Finish blacking with Coppercoat?

[Gybe Ho]

2 hours ago, Alan de Enfield said:

Isn't that statement an oxymoron ?

 

 

😀 It is until you discover Kingston Marine in East Cowes, it is a strange place and I recall it is technically a municipal boatyard that generates a profit for the local Council.

[Bargebuilder]

46 minutes ago, Bee said:

 

The Iron Bridge in Shropshire was painted in glass flake epoxy (I think) and it lasted extremely well

I understand that it is the favoured coating for many bridges, including the Forth Rail Bridge, because, in part, of its 25 year life span, but it was developed for the harsh marine environment of the offshore North Sea oil industry. It is also used in the salt water cooling intakes of nuclear power stations and to coat the ballast water tanks of ocean going tankers. 

 

Its little wonder that the boat 'blacking' industry is reluctant to promote a product with the potential of such a long life span. Yes, it can be scraped off in a collision, but it is easy to do a local repair with DIY tools and a paint brush. 

 

 

[Gybe Ho]

2 hours ago, dmr said:

 

A hull free of weed growth (which can be quite dramatic) will go faster/more efficient but I doubt its that significant except maybe on a river. Pushing a boat through a narrow shallow channel is what takes the energy.

 

 

Is it possible weed and hull performance has been overlooked in narrowboating until recently. Now there are serial hybrids cruising around with instant kW readings the dramatic increase in kW between 1.8 mph and 4 mph has become common knowledge.

 

A ritual pastime when I was moored up on a yacht was to scrub off growth around the hull from water level to an arms length below. I won't have have a tender on my narrowboat but if the towpath switches side often enough I could scrub off 2ft of growth from the towpath.

[hider]

I have used Sherwin Williams (and Leighs Paints before the take over) and have only praise for their 2 pack epoxy. Never found any better. 25 years life is attainable.

Edited July 18 by hider

[MtB]

3 hours ago, dmr said:

Antifoul is just not done on the cut so this suggests its not required.

 

I was under the impression that traditional antifoul was banned on inland waterways.

[IanD]

15 minutes ago, Gybe Ho said:

 

Is it possible weed and hull performance has been overlooked in narrowboating until recently. Now there are serial hybrids cruising around with instant kW readings the dramatic increase in kW between 1.8 mph and 4 mph has become common knowledge.

 

A ritual pastime when I was moored up on a yacht was to scrub off growth around the hull from water level to an arms length below. I won't have have a tender on my narrowboat but if the towpath switches side often enough I could scrub off 2ft of growth from the towpath.

 

It has, but that's mainly because power goes up with speed^3, and in most canals by far the biggest source of the drag is from the narrow/shallow channels, not hull surface drag. I found I can use double the power in return for half the speed on a narrow/shallow canal like the Peak Forest compared to a wide/deep one like the Sheffield and South Yorkshire...

[Gybe Ho]

4 minutes ago, MtB said:

I was under the impression that traditional antifoul was banned on inland waterways.

 

When starting this thread I was half expecting someone to raise such a point. Coppercoat leaches less toxicity than regular antifoul particularly the now banned Tributyltin antifouling used in the 1980s. Even so there must be some loss of copper into the environment over 10 years with Coppercoat which is a concern I should not overlook even if the legislation does.

[MtB]

3 minutes ago, IanD said:

 

It has, but that's mainly because power goes up with speed^3, and in most canals by far the biggest source of the drag is from the narrow/shallow channels, not hull surface drag. I found I can use double the power in return for half the speed on a narrow/shallow canal like the Peak Forest compared to a wide/deep one like the Sheffield and South Yorkshire...

 

Another effect is on a wide deep waterway, observation suggests the speed of the boat is roughly the same as speed of the water flowing over the hull (and weeds). On a thin, shallow canal one observes water flowing backwards past the hull either side so this probably happens underneath too. So there will be proportionally more weed drag on a narrow shallow canal than wide/deep. 

 

I agree though this effect will be swamped by the power is proportional to the speed cubed effect tho! 

 

 

 

 

 

4 minutes ago, Gybe Ho said:

 

When starting this thread I was half expecting someone to raise such a point. Coppercoat leaches less toxicity than regular antifoul particularly the now banned Tributyltin antifouling used in the 1980s. Even so there must be some loss of copper into the environment over 10 years with Coppercoat which is a concern I should not overlook even if the legislation does.

 

An unrelated thing to consider is how long you need the boat to last. Consider your age and how many years you think you might be boating for. I dunno about you but it is pretty pointless most of us here designing a boat to last for 50 years!  

[IanD]

8 minutes ago, MtB said:

 

Another effect is on a wide deep waterway, observation suggests the speed of the boat is roughly the same as speed of the water flowing over the hull (and weeds). On a thin, shallow canal one observes water flowing backwards past the hull either side so this probably happens underneath too. So there will be proportionally more weed drag on a narrow shallow canal than wide/deep. 

 

I agree though this effect will be swamped by the power is proportional to the speed cubed effect tho!

 

An unrelated thing to consider is how long you need the boat to last. Consider your age and how many years you think you might be boating for. I dunno about you but it is pretty pointless most of us here designing a boat to last for 50 years!  

 

And that's where most of the drag comes from -- for the water to flow backwards past the hull quite fast, it has to drop in level from bow to stern, this can be several inches as you can see looking at the bank. Which means the ~18ton boat is essentially having to be pushed uphill and that's what takes all the extra energy, not the surface drag which is what weed makes worse but which is low on low-speed canals anyway.

[Gybe Ho]

30 minutes ago, IanD said:

It has, but that's mainly because power goes up with speed^3, and in most canals by far the biggest source of the drag is from the narrow/shallow channels, not hull surface drag. I found I can use double the power in return for half the speed on a narrow/shallow canal like the Peak Forest compared to a wide/deep one like the Sheffield and South Yorkshire...

 

 Ah-ha where is the palm-headslap emoji?

 

So the counter current generated by the forward motion of a hull in a narrow waterway is a big factor particularly when the counter current has to wriggle its way past underwater weeds each side of the hull. By underwater weeds I mean growth rooted in the canal and not the hull.

Edited July 18 by Gybe Ho

[IanD]

15 minutes ago, Gybe Ho said:

 Ah-ha where is the palm-headslap emoji?

 

So the counter current generated by the forward motion of a hull in a narrow waterway is a big factor particularly when the counter current has to wriggle its way past underwater weeds each side of the hull. By underwater weeds I mean growth rooted in the canal and not the hull.

Yes but it's not the drag from weeds in the current -- on canal bed or boat -- that causes most of the drag, it's "going uphill".

[Gybe Ho]

1 hour ago, IanD said:

And that's where most of the drag comes from -- for the water to flow backwards past the hull quite fast, it has to drop in level from bow to stern, this can be several inches as you can see looking at the bank. Which means the ~18ton boat is essentially having to be pushed uphill and that's what takes all the extra energy, not the surface drag which is what weed makes worse but which is low on low-speed canals anyway.

 

 

It is said that an F1 car can drive along a tunnel roof upsidedown because of the aerodynamic downforce. I can see a low speed version of the same in effect with a narrowboat. My old sailing yacht had a partially open stern and I could watch the stern wake under speed. At 0 knots the hull to stern joint was 3" above water level but at 7 knots the stern squatted down by 5" to 8". I had assumed this was a hydrodynamic suction effect.

 

Could both this effect and your uphill observation come into play with a narrowboat. The proximity of the canal bottom would help promote a suction ground effect similar to that achieved on an F1 racing car with side skirts.  

Edited July 18 by Gybe Ho

[Tony Brooks]

13 minutes ago, Gybe Ho said:

 

It is said that an F1 car can drive along a tunnel roof upside because of the aerodynamic downforce. I can see a low speed version of the same in effect with a narrowboat. My old sailing yacht had a partially open stern and I could watch the stern wake under speed. At 0 knots the hull to stern joint was 3" above water level but at 7 knots the stern squatted down by 5" to 8". I had assumed this was a hydrodynamic suction effect.

 

Could both this effect and your uphill observation come into play with a narrowboat. The proximity of the canal bottom would help promote a suction ground effect similar to that achieved on an F1 racing car with side skirts.  

 

Exactly the same on my narrowboat on the Thames, but much more so if I ever went too fast on many canals. I think the stern dropping is caused by the prop pushing water away from the stern faster than it can get past the boat and into the evacuated area.

 

By looking at the bank (piling) at the bow or a little ahead of it you will see the level rise, then fall as the boat passes that point and finally rise again as the boat passes. That is because the boat is literally bulldozing the water ahead of itself.

 

That gives two reasons the boat on canals often have to push themselves up hill.

 

If you are so concerned about this sort of thing, then perhaps you should think about a shallow V hull, perhaps with angled chines, so water can get around the hull easier.

[IanD]

3 hours ago, Tony Brooks said:

 

Exactly the same on my narrowboat on the Thames, but much more so if I ever went too fast on many canals. I think the stern dropping is caused by the prop pushing water away from the stern faster than it can get past the boat and into the evacuated area.

 

By looking at the bank (piling) at the bow or a little ahead of it you will see the level rise, then fall as the boat passes that point and finally rise again as the boat passes. That is because the boat is literally bulldozing the water ahead of itself.

 

That gives two reasons the boat on canals often have to push themselves up hill.

 

If you are so concerned about this sort of thing, then perhaps you should think about a shallow V hull, perhaps with angled chines, so water can get around the hull easier.

That's why more power just makes the stern squat down more in shallow water as the prop sucks water from under the boat -- a steeper hill to climb, more power used but no more speed...

Edited July 18 by IanD
Correction

[peterboat]

10 hours ago, David Mack said:

Single pack blacking would probably be fine. I was specifically questioning why you would apply 2 pack epoxy over a single pack coating.

Zinga is a single pack coating, so is Zinga blacking and so is keelblack. I have had no problem with adhesion between coats and it's over 10 years since zinga was first done. All I do is power wash it with a steam cleaner, I abrade any damaged areas coat with zinga then 3 coats of keelblack waterline and below one coat above

[Gybe Ho]

1 hour ago, Tony Brooks said:

If you are so concerned about this sort of thing, then perhaps you should think about a shallow V hull, perhaps with angled chines, so water can get around the hull easier.

I can see the technical logic in your suggestion but oh the loss of sq inches in my floating apartment floor plan. Given the longterm decline in canal maintenance I wonder if it is time to trade reduced ballast and draft for a pair of bow and stern thrusters to keep directional stability.

[blackrose]

12 hours ago, Tony Brooks said:

I thought Coppercoat was simply a hard copper antifouling, not corrosion protection, especially as GRP hulls do not need such protection.

 

That was my understanding too. 

 

I'm so for innovation but it sounds like the OP is trying to reinvent the wheel. Properly applied epoxy will last the best part of a decade. If you want to get the boat out after 5 years to inspect it and repair any scrapes you'll have to abrade back a layer of copper paint to get the new epoxy to bond. Assuming it's still there is course. Just forget the copper and use several coats of a good epoxy.

[Gybe Ho]

1 hour ago, IanD said:

That's why more power just makes the stern squat down more as the prop socks water from under the boat -- a steeper hill to climb, more power used but no more speed...

The same stern squat behaviour can be seen under sail power though I don't doubt the prop suction effect as well. A heeled over yacht under sailpower must have specific hull suction effects due to the immersed curved topsides.

 

The Coppercoat discussion wandered in this direction because I was overestimating the benefit of Coppercoat's anti fouling property. Hull growth even just slime can be a deciding factor in winning a sailing race. I am now convinced there are much larger factors at play with narrowboat hull propulsion efficiency.

 

I think this rules out coppercoat and if I want an abrasion resistant blacking @Bargebuilder has pointed out a better alternative with embedded glass granules.

 

The remaining uncertainties in my plan are when to apply a good 10 year epoxy paint layer to a new shell build. I assume the shell builders do not paint the baseplate underside and only some have an onsite setup for shot blasting. I have read that a slightly corroded hull that is then sandblasted creates a better keyed surface for epoxy than sandblasted new steel plate.

 

All these considerations lead me to a conclusion the best plan is to accept the default primer and blacking offered by a shell builder and then do a serious longterm below water epoxy paint mid summer after the hull has sat in the water for a year.

[Tony Brooks]

10 hours ago, Gybe Ho said:

I can see the technical logic in your suggestion but oh the loss of sq inches in my floating apartment floor plan. Given the longterm decline in canal maintenance I wonder if it is time to trade reduced ballast and draft for a pair of bow and stern thrusters to keep directional stability.

 

I would have thought that from your time with GRP yachts, you would have noticed at least one where the floor boards stop where they meet the hull/chine. Often the thickness of the board takes up a great deal of the chine vertically and what is left of the exposed chine is under cupboards or other fittings. In effect, very little storage area is lost to any chine. If you stuck with just a chineless V bottom, I don't see how any storage area would be lost.

 

As you will be using thick scaffold boards, the parts that meet any upward slope of the hull can be tapered so they present a flat top close to the hull. If you get the taper right, the sloping baseplate will support the thinner area of the board, so it would support heavy weights.

 

Are you aware that Springer narrowboats had V bottoms maybe 50 years ago? They are not new, and the shallower draft allows space for a bit of a keel to help directional stability.

 

Anyway, your boat, so your choice, but I can't see much advantage in the Coppacote idea to make it cost-effective.

10 hours ago, Gybe Ho said:

I have read that a slightly corroded hull that is then sandblasted creates a better keyed surface for epoxy than sandblasted new steel plate.

 

Allowing the hull to rust removes the mill scale, so the scale and not fall off, taking any coating with it later. Hopefully, DECENT sand/shop blasting would remove the mill scale.

Edited July 19 by Tony Brooks

[Gybe Ho]

7 minutes ago, blackrose said:

I'm so for innovation but it sounds like the OP is trying to reinvent the wheel.

 

 

My main motivation for considering coppercoat was all the sad cases documented on YouTube of hulls requiring £5k to £10k of welding just to restore structural integrity in old narrowboats just purchased for less than £40k. There must be a systemic pattern of build or maintenance failure at play. I also saw a shocking example of a middle aged boat with no baseplate paint protection. A third of the baseplate required overplating after a surveyor examined strange deep pitting that might have been electrolysis driven.

[Alan de Enfield]

24 minutes ago, Gybe Ho said:

 

My main motivation for considering coppercoat was all the sad cases documented on YouTube of hulls requiring £5k to £10k of welding just to restore structural integrity in old narrowboats just purchased for less than £40k. There must be a systemic pattern of build or maintenance failure at play. I also saw a shocking example of a middle aged boat with no baseplate paint protection. A third of the baseplate required overplating after a surveyor examined strange deep pitting that might have been electrolysis driven.

 

It can be the condition of the water and / or where they are kept. One memer on this forum went from 'loads a thickness to amost being a submarine in 18 months.

 

 

 

 

And he is not unique - several other reported similar

 

 

 

 

Nothing to do with quality of the build, nothing to do with lack of maintenance

 

It can just be electrical currents in the water, or it can be microbial corrosion.or a myriad of other problems.

 

Would you like any other little rays of sushine, or do you prefer the fiction of Narrowbaoting as viewed on You Tube ?

Edited July 18 by Alan de Enfield

[ditchcrawler]

Have you considered putting a mast and sail on this Narrowboat you are designing, it would be fun shooting bridges, there are about 3 to the mile.

 

[Gybe Ho]

44 minutes ago, Alan de Enfield said:

Nothing to do with quality of the build, nothing to do with lack of maintenance

 

It can just be electrical currents in the water, or it can be microbial corrosion.or a myriad of other problems.

 

Would you like any other little rays of sushine, or do you prefer the fiction of Narrowbaoting as viewed on You Tube ?

 

Yes give me more. Microbes corroding steel ouch that is a new one on me? I have just been reading and catching up on MIC.

 

I presume that despite the myriad of reasons a hull might reach a point of structural crisis you do approve of painting a baseplate within a year of shell fabrication? And fitting of an isolating transformer?

 

Have a look at the baseplate corrosion in this video, quite bizarre don't you think?

 

https://www.youtube.com/watch?v=-WbgQNUtsAw&t=40s

1 hour ago, ditchcrawler said:

Have you considered putting a mast and sail on this Narrowboat you are designing, it would be fun shooting bridges, there are about 3 to the mile.

 

I did read an account of a Cornish Shrimper (19ft shallow draft cutter sailing boat) doing a circumnavigation of King Arthur's realm by navigating from London along the K&A and the rest of the journey via sea.

[Alan de Enfield]

8 hours ago, Gybe Ho said:

I presume that despite the myriad of reasons a hull might reach a point of structural crisis you do approve of painting a baseplate

 

I have never had a base plate painted.

On a 1998 boat (Reeves 12mm base plate) in 2014 I had it out for blacking (not the base plate) and asked them to measure the base plate. It varied slightly from 12mm to 12.5mm (apparently within manufacturers tolerances of 12mm +/- 1mm) Not a single pit was found.

 

I am not a follower of the 'base plate painting camp', but your boat you can do what you want wth it.

[Bargebuilder]

10 hours ago, Gybe Ho said:

when to apply a good 10 year epoxy paint layer to a new shell build. I assume the shell builders do not paint the baseplate underside and only some have an onsite setup for shot blasting

The steel of my new build came primed from the steel supplier. This was slurry blasted off leaving very rough, shiny, but wet steel. Fortunately, the Chemco surface tolerant primer is designed to go directly onto wet, gingered steel, so the priming can happen without delay.

 

Some boatyards no longer allow dry grit blasting to protect nearby boats, but wet blasting avoids the clouds of dust and wet steel isn't a problem when you use the correct primer.

As for base plates, I painted the bottom of my barge. Fish are able to extract oxygen from water to "breath" at much greater depths than 60-90cm, so there is definitely enough to rust steel. Most scratches and bumps on a narrowboat are along the sides, the base plate less so. If glass flaking the base plate is within budget, it can only prolong the life of the steel and possibly improve the re-sale value of the boat when you eventually sell.