Blacking with Two Pack Epoxy

[plainsman]

I've been quoted £3k for grit blast and two pack coating.  I'm thinking a bit of careless steering and one could scrape through the coating, yard says small damage can be touched up but I assume once mixed this stuff cannot be stored and remixing a small amount wouldn't get the correct proportions.  Any views on this and is £3k worth it?

[Dr Bob]

For touching up, you would need to pour off a can of each of the two parts prior to mixing which can then be used when doing touch ups. If you do this, make sure each of the two components is fully mixed before decanting off each can. These coatings are usually designed to go over well prepared steel so doing a touch up is not quite that straight forward and will need to get back to bare metal in the area of damage and a good key sanded into the epoxy.

 

I was a paint chemist in a  previous life and am not convinced over the economics. Assume the 2 pack lasts 10 years, then that is £3K spent today versus say £600 every two years (you didnt say how long the boat is) - which is £3K (but prices will go up). Add on to that though if you look at Discounted cash flows..ie money of today, the 2pack option is then more expensive. Add on that you will lift the boat out every 4 or 5 years to check it or for repairs etc and that is additional cost. Our current boat is 15 years old and we blacked it last year for £600. At the moment I am leaning to the £600 every 2 years option but that could change if I see enough compelling evidence that a 2 pack is better. I do like the sound of the zinger stuff.

 

A final add on is that after 8 months since blacking, the waterline (and below) is plastered with growth and coming from a lumpy boat background, could do with antifouling. The 2 year cycle helps here. I've not seen anything on here about fouling and effect on fuel consumption but on our lumpy water boat it certainly affected boat speed - not a problem on the cut.

 

eta......mixing proportions for retouching is not ultra critical. I'd gues a 10% error will be fine.

Edited May 24, 2018 by Dr Bob

[Boater Sam]

I have used 2 pack for 18 years on this boat. In that time it has been out and scars touched up 3 times, with one coat extra over the whole hull each time. I can do a coat with 4 litres @ about £10 a litre.

So that's 3 drag outs or dockings at around £300 a time + £120 for paint. I reckon £1020 for 18 years hull protection is pretty economical.

I have had 2 sets of 4 new anodes, and one pair of rudder bearings.

The hull has had one bad scrape which corroded a bit and was welded over in all that time.

At repainting time I only clean off with a water lance to remove the green slime and  avoid ripping into the paint, scrapes get a quick grind to clean them out and 2 touchup coates, then a full coat all over. Takes 2 days + 1day curing then back in the water.

In between dockings I brush off the weed growth occasionally if we are moored up for a long time i.e. over winter, but when we are cruising I find most of it disapears anyway.

Edited May 24, 2018 by Boater Sam

[dmr]

Epoxy is good.

Dunno how long your boat is but 3k is a reasonable price, though not a bargain.

 

Yes, you will put some scrapes on it. You could keep a little of the unmixed parts to mix later for touching up. If you mix by weight and use suitable scales then you can mix small amounts accurately. With a "drug dealer" electronic balance (eBay etc) you can mix Very small quantities accurately. Some epoxies only come in big tins so do keep a little in reserve.....but but but....

 

I reckon you still need to come out of the water every 3 or 4 years for an inspection and touch up so you will have all the dry-dockings costs. I believe it is then normal practice to take the scrapes back to bare metal, linish the whole boat, and put another couple of coats on the entire boat. Its still worth keeping a little bit in reserve for touching up above the waterline, I forgot to do this both originally and during the 3 year touch up!

 

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

[Dr Bob]

3 hours ago, Boater Sam said:

I have used 2 pack for 18 years on this boat. In that time it has been out and scars touched up 3 times, with one coat extra over the whole hull each time. I can do a coat with 4 litres @ about £10 a litre.

So that's 3 drag outs or dockings at around £300 a time + £120 for paint. I reckon £1020 for 18 years hull protection is pretty economical.

I have had 2 sets of 4 new anodes, and one pair of rudder bearings.

The hull has had one bad scrape which corroded a bit and was welded over in all that time.

At repainting time I only clean off with a water lance to remove the green slime and  avoid ripping into the paint, scrapes get a quick grind to clean them out and 2 touchup coates, then a full coat all over. Takes 2 days + 1day curing then back in the water.

In between dockings I brush off the weed growth occasionally if we are moored up for a long time i.e. over winter, but when we are cruising I find most of it disapears anyway.

Doing it yourself is obvioulsy a much cheaper way of doing it. The OP is however looking at a £3K up front cost plus then a recoat every 6 years on your model. If a yard is doing the painting then the cost adds up.

Its good to hear you have had 18 years out of it. How long do you guess you can keep to this regime? I known epoxies and coal tar epoxies for off shore splashzone use but little experience of performance on narrowboats.

It would be interesting to see some data on corrosion vs coating systems used. Does any data exist? I would have thought the surveyors would have a good handle on this as they are looking at corrosion and can see the paint systems in use. Some independent data would be really interesting to see.

[larryjc]

We got ours done for £1k last year including haul out.  But we weren't blasted back to bare metal, only pressure washed as we had a bitumen type that you can two pack over.  That was on the L&L between Wigan and Liverpool.

[system 4-50]

4 hours ago, dmr said:

Epoxy is good.

Dunno how long your boat is but 3k is a reasonable price, though not a bargain.

 

Yes, you will put some scrapes on it. You could keep a little of the unmixed parts to mix later for touching up. If you mix by weight and use suitable scales then you can mix small amounts accurately. With a "drug dealer" electronic balance (eBay etc) you can mix Very small quantities accurately. Some epoxies only come in big tins so do keep a little in reserve.....but but but....

 

I reckon you still need to come out of the water every 3 or 4 years for an inspection and touch up so you will have all the dry-dockings costs. I believe it is then normal practice to take the scrapes back to bare metal, linish the whole boat, and put another couple of coats on the entire boat. Its still worth keeping a little bit in reserve for touching up above the waterline, I forgot to do this both originally and during the 3 year touch up!

 

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

^^^^  wot he said.

[dmr]

4 hours ago, Dr Bob said:

For touching up, you would need to pour off a can of each of the two parts prior to mixing which can then be used when doing touch ups. If you do this, make sure each of the two components is fully mixed before decanting off each can. These coatings are usually designed to go over well prepared steel so doing a touch up is not quite that straight forward and will need to get back to bare metal in the area of damage and a good key sanded into the epoxy.

 

I was a paint chemist in a  previous life and am not convinced over the economics. Assume the 2 pack lasts 10 years, then that is £3K spent today versus say £600 every two years (you didnt say how long the boat is) - which is £3K (but prices will go up). Add on to that though if you look at Discounted cash flows..ie money of today, the 2pack option is then more expensive. Add on that you will lift the boat out every 4 or 5 years to check it or for repairs etc and that is additional cost. Our current boat is 15 years old and we blacked it last year for £600. At the moment I am leaning to the £600 every 2 years option but that could change if I see enough compelling evidence that a 2 pack is better. I do like the sound of the zinger stuff.

 

A final add on is that after 8 months since blacking, the waterline (and below) is plastered with growth and coming from a lumpy boat background, could do with antifouling. The 2 year cycle helps here. I've not seen anything on here about fouling and effect on fuel consumption but on our lumpy water boat it certainly affected boat speed - not a problem on the cut.

 

eta......mixing proportions for retouching is not ultra critical. I'd gues a 10% error will be fine.

 

The first bill is the big one because it includes the shot blasing.   The subsequent touch up/repair dockings will cost a bit more because the epoxy is more expensive. The preparation is maybe a little more when re-coating epoxy but there's not much in it. With epoxy I reckon every three or four years for a docking, it really should be every two years for conventional blacking, especially if you use the boat, so maybe epoxy is actually cheaper.   I suppose one day it will be time to take it all off and start again and I suspect this would be a more costly shot blast. Having used conventional blacking for several years, and now had epoxy on for 6 or so, I can say that epoxy is much much better. One of its big advantages is that it totally stops any existing pitting.  It will be time to come out of the water again next year (or maybe the year after) and my only decision is whether to get the base plate blasted and epoxied.

 

I suspect epoxy does help the weed to cling on a bit more, When I used to race in the Solent we worried about weed, on the cut there are more important things to worry about like drinking too much and spurious rebrandings etc etc

 

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

[Boater Sam]

To recap, when the initial 2 pack was applied 18 years ago I scraped the hull to bare steel, rubbed it over with coarse emery paper and did not grit blast, it has never shown any sign of flaking off.

The hull had some light pitting, the previous owner had not blacked for some time as the boat was on brokerage for a while. That is not evident now as there are a total of 6 coats now plus an initial coat of zinc 2 pack onto bare steel.

Remember when good boats sat on brokerage for a while?

The paint makers, then Leigh Paints of Bolton, now Sherwin Williams, suggested this 2 pack, its what is used on supertankers, they only get done once in their lives usually as there is nowhere big enough to dock them. A suggestion that the coating life would exceed 20 years was made at the time.

[nicknorman]

I’m a fan of epoxy. We had our boat blasted and 2-packed in 2012. We took the boat out in 2016 but it didn’t really need it. We jet washed it and, having removed the green stuff and mud, you couldn’t really see where the water line was. Certainly no hint of rust except on the rubbing strakes. I see so many boats with conventional blacking that are rusty at the waterline. A bit of diesel or oil in the water seems enough to dissolve it!

[cuthound]

Photos of mine at 10 years old. Been docked every 3-4 years. 

 

 

No underwater scrapes at all. 

 

I would definitely recommend 2 pack blacking.

[Drayke]

Had our hull shot blasted in 2008, put on five coats of 2pack, out again in 2014 hull sound but just a couple of small patches had come off around anodes. Two more coats added. Certainly no rusting around waterline.

[blackrose]

 

On 24/05/2018 at 16:10, dmr said:

 

The first bill is the big one because it includes the shot blasing.   The subsequent touch up/repair dockings will cost a bit more because the epoxy is more expensive. The preparation is maybe a little more when re-coating epoxy but there's not much in it. With epoxy I reckon every three or four years for a docking, it really should be every two years for conventional blacking, especially if you use the boat, so maybe epoxy is actually cheaper.   I suppose one day it will be time to take it all off and start again and I suspect this would be a more costly shot blast. Having used conventional blacking for several years, and now had epoxy on for 6 or so, I can say that epoxy is much much better. One of its big advantages is that it totally stops any existing pitting.  It will be time to come out of the water again next year (or maybe the year after) and my only decision is whether to get the base plate blasted and epoxied.

 

I suspect epoxy does help the weed to cling on a bit more, When I used to race in the Solent we worried about weed, on the cut there are more important things to worry about like drinking too much and spurious rebrandings etc etc

 

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

How often a hull painted with epoxy will need to come out of the water will depend on how well the job was done in the first place including the prep and number of coats, what grade of hardener was used (standard/winter grade), and whether the boat was left long enough out of the water prior to being relaunched. Some are not given enough time because people don't read the spec sheet and application guides for the paint and curing will stop as soon as the boat hits the water. Partially cured paint won't come off, but it won't last nearly as long as properly cured epoxy.It will also depend on how much abrasion that hull is subjected to between dockings. I pressure washed a 90ft Thames steam passenger launch that had been epoxied more than 10 years earlier. Granted, the boat had just been left to deteriorate over that time and had hardly been moved, but the paint was still almost perfect. We refurbed the whole boat including pulling out the engine and boiler to repair it, pulling out the coal bunkers, and we took the inside of the hull back to metal and epoxied it. But we didn't even have to repaint the hull below the waterline the condition was that good.

 

I put 4 coats of Jotamastic 87 on my boat 4 years ago (DIY) and I'm expecting not to have to get it out again for another 6 years. It's not just the expense of more frequent dockings that's saved, for me it's the sheer effort involved in blacking my widebeam by myself. If I'm doing the job then I'll do it properly and I want it to last, and you don't get any sort of longevity from bitumen. But of course if you want to inspect your sterngear and anodes then you might want to dock an epoxied boat more than once a decade.

 

 

 

 

 

Edited May 25, 2018 by blackrose

[Bee]

Snap! same stuff, 4 coats, don't want to crawl under the thing for a few years, still picking Jotumastic out of my hair.

[blackrose]

Ohh I like your bottom! 

 

You're right, the fewer times I need to crawl under here and paint the better!

 

Edited May 26, 2018 by blackrose

[blackrose]

In case anyone was wondering from my pictures, I used Jotamastic 87 with aluminium for the first 2 coats. The aluminium gives increased abrasion resistance and comes in silver or red tint so you can alternate on the second coat and easily see where you've painted. I used standard Jotamastic 87 in black for the 3rd and 4th coats. 

Edited May 27, 2018 by blackrose