big deal.
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Old 24-07-2010, 07:22   #8
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Those sounds harsh, And go against the manufacturer's instructions on the paint's I've used: Pettit and Interlux.

If hard stuff doesn't just fall away you paint is done, gone, toast. Simply recoat. No big deal.
Well, I'm probably thinking of a diferent pad than what you're thinking of. I'm not thinking of a pad that's used as a replacement for sandpaper or steel woll, I'm thinking of a cleaning pad. Just like the pressure washer, the success or failure depends not only on the tool(s) used, but the touch and skill of the person using them.

In my area, we employ divers to clean out hulls every few weeks in the summer and every couple months in the winter. They use plastic scrapers and plastic abrasive pads.

Recoating is somewhat of a "big deal". There's scraping and sanding, dealing with hazzardous materials, applying the paint (two coats), moving the stands and blocking, then preparing and painting the remaining surfaces.
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Old 24-07-2010, 07:23   #9
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A pressure wash will NOT remove ablative antifoul. You wish it was that easy. Just have the operator do enough to get rid of the growth - like a meter away. If the growth doesn't just fall away you need new antifoul anyway. Or use a garden hose and a soft cotton cloth - like a diaper.
+1

I don't know what the other guys are talking about. Well-applied ablative antifoul will withstand multiple pressure washings as long as the work is done with care. We get two years or more out of a good anti-foul job but we pressure wash usually three times a year.

As someone said, it does depend on what kind of fouling you get. We are in cold water and besides that our marina is a couple miles up the Hamble River, so the fouling is fairly light and washes off fairly easily. Your antifouling won't last as long if you are getting heavily encrusted between scrubbings.
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Old 24-07-2010, 07:47   #10
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In my area, we employ divers to clean out hulls every few weeks in the summer and every couple months in the winter. They use plastic scrapers and plastic abrasive pads.
My instructions say to use a diaper. I've never in 10 years used a scraper or plastic pad on my ablative bottoms. Sounds expensive. However I certainly did where the ablative had worn away to gelcoat on leading edges during a long passage.

If the boat is already hauled, and the ablative is in basically good condition and nearing it's half-life, a pressure wash, light sanding, and recoat is almost trivial.
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Old 24-07-2010, 08:37   #11
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Only had pressure washing on my ablative paint once, for the experience and for the luxury, and it cleaned up nicely. Should be done soon after hauling.
The rest of the time I dive on it (originally free diving but now with a hookah) to inspect/change the zincs and clean the paint. I clean with a nylon bristle brush for slime and grass and a plastic drywall spatula or metal putty knife to knock any barnacles off. Plus a screwdriver to clean out the insides of through-hulls. On my 40 footer this takes between an hour and an hour and a half.
It would be cost-prohibitive as well as very inconvenient to haul out for a zinc inspection and to clean the hull. These are easily done in the water. If you don't want to do it yourself, get a recommendation on a diver.
It is my (perhaps imperfect) understanding that the ablative paint needs to slough its outer layer to expose the newer paint below. So when I clean, I get a little cloud of red which follows me around the boat. And the pressure washing would likely do the same.
(Once I coated the bottom of my RIB with the same ablative - no prep, just brushed it on to see if that would help with the growth on the dinghy bottom. It did, quite a lot, so I decided to do it "right" the next time, fiberglass primer etc etc - I had to use sandpaper to get the old paint off! The stuff sticks better than you would expect.)

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Old 25-07-2010, 00:52   #12
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Thanks all.

Sounds like the first action will be to don mask and fins and check out whats growing and condition of anodes before confirming whether a haul out is really needed at the start of the season. However, I think I will wait until the Tasmanian summer is a little closer (-2 degree C frost this morning)!!

I hadn't thought of changing anodes underwater. This would be possible for the volvo anodes that protect the propellor. The anode protecting the sail drive leg might be another matter. It requires the prop to be removed first and I can just see various critical parts dropping through my fingers and into the murky depths!
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Old 25-07-2010, 04:10   #13
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Hi Sweet As,
I'm with those who say pressure washing ablative paint is going to be OK, but we also tend to wipe the bottom each month or so (in fact whenever I get a chance) and if you do it reguarly then you'll find a divers mesh glove on its own is sufficient.
You are right on the ease of changing the prop end anode underwater - but equally correct not to try removing the prop and try the same on the leg anode. We carry a 5 litre 'pony' tank so I can do such jobs without having to surface.
But what you might wish to consider if your anodes go in a quicker cycle than the paint, is to consider hanging a wired anode over the side? We got used to this concept years back with a alloy boat and continued ever since wiring it back to the prop shaft or sail drive. Much easier to replace one of those when that is required.
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Old 25-07-2010, 05:44   #14
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Hi Sweet As,
I'm with those who say pressure washing ablative paint is going to be OK, but we also tend to wipe the bottom each month or so (in fact whenever I get a chance) and if you do it reguarly then you'll find a divers mesh glove on its own is sufficient.
Spent yesterday swimming around the hull giving her a gentle wipe over. Used one of those black scrubbing pads from the chandlers and very little paint came off. Checked the condition of the prop with my feet which I can just reach so don't even need to snorkel. Portsmouth Harbour water is a lovely green soup, so difficult to see more than a few inches anyway.

However the water is 18C, in the winter we would dry her out on a scrubbing grid, one of the nice things about big tides.

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Old 25-07-2010, 09:21   #15
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I hadn't thought of changing anodes underwater. This would be possible for the volvo anodes that protect the propellor. The anode protecting the sail drive leg might be another matter. It requires the prop to be removed first and I can just see various critical parts dropping through my fingers and into the murky depths!
For those of you sporting Yanmar saildrives, next haulout, consider installing this zinc, or have your diver do it now. You will never have to pull your prop to change the zinc again:

196440-02660 Yanmar Saildrive Split Ring Zinc Anode
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