DIY Antifouling removal

AntarcticPilot

AntarcticPilot

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Joined
4 May 2007
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Location
Cambridge, UK
www.cooperandyau.co.uk
Some of this has been covered on another thread (http://www.ybw.com/forums/showthrea...-off-boats-antifouling-bilges-etc-CO2-Dry-Ice), but a dedicated thread might flush out solutions that were off-topic.

I need to remove the antifouling from Capricious in order to apply Coppercoat. I want to do it myself; cost is a factor, and I am (fairly) time rich at the moment. However, I don't want to spend weeks doing it; I might have enough time, but my sanity would suffer along with my arm muscles from working upwards.

I am considering wet blasting; that seems to be fairly benign, and I can hire equipment for around £200. Dry blasting is out on both environmental and lack of skill considerations, unless someone can convince me otherwise - the equipment hire would be about the same.

I've done manual scraping - it is too slow, and in any case I'd be woried about the quality of the result.

Any other suggestions, or advice about abrasive media or whatever for use with a wet-blasting solution?
 
I had mine done for me a few years ago, by wet sand blasting. The person with the equipment had just got it, and so I volunteered to be a (cheap) guinea pig. It did a good job. Now every winter, I thoroughly wet sand the bottom, to avoid any build-up. I use a pad device with a universal joint, on a long handle, meant primarily for sanding ceilings. I use abrasive gauze which is excellent.
Anyway, back on topic, it may depend on where your boat is. Many boat yards will only allow blasting-off to be done in a particular screened area, because of the potential for damage to other boats. It is often a requirement that all removed material is collected and properly disposed of. If your boat has to be moved to let you do the blasting, it may involve extra cost.
 
I admire your nerve but having seen it being done by someone experienced there is absolutely no way I would try DIY - particularly on my own boat!
 
I know you have already tried manual scraping as taking too long and not giving a clean enough finish, but that is the best, and cheapest method I have found. A couple of winters ago we scraped the a/f off my j-92 in one morning
We used one Sandvik scraper and four blokes. One person would scrape for as long as they could, generally about ten minutes, then pass the scraper on while he rested. This carried on until the job was done. In rotation we had 3 managers and one worker. One was a council worker so felt right at home. We got the whole boat done on about 4 hours. If we had 4 scrapers I don't think we would have finished much quicker as you simply cannot scrape for more than 10 minutes.

You do have to have the right scraper.
 
Air driven DA sander with mesh abrasive pads (scotchbright or floor sander pads) stream of water from a hose to keep the area wet and away you go
 
vyv_cox said:
In the past we have found Dilunett to be pretty effective, followed by scraping while it is still fairly soft. I'm not sure if the product remains as it was since changes to regulations about methylene chloride but the promotional material on it seems persuasive. http://www.owatrol.com/index.php?langue=en&page=produits-dilunett
Click to expand...

The MSDS at http://www.boatpaint.co.uk/datasheets/deks_olje/Dilunet Gel 16-6-04.pdf shows the only active ingredient as caustic soda.
I've never tried Dilunet but have tried caustic soda and had little success. Must depend which antifoul I suppose.
Methylene chloride attacks gel coat. Yes, I learned the hard way.
 
First of all, thanks for the suggestions - please keep them rolling in, as I won't be doing this until the weather improves - probably in May!

A couple of clarifications.
  1. The work-force is myself and my wife; I am not big and she is tiny. We are not old, but I am past 60! Anything requiring significant physical effort is therefore out - that's why I am considering blasting techniques. Scraping abd sanding aren't really feasible; we'd be finished off before the job was done!
  2. Our time will be limited - we travel 400 miles to the boat, and my wife works full-time. So there isn't an option of chipping away at it a bit at a time; the job will have to be done over one or two days.
  3. The resulting surface needs to be ready for application of Coppercoat; lightly abraded is ideal. The keel needs to be clean, bright metal ready for application of zinc-rich epoxy primer.

So far, Dilunett looks interesting; I note that the manufacturer recommends using a pressure washer to remove the loosened paint. For a 31' boat, 5 litres looks about right; anyone care to comment on that? Also, I note that the stuff remains active for up to 12 hours, and that Owatrol recommend that it be given plenty of time to work, which might explain people's differing experiences. Despite the expense, it would actually be cheaper than hiring the wet blasting system. However, there's still the problem of getting any rust etc. off the iron keel, and I want to do as good a job as possible to ensure the Coppercoat is well adhered and future rusting inhibited as far as possible.

Someone mentioned that the blasting system might be a bit vicious, with the potential to remove gel-coat. I'd understood that blasting with soda was relatively benign, and would not harm the gel-coat. Can anyone reconcile this? I'd only expect to use grit on the keel, where it would satify the requirements of removing rust and scale.

I am, of course, already talking to the marina about environmental and pollution control aspects of the work. These may limit the options for DIY, though I note that professional blasting does take place at the marina.
 
Troubadour said:
The MSDS at http://www.boatpaint.co.uk/datasheets/deks_olje/Dilunet Gel 16-6-04.pdf shows the only active ingredient as caustic soda.
I've never tried Dilunet but have tried caustic soda and had little success. Must depend which antifoul I suppose.
Methylene chloride attacks gel coat. Yes, I learned the hard way.
Click to expand...

I used caustic soda mixed with wallpaper paste. I left the paste on for about 30 minutes. It seemed to work quite well. It softened the antifouling enabling it to be scraped off quite easily with no damage to the epoxy coating underneath. Much easier than dry scraping.
 
They are retoring the Steam Launch Osprey at the Steam Boat Museum. They stripped it all back to bare wood by dry blasting it with crushed walnut shells. This took all the coatings off the wood without damaging the wood itself.
 
I am currently scraping several layers of old AF off the hull of my steel boat - I don't want to get back to bare metal as there is no corrosion and the integrity of the base paint is sound - so grit / sand blasting is out.

I set to with a manual scraper (tungsten blade) and found it hard and slow going. A friend suggested a mechanical scraper in the form of a multi-tool device. Bosch and others do them but I got one from Aldi for £29.99 plus an extra £10 for replacement blades and fittings. It has speeded the process up immeasurably and combined with a random orbital sander it is getting me where I need to be.
 
Got to do this job myself, has anyone tried the sandblater attachment which Karcher sell. It uses kiln dried sand from the likes of B&Q can see it being powerful enough to damage the gelcoat.
 
tyce said:
Got to do this job myself, has anyone tried the sandblater attachment which Karcher sell. It uses kiln dried sand from the likes of B&Q can see it being powerful enough to damage the gelcoat.
Click to expand...

I wondered about this, as well. I asked Ewan of AMC, the Coppercoat people, and he reckoned it wasn't suitable for large areas - OK for a small area, but not up to a large project. But I would be interested if anyone has experience of one.
 
We want to do much the same as the OP but had been discouraged by the immensity of the task (large amounts of money) or large amounts of effort. Walnut shell offers a whole new concept and presumably there would be other granules that might be better still - the trouble being to find out before you strip all the gel coat and any filler off! I know olive stones were used, but I think, whole, in a similar application and coconut shell must be in vast supply (it used to be imported to the UK to make activated carbon).

I thought I had read that it was possible to add an attachment to a 'domestic' high pressure pump and hose to allow introduction of an abrasive medium - but had not actually confirmed this. If this were possible then introduction of whatever was cheaply available and that worked might be possible. Pool salt and soda are options but sand, garnet, crushed glass and similar seem too aggressive.

Jonathan
 
I paid £250-00 cash to have the boat sand blasted. Cannot see the advantage of scraping by hand
By the way - forget coppercoat it is hopeless
I have 2 boats one done in Copper coat & one in Copper Tec
the Copper tec performs marginally better. I say "marginal" but it is better
the only advantage of coppercoat over normal antifoul is that you only have to jet wash it & the saving in cost of antifoul (along with associated labour)will cover the cost of the obligatory mid season haul out & scrub
Coupled with the winter layup as well it means 2 washes but no personal labour
 
1. This is the one time where it pays to have been less than perfect in the application of previous coats of antifoul, but I suspect that Antarticpilot has a habit of not taking short-cuts.
2. I don't doubt Daydream believer's experience with Coppercoat but it is at variance with that of the vast majority of C'coat users, including this one.
3. Wet blasting, whilst far gentler than dry-blasting, can be expected to leave some degree of gelcoat pitting which will need filling and fairing. This is not too onerous, since the general surface profile will be retained, but it is an extra task. If necessary, epoxy with micro-balloons is much easier to sand than microfibres.
4. If hand-scraping, I'd be inclined to use a caustic soda/wallpaper paste mix only for the most stubborn areas. Depending on the thickness of existing antifoul, more than one application may be required.
 
Two 1" chisels used in rotation plus an old fashioned grinding wheel.
Turn the chisel in use over and hold with forefinger under the blade and thumb over the blade. This, coupled with a fairly "square" edge to the chisel blade will rip off the AF in flakes quicker than you can say "bobs etc".
More time is spent sharpening the chisels than ripping, hence the need for two chisels. If one operator is fairly weak then he/she can be the dedicated sharpener.
I have removed about half a sguare metre in no more than 10 minutes using this method.
 
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