How do you go about blacking your boat?

[dmr]

Yep i nearly forgot the weed hatch and the rudder tube.

 

20 littes is what i used on 2 coats but i had a spare 2 days in the dry dock so did another coat.

 

Sounds like you were lucky my paint come off in shards, it was two pack as well.

 

I dont rate two pack its very brittle, i use to be a paint sprayer and now i kinda prefer the goopy vinyl tar stuff (it goes on real thick and easily with a fury cloth type roller. :-)

 

So far Coflex has not greyed.

 

Which 2 pack have you seen that is brittle?

 

The three commonly stated problems with two pack are:

1 Its brittle

2 it lifts off in sheets and the water gets behind it

3 Any local damage will result in severe rusting in the exposed areas.

 

Does anybody have any first hand experience of these things or are they stories put about by yards who are not able to shot blast?

3 is silly because it would apply just as much to conventional blacking.

 

Two pack is certainly much harder than single pack but I would not say brittle. We have put a fair few scrapes on ours that have gone right through but the damage is localised with no signs of adjacent lifting or brittleness.

 

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

[reg]

Point of order your honour:

It's ZINGA not Zinger.

[Chewbacka]

A soft coat like bitumen will tend to smear rather than chip and flake, and can leave a film behind that gives a degree of protection. The characteristic of 2 pack epoxy is that it is very strong and if put onto mill scale will stress the bond between the mill scale and steel possibly resulting in delamination. Contamination of the steel surface - oils etc - will also result in poor adhesion which could also result in delamination.

Delamination can also be triggered by mechanical damage to the coating if the bond is poor - mill scale, contanination etc.

This is maybe where the brittleness complaint comes from.

 

Either way the result can be "Sounds like you were lucky my paint come off in shards, it was two pack as well."

 

So there is no point in 2 pack without very good prep.

 

I have often wondered if doing a strip 6 inches above and below the water line in 2 pack (with proper prep) followed by a more traditional blacking over the entire side up to the gunnel's would actually be better from a cost and performance view.

Edited November 28, 2016 by Chewbacka

[WotEver]

Point of order your honour:

It's ZINGA not Zinger.

 

However it's spelt, how good is it?

[Greylady2]

Which 2 pack have you seen that is brittle?

 

The three commonly stated problems with two pack are:

1 Its brittle

2 it lifts off in sheets and the water gets behind it

3 Any local damage will result in severe rusting in the exposed areas.

 

Does anybody have any first hand experience of these things or are they stories put about by yards who are not able to shot blast?

3 is silly because it would apply just as much to conventional blacking.

 

Two pack is certainly much harder than single pack but I would not say brittle. We have put a fair few scrapes on ours that have gone right through but the damage is localised with no signs of adjacent lifting or brittleness.

 

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

Ive seen all three of them in mass, if only i took a picture of how many britle big sheets came off, the previous owners used hempel 2k epoxy blacking.

 

Even though the hull was not shot blasted it was extremely britle to snap and it had cracks in it in places.

 

Ive used different types of two pack in my job and most of them are brittle or go brittle with age and crack.

Edited November 28, 2016 by Greylady2

[reg]

Did mine last Jan_Feb so too early to tell yet won't really know until I take it out again. During my research, which basically consisted of asking around and looking at case studies I came to the conclusion that it could be very effective IF THE CORRECT LEVEL OF GRIT BLASTING, was used. The levels required can be found here

http://www.classcoat.com/index2.html

I ignored my own research and did the entire job using Tercoo tools, this is not the way to do it unless for smaller areas. Hopefully the water line will be good as I used fresh Tercoo tools and abundant enthusiasm.

As I said above too early to give a full report yet.

Another expensive error I made was to 2 pack in the middle of winter and also not to use the recommended barrier level between the ZINGA and the 2 pack.

I believe ZINGA to be a very good product if applied correctly, which they are at pains to point out. If you try to cut corners and costs like I did then the results may be unpredictable

Edited to add:

I rate Tercoo tools very highly but not for doing a complete 57ft hull

Edited November 28, 2016 by reg

[Geo]

Ive seen all three of them in mass, if only i took a picture of how many britle big sheets came off, the previous owners used hempel 2k epoxy blacking.

 

Even though the hull was not shot blasted it was extremely britle to snap and it had cracks in it in places.

 

Ive used different types of two pack in my job and most of them are brittle or go brittle with age and crack.

 

I think a lot of the problems with two pack coming off in sheets is down to preparation. If there is any mill scale etc the two pack will not adhere to the metals as t drys and cures, thus if there is slight damage water can get behind the two pack and lift it off in sheets. It seems that if two pack is being used shoot blasting in an important part of the preparation to make sure all mill scale is removed and the steel surface gives a good key that the two pack can grip to.

[reg]

http://www.classcoat.com/2353.html

 

 

 

Just thought I would add this quote from the above link:

'

"It cannot be stressed strongly enough that the key to Zinga's long life is in the thorough preparation of the steel substrate to the correct specification."

[Greylady2]

I think a lot of the problems with two pack coming off in sheets is down to preparation. If there is any mill scale etc the two pack will not adhere to the metals as t drys and cures, thus if there is slight damage water can get behind the two pack and lift it off in sheets. It seems that if two pack is being used shoot blasting in an important part of the preparation to make sure all mill scale is removed and the steel surface gives a good key that the two pack can grip to.

I agree geo, another problem with 2k is that it spider crack on impact when it is or has gone brittle where as something vinyl tar based will just flex.

[Jim Riley]

I had a yoghurt pot for years, bought a project NB 2 years ago. Dry docked in hebden Bridge (£300 pw) got a survey done, set about blacking when it passed, with a couple of recommendations for welding.

 

I used wire cup brush then 2 coats of intertuf, 3 on waterline. I also did the baseplate, mainly because the water level on my mooring goes up and down, sometimes end up dry under boat.

It's due again in May, doing it myself again, interested to see what's gone on with baseplate. There is currently a small amount of rust on the waterline. It would be possible, when the pound is low and boat sitting in the dry, for the blacking faeries to sneak in and touch up the waterline, CRT rules say I couldn't possibly do that.

[blackrose]

I agree geo, another problem with 2k is that it spider crack on impact when it is or has gone brittle where as something vinyl tar based will just flex.

You're generalising about two-pack epoxy paints - possibly based on bad prep. In my experience the ones I've used don't go brittle and don't crack. Jotamastic is quite flexible. If you don't prep properly any paint system will fail prematurely. If on the other hand people can't be bothered to do the prep (as is often the case with many so called professionals who black canal boats), then slapping on an inferior product probably makes more sense.

 

But once again I ask the question, is vinyl tar (coflex) used commercially on very large projects, or just on canal boats? That's the test as far as I'm concerned.

Edited November 28, 2016 by blackrose

[Chewbacka]

You're generalising about two-pack epoxy paints - possibly based on bad prep. In my experience the ones I've used don't go brittle and don't crack. Jotamastic is quite flexible. If you don't prep properly any paint system will fail prematurely. If on the other hand people can't be bothered to do the prep (as is often the case with many so called professionals who black canal boats), then slapping on an inferior product probably makes more sense.

 

But once again I ask the question, is vinyl tar (coflex) used commercially on very large projects, or just on canal boats? That's the test as far as I'm concerned.

Interesting question, but most large commercial project - boats - are salty water boats so a different environment.

Work boats on fresh water are sometimes not even painted just left to rust slowly, though many are. No idea what the painted ones use.

[Greylady2]

If on the other hand people can't be bothered to do the prep (as is often the case with many so called professionals who black canal boats), then slapping on an inferior product probably makes more sense.

 

A bit rude want it.

 

17 years as a qualified painter sprayer motor trade/comercial coatings and aviation.

 

Guess i better shut up and keep my nose out.

Edited November 28, 2016 by Greylady2

[dmr]

We were done in International two pack a few years ago, I think it was 3 but it might be 4. The International has a slightly rough matt appearance and gives the impression of been a bit flexible rather than really hard.

 

We dry docked this summer to have a look. Wish I had taken some photos now. Lots of holes and scrapes, mostly small, but otherwise the stuff was still really well stuck on. We do over 1000 miles each year so some damage was to be expected but I was still surprised at how many holes we had made. In a couple of places it looked like it had worn/abraded off rather than impact damage. Most damage was a bit above and a bit below the waterline, this must correspond to protruding lock gate collars etc. Except for the scrapes the general condition of the epoxy at the waterline was very good. With conventional blacking we used to see quite a bit of rust after 2 years.

I abraded all the damaged bits back to good bare metal with a wire cup brush. The yard linished/roughed up everywhere else and put two more coats on. Will look again in 3 or 4 years time.

 

I conclude that with a much used boat the two pack will not give the often stated 7 to 10 years between docking but will provide much much better protection for the boat with some remedial work needed every 3 or 4 years.

 

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

[dmr]

A bit rude want it.

 

17 years as a qualified painter sprayer motor trade/comercial coatings and aviation.

 

Guess i better shut up and keep my nose out.

 

I suspect that proper two pack blacking is very different to, and much more flexible than automotive two pack paint. The two pack on our boat is quite thick looking stuff and would not look at all good on a Jaguar.

Over the last few years I have also become a big fan of Armourguard ST epoxy primer and this is designed to be slightly flexible. Done the front and back deck floors, inside the weedhatch, and locker floors and so far its looking very promising.

 

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

and shutting up and keeping your nose out is not the done thing on this forum

[ditchcrawler]

A bit rude want it.

 

17 years as a qualified painter sprayer motor trade/comercial coatings and aviation.

 

Guess i better shut up and keep my nose out.

Don't get in a huff. Very few boatyard follow the manufacturers instructions for applying blacking. I have never had my boat blacked where its been out of the water for more than a week so probably only 3 full days after the final coat was applied.

[system 4-50]

my two-packed boat was a bit flaky but only near the anodes, and underneath it was perfect, shiny clean.

[blackrose]

Interesting question, but most large commercial project - boats - are salty water boats so a different environment.

 

Yes, a much harsher environment.

 

A bit rude want it.

 

17 years as a qualified painter sprayer motor trade/comercial coatings and aviation.

 

Guess i better shut up and keep my nose out.

No it wasn't meant to be rude, I was talking in general about people (boatyards) who are paid to black boats and we all know how slack their standards can be - it's a well-trodden topic of discussion on this forum. I didn't mention you. However if you insist on taking such comments personally that of course is your prerogative.

Edited November 28, 2016 by blackrose

[Geo]

A bit rude want it.

 

17 years as a qualified painter sprayer motor trade/comercial coatings and aviation.

 

Guess i better shut up and keep my nose out.

 

Don't think he was meaning to be rude to you. I think he was thinking about some of the poor blacking type work done in yards around the canal system. Where preparation can be as little of a quick spray off, bang on a coat of blacking. Once that has been left for 4 hours or so bang on another. Wait a few hours bang on another coat at the waterline and back in the water. I have seen boats supposedly fully blacked on and off a slipway in less than two days in October. When the boat hits the water the solvent from the blacking can be seen on the water.

 

It is many years since I have had a boat blacked but I understand with the increase in the number of boats on the canals the more cheap blacking places have appeared. Well not that cheap just enough under the normal price to be attractive and they apparently turn boats around quite quickly.

[nicknorman]

We recently took our boat out of the water 4.5 years after it was blasted and 2-packed with Sigmacover 300. It didn't really need doing but I just wanted to have a look. There was some abrasion / rust on the rubbing strakes and, since the blacking does go grey/brown over time, if we'd just touched it up it would have been really blotchy.

 

Anyway we jet washed it, scrubbed it a bit and have it a lick with an orbital sander / 80 grit and it looked like this. You can barely make out where the water line is. Certainly no hint of coming off in chunks, and virtually zero rust anywhere except a bit on the strakes.

 

 

It does look brown in the photo, sanding it seemed to turn it brown. We then gave it an additional coat so now it's all shiny black again!

Edited November 29, 2016 by nicknorman

[Geo]

I used to paint the top strake upwards with a black hammerite smooth which made for easy touching up of the top strake. Can't remember now how badly the lower strakes used to get damaged but I do not remember it was not noticeable when using a standard blacking. But she was a boat of ripe years so I seem to remember the hull sides were not vertical and the top rubbing strake took the damage in locks etc.

[dmr]

We recently took our boat out of the water 4.5 years after it was blasted and 2-packed with Sigmacover 300. It didn't really need doing but I just wanted to have a look. There was some abrasion / rust on the rubbing strakes and, since the blacking does go grey/brown over time, if we'd just touched it up it would have been really blotchy.

 

Anyway we jet washed it, scrubbed it a bit and have it a lick with an orbital sander / 80 grit and it looked like this. You can barely make out where the water line is. Certainly no hint of coming off in chunks, and virtually zero rust anywhere except a bit on the strakes.

 

IMG_2806.JPG

 

It does look brown in the photo, sanding it seemed to turn it brown. We then gave it an additional coat so now it's all shiny black again!

 

No scrapes anywhere? How do you do that?, and you boat in Birmingham too. Perhaps we need to get some boat handling lessons from you. I am amazed that you have not taken the paint of those rivets, we have some slightly protruding welds and they get scraped in no time at all.

 

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

[nicknorman]

 

No scrapes anywhere? How do you do that?, and you boat in Birmingham too. Perhaps we need to get some boat handling lessons from you. I am amazed that you have not taken the paint of those rivets, we have some slightly protruding welds and they get scraped in no time at all.

 

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

But I think that's the point, we DO scrape sometimes, everybody does. And we always whack the top paddles right up straight away so the boat bangs around in the lock a bit. However the rubbing strakes get it, they are reasonably "fat" and of course there is the strake below the water line that some boats lack. We've also done a bit of ice-boating, though not too thick. It didn't have any effect on the blacking at the bow. But with the 2-pack it just abrades a bit and is really well attached to the substrate so it only comes off exactly where it touches, and it is quite hard so takes minor scrapes in its stride.

 

It is interesting that when sanding it, there was zero clogging of the sandpaper so it is not like 1-pack at all. It just came off as a fine dust as if it were paint.

Edited November 29, 2016 by nicknorman

[Dalslandia]

1. it must be black colour, other is will be no blackening.

2. use Jotun Jotamastic or similar.

3. will not rust in the waterline

4. have a Singa

[Jrtm]

1. it must be black colour, other is will be no blackening.

2. use Jotun Jotamastic or similar.

3. will not rust in the waterline

4. have a Singa

You stole my thought at no 1. It must be back my answer was not to paint it a diffrent colour