Base Plate Concern

[Troyboy]

If you actually mean 17 years, then yes, they nearly all do.

 

Just sold a mid-range 20 year old, and, line most of that age it had a 10mm base-plate.

 

You need to go back more than 20 years to find large numbers of boats being built with bottoms of less than 10mm.

I stand corrected on 17 year old boats ,it appears most had 10mm baseplates , although not the one subject to this thread . I still maintain 30 year old boats were normally 6mm.

 

I'm still intrigued as to why after only 17 years there are such deep pits ,I suspect inferior steel .

[Neil Smith]

Just off topic slightly but I want to paint the bum of my new 58foot shell (10mm) in 2 pack, but it is only 6" off the ground any suggestions please.

 

Neil

[onionbargee]

Different boats exist in all kinds of different situations, different water qualities, stray electrical currents in marinas, ect. How is it possible to compare.

[MtB]

Just off topic slightly but I want to paint the bum of my new 58foot shell (10mm) in 2 pack, but it is only 6" off the ground any suggestions please.

 

Neil

 

 

Tip it up sideways, then you should be able to reach.

 

Hope that helps.

[SamKingfisher]

 

 

Tip it up sideways, then you should be able to reach.

 

Hope that helps.

Mike don't be silly, I think the boat is probably at least a two man lift. Better to get a flock of angora rabbits, put the paint on their fur and release under the boat. Repeat until fully covered.

[David Mack]

I'm still intrigued as to why after only 17 years there are such deep pits ,I suspect inferior steel .

 

Or it has been left plugged into a mains connection for long periods without an isolation transformer or galvanic isolator.

 

[ditchcrawler]

Just off topic slightly but I want to paint the bum of my new 58foot shell (10mm) in 2 pack, but it is only 6" off the ground any suggestions please.

 

Neil

Get it picked up and put on trestles

[Neil Smith]

I cant as it is under a poly tunnel whilst fitting out, and a crane to lift it would cost £400 ouch. Was thinking of a roller on a long pole but not sure I could get enough pressure on it.

 

Neil

[John V]

Mike don't be silly, I think the boat is probably at least a two man lift. Better to get a flock of angora rabbits, put the paint on their fur and release under the boat. Repeat until fully covered.

 

 

The Fluffy Bunny Society enforcement team is watching you !!!

[J R ALSOP]

Well to put in my case, my Lords, mine was built 36 years ago and bottom and sides are 10mm.

[tillergirl]

You are unlikely to find a boat anywhere near that age with no pitting.

Our boat is 22 years old no pitting on baseplate at survey in 2013 and only two places where the hull shows signs of pitting of 0.01mm.

 

If the OP really likes the boat perhaps they should reflect replating into the price offered

Edited June 24, 2015 by tillergirl

[Alan de Enfield]

I don't think most 17 year old boats had 10mm base plates , more recent ones maybe but I suspect..............

 

 

Just to add further evidence - 17 years ago was1998 (I think)

 

Our 1998 Reeves has a 13mm base plate, never blacked and had no measurable pits at its last survey.

[Bee]

Why does steel underwater pit whilst steel above water just rusts? If you look carefully at most pits they are shiny which suggests electrolysis to me. Thing is though if you paint the pit it seems to stop the erosion in that one place. Ithink that there are a lot of variables when it comes to electrolysis in boats and odd things happen. I paint everything.

[Neil2]

Why does steel underwater pit whilst steel above water just rusts? If you look carefully at most pits they are shiny which suggests electrolysis to me. Thing is though if you paint the pit it seems to stop the erosion in that one place. Ithink that there are a lot of variables when it comes to electrolysis in boats and odd things happen. I paint everything.

 

As I understand it, pitting is a situation where the centre of the pit is acting as an anode, and the surrounding area is cathodic, ie it is an electrochemical reaction which presumably works more efficiently when the metal is constantly immersed in water? But what I don't understand is why this doesn't seem to happen on the inside of steel boats. For example I cleaned out a neighbour's integral tank earlier this year and though there were piles of flaking rust, once I scraped it all away the metal underneath was smooth, almost like new. I've also witnessed this in wet cabin and engine bilges.

 

FWIW I had my boat grit blasted recently and the never-blacked base plate was covered in small craters ie pits, except in the immediate vicinity of the anodes. By contrast the uxter plate - blacked regularly - looked like brand new metal. Interestingly pitting on the hull sides was almost non existent at the waterline, but noticeable lower down which conflicts with the received wisdom about rusting being more of an issue where water and air are constant companions. I reckon it's electrolytic reactions in deep water that causes serious corrosion in narrowboats. Quite why some boats seem immune to it is still a mystery.

 

I do wonder if the anecdotal evidence of base plates that don't seem to rust at all is confined to deeper draughted boats that are almost skimming the bottom of the canal most of the time. I suspect a baseplate that spends most of its life in a silty/muddy environment might very well be afforded some sort of protection, I'm just guessing.

[DHutch]

I'm waiting for those from the ' No need to black the base plate ' camp to comment on this thread . I have always painted the base plate on my boat and when surveyed for insurance purposes the surveyor made positive comments in his report .

Is the INSIDE of the base plate you need to psint.

 

 

Daniel

[John V]

Neil that's interesting and I wonder if it ties in to an article I was trying to understand a while back (it got a bit too advanced for my brain to handle)

There is apparently some sort of correlation between magnetic fields that underwater (and underground) steel is exposed to and the corrosion that occurs. A water tank is in effect a Faraday cage and the inside will be protected from exposure to stray magnetic fields and thus corrode less.....I seem to remember there was something in the article that reference overhead power distribution systems.........I will see if I still have the article tucked away somewhere

[Bee]

Its a bit of a puzzle, I, too have shovelled loads of scale from inside a boat and found no pitting, just old fashioned rust, I docked my boat this year after 5 years. Minor pitting on the sides, slight pitting in very few places underneath below the chines, bottom (painted) was fine (its not a narrowboat) but the rudder which has magnesium anodes was pitted a lot, the mag anodes are placed as suggested by the makers. I am nearly convinced that anodes don't make a lot of difference but a good coat of epoxy and a lift out every 3 years is the way to go. I docked the boat in Holland and shared the slip with what I thought was a nearly new large steel cruiser, no anodes, slipped and painted every 3 years, turned out to be 40 years old and perfect.

[Neil2]

Like a lot of owners I too was sceptical about the value of anodes and seeing my boat blasted back to bare metal has sort of reinforced that view. As I said earlier, the hull in the immediate area of the anodes was almost untouched, but this was maybe just a couple of feet either side. On my boat that still leaves around 40 feet or so of "unprotected" steel. I reckon you would have to fit anodes every couple of metres along the boats length to make a real difference.

 

I hear what other members say about their pristine unpainted baseplates but if I was having a new boat built it would be first line of the spec that the entire hull must be at least epoxy coated - I've gone down the zinc coating (and epoxy) route which pretty much gives you peace of mind for the foreseeable future and to be honest I don't think the cost of the exercise is that great - certainly compared with the price of having the above water bits professionally painted. I see boats in our marina where the owners have spent £8-10,000 on having the cabin repainted but they are still slapping oil based tar on the hull every few years. I think it's madness.

[gazza]

Google differential aeration corrosion to understand a bit more about the subject.

 

Bituminous paint is not the solution but no bugger listens anyway

[Bee]

TOWIE, the only way is epoxy - and all over the underneath as well

[blackrose]

 

The only thing I would say about that is...the specifications and standards may be more precise for a particular grade of steel and it may in deed have more predictable and reliable qualities but that doesn't mean to say that the boat builder of today is necessarily using as good quality a grade of steel as one 30 years ago

 

The only thing I would say about that is... If a boat builder isn't using the correct grade of steel then that is an entirely different issue.

 

I think they should be using BS 43A grade and although I don't have the data I'd assume that the vast majority are, and that in this respect standards are higher than they used to be too. What makes you think it used to be better? Anyway, if they are not using the correct grade of steel then there's something very wrong.

Edited June 27, 2015 by blackrose

[blackrose]

Isn't that the truth. Anyone know what grades builders are using, and for that matter what grades are available

 

Is it? I really don't know. What data or evidence do you have on the numbers of boat builders using the wrong grade of steel compared to 30 years ago?

 

My guess is that it was worse back then because regulations are tighter now, but as I said, I have no evidence so I'll avoid making definitive statements about "the truth".

Edited June 27, 2015 by blackrose

[John V]

 

The only thing I would say about that is... If a boat builder isn't using the correct grade of steel then that is an entirely different issue.

 

I think they should be using BS 43A grade and although I don't have the data I'd assume that the vast majority are, and that in this respect standards are higher than they used to be too. What makes you think it used to be better? Anyway, if they are not using the correct grade of steel then there's something very wrong.

Where did I say that boatbuilders today are not using the correct grade of steel?

 

If steel was of more variable a quality in the past, some of it was of a better quality than the required standard today. If a boatbuilder in the past was using the highest grade he could obtain it probably was of better quality than that he would be required to use now.

[Neil2]

The quality of steel issue is a big red herring as far as I'm concerned. And the notion that boat builders of 30-40 years ago were more consistently using the correct grade of shipbuilding steel compared to more recent times I find hard to swallow.

 

The problem is there's no incentive for anyone to do some proper structured research. If we were discussing oil rigs in the North Sea doubtless Shell and BP have spent a lot of time and money on finding out what happens to the underwater parts of their platforms. But as far as the cottage industry of narrowboat building goes it seems that increasing the thickness of the baseplate and hoping for the best will be the trend for some years yet.

[Troyboy]

Is the INSIDE of the base plate you need to psint.

 

 

Daniel

 

Both although the inside of my baseplate is covered in concrete slabs so won't be repainted for many years . I'm beginning to think painting the base plate is almost as controversial as cassette or pump out.