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Blacking


Catali

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Crunch time is approaching and a decision is needed: stay with the trad bitumen or fork out for pitch epoxy? A can of worms, I know, but would be v grateful for opinions. Anyone know a rough price comparison? (Per foot or per meter.) We are 30 yr old Nb, 55 foot. Our first time blacking. Might consider trad bitumen blacking ourselves, but possibly not with the pitch epoxy…sounds a bit more technical. Thanks folks! (Sorry if this is a FAQ. Is there a link I should look at?)

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Bitumen can be done over existing sound blacking (after pressure washing and removing rust and loose blacking). Epoxy will require the hull to be grit blasted back to bare metal. Blasting is a messy process and not every yard that does blacking can offer blasting.

Blasting and epoxying are professional tasks. Bitumen can de done DIY.

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If your doing it this winter I'd want at least a week, preferably two weeks in the dock to get get it thoroughly dry and give extra long drying times between coats. Before the first coat I'd use a fan heater or hair dryer to make sure it's not damp following up with the blacking brush.

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You can no longer use pitch epoxy.  It was banned a while back, because it contained tar. There are other, more expensive, epoxy based paints available.  You can even get them in different colours so you can see where you have painted.

As said  above you really  need to have the boat abrasive blasted before you apply epoxy.  There are products which claim to be  compatible with bitumen based coatings, but you are then relying on the existing  bitumen as the coat sticking your expensive new epoxy to the steel.

 

Applying epoxy is not much harder than applying bitumen. You need a good stirrer to mix the two parts together.  One of the drill powered ones is good, or a couple of washers welded edge on to on a bit of steel bar in a mains  drill.  Pick the right stuff and roller and brush works for getting it on the boat.  Some epoxies can be HVLP sprayed too. Temperature is important for the epoxy to cure so you need to do the job in late Spring through early Autumn, or find a heated dock/slipway.

In all cases read the instructions, data sheet and safety information carefully, then do what it says.

 

As far as benefit over bitumen  goes, you really need to be keeping the boat for at least 10 years to get the benefits. The best part is that the epoxy does not get dissolved by the permanent thin layer of diesel on the canal water, so waterline rusting  is eliminated. The next good bit is that epoxy is quite slippery, so weed growth eventually  washes off as you are boating.  Epoxy is tougher than bitumen, so tends to survive normal  bumps and grinds better, though it still wears away on the guard irons.  Docking intervals can be extended from 2 years and the work needed at each docking is reduced to pressure washing then treating and recoating any areas of mechanical damage. I have tended to put an extra coat on every 4 years, but that was just me, not really merited by the state of the epoxy.   You can expect the epoxy to last at least 10 years if well maintained.  Mine was done first in 2010 and survives still, despite the best part of 500 hours boating every year since.

 

N

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2 hours ago, BEngo said:

You can no longer use pitch epoxy.  It was banned a while back, because it contained tar. There are other, more expensive, epoxy based paints available.  You can even get them in different colours so you can see where you have painted.

As said  above you really  need to have the boat abrasive blasted before you apply epoxy.  There are products which claim to be  compatible with bitumen based coatings, but you are then relying on the existing  bitumen as the coat sticking your expensive new epoxy to the steel.

 

That's true but if the old black is sound does it matter and the epoxy is not that much more expensive and it doesn't disappear along the water line as soon as it smells diesel. 

Edited by ditchcrawler
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All seagoing structures that I know of, oil rigs, ships, bits of bridge or anything else is epoxy coated. The Iron Bridge just up the road from me is epoxy painted. Anything that the owners want to last is epoxied. Nobody who is serious about stopping corrosion would use bitumen. Canal boats should have used epoxy for the last 20 or so years.  Thing is that boat builders for donkey's years have been spraying a coat of black gooey stuff on their boats as they leave the yard thus giving the new owner a problem as well as not painting the bottom as its too difficult.  However.... it is now easier than it used to be to get your boat hauled, craned, or docked than it used to be so I think in your case I would use bitumen and just re do it every couple of years. In most if not all of Europe tar is illegal to use as it is toxic, I would imagine the UK might also ban tarry stuff too but who knows.  Basically, of you can keep a layer of paint between the steel and the water then you are protecting the hull (Don't tell anybody but I use bitumen above the waterline as it is cheap, easy, and wears well)

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Thank you all so much for your thoughts. Much food for thought there. Next job, I think is to talk to some local boatyards to see what facilities they offer and prices, of course. I imagine that we need to get booked in somewhere ….and then coordinate that with some decent weather!!!

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10 minutes ago, Catali said:

and then coordinate that with some decent weather!!!

 

I wouldn't plan on doing it before April / May unless you can find a heated dry dock for a couple of weeks - one week to get it up to temperature and one week to do the job.
if using 'Blacking' the steel needs to be warm (above the dew point) otherwise you are painting on top of 'water' and it will not stick.

Once the air temperature is consistently above about 8 degrees, night & day (more is better) then you can consider doing it outside.

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18 minutes ago, Alan de Enfield said:

 

I wouldn't plan on doing it before April / May unless you can find a heated dry dock for a couple of weeks - one week to get it up to temperature and one week to do the job.
if using 'Blacking' the steel needs to be warm (above the dew point) otherwise you are painting on top of 'water' and it will not stick.

Once the air temperature is consistently above about 8 degrees, night & day (more is better) then you can consider doing it outside.

There is no month of the year where night time temperatures can be guaranteed to stay above 8.  Especially not April or May when overnight frosts are quite common.

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On 23/10/2021 at 12:07, Catali said:

Crunch time is approaching and a decision is needed: stay with the trad bitumen or fork out for pitch epoxy? A can of worms, I know, but would be v grateful for opinions. Anyone know a rough price comparison? (Per foot or per meter.) We are 30 yr old Nb, 55 foot. Our first time blacking. Might consider trad bitumen blacking ourselves, but possibly not with the pitch epoxy…sounds a bit more technical. Thanks folks! (Sorry if this is a FAQ. Is there a link I should look at?)

 

Some cost comparisons:

 

Dry Dock (nortoncanesboatbuilders.co.uk)

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4 minutes ago, Tim Lewis said:

Of course, you wouldn't normally grit blast a boat without immediatelt painting it though

 

No of course 👍

but just interesting to see the cost of grit blasting. 
I might go down the 2 pack route and the painting could possibly be done myself. 
It just gives a ball park figure to start at

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