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My boat has always been blacked with normal bitumen previously, but has now been done with two pack epoxy.  If this needs touching up before the next blacking, what should i use? Is it OK to bung some bitumen on it or do i need some of the proper stuff, and if so, what is it?

Edited by Arthur Marshall
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Find out what epoxy was used and get some of that, trouble is it usually comes in quite big pots, unless its International which comes in Huge  pots at £400 a go. See if the boatyard can give you a little bit next time they do a blacking job. Its possible to mix very small quantities using electronic "drug dealer" scales that are dead cheap on eBay.

 

.............Dave

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Most two-part epoxies can be over-painted, and as the others have said, if you can do it with the same stuff then that's the best way forward. You'll need to abrade the surface with a medium grade paper and dust well. Ideally spirit wipe the abraded surface with a clean cloth dampened with the correct thinners for the two-pack before painting.

 

If you can't find what two pack was used then I'd recommend Jotamastic 87 as it's very surface tolerant. You can get it in black but it will turn grey over time. If you want black black then use Jotamastic Hard Top. The cans (A+B) are 4.7 litres and 2 cans will easily do one coat on a 70ft narrowboat (not Inc baseplate) It's about £50/can. Hardeners come in standard or winter grade but if you're just out of the water for a week or less I'd choose the latter even in summer. I managed to mix and paint a whole can by myself within the 90min pot life but that was standard grade, don't try that with WG because you've only got about an hour depending on ambient temperature. You can mix in smaller quantities (by volume, not weight) but however you're mixing you must mix part A thoroughly in the big can first before adding part B. Or use containers to mix smaller amounts with part B. You'll need some Jotamastic thinners 17 as well and unfortunately that's only available in 5 litre cans.

 

All the data sheets and instructions can be found as PDFs online.

Edited by blackrose
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OK time for a confession, I have just had 2 pack on top of just high pressure water blasted bitumen not clean blasted steel. It was something I gave a lot of thought and really hadn't made up my mind until actually in dock. What I mulled over in my mind several time was, I know bitumen doesn't really work, I am convinced its actually porous and lets water through. 2 pk In my opinion form all my years offshore should go on clean blasted steel, but if it holds on the remaining bitumen, semi clean steel will it be better than bitumen. Cost wise it was only the difference in paint costs, so watch this space for a posting from me in about 3 years time.

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54 minutes ago, Richard10002 said:

Is it not a good idea to lift the boat every 2-4 years anyway and,assuming you do, it’s not too much trouble to give it a few coats of bitumen?

If that was for me, I budget for getting the bloke at the yard to do it for me. Keeps money in circulation, him in work, I can do other stuff while it's happening. He's always used bitumen before as that was what was already there, but it's been resteeled and I understand the bitumen mostly came off with the millscale, so he took the rest off and used two pack on the steel. 

ETA it's not the painting so much I can't do, it's the bending up and down getting the blasted stuff on the brush. An hour of that and I can't walk any more. 

Edited by Arthur Marshall
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10 minutes ago, Arthur Marshall said:

If that was for me, 

Not at all, just a comment on the fact that two pack generally lasts a long time, (10 to 12 years or so?), and some seem to intimate that there is no need for the two yearly lift and splash.

 

If you didn’t lift your boat for 10 years, I’d guess there are lots of things that could go wrong down there, and remain unseen.

 

Im no expert, and could be wrong :) 

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2 hours ago, blackrose said:

Most two-part epoxies can be over-painted, and as the others have said, if you can do it with the same stuff then that's the best way forward. You'll need to abrade the surface with a medium grade paper and dust well. Ideally spirit wipe the abraded surface with a clean cloth dampened with the correct thinners for the two-pack before painting.

 

If you can't find what two pack was used then I'd recommend Jotamastic 87 as it's very surface tolerant. You can get it in black but it will turn grey over time. If you want black black then use Jotamastic Hard Top. The cans (A+B) are 4.7 litres and 2 cans will easily do one coat on a 70ft narrowboat (not Inc baseplate) It's about £50/can. Hardeners come in standard or winter grade but if you're just out of the water for a week or less I'd choose the latter even in summer. I managed to mix and paint a whole can by myself within the 90min pot life but that was standard grade, don't try that with WG because you've only got about an hour depending on ambient temperature. You can mix in smaller quantities (by volume, not weight) but however you're mixing you must mix part A thoroughly in the big can first before adding part B. Or use containers to mix smaller amounts with part B. You'll need some Jotamastic thinners 17 as well and unfortunately that's only available in 5 litre cans.

 

All the data sheets and instructions can be found as PDFs online.

Wot he said!

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2 hours ago, ditchcrawler said:

OK time for a confession, I have just had 2 pack on top of just high pressure water blasted bitumen not clean blasted steel. It was something I gave a lot of thought and really hadn't made up my mind until actually in dock. What I mulled over in my mind several time was, I know bitumen doesn't really work, I am convinced its actually porous and lets water through. 2 pk In my opinion form all my years offshore should go on clean blasted steel, but if it holds on the remaining bitumen, semi clean steel will it be better than bitumen. Cost wise it was only the difference in paint costs, so watch this space for a posting from me in about 3 years time.

2 pack epoxies work by stopping water getting to the steel. There is some permeation so they are formulated to stick to the steel very well so if a rust spot starts, it does not undercut the coating and allow the rust to spread. 

If you there fore put it on over traditional blacking, it will not have that adhesion. I agree it will reduce water permeation but could delaminate if too thick or too strong. If it lasts over winter then you should be good for 2 or 3 years and maybe more but the thermal shock could delaminate big areas. 

Please do keep us posted. I am really interested to hear how you get on. I may be tempted to follow your lead. I'm getting mine blacked in a couple of weeks with the bog standard stuff as I like the idea of taking it out every two years, but the xtra paint cost isn't too high. Maybe next time. Do tell us if it falls off in sheets next winter.

2 hours ago, Richard10002 said:

Is it not a good idea to lift the boat every 2-4 years anyway and,assuming you do, it’s not too much trouble to give it a few coats of bitumen?

I like the idea of taking it out every two years. On our lumpy water boat, we used to dive on it every month to clean the bottom ....but then we did race it. 

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Funny how we have different views. I hate taking the boat out too often! It was built to be in water :)
I used to take it out about three yearly, but having got fed up with bitumen I had it blasted and two packed at ten years old. It will be taken out next year (15 years old) for pressure washing, inspection and any remedial work, but having had it on a severe list last year and scrubbing the waterline, the two pack seemed in amazing condition.
 

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9 hours ago, catweasel said:

Funny how we have different views. I hate taking the boat out too often! It was built to be in water :)
I used to take it out about three yearly, but having got fed up with bitumen I had it blasted and two packed at ten years old. It will be taken out next year (15 years old) for pressure washing, inspection and any remedial work, but having had it on a severe list last year and scrubbing the waterline, the two pack seemed in amazing condition.
 

I suppose it is habit. With our lumpy water boat, we used to moor up against a wall at high tide and water jet and antifoul as the tide went out. Every year! It was nice to check everything out and make sure no problems.......but it was GRP. I guess everything is going to be ok for a steel boat for 10 years plus but it's not normal to us to carry round the vast forest of flora that we have growing below the waterline. We don't do severe lists any more!!:)

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2 hours ago, Dr Bob said:

I suppose it is habit. With our lumpy water boat, we used to moor up against a wall at high tide and water jet and antifoul as the tide went out. Every year! It was nice to check everything out and make sure no problems.......but it was GRP. I guess everything is going to be ok for a steel boat for 10 years plus but it's not normal to us to carry round the vast forest of flora that we have growing below the waterline. We don't do severe lists any more!!:)

Yes I can see it is a very different situation with sea boats. The only experience I have of same is when we chartered a yacht from Falmouth a good few year ago. I remember the owner/skipper scrubbing the hull after the tide went out. We shouted encouragement from the pub. 

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3 hours ago, Dr Bob said:

I suppose it is habit. With our lumpy water boat, we used to moor up against a wall at high tide and water jet and antifoul as the tide went out. Every year! It was nice to check everything out and make sure no problems.......but it was GRP. I guess everything is going to be ok for a steel boat for 10 years plus but it's not normal to us to carry round the vast forest of flora that we have growing below the waterline. We don't do severe lists any more!!:)

 

When I bought my boat I had her dry docked for the survey. I was amazed at how many fresh water mussels were attached to the baseplate. The whole baseplate was covered. Soon came of with a pressure washer though.

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13 hours ago, Dr Bob said:

2 pack epoxies work by stopping water getting to the steel. There is some permeation so they are formulated to stick to the steel very well so if a rust spot starts, it does not undercut the coating and allow the rust to spread. 

If you there fore put it on over traditional blacking, it will not have that adhesion. I agree it will reduce water permeation but could delaminate if too thick or too strong. If it lasts over winter then you should be good for 2 or 3 years and maybe more but the thermal shock could delaminate big areas. 

Please do keep us posted. I am really interested to hear how you get on. I may be tempted to follow your lead. I'm getting mine blacked in a couple of weeks with the bog standard stuff as I like the idea of taking it out every two years, but the xtra paint cost isn't too high. Maybe next time. Do tell us if it falls off in sheets next winter.

I like the idea of taking it out every two years. On our lumpy water boat, we used to dive on it every month to clean the bottom ....but then we did race it. 

As I say it took a long time to make my mind up, I understand that the museum at ellesmere port have used this system. I am not 100% happy with the idea of using 2 pack like this, not ideal but hopefully better than bitumen. Time will tell.

  • Greenie 1
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17 hours ago, ditchcrawler said:

OK time for a confession, I have just had 2 pack on top of just high pressure water blasted bitumen not clean blasted steel. It was something I gave a lot of thought and really hadn't made up my mind until actually in dock. What I mulled over in my mind several time was, I know bitumen doesn't really work, I am convinced its actually porous and lets water through. 2 pk In my opinion form all my years offshore should go on clean blasted steel, but if it holds on the remaining bitumen, semi clean steel will it be better than bitumen. Cost wise it was only the difference in paint costs, so watch this space for a posting from me in about 3 years time.

Its not ideal but if you use a surface tolerant epoxy, remove all the loose stuff, degrease, and have a fairly textured surface (not polished smooth with a sanding disc) then I suspect you will probably do ok.

 

When we did our first epoxy repair docking the bare areas were all down to impacts and scrapes. There was one small area where the epoxy might have fallen off, but even that was more likely down to a scrape.

 

Did our side lockers about 4 years ago and got most of the old paint and rust out with an angle grinder but it was far from perfect. Epoxy is still 99.9% stuck on.

 

.............Dave

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22 hours ago, ditchcrawler said:

OK time for a confession, I have just had 2 pack on top of just high pressure water blasted bitumen not clean blasted steel. It was something I gave a lot of thought and really hadn't made up my mind until actually in dock. What I mulled over in my mind several time was, I know bitumen doesn't really work, I am convinced its actually porous and lets water through. 2 pk In my opinion form all my years offshore should go on clean blasted steel, but if it holds on the remaining bitumen, semi clean steel will it be better than bitumen. Cost wise it was only the difference in paint costs, so watch this space for a posting from me in about 3 years time.

There was a guy on FB who did exactly the same thing to his boat and was adamant that grit blasting was not necessary. A very high pressure clean off leaving only the well stuck bits of the original coat (even if that coat was bitumen) was good enough, he said. Be interesting to see how you get on as it was a very convincing argument and I am now tempted!

Edited by Traveller
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7 hours ago, cuthound said:

 

When I bought my boat I had her dry docked for the survey. I was amazed at how many fresh water mussels were attached to the baseplate. The whole baseplate was covered. Soon came of with a pressure washer though.

Did they taste  OK?

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23 hours ago, ditchcrawler said:

OK time for a confession, I have just had 2 pack on top of just high pressure water blasted bitumen not clean blasted steel. It was something I gave a lot of thought and really hadn't made up my mind until actually in dock. What I mulled over in my mind several time was, I know bitumen doesn't really work, I am convinced its actually porous and lets water through. 2 pk In my opinion form all my years offshore should go on clean blasted steel, but if it holds on the remaining bitumen, semi clean steel will it be better than bitumen. Cost wise it was only the difference in paint costs, so watch this space for a posting from me in about 3 years time.

Our boat was 2 packed in 2015. The bitumen blacking was removed by scabbling, to provide a pretty clean steel base for the 2 pack (Jotamastic 87).  It was suggested at the time that this coat would last between 5 and 7 years, and that we should have it out of the water after 5 years to check for scarring.

 

We used the boat thereafter for 6-7 months cruising in the summer, mooring in a marina over the winter.

 

Last year I could see several scars above the waterline, so booked into Aqueduct marina for a lift out, jet wash, and a week in their DIY shed for a bit of touching up. I bought all the necessary kit for doing the Jotamastic and it was all looking good until the jet washer hit the side of the boat!  All the 2 pack left on the boat just fell off!

 

We were left with two options - continue water blasting and then bitumen black it,  or grit blast and 2 pack.  We went for the latter, more expensive, option........

 

All I will say is that when I looked at the grit blasted steel, before the 2 pack was applied, and compared it to the previous, scabbled, effort - I could see why the previous blacking didn't stay on very well.  I reckon your 3 year estimate is about right.

 

To the OP - if you look in the For Sale section, you may find just what you need!!!!

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1 hour ago, Boredrider said:

.

To the OP - if you look in the For Sale section, you may find just what you need!!!!

I did - and lo!  Oddly, it showed on my tablet but I couldn't track it down on the PC.  Then I tried to PM you, spelt the name wrong.... Irritatingly, I was in Willaston and Heswall yesterday and Birkenhead on Monday.  I lived in New Brighton and West Kirby for years.

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