Anti foul grit blast removal, your experiences welcome

[Greg01]

Has any body used a anti foul grit blast removal service (wet and dry), if so I would like to hear about it.

 

[DAKA]

I had a trial section done on my old corniche of a gentle soda blast, but decided the way forward was with an Electric chisel, it produced shiny gel coat

 

[Questor]

Hi Greg

I have on the Targa. It beats doing it by hand, but not sure if I'd do it again though. Needed to get the gel man in afterwards to do (quite) a bit of touching up.

So where's the Thunderhawk? Been listening out for it, but so far no joy.

R

 

[KevB]

I had mine done by symblast. First class results but it will show up any imperfections in your gelcoat.

 

[oldsaltoz]

Soda or soft blasting is only as good as the bloke holding it, so be warned.

Results will vary.

 

[DAKA]

I had mine done but it will show up any imperfections in your gelcoat.

The 'imperfections' you mention are not really imperfections, they are naturally occurring bubbles of air which are produced during mixing , as the gel cures the bubbles are trapped , gel coat is designed to be thick enough for these naturally occurring bubbles to remain water tight for the life expectancy of the boat , as long as the hull is allowed to dry for a month every other year the bubbles will be just fine as long as not disturbed.

Reducing the thickness of the gel by any means including sanding, over polishing and slurry blasting will expose the naturally occurring bubbles so they become 'imperfections' pin prick holes that need filling, over painting with epoxy does not work as the epoxy heats up so does the air in the pin prick hole and forces a new pin prick hole in the epoxy.

Some modern boat building techniques reduce the bubbles by mixing the gel coat in a vacuum, the first Manufacturer to adopt this technique was Bayliner , the only other manufacture I am aware of is Valiant but I expect there could be more that have adopted this in the last few years but they are unlikely to need a build up of antifoul removing yet.

 

[Questor]

We too had the bubbling issue. Like Kevin, we used Symblast, and was very pleased with the end result, but did not expect all the pinholes, and was kinda worried when I first saw them.

Mr Symblast was very keen to epoxy the hull, but I wasn't, hence refilling all the holes with gelcoat.

The blasting left a good finish / key for re-antifouling

 

[volvopaul]

Id use the ice blast system, its very gentle, doesnt damage paint or gel coat and there is very little mess to clear up afterwards, all compareable on price to other systems, it will make outdrives look like new, and you dont have to mask off the bellows etc.

 

[DIW]

Anti-foul grit blast removal

I haven't used it but the next Boat to me on the hard was done by Symblast which resulted in my entire boat and interior being covered in fine gritty dust which we were still removing 12 months later, not a happy Bunny.

 

[KevB]

I haven't used it but the next Boat to me on the hard was done by Symblast which resulted in my entire boat and interior being covered in fine gritty dust which we were still removing 12 months later, not a happy Bunny.

Interesting cause they used soda crystals when they did mine so nothing left except the old antifoul which they cleaned up and took away with them.

 

[DIW]

Anti-foul grit blast removal

Interesting cause they used soda crystals when they did mine so nothing left except the old antifoul which they cleaned up and took away with them.

This occurred in 2006, so they may well have changed their system and materials since then !

 

[Elessar]

Has any body used a anti foul grit blast removal service (wet and dry), if so I would like to hear about it.

cant give customer names but happy to show you work we've done if you're nearby?

 

[symblastpaul]

Concerning the comment regarding the mess left by Symblast-Personally I have no Knowledge of your case but will state that we do our utmost to contain the blasting debris by very carefully tenting in and the use of a clamping method that stops debris escaping from the top of the tent, in addition I always wash down with a decent high volume pressure washer (15 litres per min) and will usually wash down nearby vessels to make damn sure no one has a reason to moan, on leaving a premises I or my staff on the rare occasions when I am not there will get a yard manager to inspect the site before we leave-this also is good as they can see we do a good job and are then happy to recommend us in future. If someone does have a gripe it is best to contact myself as I can then rectify if we genuinely are at fault.
Incidentally my yacht in Southampton gets covered in black dust which I need to wash off quite regularly-I just get on and do it you know.

 

[Scarron]

Antifoul removal co. blasted mine recently, did an excellent job, can't speak highly enuf of them. I still haven't got around to painting the bottom yet so if you are passing Southampton you would be welcome to have a look at the finish they achieved - the boat is in my drive, six feet from the house and although a messy process they contained it well and cleaned up properly afterwards.
A happy customer.

Paul.

 

[oldgit]

Interested !

Just out of interest, why would you go to the trouble of de pinholing hull when it will never be seen under a thick coat of A/F.?

 

[Questor]

Just out of interest, why would you go to the trouble of de pinholing hull when it will never be seen under a thick coat of A/F.?

In our case, mainly as I wanted perfection, and wouldn't have been content with myself in not doing it. One or two holes were missed, and even now after 4 coats of antifoul, you can indeed still see them.

 

[DAKA]

Just out of interest, why would you go to the trouble of de pinholing hull when it will never be seen under a thick coat of A/F.?

The fibreglass needs to be kept dry, it is slightly porous.
The gel coat is the water proof bit.

The gel coat has to be kept as thin as possible or it will crack.

The manufacturers make the gel as thin as possible but take into account the bubbles in the gel.

If you reduce the gel thickness and expose the bubble holes the gel will no longer be thick enough to be water proof, over 18 month to 36 months water will seep into the fibreglass and you will get osmosis.

 

[oldgit]

The fibreglass needs to be kept dry, it is slightly porous.
The gel coat is the water proof bit.

The gel coat has to be kept as thin as possible or it will crack.

The manufacturers make the gel as thin as possible but take into account the bubbles in the gel.

If you reduce the gel thickness and expose the bubble holes the gel will no longer be thick enough to be water proof, over 18 month to 36 months water will seep into the fibreglass and you will get osmosis.

Was always under the impression that the gel coat is make the boat look pretty and for no other reason.
Other wise all those military boats with no gel gelcoat at all would have developed Ossymosis and sunk by now ?

 

[DAKA]

The submarines did indeed suffer with very serious osmosis...........and did frequently SINK !

Alright the last bit was a bit tongue in check but it is true osmosis did used to be common on the subs, I dont know what they are made of now and I have no idea if they got around the problem.

 

[symblastpaul]

Gel Coat is considered a semi permeable membrane, it as applied as a decorative finish and though some manufacturers do not use below the waterline (preferring to use pure un-tainted by pigment resin-which is more waterproof) it was found that the opaqueness of ungelcoated hulls (below w/l) was disconcerting, especially when in your berth you could not only hear the waves lapping at the hull but see them as well!
With the development of better resins used in the laminating process along with better gelcoats osmosis is not the concern of today's manufacturer as it won't happen within the warrantee period-or at least it shouldn't.