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Two Pack or Bitumen


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Good morning all. 
I am currently in process of buying a Widebeam and it is due to come out for survey . Whilst out we are planning to Black the hill. The boat originally new was coated with two pack epoxy but the current owner covered that with Bitumen in 2020. 
Which should be use ? I understand two pack cannot be applied over Bitumen and also been told the two pack Hull should of been prepared before applying Bitumen. 
Any help gladly appreciated. 

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Shame it's been bitumened.  But if the bitumen coating is sound then I'd be tempted to apply more of the same. You will still be benefitting from the protection of the original 2 pack underneath. But if the bitumen all comes off when the hull is pressure washed then you have a free hand on what to do next. The epoxy will still need abrading to give a key for what follows.

The problem is you won't know for sure until the boat is out of the water and pressure washed, so you won't know what coating materials to buy in advance.

  • Greenie 1
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13 minutes ago, Gavlar1980 said:

Good morning all. 
I am currently in process of buying a Widebeam and it is due to come out for survey . Whilst out we are planning to Black the hill. The boat originally new was coated with two pack epoxy but the current owner covered that with Bitumen in 2020. 
Which should be use ? I understand two pack cannot be applied over Bitumen and also been told the two pack Hull should of been prepared before applying Bitumen. 
Any help gladly appreciated. 

 

May I suggest that you reach an agreement with the current owner - when you get the survey results it may be in a poor condition and you decide not to proceed and will have spent £100s (or £1000s if you go for 2-pack) painting a boat that is not yours.

 

Have you also checked with the place it is being lifted ? A lift out for survey is usually for a few hours only and then is dropped back in, they will need to agree that it can be lifted and left on the hard for 7-14 days and then lifted back in.

 

Be very careful if painting /blacking at this time of year - the cold and damp steel (dew point) can mean that the paint doesn't adhere very well and could simply drop off when you put it back in the water. Many (most ?) companies who do blacking will avoid doing it before April / May at the earliest.

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3 minutes ago, David Mack said:

Shame it's been bitumened.  But if the bitumen coating is sound then I'd be tempted to apply more of the same. You will still be benefitting from the protection of the original 2 pack underneath. But if the bitumen all comes off when the hull is pressure washed then you have a free hand on what to do next. The epoxy will still need abrading to give a key for what follows.

The problem is you won't know for sure until the boat is out of the water and pressure washed, so you won't know what coating materials to buy in advance.

When is this due to happen. Inside shed or outside. Consider the weather 

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Obviously the best solution is grit blast and new 2-pack. However that is expensive! If the bitumen is mostly well adhered to the previous layer, one possible answer would be SML Ballastic epoxy 2-pack which they claim can be applied over existing bitumen. Not sure how good an idea that is, but if the manufacturer proposes it then presumably it works reasonably well.

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Two pack costs more to apply, but lasts a lot longer (if you don't scrape it all off whilst moving the boat).

 

So really a pay more now vs pay more later decision. Worth the extra for epoxy if you're mostly leaving it in a marina and it'll still be immaculate five years later, bitumen if you're expecting to need to redo it in a couple of years after bouncing it off every lock wall and scraping it on every irregular bank around.

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8 minutes ago, enigmatic said:

Two pack costs more to apply, but lasts a lot longer (if you don't scrape it all off whilst moving the boat).

 

So really a pay more now vs pay more later decision. Worth the extra for epoxy if you're mostly leaving it in a marina and it'll still be immaculate five years later, bitumen if you're expecting to need to redo it in a couple of years after bouncing it off every lock wall and scraping it on every irregular bank around.

We had our boat blasted and 2packed in 2011. We took it out of the water in 2016 but, having jet washed and generally cleaned it, you couldn’t see where the waterline had been. So we really didn’t need to have bothered. We did apply a further coat of the 2-pack though (having abraded it) because the biggest problem was that the stuff had gone very grey. We are going to take it out of the water again this year (so that’s 12 years later!, and 7 since we last had it out), in part because we recently rather overdid the ice breaking and there is some shiny steel (now no doubt rusty steel!) showing at the bow. I suspect the waterline will still be invisible elsewhere. When we were on the Thames last summer, the clear water showed that there was no significant rust below the water line.
It really is great stuff, there is a bit of rust on the rubbing strakes but that’s it. I think with bitumen it can allow water to seep in between the bitumen and the hull in places where it is not well adhered - bitumened boats often look a bit rusty around the waterline even when most of the coverage is still sound.

Edited by nicknorman
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I suppose a lot depends on the condition of the 2pk when the bitumen was applied, if it was still good then the bitumen is only cosmetic and if its in good nick after pressure washing a new boat of bitumen would be the same. If its not breaking down not a lot of point taking it off, the next job may not be to the same standard, especially this time of the year.

  • Greenie 1
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Just now, Gavlar1980 said:

Thanks for all your advice . The boat is coming out the first week in March and is on hard standing outside for a week after the survey. We could possibly consider blacking next year but was hoping to save some money as it’s already out. 

 

I think contemplating blacking a boat outside in early march is a bad idea!

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7 minutes ago, Gavlar1980 said:

Thanks for all your advice . The boat is coming out the first week in March and is on hard standing outside for a week after the survey. We could possibly consider blacking next year but was hoping to save some money as it’s already out. 

 

 

If you do it early March , you'll probably be doing it again in May 2023.

Edited by Alan de Enfield
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You probably won't know till you get it out of the water. In my experience bitumen doesn't stick well to epoxy so pressure washing could well leave a patchwork of all sorts of paint. If that is the case it could be best to buy a cheap sander, a box of discs and wreck the sander abrading the surface and then use an epoxy primer over the lot and then a top coat - you would need to check with the makers but it might be the best solution.

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