Sand Blasting hull

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rays

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Last February, when we anti fouled, we had a lot of old antifouling flaking off and decided that, next time it would all have to come off. The boat is 10 years old. Does anyone have experience of scraping the old stuff off versus sandblasting? I've been quoted £380 to sand blast the boat and, whilst this is a lot of cash, I'm not sure that SWMBO and I can handle weeks in the cold with a hand scraper!

Is sand blasting safe? Can it go too deep? apparently, our hull has been copper-coated at some stage and I presume it would make sense to leave this layer on. I think someone told me that to coppercoat the hull it had to be epoxied first? Also, the keel was epoxied from new apparently, and isn't flaky so i suppose this doesn't need stripping?
Lot's of questions here. Hope someone can advise.
Also, looking for a recommendation for sandblasting on the Orwell or close. Had a quote from Air Blast . Can anyone recommend.

Thanks .
CD
 
I had my hull blasted a couple of years ago with one of the modern systems (the one using hot water). Worth absolutely every penny both for the end result and for the hours of grovelling under the boat saved.

And I'm not renowned for spending money normally doing all my own work on the boat. But having scraped one in the past I would never do so again.
 
SWMBO spent a winter under one of our boats attacking the thing with scrapers and chemicals. Just after she'd cleaned the last bit off some Smart Arse came by and said "Coo! My chum would have blasted that for £120 cash". She nearly killed him!
 
I've scraped our hull back to the white GRP and I have to say that it was a life-changing experience; I don't think I'll be doing that again. Having said that when completed it was mega satisfying and without doubt is kinder on the hull than the sandblasting methodology. I've looked at hulls that have been blasted and there is definetely an "eggshell" finish left, it does take the top coat of gel coat off. I believe that the soda blasting more modern techniques are gentler than sand blasting. My boat had been epoxy coated when new and by manual scraping I managed to not damage the epoxy coat which I don't believe is possible if snad blasting. Like yours, my boat was ten years old when I did it. The experience leaves you neurotic about the cleaning and application of subsequent antifoul coats - you really don't want it flaking again! I also now only apply one coat annually so as to slow the build up of paint residue. Whilst I had the hull clean I added five coats of Gelshield to add further osmosis protection.

As regards Coppercoat; the copper is suspended in an epoxy so when one applies Coppercoat one is also applying epoxy ( i think, I'm no expert).
rob
 
I wish I could remember the name of the system used on my boat (it was well publicised at the time) but it certainly was sensitive. It left a matt finish but thats what you want if you are going to epoxy - but it could be used gently enough to run over plastics or paint without damage
 
Slurry blasting or the later soda blasting is much kinder on the hull than dry-sand blasting.
If the hull hasn't been blasted before - be prepared for voids and pits to appear where it cuts out 'dry' laminate / air pockets.
If you have coppercoat or epoxy - be prepared for that to be penetrated if not removed.

The process is a good one to do on boats that tend to build up layers over years ... even with eroding AF you still get layers forming that left become extremely difficult to deal with by hand.
Funny thing is it's the one area that Bilge Keel boat owners have disadvantage .... that section between keels is a right so & so to deal with ... Fin / long keelers smile ..... so getting a blaster in ... not a bad idea.

One proviso ? make sure the guy is experienced and you can get recc'dations from other boats ... nothing worse than an experienced blaster who's used to cleaning up wrought iron work ! GRP won't take it !
 
Rob - you are an expert. Coppercoat is an epoxy with a suspension of fine, pure copper powder.(These copper coatings occasionally fail because the epoxy wasn't applied correctly, but when applied as per manfacturers recommendations, they can be superb.)

Cambridgedon - blasting IS safe, in the right hands. I had my 40ft ferro cement boat grit blasted to remove the antifoul, but the blaster stopped early as he noticed the boat had an alkyd rubber primer, which absorbed the grit blast whilst 'scalloping' the cement each side.

I finished the job with a scaper, so sympathise with anyone who wants to avoid this full-body workout in the depths of winter. Believe me, a professional marine blast is money well spent, and the price quoted is about right.

You need a marine expert, not the bloke who can do it for £120. Yes, boats can be damaged by over-enthusiastic blasting, but what careful blasting does is:

Remove every trace of antifouling, however thick it is.

Blast away any barnacles, and clean up the metal on skin fittings and rudder fixings.

Leave the surface of the gelcoat (or coppercoat epoxy) with a matt surface absolutely ideal as a 'key' for any further treatments.

Occasionally knock off the tops of osmotic blisters!

Here's a tip. If you decide to have it done, put a notice in your local yacht club to see if anyone else would like to have their hulls blasted at the same time. A lot of the cost for the blaster is in the transport, so if he can blast several hulls in one location, his costs will come down, and he will show his appreciation with a group discount.

Hope this helps. It's just too cold for hand-scraping!

Incidentally, I made a short film of the blasting process which you can find on YouTtube. No link, I'm afraid ( I'm still a bit of a technophobe) but you can find it under a search for 'How to prevent osmosis blisters on your yacht hull' or under 'Practical Boat Owner.' You'll also find a couple of experimental motorboat tests there as well.

Blast - don't scrape...unless you need the exercise!

Jake
 
Spend £25 or so on a couple of long handled scrapers with good quality carbide blades and set aside a weekend for scraping. You will then be able to take SWMBO for a slap up meal, with plenty of change, and you will still have the scrapers to use again in 10 years time. N.B. Recently saw a nearby 36 footer 90% finish scraped in a day by one person by this means.
PS you won't notice the cold!
 
[ QUOTE ]
Spend £25 or so on a couple of long handled scrapers with good quality carbide blades and set aside a weekend for scraping. You will then be able to take SWMBO for a slap up meal, with plenty of change, and you will still have the scrapers to use again in 10 years time. N.B. Recently saw a nearby 36 footer 90% finish scraped in a day by one person by this means.
PS you won't notice the cold!

[/ QUOTE ]

Fancy doing my bilge keeler ? Only 25ft ... but a right pig to get under .....
 
Soda blasting is the way to go, pay a professional with some recommendations behind him - not someone hot from the local hire shop with a blaster.
They need to take on the responsibility to operate under 'elfin safety regs' and deal with the waste according to local bye laws and not 'custom & practice'
Try and let the hull 'dry' for a few weeks before anything happens, expect to be putting a new epoxy coat on the hull - and let that wait before the anti foul - it's worth it

We remain disappointed with the performance of Copper Coat - even though we went through all this preparation. If I knew then etc, then I'd have gone for anti foul and been happier with the results and probably better off.
 
We're scraping at the moment, and I'll not rush to do it again!

My new (to me) boat had a very patchwork effect of peeling antifoul. "This will be easy" thought I, and so it was, for the first 30% of the area. It then got harder as we attached the areas which had obvioulsy been previously scraped.

I invested in a small electric scraper £22 delivered from Ebay (a copy of the Bosch item which has been recommended here previously) and it has been marvellous. BUt I'd still go for the blasting.

As others have suggested, have it done professionally by someone who comes recommended. I looked at a Najad recently that had had to have a full hull treatment due to the blaster (I think that's how the broker described him) being a bit over-zealous.

Next time I'm getting blasted.

Good luck.
 
I had mine cleaned using the Farrow system link

I mainly chose it because my keel was in a bad way and I thought I might as well get the hull cleaned at the same time. I paid £450 for a 33 footer.

I would try and get a recommendation of an operator from satisfied owners as the gel coat can be severely damaged by any high pressure cleaning method.

Coppercoat is an epoxy and will be hard to remove manually. You'd also better check with your antifoul manufacturer whether it can be painted over Coppercoat - this might be why your existing antifoul is flaking off?

If you're thinking of applying Coppercoat, do it in warm weather in a shed or a 'tent'. Presently British 'summers' can't be relied on to provide the correct conditions for application let alone winters!

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DSC_1928.jpg
 
Just had mine slurry blasted hull and dry blasted keel done at Foxes; very pleased with the results. Hull and keel need different methods. They VC tarred the keel & I spent about 30mins hand sanding the odd bit that needed it. Hull epoxy left undamaged. Straight on with the primer then antifoul. Done in a few hours over a couple of weeks.

It helped being out for another job......

In contrast friends are doing their boats by hand; 36' boat, 2 people working hard, 3 days to scrape off (and really not huge amounts to come off) - so if you (alone) have 6-7 spare days then go for it !!!

You pays your money and takes your choice /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif
 
Thats the name! Mine was done by the Farrow system but unlike the piccies shown , mine was immaculately clean afterwards with no trace of the vinyl undercoat the previous owner had used yet no excessive removal of gel coat.

Sadly I messed up a bit when I applied the epoxy. Working single handed I didnt have time to use a brush to smooth out so I've ended up with the classic hammerite type finish. I tell people that it works like dimples in a golf ball and makes the boat sail faster and closer to the wind.
 
[ QUOTE ]
Thats the name! Mine was done by the Farrow system but unlike the piccies shown , mine was immaculately clean afterwards with no trace of the vinyl undercoat the previous owner had used yet no excessive removal of gel coat.

Sadly I messed up a bit when I applied the epoxy. Working single handed I didnt have time to use a brush to smooth out so I've ended up with the classic hammerite type finish. I tell people that it works like dimples in a golf ball and makes the boat sail faster and closer to the wind.

[/ QUOTE ]

Turbulated flow they call it .... true ! As against Laminar flow !
 
I have just bought a Bosch PSE180E scraper following the previous discussion on this a few weeks ago. I spent about 1/2 an hour trying it out on Sunday morning. In that time I cleared what must have been getting on towards a square metre of old antifoul. At that rate its not going to take long to completely strip my 25 footer. So far I think it is £70 well spent.
 
Lots of good advice, including the bit about the dimpled surface going faster - isn't that what they say about dolphins? I've tried most methods and the most effective DIY method was a slurry blaster attachment for a Kaarcher pressure washer. It isn't anything like as powerful as the professional job, so it doesn't need the same level of skill. with a bit of decent weather I reckon you could do most cruisers comfortably in a weekend.

It can't be used in damp conditions as the sand must be of the kiln dried variety to prevent blockages in the venturi tube. You'll need to dress up in protective clothing as otherwise you'll get a facial peel to be proud of, so warmth isn't a requirement - in fact, a cold bright day would be great! We found it useful to buy ten bags of sand a time from B&Q on a Thursday (pensioners discount day) and check each one really is dry. It gives you an excuse to take a break each time you run out, too. Make sure you oput a tarp under the boat to collect the sand or you'll be treading it everywhere during the winter refit!

Lovely finish, though. a lightly abraded surface which hadn't broken through the first layer of epoxy at all.

Rob.
 
The operator told me the mottling was staining of the gel coat and he couldn't remove it without damaging it. The less said about Westerly gel coats the better..
 
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