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Newbie...hull prep for bitumen?


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I'm sure this must have been done to death, but at risk of being flamed, here we go...

 

Yesterday my wife and I completed the purchase of our first NB, a 2004 55' John White boat. Pre-purchase survey highlighted a few galvanic corrosion pits that should be spot welded before blacking in 2-pack epoxy. The boat has lived on a marina with shore power for the past 7 years, thankfully not moored against metal, otherwise the corrosion would have been much worse. Needless to say we will be fitting an isolating transformer and / or galvanic isolator.

 

So protecting the hull is a priority. However, for the time being we simply can't afford** to get it grit blasted and 2-packed, so we plan for now to get the welding done then get it bitumen blacked. We plan on having it blasted and 2-packed next Spring.

 

My question is should we:

  1. Wire brush the surface after welding and apply 3 coats of bitumen, or
  2. Wire brush, apply Fertan then apply 3 coats of bitumen,
  3. Wire brush, apply Vactan then apply 3 coats of bitumen.
  4. None of the above - do something completely different?

 

I don't mind spending the time applying rust converter, but only if it's worthwhile, bearing in mind the boat will be out for a long-term hull treatment in a year's time. How likely is a hull coated only in bitumen to deteriorate externally in 12 months? We will be putting on new anodes, of course.

 

**we can afford to get the blasting and 2-pack done, but with £2000 round trip to lift and transport the boat to a gritblasting facility, plus we want thermal zinc treatment under the 2-pack, we need to budget £5-£6k for the work. As inexperienced boaters, we can't get insurance for tidal waterways until we pass a helmsmanship course - as we are on the Lancaster canal, we would need to cross the Ribble Link to get everything done without road transport. So we're kind of trapped into this short-term solution.

 

Thanks in advance for any guidance. The boat's out of the water now, so I have all options available before putting her back in the water.

 

Survey front anode 2.jpg

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Are you doing the 2 pack epoxy because the survey said so, or would you have done that anyway.

 

I would jet wash, wire brush, Vactan any rusty areas, (not all over), then 3 coats of bitumen, with 4 coats at the waterline. (not forgetting the welding).

 

Once you have done this, you have done as much as you "need" to do for 2 or 3 years. In my experience there is no significant deterioration in 12 months. In fact, in my experience, there is no significant deterioration after almost a decade with lift outs for bitumen blacking as above :) 

 

I wouldn't do the £6k 2 pack epoxy thing, but that doesn't mean you shouldn't do it.

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1 hour ago, Richard10002 said:

Are you doing the 2 pack epoxy because the survey said so, or would you have done that anyway.

 

I would jet wash, wire brush, Vactan any rusty areas, (not all over), then 3 coats of bitumen, with 4 coats at the waterline. (not forgetting the welding).

 

Once you have done this, you have done as much as you "need" to do for 2 or 3 years. In my experience there is no significant deterioration in 12 months. In fact, in my experience, there is no significant deterioration after almost a decade with lift outs for bitumen blacking as above :) 

 

I wouldn't do the £6k 2 pack epoxy thing, but that doesn't mean you shouldn't do it.

Thanks Richard, we would do the epoxy anyway, but I accept that the bitumen and other treatment you suggest will give good protection. The boat had not been out of the water for 5 years, constantly moored and on shore power, hence the deterioration. I think if it had been lifted and blacked halfway through that time, we would have a better hull than we do. I like the sound of the solution you describe.

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26 minutes ago, Rob Stuthridge said:

Thanks Richard, we would do the epoxy anyway, but I accept that the bitumen and other treatment you suggest will give good protection. The boat had not been out of the water for 5 years, constantly moored and on shore power, hence the deterioration. I think if it had been lifted and blacked halfway through that time, we would have a better hull than we do. I like the sound of the solution you describe.

I see no mention of treating the baseplate, indeed, no mention of its condition either. I would suggest power wash, weld all pits, wire brush on an angle grinder, Fertan on rusty areas, wash and dry and 3 coats modified bitumen.

To all hull areas including the baseplate.

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Just now, Tracy D'arth said:

I see no mention of treating the baseplate, indeed, no mention of its condition either. I would suggest power wash, weld all pits, wire brush on an angle grinder, Fertan on rusty areas, wash and dry and 3 coats modified bitumen.

To all hull areas including the baseplate.

Thanks Tracy, the baseplate is in good shape, so no treatment or protection was advised by the marine surveyor. What do you mean by 'modified' bitumen?

 

Do you have a technical / performance reason for advocating use of Fertan rather than Vactan?

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1 minute ago, Rob Stuthridge said:

Thanks Tracy, the baseplate is in good shape, so no treatment or protection was advised by the marine surveyor. What do you mean by 'modified' bitumen?

 

Do you have a technical / performance reason for advocating use of Fertan rather than Vactan?

Straight bitumen is not very environment friendly. Modified like Comastic and others is a blend.

 

Still worth treating the base plate. Just because its 10mm thick doesn't mean it will last for ever with no blacking, it will pit just as easily as the sides.

 

Vactan is a  vinyl primer with tannic acid and needs no washing off but I am not convinced that it is the best under blacking. Fertan is straight tannic acid and requires washing off to activate fully. Which leaves nothing behind but treated rust.

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2 hours ago, Tracy D'arth said:

Straight bitumen is not very environment friendly. Modified like Comastic and others is a blend.

 

Still worth treating the base plate. Just because its 10mm thick doesn't mean it will last for ever with no blacking, it will pit just as easily as the sides.

 

Vactan is a  vinyl primer with tannic acid and needs no washing off but I am not convinced that it is the best under blacking. Fertan is straight tannic acid and requires washing off to activate fully. Which leaves nothing behind but treated rust.

 

I thought that modified bitumen such as Comastic have gone the way of most other effective paints and bedn banned?

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With your rust treatment plans you need to allow an additional 48 hours drying if using Vactan under the present temperature regime, and 48 hours PLUS the washing off and drying time if using Fertan.

This was one of the big failings in Keelblacks stated benefit of "Reduced Dock Time", as they hadnt consulted Fertan on full drying and curing time.

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3 hours ago, Tracy D'arth said:

Straight bitumen is not very environment friendly. Modified like Comastic and others is a blend.

 

Still worth treating the base plate. Just because its 10mm thick doesn't mean it will last for ever with no blacking, it will pit just as easily as the sides.

 

Vactan is a  vinyl primer with tannic acid and needs no washing off but I am not convinced that it is the best under blacking. Fertan is straight tannic acid and requires washing off to activate fully. Which leaves nothing behind but treated rust.

I see, thank you.

15 minutes ago, matty40s said:

With your rust treatment plans you need to allow an additional 48 hours drying if using Vactan under the present temperature regime, and 48 hours PLUS the washing off and drying time if using Fertan.

This was one of the big failings in Keelblacks stated benefit of "Reduced Dock Time", as they hadnt consulted Fertan on full drying and curing time.

I'll remember that. Thank you Matty.

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Posted (edited)

I've just reserved grit-blasting and 2-pack epoxy treatment at Tarleton Boatyard for June/July 2022 with an option to potentially bring the boat in earlier if they get a cancellation. So I'm leaning towards modified option 2: Wire brush, apply Fertan - rinse off, wait 48 hours to dry, apply 3 coats of bitumen on the whole hull with 4 at the waterline. I don't have facilities at the yard to get the baseplate blacked, so will need to leave that as is for now, but will look at having it grit blasted and 2-packed at Tarleton next summer.

Edited by Rob Stuthridge
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7 minutes ago, Rob Stuthridge said:

I've just reserved grit-blasting and 2-pack epoxy treatment at Tarleton Boatyard for June/July 2022 with an option to potentially bring the boat in earlier if they get a cancellation. So I'm leaning towards modified option 2: Wire brush, apply Fertan - rinse off, wait 48 hours to dry, apply 3 coats of bitumen on the whole hull with 4 at the waterline. I don't have facilities at the yard to get the baseplate blacked, so will need to leave that as is for now, but will look at having it grit blasted and 2-packed at Tarleton next summer.

If its coming out in 12 months for blasting and 2 pack I would do a cheap job now after the welding is done, It only has to hold up for a year

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22 minutes ago, ditchcrawler said:

If its coming out in 12 months for blasting and 2 pack I would do a cheap job now after the welding is done, It only has to hold up for a year

That's what we wondered, Ditchcrawler...but we'd still want to treat any rust before blacking. We're only concerned that we do enough to prevent deterioration until its 2-packed.

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2 pack blacking on a survey is now as common as disclaimers and the contact details of the surveyor. Whilst there is no doubt it can be a superior product if applied properly, bitumen can be fine if the correct prep work is carried out. We have seen several instances of 2 pack falling off in sheets, and also bitumen clinging on with very little corrosion to 30 year old hulls....

Arguments for both I reckon!

 

Kind regards

 

Dan

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Having owned several boats....I never go over the top on items like this.

If I spend a lot of money ..potential future purchasers won't accept my invoices for work carried out anyway, in fact I found it scares them off.

Trying to reassure by saying I had it all done and they have nothing to worry about....leaves them running away...plus their own surveyor then spotlights it to a greater extent.

 

My own philosophy is to carry out work to stop it sinking...and then get cruising.

 

Weld pits...grind...vactan......Comastic...get cruising....

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22 minutes ago, stagedamager said:

2 pack blacking on a survey is now as common as disclaimers and the contact details of the surveyor. Whilst there is no doubt it can be a superior product if applied properly, bitumen can be fine if the correct prep work is carried out. We have seen several instances of 2 pack falling off in sheets, and also bitumen clinging on with very little corrosion to 30 year old hulls....

Arguments for both I reckon!

 

Kind regards

 

Dan

Thanks for that, stagedamager.

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22 minutes ago, Bobbybass said:

Having owned several boats....I never go over the top on items like this.

If I spend a lot of money ..potential future purchasers won't accept my invoices for work carried out anyway, in fact I found it scares them off.

Trying to reassure by saying I had it all done and they have nothing to worry about....leaves them running away...plus their own surveyor then spotlights it to a greater extent.

 

My own philosophy is to carry out work to stop it sinking...and then get cruising.

 

Weld pits...grind...vactan......Comastic...get cruising....

It will probably suffice, but we negotiated enough off the asking price specifically to 2-pack the boat. I would feel dishonest if we then chose to not get the work done and would feel the need to reimburse the seller (it's just who I am as a person, no point arguing). So I think we will do the very best we can for the boat, even if it's slightly overkill. I'm happy to use a 'get-us'by' temporary blacking, provided the hull doesn't deteriorate further, then go ahead with the 2-pack. Thanks though Bobby!

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7 minutes ago, Rob Stuthridge said:

It will probably suffice, but we negotiated enough off the asking price specifically to 2-pack the boat. I would feel dishonest if we then chose to not get the work done and would feel the need to reimburse the seller (it's just who I am as a person, no point arguing). So I think we will do the very best we can for the boat, even if it's slightly overkill. I'm happy to use a 'get-us'by' temporary blacking, provided the hull doesn't deteriorate further, then go ahead with the 2-pack. Thanks though Bobby!

Very little will happen in a year

 

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Yes if you're taking it out again next spring and epoxying it don't worry about prep for the bitumen too much. Just wire brush and remove any obvious rust and if you can't remove it treat it with vactan, and then slap a couple of coats of bitumen on. Leave at least 12 hours between coats and 24 hours before the boat goes back in the water. Double those times ideally.

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2 hours ago, blackrose said:

Yes if you're taking it out again next spring and epoxying it don't worry about prep for the bitumen too much. Just wire brush and remove any obvious rust and if you can't remove it treat it with vactan, and then slap a couple of coats of bitumen on. Leave at least 12 hours between coats and 24 hours before the boat goes back in the water. Double those times ideally.

That makes sense. I think we have plenty to do on the boat while waiting for the coats to dry. Thank you!

 

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