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Coppercoat For DIDO

How to remove years of anti-fouling from the hull? Which new AF to use? We tried Coppercoat.

You all know about this: When your boat is out of the water you see what happened to your hull. And most likely you mention to yourself that it would be time to redo the antifouling. Probably you wonder whether some mending work will be enough or whether you should remove everything that has been put onto the hull over the years, scratch off everything until you can see the original gel coat again and make it all new.

You may then decide to mend it once again and do the major refit of the bottom next year, because we all know what kind of job this is.

Anyway, the time will come when no excuse will allow another "next year".

For Dido's bottom the end of the last season was the point where to make a fundamental decision: everything on the bottom had to be removed and something new had to be applied. Thus, this raised two questions. First: How to remove the old stuff both entirely and conveniently (if one might hope that there could be any kind of "convenience" in that sort of work). Second: What antifouling to put on Dido's hull then?

Old Anti-Fouling

Removing The Old Stuff

Sanding and scratching for many hours, if not days. This is the usual approach. And this is probably the major reason why most of us hate thinking about a new antifouling so much. Instead of starting sanding and scratching immediately I spent some hours with Google in the internet. This was my result:

I ordered some bottles of "Dilunett", a paint remover to remove any single-component coating (would not work with 2-components coatings), such as most AFs, and I ordered a "wet sandblasting device" that would work with my pressure washer. So it is not actual "sandblasting" but it is rather "wet blasting with some sand". Details below.


This paint remover is not too expensive and it is highly effective, I found out. If you want to use a paint remover you must make sure that it will not affect the GRP, especially the polyester resin of the gel coat. "Normal" paint removers contain chemicals that will aggressively soften the gel coat. Dilunett does not. Second reason why I used Dilunett of all paint removers: Most paint removers for boat hulls need to be covered with some sort of plastic foil for some hours in order not to dry out but do their job. Not so Dilunett, since it is solventfree.

What the hell is this Dilunett? Basically, it is a very simple substance that you even might make yourself: caustic soda resolved in water plus a thickener (otherwise it would run down the hull like water) plus an indicator color that indicated when the paint remover has done its job. Dilunett is a brand of OWATROL.

The paint remover has a consistency like jelly or jam. You apply it richly with a brush or so (the brush might vanish during the job if it is not resistant against caustic soda. Soft nylon brushes are appropriate).

Paint Remover Applied Paint Remover Applied 

Pressure Washing & Wet Sandblasting & Neutralizing

To coat the whole hull of Dido took me about one hour. Then the best phase starts: You wait until the paint remover changes its color to a brown tone, which will take a couple of hours. This indicator color shows that you can take the next step: Take the pressure washer and wash down the hull. If available use a rotating dirt blaster nozzle. This took me about another hour or so.

After that about 80 per cent of the old antifouling (at least 8 layers of old AF in one step!) were removed. Then I changed the rotating nozzle to a “wet sandblasting nozzle” (for 19.99 from the internet) and went over the hull again, but now with a mixture of sand and water, so to say. I used absolutely (!) dry quartz sand / silica sand from the Home Depot for 6.99 per 25 kg bag (50 lbs). I needed 4 bags for Dido. This wet sandblasting thing overwhelmed me. It is a quite dirty job, true, but it is so effective and so easy. It removes really any coating – BUT it does no harm to the gel coat (dry sandblasting does!). How do I know? Below all the layers of antifouling Dido has a coating of GelShield or something similar for osmosis protection. This is more or less an epoxy resin coating. Dilunett did not harm the GelShield coating, nor did wet sandblasting. If it did, you would easily see it as the GelShield coating is light gray.

Then there were still some small spots where I had to work after: around the skeg and the thru-hulls. Finally, I put 1 kg / 2 lbs. of citric acid (4.99 from the supermarket, there at the “How to bake a cake-department”) into a big bucket of water and washed down the hull again to securely neutralize the caustic soda of the paint remover.

karch1 karch2 karch3

karch4 wsb1 wsb2



So, removing of all old antifouling took me about 6 hours net work.

  • Practically, I started to apply the paint remover in the evening of the first day (1 hour). As it was October and not too warm. I could leave it on the hull until morning (usually you would wait not that long).
  • The other morning, I washed it down (1 hour).
  • Then the wet sandblasting (2 hours).
  • Then some spots where neither the paint remover nor the pressure washer did their job thoroughly (like the skeg, some parts of the rudder, the thru-hulls, and alike) (1.5 hours).
  • Then the final cleaning with citric acid from the supermarket to securely neutralize the caustic soda (0.5 hours).

As I did it the first time this way, I lost time by driving to the Home Depot several times. The first quartz sand that I had bought was to wet (but cheap, so take the more expensive one at the first time), I ran out of Dilunette, so I had to go to the drug store to get caustic soda and experiment with various thickeners, such as wallpaper glue or maize starch (glue worked well), go and get new brushes to apply the paint remover as the “natural bristle brushes” did not work and so on.

Anyway, no pain in the shoulders and the neck after hours of sanding. No red marks around the nose from the dust mask. No antifouling in the ears (well, I have to admit that it was quartz sand in my case, which was in my ears). Compared with the traditional way of removing coatings it was easy, fast and only little pain – and it was affordable (someone recommended dry ice blasting, even more effective, even less dirt, but prohibitively expensive. It would have been some 800-1,000 for Dido’s hull – only for removing the old stuff).

The New Antifouling

Over the winter Dido was on land, so the hull could thoroughly dry out. This was the time to make a decision on the new coating. The choices were:

  • “normal” hard antifouling for the displacement type hull of Dido, like the ordinary ones from the chandlery catalogues
  • “high performance” antifouling, like the ones with Teflon
  • “new age antifouling” based on Nano technology or “Lotos effect”
  • Epoxy plus copper powder, like CopperShield or CopperCoat

What I knew from the past (by experience), from the internet and from talks to other skippers was:

  • “Normal” antifouling means re-painting every two years, and after several years I’d end up where I already was: getting rid of the all those layers again. Hardly any improvement, thus.
  • Teflon-antifouling means: you have to stick to those AFs as nothing will stick to Teflon (apart from micro-organisms – ha-ha!). And still to be renewed every 2 to 3 years. For me a clear no-go.
  • “Nano-antifouling”. Though an interesting technology I did not want to be within the first generation (beta-tester, like for “some” software products). Maybe for the next boat.
  • CopperCoat/CopperShield: Bloody expensive and this “10 ys. worry-free, only pressure washing needed, if at all” sounds too good to be true. If it was so, everyone would use it. But hardly anyone does.

It was only last summer (it was clear to me then that something needed to be done to Dido’s hull) that I talked to some skippers on the Adriatic. Three of them had CopperCoat on their hulls, and they approved the statements of the advertisements. It should be even better than the ads promised.

Frankly speaking, I still was not sure. But a decision had to be made:

  • Normal AF: no improvement
  • Teflon-based: no-go
  • Nano: no one I know or ever talked to uses it.
  • CopperCoat: let’s give a try.


So, I ordered it. It was about EUR 380 / USD 530 for Dido’s hull. You know that ladies from the seventies are particular and delicate. I applied it – as the video and the manual says – within one day. The whole thing was done from 9 to 5.

Now after two months it is too early to say much. But from the past I know that on the sunny side of the hull usually after 2-3 weeks (if the boat does not move) one can see green stuff growing, although with proper antifouling this green stuff vanishes after some 10 nautical miles driving.

Right now there grows nothing at all on either side.

And probably you won’t believe: Dido is ½ knot faster than she was before.

CopperCoat CopperCoat CopperCoat

Update August 2013

We "coppercoated" DIDO in June 2011.

For our conditions (during the summer on the Mediterranean; April, May, June, September, October on the River Danube; November till March out of the water) Coppercoat works perfectly: no growth of anything on the hull, no wear of the antifouling.

Some of the "pessimists" still try to tell us that in our case no AF would be necessary at all (some time in fresh water / some time in salt water / out of the water for 5 months) or things like that. They are wrong of course. We have no davits, and the dinghy is in the water all the time during summer. After one month the hull of the dinghy is covered with algae and other stuff after three weeks in the Mediterranean. Also, DIDO's propeller (which is not painted with Coppercoat or any other AF) is covered with organisms etc.

May they talk. We are happy as we know that Coppercoat has worked for our needs so far.

Update October 2018

Still good. Coppercoat payed off well.

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