Blasting and blacking

[ROBDEN]

Morning.

 

Live-a-board on a 57ft nb that needs blacking this year.

Can go anywhere to get it done.

 

The sides are looking a bit scabby so thinking of having it

grit/sand or whatever blasted.

 

Does it get inside the boat and how long does the blasting take approx’?

 

Any recommendations as to where and the cost please?

 

Any advice will be much appreciated.

 

Rob….

[b0atman]

Debdale do a good job but I a year later have still not received any paperwork ?

[blackrose]

There's no real point paying for expensive grit blasting if you're just going to repaint it with bitumen based blacking. I'm about to have my boat grit blasted to get all the bitumen off so that I can repaint it with a two-pack epoxy paint.

 

Assuming it's painted with bitumen and you're re-painting with the same type of paint, then all you need to do is pressure wash yours and go over with wire brushes to get any loose flakey stuff off before repainting.

Edited May 25, 2015 by blackrose

[Murflynn]

I read it that the OP is concerned about painting the sides of the cabin, maybe?

[blackrose]

I've never heard of anyone blacking the cabin sides, but if the cabin sides are being blasted then doing it properly means the windows would need to be removed. The sand/grit gets everywhere and ply sheets can go over the window apertures.

Edited May 25, 2015 by blackrose

[valrene9600]

Debdale do a good job but I a year later have still not received any paperwork ?

What paperwork? Do you mean a receipt for the cost.

[Silebyman]

Pretty much any boatyard with a slipway will offer blacking. The normal route is to jet wash the sides which takes off all the old blacking.

You can either black it yourself if you have the time or pay the boatyard to do it for you.

I paid my local yard to do my 57ft boast. 3 coats approx £500.

[ROBDEN]

I read it that the OP is concerned about painting the sides of the cabin, maybe?

No. Below the gunwhales.

 

There's no real point paying for expensive grit blasting if you're just going to repaint it with bitumen based blacking. I'm about to have my boat grit blasted to get all the bitumen off so that I can repaint it with a two-pack epoxy paint.

 

Assuming it's painted with bitumen and you're re-painting with the same type of paint, then all you need to do is pressure wash yours and go over with wire brushes to get any loose flakey stuff off before repainting.

Was thinking, maybe two pack.

I removed the flakey stuff before but you can still see where the old paint/bitumen was.

[blackrose]

If you want a yard to do the whole grit blasting and two-pack epoxy job it's not cheap. I'm paying for a dry dock (£200 for a week - half price after last years debacle when I couldn't get in), a local grit blaster (£400) and enough Jotamastic 87A and 87 for 4 coats on a 57' x 12' widebeam (£500) which I'm painting on myself. I was previously quoted about £6k from a yard to do the whole job - and that only included 2 coats!

 

I'm familiar with this paint as I used to use it when I worked in a boatyard. If you do it yourself you need to read the specification sheet for any two pack epoxy paint before attempting to use it (not just what's written on the can). You need to know surface prep requirements, how to mix, pot life, application, coverage/thickness, etc. It's not as simple as bitumen.

Edited May 25, 2015 by blackrose

[blackrose]

Got the grit blaster in today. The grit is EVERYWHERE! He says he'll blow it all off the boat afterwards. I reckon I'll be vacuuming for weeks...

 

The steel looks really good considering it's been 5 years since it was last docked. There's no pitting anywhere. If I was just using bitumen again I'd definitely put a couple of coats of Primocon underwater primer underneath first. That stuff has stuck to the steel really well even after the bitumen flaked off.

[John V]

What sort of grit did they use? When mine was done they used garnet sand, I seem to recall that they said it was better and cleaner than the black grit that a lot of firms use

 

John

[blackrose]

I'm not sure it's beige sand with green bits so perhaps garnet sand? Anyway it's doing the job ok.

Edited May 26, 2015 by blackrose

[John V]

Sounds like it....mine had red bits in but I believe garnet comes in various colours.

[David Mack]

If you want a yard to do the whole grit blasting and two-pack epoxy job it's not cheap. I'm paying for a dry dock (£200 for a week - half price after last years debacle when I couldn't get in), a local grit blaster (£400) and enough Jotamastic 87A and 87 for 4 coats on a 57' x 12' widebeam (£500) which I'm painting on myself.

 

Have you got lots of help? Four coats on a boat that size in a week, allowing for the specified time between coats and time before immersion sounds like a tall order.

[ditchcrawler]

Got the grit blaster in today. The grit is EVERYWHERE! He says he'll blow it all off the boat afterwards. I reckon I'll be vacuuming for weeks...

 

It does

[blackrose]

Sounds like it....mine had red bits in but I believe garnet comes in various colours.

I asked him, he said it's glass.

 

Have you got lots of help? Four coats on a boat that size in a week, allowing for the specified time between coats and time before immersion sounds like a tall order.

I can get around this boat by myself in about four hours. One coat per day, 24 hours between coats and 24-48 hours before immersion. Should be ok, but if anyone wants to help I'm at harvington on the Avon.

 

The grit blaster finished at about 2.30pm today but even though he blew most of the grit off the boat with a compressor when he finished, it still took me about 3 hours to clean up. So I didn't manage to get the first coat on today. Hopefully it won't flash rust overnight, but the paint is supposed to be tolerant of flash rust.

Edited May 26, 2015 by blackrose

[Alan Saunders]

Good luck in finding a sand, grit, whatever blasting facility for less than the £6,000 quoted above. When I enquired the charge was justified by the huge cost of containing and disposing of material that may be classified as toxic.

 

Rust and bitumen, dirty but not surely not toxic, nothing a particle filter could exclude? Well done Blackrose.

 

Alan

[blackrose]

The grit blaster bloke only charged me £350 in the end. With the dock, blasting and paint I'll have done the job myself for £1100. Bit better than £6000.

Edited May 27, 2015 by blackrose

[John V]

when I had Sabina H gritblasted I had to agree to cleaning the drydock and removing and disposing of the grit, that was a mammoth task. Used 2 of those "Hippo" bags you get from DIY stores where the price includes collection. As I said, hard bl@@dy work but was the only way the drydock would agree to allow the job, and it knocked a big chunk off the bill from the blast contractor. The other big saving was doing the pressure washing myself. That had to be checked for salt contamination and it had to be done twice as some areas still had salt after the first wash (lapstrake construction, so leaching out of seams). That had to be spot on or I wouldn't get a guarantee on the paint.

[cuthound]

My boat has been "zinga'd" and 2 pack epoxied (in grey) from new and then painted in bitumastic to the gunwhales.

 

Does this mean I will have to grit blast back to bare metal when the epoxy needs replacing, or can the bitumen be jet washed off and the epoxy sanded over, repairs made good and recoated?

[blackrose]

That sounds odd to me Cuthound. Painting bitumen on top of epoxy paint sort of defeats the object.

 

Anyway it seems that David was correct and I have not given myself enough time because Jotamastic 87 takes a week to cure. While I already knew this, I was under the impression that curing continued underwater which having spoken to Jotun today is apparently not the case. Fortunately nobody is booked into the dock after me and they've allowed me to stay for another week for 200 quid. Oh well, it's only money...

 

I also miscalculated when I said I could get around my boat in 4 hours. I can with bitumen, but this two pack is much harder work and its taking me closer to 6 hours. Consequently I am cream crackered!

Edited May 27, 2015 by blackrose

[cuthound]

That sounds odd to me Cuthound. Painting bitumen on top of epoxy paint sort of defeats the object.

Anyway it seems that David was correct and I have not given myself enough time because Jotamastic 87 takes a week to cure. While I already knew this, I was under the impression that curing continued underwater which having spoken to Jotun today is apparently not the case. Fortunately nobody is booked into the dock after me and they've allowed me to stay for another week for 200 quid. Oh well, it's only money...

I also miscalculated when I said I could get around my boat in 4 hours. I can with bitumen, but this two pack is much harder work and its taking me closer to 6 hours. Consequently I am cream crackered!

Yes it is odd. Even more curious is that the previous owner had it blacked with bitumastic every 2 years!

 

I recall reading in another thread that someone recommended painting 2 pack with bitumastic if the type of 2 pack was unknown, before adding another coat of 2 pack.

[blackrose]

Are you sure it's not a type of two pack that looks like bitumen? I think they call it pitch epoxy.

[cuthound]

Pretty sure, I'll check in the manual tomorrow, as it states what manufacturer and type of paint was used.

[cuthound]

Had a quick look in the boat's manual.

 

Underwater: Intertuf over Interzone 954 over Zinga

 

Gunwales: Intertuf

 

Unfortunately it doesn't specify the type of Intertuf is used as a top coat. It appears that Intertuf 16 is a comastic single system, whilst Intertuf 203 is a 2 pack. I think it is a single system paint, as it comes off when rubbed with a cloth dampened in white spirit.