Wet blasting the hull

[superheat6k]

Has anyone direct experience of wet blasting their hull to remove old AF using sand, soda or ground glass ?

Was it effective ?

Is gel coat damage likely ? I don't want to otherwise damage the Gel beyond surface roughening / keying.

How much and what media did you use ?

Does the media draw easily into the blasting kits easily or does it forever clog up ?

Thanks.

 

[ianj99]

My 36' steel hull was done professionally with wet glass beads to remove 30years of AF remnants.

Once the operator had discovered the optimum distance / pressure etc, he was able to do it without also taking off the epoxy. (of course most of his customers' probably owned grp boats so he'd not have had any issues with them).

Its not a job I'd want to attempt myself - it took the expert two days and made a hell of a mess.

 

[Seajet]

Yes, very messy so check your club or yard rules about collecting waste.

Even more importantly, only use recognised people who can give checkable references.

A few years ago 6 large boats at my club were approached by a hull blasting outfit and clubbed together to have it done.

The idiot/s blasted off their gelcoats as well despite assuring them he wouldn't, result a lost season for the boats and lots of expense, I don't know how it worked out in the end legally but one owner was so hacked off he gave up boat ownership.

Get satisfied customers to call and ask around !

 

[Daydream believer]

I had my boat sand blasted & the yard had it moved to an area where the mess would not cause an issue. I was in attendance throughout the work & the chap was extremely careful not to damage the gel coat. In the end I had to spend 6 hours (31 ft fin keeled hull) sanding off some antifoul in thin areas where it had not been fully removed as he was loathe to go further. It was not difficult & i took my time so i ended up with a finish that looked like a sheet of A4 paper.
It took me a further 6-8 hours to remove the 2 inch band around the waterline, ( very thick as I always did extra coats here) as he did not want to damage anything above that level so kept clear.
Within an hour of finishing I primed the keel with epoxy primer. I applied copper coat to the hull later, when the temperature was higher.

I can see that if someone who was not skilfull might mess this up but I was lucky & was in attendance anyway.

In 1999 I had my wooden clinker built Stella sand blasted inside & outside (I had stripped it to hull & deck beams first) & some holes were blown right through the hull where there was rot. It exposed wood around the roves because the wood around them was rotten & i could push them in & out.
There were some planks that had sprung at the bow that had been plugged with pitch. The blasting blew the pitch out so I was easily able to re fit the planks correctly. Inside the hull it removed all the paint between every rib, It blew out the rot in the transom & a couple of knees saving loads of work. It also exposed places where the original planks had been fitted by Tucker Brown with worm holes in them. Any filler applied in the life of the boat was removed.
I recommend doing it with an old wooden boat, as it makes a brilliant key for the epoxy sheathing inside & out plus exposes all the problem areas. It enabled me to dry the boat out really well & I got it down to below 10/11 % W/C

 

[Lightwave395]

Have my 12M sailboat done in Cowes last November by these guys: http://www.agrovesfabrication.co.uk/anti-foul-removal/
They did a really good job a sensible price, would certainly recommend them, they were also clean enough that they are allowed in to do it on the new fancy brick paved yard at Cowes Yacht Haven !

 

[ghostlymoron]

My Mirage was dry blasted after an accident. The work was done by Firmhelm at Pwllheli and the blasting carried out by their usual subcontractor. It was described as 'light blasting' and removed all the antifouling and left a mildly abraded surface for repainting. It's very important to use an experienced contractor as serious damage can be caused by too heavy an approach.

 

[Bandit]

I have an Aquastar 48 2001 vintage that has never been blasted.

I have had the boat since 2008, god knows what the antifouling was before me. It wa coming off in flakes back to a Gelshield type coating. I bit the bullet and had it slurry blasted with fine crushed glass back to the original Gelshield type coatings the waterline was hand finished to retain the boot topping and minor filling of any voids was undertaken.

After wet blasting with fine crushed glass the Gelshield type coating was damaged , on a hull with no Gelshield type coating the finish feels like emulsion paint, a good operative can leave the gel coat undamaged although voids will show if there are any.

The hull was in a good condition except around the bow thruster.

I considered Coppercoat but decided on five coats of International Gelshield followed by two coats of International Micron 350 a hard antifouling.

The work was undertaken by the Marine & General Boatyard in Guernsey, pictures are on their Facebook page.