Two pack Hull coating

[LadyG]

I might have the boat out, and jet washed this year, the original two pack looks in excellent condition after twenty years, but previous owner put bitumen blacking on some repairs, so that needs to come off and re done.

Which primer do I use after wire brushing, 750ml should do it. Isopon 182 looks OK, for cars! 

Then which two pack epoxy? Its a 57 ft boat. 15 to20 litres should do it. 

Should I buy a fence brush for first coat of epoxy then a roller for second? 

I have five days to do the work, yard does the jet wash. 

Tx

 

Edited April 24, 2021 by LadyG

[Alan de Enfield]

If you are planning to use 2-pack then every iota of the blacking MUST be removed (otherwise you get blistering and poor adhesion) you cannot just put even a 2-pack primer over blacking, and if you use a single-pack primer you cannot put a 2-pack over the top of it.

 

This is why a boat that has previously had blacking MUST have the hull sand-blasted down to bare metal.

[MarkH2159]

I would look at touch up repairs using SML Ballistic Epoxy Primer as a first coat then whatever decent 2 pack topcoat takes your fancy.

 

SMLstate that their Ballistic Epoxy will go on and adhere well to old hardened residual bitumen so long as all the loose stuff is removed.

Edited April 24, 2021 by MarkH2159
More info

[LadyG]

36 minutes ago, MarkH2159 said:

I would look at touch up repairs using SML Ballistic Epoxy Primer as a first coat then whatever decent 2 pack topcoat takes your fancy.

 

SMLstate that their Ballistic Epoxy will go on and adhere well to old hardened residual bitumen so long as all the loose stuff is removed.

That is what they state, but this has been challenged by some respected coating experts on here. The volume is small, so I'd be forking out an extra £50, that's against my principles. 

Edited April 24, 2021 by LadyG

[blackrose]

I assume you don't know which two pack epoxy was used previously? Ideally you should use the same stuff but if not most epoxies are compatible.

 

You shouldn't really need any primer. Epoxy paint is a primer. Certainly don't use any single pack primer.

 

I used 2 coats of Jotamastic 87 with aluminium followed by 2 coats of Jotamastic 87 black. It's since been superseded by Jotamastic 90.

 

 

 

[ditchcrawler]

1 hour ago, Alan de Enfield said:

If you are planning to use 2-pack then every iota of the blacking MUST be removed (otherwise you get blistering and poor adhesion) you cannot just put even a 2-pack primer over blacking, and if you use a single-pack primer you cannot put a 2-pack over the top of it.

 

This is why a boat that has previously had blacking MUST have the hull sand-blasted down to bare metal.

I know of at least two locations that now put 2 pk over Bitumen, mine was done 2 years ago and from what I can see still looks good, next year when its out and washed down I will let you know

2 hours ago, LadyG said:

I might have the boat out, and jet washed this year, the original two pack looks in excellent condition after twenty years, but previous owner put bitumen blacking on some repairs, so that needs to come off and re done.

Which primer do I use after wire brushing, 750ml should do it. Isopon 182 looks OK, for cars! 

Then which two pack epoxy? Its a 57 ft boat. 15 to20 litres should do it. 

Should I buy a fence brush for first coat of epoxy then a roller for second? 

I have five days to do the work, yard does the jet wash. 

Tx

 

Airless Spray is the proper way to do it IMO

[Tracy D'arth]

Are you doing the baseplate too?  Many surveyors say that it is essential.

[ditchcrawler]

31 minutes ago, Tracy D'arth said:

Are you doing the baseplate too?  Many surveyors say that it is essential.

Mine has been done 

Edited April 24, 2021 by ditchcrawler

[Alan de Enfield]

5 minutes ago, ditchcrawler said:

I know of at least two locations that now put 2 pk over Bitumen, mine was done 2 years ago and from what I can see still looks good, next year when its out and washed down I will let you know

Airless Spray is the proper way to do it IMO

 

Simply going by the application instructions (that there must be no single pack paint at all) from when I did mine.

You can out put single pack over 2-pack but not the other way around.

Edited April 24, 2021 by Alan de Enfield

[Tracy D'arth]

There are surface tolerant epoxy 2 pack paints available.

[blackrose]

6 minutes ago, ditchcrawler said:

Mine has been done

 

Mine hasn't. If it had been easier I'd have done it but I've never found a dry dock with enough clearance to prep the baseplate. Last time I looked it was fine, just some light surface rust which brushed off by hand.

[blackrose]

15 minutes ago, ditchcrawler said:

I know of at least two locations that now put 2 pk over Bitumen, mine was done 2 years ago and from what I can see still looks good, next year when its out and washed down I will let you know

Airless Spray is the proper way to do it IMO

 

You can put two pack over bitumen if you want to. It will stick to it but it's a waste of good epoxy. A paint system is only as good as its weakest link.

 

The "proper way"  of applying any paint is whatever is outlined in the technical data sheet. For many epoxy paints application by brush is fine as long as the rest of the instructions are followed.

[ditchcrawler]

29 minutes ago, Alan de Enfield said:

 

Simply going by the application instructions (that there must be no single pack paint at all) from when I did mine.

You can out put single pack over 2-pack but not the other way around.

Maybe a different brand of 2Pk

21 minutes ago, blackrose said:

 

Mine hasn't. If it had been easier I'd have done it but I've never found a dry dock with enough clearance to prep the baseplate. Last time I looked it was fine, just some light surface rust which brushed off by hand.

Northwich on the Weaver 

[matty40s]

1 hour ago, ditchcrawler said:

I know of at least two locations that now put 2 pk over Bitumen...

Did you have Comastic, or normal bitumen??

[cuthound]

Diesel removes normal bitumen blacking, so I would remove the localised repairs which have bitumen blacking on by scrubbing it off with diesel.

 

You can then get the boat reblacked with 2 pack.

[system 4-50]

Is it possible to crane a narrowboat on to its side to black the bottom without major problems?  Assuming I take the fine-bone china out of the cupboard first?

[roland elsdon]

Yes.

Anything is possible but not necessarily desirable.

probably best add empty toilet to prior jobs, oh and the diesel tanks and the engine oil.

[haggis]

4 hours ago, ditchcrawler said:

Maybe a different brand of 2Pk

Northwich on the Weaver 

When Kelpie was done a bit after Harnser in Northwich Dry Dock they had a device which the operator could lie on to do the base plate. Kelpie had the same treatment as Harnser and it still looks good but we will know more in September when we are in the dry dock again. 

Can't think of many dry docks where the floor is dry and clean enough to lie on !

 

Haggis

[LadyG]

5 hours ago, ditchcrawler said:

I know of at least two locations that now put 2 pk over Bitumen, mine was done 2 years ago and from what I can see still looks good, next year when its out and washed down I will let you know

Airless Spray is the proper way to do it IMO

Sounds like a bodger tbh

Edited April 24, 2021 by LadyG

[ditchcrawler]

2 hours ago, system 4-50 said:

Is it possible to crane a narrowboat on to its side to black the bottom without major problems?  Assuming I take the fine-bone china out of the cupboard first?

British Waterways has a boat manipulator in the Bradley workshop for turning Narrowboats upside down

[haggis]

14 minutes ago, LadyG said:

Sounds like a bodger tbh

I don't think so as the company has done a lot of research on this method of blacking and have been doing it for several years.  if it wasn't working  I think we would have heard about it and they wouldn't be so busy. However the proof will be when we go back in September to get the blacking done again but from what we can see it still looks good. 

 

Haggis

[ditchcrawler]

20 minutes ago, LadyG said:

Sounds like a bodger tbh

Best you have it grit blasted then

[LadyG]

6 hours ago, Tracy D'arth said:

There are surface tolerant epoxy 2 pack paints available.

Have just had the baseplate thoroughly scraped and polished on the Chesterfield, but I am not going to bother with grit blasting, zingering and all the rest of it, its a just the hull sides, a topcoat. I'll be long gone before boat sinks. 

It's the hull, needs re coating after 20 years, still in excellent condition, not going to do anything other than two more coats of the same. 

 

Edited April 24, 2021 by LadyG

[LadyG]

36 minutes ago, ditchcrawler said:

Best you have it grit blasted then

Sorry, the existing coating is excellent after twenty years, apart from about 1 sq m covered in bitumen,. I am not going to spend £2K, on grit lasting. 

Edited April 24, 2021 by LadyG

[ditchcrawler]

4 minutes ago, LadyG said:

Sorry, the existing coating is excellent after twenty years, apart from about 1 sq m covered in bitumen,. I am not going to spend £2K, on grit lasting. 

Sounds like a bodge tbh