Stripping antifoul back to gelcoat for epoxying

[seanfoster]

I have seen a few other threads on this topic, and bought a Bosch stripper to help with this job.

Are there any methods of removing antifoul that anyone else has found effective? Any good paint stripper type products (non swindlery products!) that are good?

I'm planning on applying an epoxy coating to the bare gelcoat.

 

[oldsaltoz]

I have seen a few other threads on this topic, and bought a Bosch stripper to help with this job.

Are there any methods of removing antifoul that anyone else has found effective? Any good paint stripper type products (non swindlery products!) that are good?

I'm planning on applying an epoxy coating to the bare gelcoat.

Sorry but you will have to strip the gel coat off below the water line or the hull will take forever to dry.

And, it's very important that the hull is dry before and epoxy is applied or the moisture will be trapped and cause worse problems down the track.

I use a standard angle grinder with a 40 grit flexible disc designed to grind concrete.

One disk will do about 100 square metres, an average 30 footer can be done in a day after a long breakfast.

Sentential to protect yourself, full disposable overalls, Good quality mask, not the sill paper things,tape up zippers, wrists and ankles, full face shield and a beanie hat. Put a full ground sheet down to collect the rubbish and droppings.

If using a stripper check the blades have rounded corners before you start.

When you finish take moisture measurements, then wash down to remove any dust and clean up the now wet rubbish, not healthy if it blown around.

Depending on the weather and moisture content, it could take a very long time to dry out enough to seal with an epoxy.

When you are ready to apply the epoxy, remember that you can avoid sanding and washing between coats by applying wet on tacky.

Before you sand any cured epoxy it should have a running hose on it starting at the top and working down, rub with plastic kitchen scourers, you will know it's clean, the water will no longer form beads like seen on freshly polished car. This is quick and easy as long as you pay attention, it removes the residue left by the curing process.

If you sand with washing, you are only spreading the contamination.

Good luck.

 

[Phideaux]

I have seen a few other threads on this topic, and bought a Bosch stripper to help with this job.

Are there any methods of removing antifoul that anyone else has found effective? Any good paint stripper type products (non swindlery products!) that are good?

I'm planning on applying an epoxy coating to the bare gelcoat.

You don't say why you want to apply an epoxy coat?

If you're looking to treat "osmosis" or are applying the epoxy as a barrier coat, then you might want to read some of the literature. I would suggest for further information on “Osmosis” and its chemistry, you visit http://www.osmosisinfo.com/ and read what Bengt Blomberg has to say. Also, Fibreglass Boats by Hugo Du Plessis offers good advice.

Everything I've read makes me think that removing the gelcoat is a action of last resort.

 

[macd]

I have seen a few other threads on this topic, and bought a Bosch stripper to help with this job.

Are there any methods of removing antifoul that anyone else has found effective? Any good paint stripper type products (non swindlery products!) that are good?

I'm planning on applying an epoxy coating to the bare gelcoat.

Don't know what a Bosch stripper is, other than a pole-dancer from Berlin.

Best tool is a Bahco scraper or equivalent, about £10 from B&Q last time I looked. Laborious job, though.

If any of the antifoul needs softening, a strong caustic soda solution thickened with wallpaper past works as well as any of the proprietory products at a fraction of the cost. I'm no chemist but have read that Nitromors (active ingredient dichloromethane) is not kind to GRP.

Other posters points about why you're doing it are well-made.

 

[Chris_Robb]

It depends why you are doing this. Is it just for a protective coating? If so, get the hull slurry blasted, sand with 80 grit on an orbital (£24 from Screw fix) and then apply either International Gelshield2000, or Blakes.

The choice of which will be determined by when you want to do it - ie early in the season, or when it is guaranteed dry and warm, Gelshield for the former.

 

[mainmarine]

I have seen a few other threads on this topic, and bought a Bosch stripper to help with this job.

Are there any methods of removing antifoul that anyone else has found effective? Any good paint stripper type products (non swindlery products!) that are good?

I'm planning on applying an epoxy coating to the bare gelcoat.

Keep a good file with you and sharpen up the blade frequently. I did my 28 foot boat a couple of years ago using my old Bosch stripper and coated with epoxy after, it did not have any Osmosis but hopefully will give it another 30 years of life.

 

[pcatterall]

I think that the scraping is well covered. I've used various hand scrapers to good effect. I usually just do a couple of hours and then find another job fro a break!!
Concerning epoxy coating, I would urge you to read the excellent article by Nigel Clegg.
I tried to copy the link without success but its in my recent thread 'good and bad moisture'
There is a suggestion that (at some stages in the osmosis cycle) epoxy treatment is, at best, not effective. In newer hulls it seems possible to dry out and epoxy, in older hulls with no blistering epoxy treatment may not work and it is better to wait for blistering to show then give the hull the full treatment which involves removing the gell coat ( at least) removing all traces of the osmosis and then epoxying ( plus fill and fair) painting etc.
Good luck

 

[seanfoster]

Thanks for your replies!

To expand, the boat has been sitting in a garden for over 7 years so I think it will have dried out by now!!!

(I've just bought the boat and starting to refurbish it).

I have it on my driveway and I'm not planning on getting it in the water this year, so I'm going to spend a leisurely year getting it back to it's former glory.

There are no signs of osmosis whatsoever (and I've spent a long time going over the hull) but I was going to go with Joton Penguard, which is an epoxy primer. It is very reasonable compared with products such as gelshield, costing just under £35 for 5 litres which will be enough for 3 coats on my boat (Dufour 1800).

I'm really just wanting a bit of extra insurance against boatpox, finished with a vinyl barrier coat then antifoul (all Jotun products).

 

[mainmarine]

Thanks for your replies!

To expand, the boat has been sitting in a garden for over 7 years so I think it will have dried out by now!!!

(I've just bought the boat and starting to refurbish it).

I have it on my driveway and I'm not planning on getting it in the water this year, so I'm going to spend a leisurely year getting it back to it's former glory.

There are no signs of osmosis whatsoever (and I've spent a long time going over the hull) but I was going to go with Joton Penguard, which is an epoxy primer. It is very reasonable compared with products such as gelshield, costing just under £35 for 5 litres which will be enough for 3 coats on my boat (Dufour 1800).

I'm really just wanting a bit of extra insurance against boatpox, finished with a vinyl barrier coat then antifoul (all Jotun products).

I used this:Blakes Hempel GelProtect SFE200, the Jotun product you quoted is an epoxy primer.

 

[pcatterall]

Just made 'a start' on that 'Bengt Blomberg' article. Fascinating and good to read about a long term 'study' where the theory and examination of the physical results are well combined. 'Osmosis' occurs over the very long term and its physical manifestations only become apparent after years so there is lots of opportunity for unsubstatiated theories to develop.
In the nigel Cegg article I read that there were some 'claims' that hot vac appeared to improve the hulls 'rigidity' this seems supported by Blomburg when he says that 100% curing needs around 100 degrees. I am keen to read the whole article now...goodbye!!

 

[rob2]

It sounds as if you currently have the perfect opportunity to set the boat up for really low maintenance over the next few years. Once you get under the turn of the bilge to scrape, sand or paint, you'll discover why all sailors have bad backs!

I would suggest sand blasting to strip. It can be done with a Kaarcher pressure washer and bags of kiln dried sand. It's not particularly quick, but allows you to achieve a completely clean surface with an even, slightly abraded surface - perfectly keyed for further work. Epoxy barrier system next. Then whilst you're in rollering mode, apply Coppercoat, so you won't have to crawl around under there for another ten years. When you price it up, you'll find it's cheaper than antifouling each year for a decade, too (and it works better, for me).

Rob.

 

[oldsaltoz]

There are no signs of osmosis whatsoever (and I've spent a long time going over the hull) but I was going to go with Joton Penguard, which is an epoxy primer. It is very reasonable compared with products such as gelshield, costing just under £35 for 5 litres which will be enough for 3 coats on my boat (Dufour 1800).

I'm really just wanting a bit of extra insurance against boatpox, finished with a vinyl barrier coat then antifoul (all Jotun products).

If you want a really good look at the hull, use a torch light after dark, the darker the better, shine along the hull at a narrow angle, you well pick up a few old repairs too.

Also double check that the epoxy primer you plan to use is not just that, "a primer for epoxy" with no epoxy content of it's own to provide protection.

Not much sticks to epoxy, hence special primers and preparation are needed.

Good luck.

 

[mainmarine]

If you want a really good look at the hull, use a torch light after dark, the darker the better, shine along the hull at a narrow angle, you well pick up a few old repairs too.

Also double check that the epoxy primer you plan to use is not just that, "a primer for epoxy" with no epoxy content of it's own to provide protection.

Not much sticks to epoxy, hence special primers and preparation are needed.

Good luck.

It was my concern that the Jotun is only a primer, as you only expect to do it once it's worth paying the extra for proper epoxy coating.

 

[vyv_cox]

When I did mine I used the £10 scraper referred to above. It was rather laborious but taken steadily not too bad on a 35 ft boat. A bit of orbital sanding to finish off, then Gelshield 200. Alternating coats of grey and green, five in all, then a coat of hard scrubbable A/F while the final Gelshield coat was still tacky.

I wouldn't try to save a few pounds by using a cheap substitute. This isn't the kind of job you want to do again when the cheap one doesn't work.

 

[seanfoster]

Thanks, I may have mistakenly thought that Penguard was a similar sort of product to the others mentioned - Shepherds website says

"Penguard HB is a high build, two-pack pure epoxy primer. It has excellent adhesion to grp and should be used when painting over the gelcoat for the first time. It is extremely water resistant and will help prevent osmosis. "

So not a complete protection system by the looks of it.

 

[yacht surveyor]

Be careful to ensure that all the requirements of the manufacture of the paint are followed when preparing the hull. Badly applied epoxy will, in time, cause you more problems than you currently have.

I have come across blisters the size of fried eggs between epoxy coatings and the original gelcoat during surveys. This has inevitably been an owner applied "osmosis repair". When the blisters are opened up, the gelcoat below has been fine, with no blisters or defects where the epoxy layer blisters had been.

Incidentally this is also true of badly prepared applications of copper coat type finishes as they are epoxy based. Note that the problem is the preparation - not the copper coat itself.

The boat may have been out the water for some years, but either hire/buy a moisture meter or get someone to check it out for you before you apply anything. You don't want it falling off in the near future.

If there is no current problem, then I personally would leave it alone.

The article on osmosis mentioned previously can be found at this location.
Have a look at page 12 for recommendations for when to repair. Also take note of his advice for treatment preparation.

Nigel also hires Tramex Skipper meters see page 8 of his catalogue.
Martin

 

[lw395]

Different scrapers work better on different antifouling in different states of dampness and thickness.
Sometimes a Harris Tungsten carbide one from screwfix is quick, you can cut planer blades in half with a dremel for cheaper refills!
There is a version /different make with a vacuum attachment, worth thinking about?

Other times I've found a wide wood chisel to be quicker and easier.
Other times again, really coarse wet and dry, wet can be your best friend.

I just try different tools to see what goes well.
Never tried the Bosch thingy, I might get one if the manual methods were turning out slow.

Slurry blasting is worth thinking about too, if DIY is taking too long, I was amazed when I saw how well this did a wooden boat.

 

[Chrissie]

Anti foul is nasty stuff, it is a nightmare to scrape off, you need proper respiratory protection, I didnt always wear mine, took months for the cough to go
There are a couple of liquid removers available, expensive but they do work. Paint stripper, nitromors etc. dont work.

If you are using gel shield, at least seven coats, this will make the hull slightly more waterproof, there are time limits and temperature ranges to abide by. Make sure you treat any problems on the hull before you coat it. Gel shield by international, can be googled, there are full instructions and advice on their website.
There are other epoxy coatings but I have only used Gel shield, and found it very good.

 

[Cantata]

It depends why you are doing this. Is it just for a protective coating? If so, get the hull slurry blasted, sand with 80 grit on an orbital (£24 from Screw fix) and then apply either International Gelshield2000, or Blakes.
The choice of which will be determined by when you want to do it - ie early in the season, or when it is guaranteed dry and warm, Gelshield for the former.

At the risk of a slight thread drift -
I have a 13-year-old Moody, which spends most winters out on the hard.
I have just had the antifoul cleaned off back to the gelcoat (Farrow System job).
The type has no history of osmosis problems, nor is there any sign of a problem on mine.
Should I bother with the time and expense of applying Gelshield or similar, or just slap antifoul primer on it and go from there?

 

[BabaYaga]

Beside the hand scrapers and the chemical paint strippers there are also the rotating scrapers/blasters:

http://www.cirrus-systems.co.uk/index.php/Perago-Rotating-Blaster.html

I have used the scraper model on two occasions to remove layers of old antifoul from the (epoxied) hull. Takes some time, but the result is neat.

However, when I was to apply the epoxy 15 years ago I had the hull sand blasted. This would be my first recommendation, as it will give a very good surface for further treatment, like others have said. An additional benefit is that the blasting will knock open any small cavities beneath the gelcoat surface. They should be filled before the epoxy barrier goes on.