Hull blacking?

[heckmotor]

Couldn't justify my home marina's quote for a quality grit blast and 2-pack application, as it would double the value of our old boat, and it would end up looking better upside down, so I spent last weekend scraping several layers of old paint and blacking off the hull with a 1" carpenter's chisel before giving it a wizz with an abrasive disc, and am quite pleased with the result - couldn't have got the same back-to-metal result with just the rotary power disc or wire brush, because it would just have clogged.

 

Has anyone got any thoughts on how to get a good-looking durable coating to take maximum advantage of the effort we've put it, and on what priming might be necessary? My plan was to Fertan the steel and red lead prime before applying Comastic, but Spencer Coatings suggest an epoxy primer, or direct application onto unprimed metal. I wondered about 2-pack, as I'd like to use the best materials, even though I'm not wanting to spend more than I need to. The main thing is that I don't want to do the wrong thing after putting so much effort into the stripping.

[Windjammer]

Surely work out what blacking product you are prepared to pay for and then consult the manufacturers application instructions ?

 

How long before you expect to drydock and black again ?

[Machpoint005]

I'd have thought two coats of traditional blacking, a good set of anodes, and repeat every two years.

 

Ian

[Phil Speight]

Couldn't justify my home marina's quote for a quality grit blast and 2-pack application, as it would double the value of our old boat, and it would end up looking better upside down, so I spent last weekend scraping several layers of old paint and blacking off the hull with a 1" carpenter's chisel before giving it a wizz with an abrasive disc, and am quite pleased with the result - couldn't have got the same back-to-metal result with just the rotary power disc or wire brush, because it would just have clogged.

 

Has anyone got any thoughts on how to get a good-looking durable coating to take maximum advantage of the effort we've put it, and on what priming might be necessary? My plan was to Fertan the steel and red lead prime before applying Comastic, but Spencer Coatings suggest an epoxy primer, or direct application onto unprimed metal. I wondered about 2-pack, as I'd like to use the best materials, even though I'm not wanting to spend more than I need to. The main thing is that I don't want to do the wrong thing after putting so much effort into the stripping.

Bitumen based primers ( like Comastic etc ) are best applied to bare steel.No primer.

Cheers

Phil

[kingfisher]

if you have cleaned the hull back to steel then epoxy primer and two pack as spencer suggests is the way to go ,it will still need coming out every2- 4 years to patch the scratches as well as annode /stern gear checks etc ,

comastic again is excellent but every last bit of bitumen has to be removed for those 2 methods

if i had a boat from new then 2 pack gets my vote (or should that be if i had a boat)

[Windjammer]

From 2 to 4 years is quite a difference in drydock cycles - 4 drydocks every 8 years if its 2 and only 2 drydocks every 8 years if its 4.

The anodes on some boats erode very slowly and some blacking products are more durable than others.

 

it will still need coming out every2- 4 years to patch the scratches as well as annode /stern gear checks etc ,

[Timleech]

Bitumen based primers ( like Comastic etc ) are best applied to bare steel.No primer.

Cheers

Phil

 

Oh dear Phillip, you've committed a cardinal error

Though not in terms of your actual advice.

 

Comastic is NOT bitumen based, and is not compatible with bitumen based paints.

It's still best applied to bare steel, though

 

Tim

[kingfisher]

From 2 to 4 years is quite a difference in drydock cycles - 4 drydocks every 8 years if its 2 and only 2 drydocks every 8 years if its 4.

The anodes on some boats erode very slowly and some blacking products are more durable than others.

i cant tell boaters when they should dock there boats (every year would be great ) but more of a comment that is the percievd average, some customers do come yearly , one even comes with no annodes !! as you say some products do vary in durability .there are to many variables on this subject as we all no.

perhaps some one could put a poll up to see who uses what and how often

[sueb]

It depends if you intend moving in the winter. Whatever you put on will be ripped off by ice.

Sue

[blackrose]

Has anyone got any thoughts on how to get a good-looking durable coating to take maximum advantage of the effort we've put it, and on what priming might be necessary? My plan was to Fertan the steel and red lead prime before applying Comastic, but Spencer Coatings suggest an epoxy primer, or direct application onto unprimed metal. I wondered about 2-pack, as I'd like to use the best materials, even though I'm not wanting to spend more than I need to. The main thing is that I don't want to do the wrong thing after putting so much effort into the stripping.

 

Red oxide primer is slightly porus and we have all seen steel superstructures that were not given a top coat fairly promptly starting to show rust coming through, sometimes in a matter of months. So I think you'll appreciate that red oxide primer is certainly not designed for much more severe underwater applications! If you want to prime below the waterline you should use a xylene based primer such as International Primocon.

Edited May 9, 2008 by blackrose

[Phil Speight]

Oh dear Phillip, you've committed a cardinal error

Though not in terms of your actual advice.

 

Comastic is NOT bitumen based, and is not compatible with bitumen based paints.

It's still best applied to bare steel, though

 

Tim

Mea Culpa. I have long understood that it was bitumen based despite it`s well known incompatability with more straightforward ones - something which was a bit of a puzzle now solved by yer g`dself. I will go now and beat myself with a bag chain.

Cheers

Phil

ps - one L in Philip by the way - the other one is a Duke of somewhere or other.

[Timleech]

ps - one L in Philip by the way - the other one is a Duke of somewhere or other.

 

Sorry about that, I wasn't sure which was the right form to use

 

Tim

[Phil Speight]

Sorry about that, I wasn't sure which was the right form to use

 

Tim

That`s quite all right. Since the depredations of 1066 we`ve had to get used to this sort of thing.

Cheers

Phil

[Eastern]

Red oxide primer is slightly porus and we have all seen steel superstructures that were not given a top coat fairly promptly starting to show rust coming through, sometimes in a matter of months. So I think you'll appreciate that red oxide primer is certainly not designed for much more severe underwater applications! If you want to prime below the waterline you should use a xylene based primer such as International Primocon.

 

I was cruising the Caldon Canal last week and saw a steel boat out of the water. It had its hull below the waterline painted with red oxide primer, and even the anodes had been painted over!

It does make you wonder.......

[Phil Speight]

Mea Culpa. I have long understood that it was bitumen based despite it`s well known incompatability with more straightforward ones - something which was a bit of a puzzle now solved by yer g`dself. I will go now and beat myself with a bag chain.

Cheers

Phil

ps - one L in Philip by the way - the other one is a Duke of somewhere or other.

It`s worse than I thought Tim. I`m even wrong about how Phil the Greek spells his name. Ah me.........

Phil

[nbtafelberg]

I gave up blacking mine, just use canal world forum stickers

[heckmotor]

Thanks for everyone’s thoughts, some more useful than others! Windjammer kicked off with ‘…work out what blacking product you are prepared to pay for’, and later added ‘some blacking products are more durable than others’ without letting on which, so I obviously hadn’t made it clear enough that these were the very questions that I was hoping for a helpful steer on?

 

Spencer Coatings describe their Comastic, which I applied to FMC ‘Lark’ some years ago, as ‘a special selected vinyl resin formulated with coal tar pitch and a range of additives’, so I was interested to see the respected Phil Speight corrected for calling it ‘bitumen-based’ …I must confess to have been unaware of the distinction, too, but I’m obviously concerned about the compatibility issue flagged by Timleech.

 

Kingfisher points out that I’d have to get right back to bare metal to be able to use epoxy primer but, without the £2000-worth of grit blasting that I can’t justify, I can’t achieve this …believe it or not, my wife and I have scraped most of the hull with 1” and ½” carpenters’ chisels (three tough days), in order to avoid the clogging of every other sort of mechanical medium, before moving on to an angle grinder and £21 heavy-duty wire cup brush from B&Q, but nothing short of blasting will ever get to bright metal. Does that rule out Comastic altogether, or just the epoxy primer? ...and how about the xylene International Primocon primer mentioned by blackrose?

 

I like kingfisher’s idea of a poll to reveal what others do, how often, and with what result – I suppose that’s just the kind of experience I was looking to tap into, and I’d expect that others would find it very useful.

 

Anyway, thanks for the feedback – I’m still not quite sure which way to go, so if anyone’s got any further ideas, I’ll be most grateful. Hopefully a Boat Safety Certificate will be in my sweaty palm by tomorrow afternoon, at the second attempt, so I need to make my mind up!

[NB Alnwick]

I like kingfisher’s idea of a poll to reveal what others do, how often, and with what result – I suppose that’s just the kind of experience I was looking to tap into, and I’d expect that others would find it very useful.

 

If it is of any help to anyone who is looking to get their hull blacked, we took 'Alnwick' to the dry dock at Welford. Les did an excellent job for under £500 - that's 62 feet of deep draughted boat in Dacrylite epoxy followed by re-painting the tunnel bands in three colours. More remarkably, we left the boat there on the Wednesday and it was floating again and tied up by Welford Wharf ready to be handed back to us on Saturday morning!

[Timleech]

Spencer Coatings describe their Comastic, which I applied to FMC ‘Lark’ some years ago, as ‘a special selected vinyl resin formulated with coal tar pitch and a range of additives’, so I was interested to see the respected Phil Speight corrected for calling it ‘bitumen-based’ …I must confess to have been unaware of the distinction, too, but I’m obviously concerned about the compatibility issue flagged by Timleech.

 

Kingfisher points out that I’d have to get right back to bare metal to be able to use epoxy primer but, without the £2000-worth of grit blasting that I can’t justify, I can’t achieve this …believe it or not, my wife and I have scraped most of the hull with 1” and ½” carpenters’ chisels (three tough days), in order to avoid the clogging of every other sort of mechanical medium, before moving on to an angle grinder and £21 heavy-duty wire cup brush from B&Q, but nothing short of blasting will ever get to bright metal. Does that rule out Comastic altogether, or just the epoxy primer? ...and how about the xylene International Primocon primer mentioned by blackrose?

 

There are 2-pack hull paints available now which are allegedly more tolerant and work quite well on a reasonably clean steel surface without grit blasting. I can't comment as I've never tried them, but have received favourable reports from others. Try askin the paint makers about this.

Comastic isn't quite as fussy about being applied to clean steel, but the solvents in it can lift older coatings if you're unlucky.

 

Tim

[Chris Pink]

Kingfisher points out that I’d have to get right back to bare metal to be able to use epoxy primer but, without the £2000-worth of grit blasting that I can’t justify, I can’t achieve this …believe it or not, my wife and I have scraped most of the hull with 1” and ½” carpenters’ chisels (three tough days), in order to avoid the clogging of every other sort of mechanical medium, before moving on to an angle grinder and £21 heavy-duty wire cup brush from B&Q, but nothing short of blasting will ever get to bright metal.

 

Not wishing to belittle your hard work but..... if it won't come off then it's probably doing it's job very well

 

Why do you want to get it off?

 

Why not just re-coat with bitumen (if it is, a white spirit will show - bitumouns paint will blacken a rag soaked in white spirit) or coal tar varnish if not

[heckmotor]

Not wishing to belittle your hard work but..... if it won't come off then it's probably doing it's job very well

 

Why do you want to get it off?

 

Why not just re-coat with bitumen (if it is, a white spirit will show - bitumouns paint will blacken a rag soaked in white spirit) or coal tar varnish if not

 

Perfectly reasonable question, Chris! To start with, we weren't able to tell what the adhesion of the several unidentified layers was, so we began to scrape and then, being dogged Capricorns (if that's not too mixed a metaphor), we just carried on. The benefit, now, will be that instead of looking like black tree bark, the hull will once again look like a smooth metal thing with a fresh coating. A good thing, I think, because the layers were not all blacking, and included both gloss paint, of more than one colour, and the red lead primer that's already been flagged as unsuitable for underwater applications.

 

Thanks, meanwhile, to Tim and to N.b. Alnwick for a recommendation that I'll take note of, and funny to think that it was posted probably no more than a mile from me, on the other side of the A361 ...I'm in Wardington!

[blackrose]

What is the recommended number of coats for two part epoxy paints once the hull has been grit blasted?

 

A boatyard I passed the other day gave me a huge quote for the job, using Blakes (Hemple?) 2 part epoxy, but they only put on two coats. I'd have thought after all that surface preparation at least 3 coats would be better?

[Hooligan50]

Hi,

two coats of two pack epoxy should be quite adequate as it goes on fairly thick. However, so long as the second coat is overcoatable then I would apply an alkyd primer and then a top coat as well making four coats. We had our hull uhp waterblasted and used this system. no grit to clean up. loverly.

 

H50