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Is two pack worth it?


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22 minutes ago, dmr said:

Boats rarely get more than a week in the drydock though many epoxies would like longer than this to fully cure. Epoxy will do a pretty good job even if the prep is not 100% perfect, and getting the full life expectancy is not critical.

 

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

 

16 minutes ago, Paul C said:

Dry dock is the worst place to paint a boat. Inevitably the boat is "tying up" the dock, so there will be an urgency to get it done and out again. Also it is just below the level of the canal, so cold, humid and not much airflow. 

 

Get the boat slipped on a trailer and there's much more opportunity to put it in a better place for painting, and (except for the hardstanding fees, which are much lower/day than drydock) there is no time pressure on the job.

Dave, you are right that you dont need a 100% perfect surface...but it needs to be not far off. For me the worry is more about moisture on the surface and temperature which Paul refers to.

It is very important to make sure you are painting onto a dry surface as moisture will cause premature failure......and is likely the cause of big chips coming off on impact but could result in the coating coming off in sheets. This is the area where boatyards will cut corners. Is the temperature of the steel above the dew point? That is a critical area to ensure it is right. You cant see the condensation that happens when the steel is under the dew point but it is there. The British weather is not conducive to ensuring surfaces are 15°C plus. It does limit the number of months where you can paint outside if not done in a 'proper' paint shop. Some paints say they can be applied at temps down to 5°C but that is asking for trouble...... how the heck does solvent evaporate out....like Paul says, in a cold and humid dry dock. I'd have no problem putting epoxy back in the water after a day or so ....as it will cure (ie cross link) under water....PROVIDING the solvent comes out in the first 24 hours ....which it will do if applied at a decent temp (ie over 15°C).

 

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1 hour ago, Dr Bob said:

 

Dave, you are right that you dont need a 100% perfect surface...but it needs to be not far off. For me the worry is more about moisture on the surface and temperature which Paul refers to.

It is very important to make sure you are painting onto a dry surface as moisture will cause premature failure......and is likely the cause of big chips coming off on impact but could result in the coating coming off in sheets. This is the area where boatyards will cut corners. Is the temperature of the steel above the dew point? That is a critical area to ensure it is right. You cant see the condensation that happens when the steel is under the dew point but it is there. The British weather is not conducive to ensuring surfaces are 15°C plus. It does limit the number of months where you can paint outside if not done in a 'proper' paint shop. Some paints say they can be applied at temps down to 5°C but that is asking for trouble...... how the heck does solvent evaporate out....like Paul says, in a cold and humid dry dock. I'd have no problem putting epoxy back in the water after a day or so ....as it will cure (ie cross link) under water....PROVIDING the solvent comes out in the first 24 hours ....which it will do if applied at a decent temp (ie over 15°C).

 

 

That is why I booked mine in for blacking and painting in August. No guarantees with the British weather, but a better chance of it remaining above 15°C during August than any other month.

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1 hour ago, Dr Bob said:

The British weather is not conducive to ensuring surfaces are 15°C plus

last time I blacked my boat Temperatures in the dry Dock were 30C plus I just kept going round and round the boat with KeelBlack as by the time I reached where I had started it had dried enough to repaint. 6 coats in 2 days finished Wednesday morning left it to cure til Friday PM so easily the 48hrs required.

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2 hours ago, Loddon said:

last time I blacked my boat Temperatures in the dry Dock were 30C plus I just kept going round and round the boat with KeelBlack as by the time I reached where I had started it had dried enough to repaint. 6 coats in 2 days finished Wednesday morning left it to cure til Friday PM so easily the 48hrs required.

It is the easiest stuff in the world to apply, I sprayed four coats on two widebeams in a day! easy as anything, thats just over the waterline for 3 coats and one up to the gunnels at the end. I of course covered any scrapes with four coats above the waterline, the coverage is very good and the spray equipment is just washed out with water easy peasy stuff

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9 hours ago, Tonka said:

Question I have is would you consider having it done to a 25 year old boat and who would you get to do it.

I reckon epoxy is even more justified on an old boat than on a new one, and for that reason I would like to get my baseplate done next time.

After 25 years you will have lost a bit of thickness and likely have some significant pitting so you don't want it to get any worse, epoxy should stop the pitting progressing almost completely, and drastically reduce the progress of any other metal loss.  You need to be sure your boat can withstand the shot blasting (there are some bad stories about) but at 25 it should be fine.

 

Choice of yards depends a lot on if you want the baseplate doing, if you do your choice is limited. I would only use a yard that has an under cover dry dock or workshop. Its then a trade off between location, price and quality. You could get a zinc spray and top notch epoxy at Debdale but it will cost. I like Canal Cruising at Stone who do a very functional job at a reasonable price. Whatever you do it will still need periodic repair as it will get scrapes depending upon how you use the boat, paying top money to get an extra year or two of life from the epoxy is not a huge factor for me as we use the boat hard.

 

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

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Thanks Dave, I was thinking about the Debdale molten zinc process, As you say it is pricey but as I am retiring April part of my lump sum should cover it. What do you do on the bit that is above the rubbing streak and below the gunnel, It has always been comastic or last year it was Keelblacked.

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25 minutes ago, Tonka said:

Thanks Dave, I was thinking about the Debdale molten zinc process, As you say it is pricey but as I am retiring April part of my lump sum should cover it. What do you do on the bit that is above the rubbing streak and below the gunnel, It has always been comastic or last year it was Keelblacked.

My rubbing strake to gunnel is in Craftmaster Raddle. Previously it was International Toplac.

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40 minutes ago, Tonka said:

Thanks Dave, I was thinking about the Debdale molten zinc process, As you say it is pricey but as I am retiring April part of my lump sum should cover it. What do you do on the bit that is above the rubbing streak and below the gunnel, It has always been comastic or last year it was Keelblacked.

That depends on how you want it to look. I think it should be black and easy to touch up as it takes a beating. I have used Andy Russel Gunwale paint but that's hard to get now. I am going to try Craftmaster black undercoat and Craftmaster black raddle next, I quite like using undercoat as a top coat on hard working parts of the boat.

 

It could be worth getting it done in epoxy when you do the rest of the boat, but you would still need to repair it a couple of times each year, either with epoxy or other black paint. Epoxy can be thicker so any scrapes would likely show through after you repair them. I am quite happy for this part of the boat to have a bit of "texture" but others might lot, especially if you like a boat to look really smart.

 

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

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On 11/08/2019 at 21:53, Dr Bob said:

Would you like the view from an expert?

 

For background, I spent 10 years as Technical manager of a group developing surface tolerant 2 pack epoxy coatings for BP Chemicals in the 80's and have significant field experience of applying them in difficult environments (ie offshore splash zone etc). I know 2 pack epoxies. I know how they need to be applied. 2 pack epoxy is the best coating for a narrow boat.

 

When applied to the manufacturers specs, the coatings should last 10 years. YES. 10 years and maybe more .......as long as they are applied right. Blacking lasts up to 2 years and can look pretty naff after just a few months. The only saving grace of blacking is that the steel is thick and boats last a long time as there is a lot of steel to corrode away.  We bought our boat over 2 years ago and had it blacked after a few months. We've just had it blacked again. Why? It wasnt the cost. This time it was more the convenience of a quick 'in and out'. I think though now having seen how our first blacking survived and now the 2nd one (which was applied by a yard in good weather) is deteriorating...although will be ok for another year or so...... I will go for a two pack in a few years time. It's not urgent to me though. There is lots of steel left. I do not worry at all about my blacking (and I know coatings).

Yes, we will switch to 2 pack but my biggest worry is finding a yard that will do it properly. I spent 10 years watching professional coating companies screwing up many many jobs even with paint inspectors monitoring the work. Temperature/moisture when applying is very difficult in the UK and the source of many problems. Last year there was an enquiry on here by someone who had a soft coating after their 2 packing and I organised some 3rd party testing of the coating in a UK based lab to check state of cure etc. The results clearly showed something had gone wrong in the application. An expensive mistake. It really does make me worry about finding a yard I can be convinced with who really knows what they are doing and don't cut corners which is the main cause of problems.

Phil Jones. Calf Heath. Our boat done 6years ago with 2pack, some pitting on the waterline needed attention before we agreed the purchase back then. I get down and scrub a random patch every 6 months with an old fashioned scrubbing brush. 

Still perfect. Cheers. 

 

 

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2 hours ago, BD3Bill said:

Phil Jones. Calf Heath. Our boat done 6years ago with 2pack, some pitting on the waterline needed attention before we agreed the purchase back then. I get down and scrub a random patch every 6 months with an old fashioned scrubbing brush. 

Still perfect. Cheers. 

 

 

I agree with this, but....

We have been drydocked twice to do repairs on the epoxy and the waterline has been fine, epoxy loss is mostly above the top rubbing strake (guard iron/D section) due to impacts/scrapings, and also quite a bit lost well below the waterline, especially right down at the bottom. This is the opposite of conventional blacking where failure is worse on the waterline. Some of the low level loss is due to scraping when moored, we do spend time in places that have a slightly sloping stone washwall, but (one for Dr Bob) I do wonder if the slight increase in water pressure at increasing depth is a factor in epoxy failure??????

 

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

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18 hours ago, dmr said:

You could get a zinc spray and top notch epoxy at Debdale

I went for belt and braces at Debdale on a brand new  hull that had been 18 months in the water having put keel black (6 coats before going into the water- it was over a original coating but can`t remember  its name). They sand blasted, zinc sprayed and then 2 packed ( cost over 5K a small price compared with other build costs- upper hull painting for example) ). Its to come out of the water at Debdale next Spring again as a small area about 60mm diameter on the waterline that has "bubbled". They video the work and give an exstensive guarantee. Will have to wait and see next Spring what the overall condition is. However I have been assured by Debdale that even though the 2 pack may have delaminated in hopefully the one spot the zinc below would have given the hull full protection. As I said I`ll see next Spring/early Summer. You pay your money and take your choice. I`m optimistic that when I part with the boat as I age (getting that way) that it will hold its value against future costs, inflation and depreciation.

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9 hours ago, dmr said:

 Some of the low level loss is due to scraping when moored, we do spend time in places that have a slightly sloping stone washwall, but (one for Dr Bob) I do wonder if the slight increase in water pressure at increasing depth is a factor in epoxy failure??????

 

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

I dont think water pressure will have any effect. When you say 'low level loss' , what do you mean? Failure of the coating is normaly down to two things, impact damage or scraping against the bank which you say does happen (in this case the non scraped coating is fine) or once there is a scrape, the air/water undercuts the coating and travels up the interface between the coating and the steel causing rust and lifting the coating off. This is why epoxies are so good - the adhesion stops the air/water undercutting.

If your 'low level loss' is just scrapes, then that cant be avoided if you keep mooring in these places (unless you use bigger tyres!). If the loss though is due to undercutting that would suggest there has been a problem when the coating was applied, ie often dampness on the steel surface after grit blasting and before applying the first coat will cause this. Dampness on the steel surface could be worse at the bottom of the hull if the dry dock isnt ventilated properly and its up to the painters to ensure the temperature is well above the dew point. Either of the above could be reasons for you issue.

A good way to test is to get a sharp pen knife and try and dig a small piece of coating off in the area where there is damage. If it lifts the paint off the steel then the adhesion is not good enough and points to poor application. If it wont budge the coating with reasonable force then the adhesion is fine.

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1 hour ago, jddevel said:

I went for belt and braces at Debdale on a brand new  hull that had been 18 months in the water having put keel black (6 coats before going into the water- it was over a original coating but can`t remember  its name). They sand blasted, zinc sprayed and then 2 packed ( cost over 5K a small price compared with other build costs- upper hull painting for example) ). Its to come out of the water at Debdale next Spring again as a small area about 60mm diameter on the waterline that has "bubbled". They video the work and give an exstensive guarantee. Will have to wait and see next Spring what the overall condition is. However I have been assured by Debdale that even though the 2 pack may have delaminated in hopefully the one spot the zinc below would have given the hull full protection. As I said I`ll see next Spring/early Summer. You pay your money and take your choice. I`m optimistic that when I part with the boat as I age (getting that way) that it will hold its value against future costs, inflation and depreciation.

 

11 minutes ago, Dr Bob said:

I dont think water pressure will have any effect. When you say 'low level loss' , what do you mean? Failure of the coating is normaly down to two things, impact damage or scraping against the bank which you say does happen (in this case the non scraped coating is fine) or once there is a scrape, the air/water undercuts the coating and travels up the interface between the coating and the steel causing rust and lifting the coating off. This is why epoxies are so good - the adhesion stops the air/water undercutting.

If your 'low level loss' is just scrapes, then that cant be avoided if you keep mooring in these places (unless you use bigger tyres!). If the loss though is due to undercutting that would suggest there has been a problem when the coating was applied, ie often dampness on the steel surface after grit blasting and before applying the first coat will cause this. Dampness on the steel surface could be worse at the bottom of the hull if the dry dock isnt ventilated properly and its up to the painters to ensure the temperature is well above the dew point. Either of the above could be reasons for you issue.

A good way to test is to get a sharp pen knife and try and dig a small piece of coating off in the area where there is damage. If it lifts the paint off the steel then the adhesion is not good enough and points to poor application. If it wont budge the coating with reasonable force then the adhesion is fine.

I am still a fan of zinger I still take her out every 2 years to apply keelblack, but that is for cosmetic reasons and to repair the impact damage of boating 

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9 minutes ago, peterboat said:

 

I am still a fan of zinger I still take her out every 2 years to apply keelblack, but that is for cosmetic reasons and to repair the impact damage of boating 

I have no experience of zinger but the theory is that the zinc will stop the undercutting mentioned in my previous post and also give some protection in areas where the coating has been knocked off. That has to be really beneficial. The only thing that worries me is that the zinc on the surface of the steel will reduce the adhesive stregnth of the coating to steel so it would be more susceptible to undercutting but that is balanced or bettered by the zinc stopping the undercutting. It does sound a very good route.

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My boat had Zinga, covered by International 954 two pack from new.

 

Had the boat out of the water for a survey when I bought it at 6.5 years old. Hull perfect.

 

Had the boat out at 10 years old, for blacking  and new anodes.  Boatyard said leave it another 2 years, doesnt need doing yet.

 

Over the two years blacking began to fail in small patches where impacts were most likely on stem post and sides where they begin to curve in towards the bow.

 

Had the boat out in August at almost 12 years old. Damage repaired locally and another 2 coats applied. 

 

Baseplate has never been painted, still no signs of pitting.

 

2 pack every time for me.

Edited by cuthound
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