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4mm overplating + epoxy. Insurance options?


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I'm in the process of selling my narrowboat and a recent survey of potential buyers reveals "bad steel" used for the overplating: 4mm plates were used... (with readings between 3.5 and 3.9 mm).
My surveyor at the time I bought it (2017) didn't flag this to me, and I (assuming I could count on an IIMS surveyor) wasn't aware of this being an issue potentially. Also the report of the previous owners (2013), didn't mention this as an issue and formulated the boat to be "in good condition" and it "should present a normal risk for insurance purposes".
I've got the sides epoxy painted, which, as I understand it (e.g. from this earlier thread:

), should protect the plates very well. But it seems it may be an issue to find an insurance for it..? I'm now insured with GJW direct. When they asked me for a survey report when the boat turned 30 years old last year, they were all fine when I sent them my hull survey with 3.7 to 3.9 readings. In fact, they accorded me time until 2027 before having to do a full survey.
Furthermore, as I understand it, insurers are concerned about the risk of sinking. I'd say that a hull where the worst pitting left a 2.6mm hull thickness, and where most side plate waterline and below readings were over 5mm (as per the pre-overplating report), overplated in 4mm, is really far more secure than just a hull of 4mm thickness, not even mentioning the epoxy protection... So, perhaps insurance companies would be willing to take such critical nuances into consideration..?

I'm curious to hear your thoughts. Particularly on what insurance options there are currently, and what about convincing them about the points I made..?
An obviously related question is: given that I had an agreement with the potential buyers to sell for £43k, with this update now, what do you think would be a fair price for the (65ft ) boat? But I guess it highly depends on the previous question!

 

Edited by Njiruk
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This is difficult. The oft quoted figure of 4mm is all very well and good and for a hefty barge carryin 200  tons of gravel there is some sense in it but for a good many steel cruisers and sailing boats 4mm is what they started out with. So far as strength is concerned most narrowboats are plenty strong enough and 4mm added onto whatever is underneath has ample strength. One problem is that testing plate thickness is a very random affair. If you strip out an old hull your eye will probably be drawn to the join between the bottom and the side on the inside of the hull, the bottom inch or so can be the worst part of the sides but many surveyors just pick out a random spot about 6" above the join on the outside. If it has always been bone dry on the inside then there's not so much to worry about. I have never seen overplating cut off a narrowboat but that could well be the worst part - and the worst part is really what you need to know about. A good coat of epoxy is about as good as it gets and so far as I have seen stops an existing  pit developing. I insure with GJW and have no complaints but other companies might not be so sensible so your buyers might indeed have a problem. 43k for a 65` boat is not a lot and if the rest of the boat is OK then it seems reasonable but you might just need a bit of luck.

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51 minutes ago, Njiruk said:

Furthermore, as I understand it, insurers are concerned about the risk of sinking. I'd say that a hull where the worst pitting left a 2.6mm hull thickness, and where most side plate waterline and below readings were over 5mm (as per the pre-overplating report), overplated in 4mm, is really far more secure than just a hull of 4mm thickness, not even mentioning the epoxy protection... So, perhaps insurance companies would be willing to take such critical nuances into consideration..?

 

As a 4mm overplate is not (very rarely) attached to the existing base plate it is not only a weak fixing but allows for ingress of waterbetween the two-plates and corrosion from both sides, you may find this article of interest.

 

Dangers of overplating.docx

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4 minutes ago, Alan de Enfield said:

 

As a 4mm overplate is not (very rarely) attached to the existing base plate it is not only a weak fixing but allows for ingress of waterbetween the two-plates and corrosion from both sides, you may find this article of interest.

 

Dangers of overplating.docx 88.49 kB · 1 download

Thanks for your thoughts Alan. Interesting.

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56 minutes ago, Njiruk said:

I'm in the process of selling my narrowboat and a recent survey of potential buyers reveals "bad steel" used for the overplating: 4mm plates were used... (with readings between 3.5 and 3.9 mm).
My surveyor at the time I bought it (2017) didn't flag this to me, and I (assuming I could count on an IIMS surveyor) wasn't aware of this being an issue potentially.

 

"Bad steel" is not a term normally used by competent surveyors. I would expect them to be far more specific about what is wrong with the steel, if anything.

 

The trouble here is, your boat will probably happily float for another 30 years regardless of the steel used for the overplating but your buyer has been spooked by their surveyor, and there is probably little you can do about that other than find another buyer. Or get them to find another surveyor who issues better surveys ;0

 

In the meantime although the forums always suggest a seller's survey is meaningless, my own experience is many buyers will place great store on a recent survey by the seller. So my suggestion is get the boat docked and have your own surveyor (same bod as last time) do another survey and show that to potential new buyers. I'd say you are quite likely to find one happy to accept yours. 

 

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1 hour ago, Alan de Enfield said:

 

As a 4mm overplate is not (very rarely) attached to the existing base plate it is not only a weak fixing but allows for ingress of waterbetween the two-plates and corrosion from both sides, you may find this article of interest.

 

Dangers of overplating.docx 88.49 kB · 3 download

I wouldn’t have thought that? 
Not saying it don’t happen like that though, it‘s probably something to look out for. 

The overplating on my boat is clearly attached to the base.

And I’ve been looking at the work of a few welders, they all appear to weld to the base.

 

I’ve a particular interest at moment because I’m waiting to have some replating done.

 

Edited by Goliath
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54 minutes ago, Goliath said:

I wouldn’t have thought that? 
Not saying it don’t happen like that though, it‘s probably something to look out for. 

The overplating on my boat is clearly attached to the base.

And I’ve been looking at the work of a few welders, they all appear to weld to the base.

 

I’ve a particular interest at moment because I’m waiting to have some replating done.

 

 

It will be 'attached' at the edges, but rarely is it welded anywhere across the width / length of the plate, that means all of the weight of the plate is 'hanging' on the edge welds. To be done 'properly' it should be welded in several places to the original base plate across the width / length of the new plate. The problem can arise where the original base plate is in poor condition and there is 'nothing' to weld to.

 

It is for these reasons that I'd never buy an overplated boat - I'd certainly buy one that needed overplating when I could specify who was going to do the work and how they were going to do it.

Buying one 'ready done' gives you no idea of if it was done to a professional standard, or at a "cowboy" standard to get it done so it could be sold.

Edited by Alan de Enfield
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Not sure what you mean. 
I’ve cut some of my plating off so I know they have been welded along their full length to the base. 
So naturally thought all would be done like that , doesn’t make sense not to. 

Mind, thinking about it mine’s an unusual case. 
I’ll post some pictures at some point in future. 

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4 minutes ago, Goliath said:

I’ve cut some of my plating off so I know they have been welded along their full length to the base. 
So naturally thought all would be done like that , doesn’t make sense not to. 

 

Yes - full length around the edges, but they should also be (at least) spot welded across the centre (or 1/3rd - 1/3rd depending on the size of the new plate) it is these welds that are often absent - Imagine a sheet of paper - support it at the edges and the middle will sag.

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On 16/02/2022 at 12:39, Alan de Enfield said:

 

As a 4mm overplate is not (very rarely) attached to the existing base plate it is not only a weak fixing but allows for ingress of waterbetween the two-plates and corrosion from both sides, you may find this article of interest.

 

Dangers of overplating.docx 88.49 kB · 5 downloads

@Alan de Enfield

I've read your document entirely, it's quite interesting, thanks. Given the serious concerns you have regarding overplating, would you say surveyors should include this in their reports? I just wonder, because I feel disappointed as my surveyor hasn't informed me about it, when I bought my boat.

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Virtually all narrowboats these days are built of steel and they are expensive things, most depreciate and deteriorate over time and after (say) 30 years or so are likely to need hull repairs (This is anything but an exact figure) If it wasn't for the practice of overplating then depreciation on a steel boat would be frightening. We don't scrap boats when they get a bit pitted and thin, we overplate them. Eventually an old boat will need some pretty major restoration but that is quite possible if the owner thinks its worth it.  Thing is that modern coatings are pretty good and boats might well last 40 - 50 years until the first bits of overplating are needed, who knows?

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2 hours ago, Njiruk said:

@Alan de Enfield

I've read your document entirely, it's quite interesting, thanks. Given the serious concerns you have regarding overplating, would you say surveyors should include this in their reports? I just wonder, because I feel disappointed as my surveyor hasn't informed me about it, when I bought my boat.

 

It is not my document, or my concerns, it is a document from a surveyor who is a member of the surveyors organisation MIIMS ( Member of the International Institute of Marine Surveyors.)

 

(The statement that I would not buy an overplated boat is 'mine').

 

When you have a survey you are paying for a CONDITION REPORT only and Surveyors are rarely forthcoming with recommendations, they will happily give you a list of work needed (and it tends to be more that is really necessary) it is called 'Ars* Covering'.

If they say something like "No - it'll be fine" then they are leaving themselves open to legal action when it proves not to be.

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4 hours ago, Bee said:

Thing is that modern coatings are pretty good and boats might well last 40 - 50 years until the first bits of overplating are needed, who knows?

But over that 40-50 years generally only the outside face of the hull gets inspected, cleaned and painted. On most boats, apart from a few thickness measurements taken every 4 or 5 years by a surveyor, you have no way of knowing whether the inside face is still in perfect condition with its original paintwork intact, generally good but with some pitting, or just a mass of rusty flakes. More boats rust through from the inside than the outside!

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  • 1 month later...

I just wanted to follow up on this thread, to react on the "Dangers of overplating" document, to correct things and to provide important nuances which may be of help for people in a similar situation.

 

On 16/02/2022 at 12:39, Alan de Enfield said:

As a 4mm overplate is not (very rarely) attached to the existing base plate it is not only a weak fixing but allows for ingress of waterbetween the two-plates and corrosion from both sides, you may find this article of interest.

 

Dangers of overplating.docx 88.49 kB · 7 downloads

 

I'm not going to comment on overplating of existing doublers, which is of secondary concern.

 

On the proposal to instead "crop out the defective steel", I would say this is more concerning since the inner side of the plates are then certainly exposed to humidity from the inside. All the more in the case of side-plating, considering the "pocket" created at the lower end of the new plate, which will allow condensation to accumulate. Moreover, it will creep between the plates as the welding is not done on the inside. Corrosion at this location is to be avoided because the expanding forces could break the weld over time.

 

Next, there seems to be a misconception on the production of corrosion. "The corrosion process requires the simultaneous presence of water and oxygen. In the absence of either, corrosion does not occur." Once all available oxygen and/or water have been converted to rust the process will stop. It is not acceptable that such important errors are made in an "MIIMS approved document". It further puts other claims made in that document in doubt.

 

Professional marine welders are used to weld boats together, which clearly are not leaking! So, there really is no higher likelihood that such professionally installed overplating would have faults. The space behind such plating is hermetically sealed. Only any potential humidity present at the time of the job could produce a small amount of rust. In the case of humidity behind paintwork, this could be an issue because small quantities can be enough to crack the paint and create an inlet for new water. ("Rust ... occupies approximately six times the volume of the original material"). This is not the case for professionally mounted overplating. Yes, if the original plating is rusting through from the inside, but (when) would that happen? Usually overplating is installed because of heavy corrosion with pitting on the outside. Once that process has been halted with the overplating, it is unlikely that e.g. a remaining 2,5mm in pits will get rusted through from the inside out. 

 

I agree that back filling the pits with welding would be a great alternative, but in cases of heavy corrosion I understand overplating is a more viable option.

 

Regarding the impact on draft. This should be looked at case-by-case. Steel is 8x heavier than water, so the calculation can be easily made with Archimedes' principle: 8x the volume of overplated steel needs to be replaced by contained underwater-level air. E.g. in my case with both sides overplated in 4mm: 8*(2*20m x 0,004m x 0,7m) = 0,896m3. To displace this volume by draft increase, the vessel's surface area of ~20m*2m=40m2 needs to lower 0,896m3/40m2 = 0,024m, or 2,4cm. That is still very reasonable.

 

The practice of "centre plate plug welds" instead of only edge welds is common on big crafts with big sections of overplating. I could imagine this to be of consideration for bottom-plate overplating on wide-beams and perhaps on narrowboats but it certainly sounds overkill to me to do this on side plating on canal boats!

 

Holding a PhD in acoustics, I can say that "propellor excited vibration" is as likely to cause cracking in welding on any other plating than overplating: very unlikely.

 

Often paperwork is present about overplating works carried out. It would be good for people to check on this. In my case a CD-R was provided with pictures and an official marine document, e.g. stating that the hull was grit-blasted prior to the works.

 

All in all, it is regrettable that such a worry-inciting document is shared online, affecting many cases which don't deserve this. I hope I'm providing a necessary counterweight to this here.

 

I find it would be more appropriate to create a document about "the dangers of bituminous paint on steel craft" - but that's another topic! 

 

 

Edited by Njiruk
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4 minutes ago, Njiruk said:

Professional marine welders are used to weld boats together, which clearly are not leaking! So, there really is no higher likelihood that such professionally installed overplating would have faults. The space behind such plating is hermetically sealed.

 

I think you overstate the general* levels of expertise in NB building and repair work on the inland waterways.

 

* not 'all'. There are some with a good reputation but they are far outnumbered by those whose work would be questioned in any other environment.

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I also wanted to share my findings on insurance options, which could save some time for others.

I contacted only a few insurance companies. These say they require a 4mm minimum hull thickness:

-GJW Direct (they say so, yet they accepted my hull survey last year, with readings down to 3,7mm)
-Westfield (I think!)
-Towergate

These insurers have no minimum hull thickness requirement:

-Ripe insurance

-Mercia Marine

-Craft insure

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4 minutes ago, Alan de Enfield said:

 

I think you overstate the general* levels of expertise in NB building and repair work on the inland waterways.

 

* not 'all'. There are some with a good reputation but they are far outnumbered by those whose work would be questioned in any other environment.

 

Yes, bunch of bodgers in many canal boat yards.

 

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On 16/02/2022 at 11:40, Njiruk said:

An obviously related question is: given that I had an agreement with the potential buyers to sell for £43k, with this update now, what do you think would be a fair price for the (65ft ) boat? But I guess it highly depends on the previous question!

 

With the overplating ins and outs. Did your boat sell?

Edited by PD1964
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We are talking canal boats here and therefore there is very little science. Massively strong construction made by welding together sections and plates of common or garden mild steel, finished with a quick coat of black 'paint' bought as cheaply as possible with no surface preparation whatsoever all done by people with no background or experience in boatbuilding. That is the baseline of the industry and anything better is an unexpected bonus. Most boats needing repair will have this start in life and the results are, to be honest, perfectly satisfactory for slogging round the canal system. There are some very good builders around but you will pay an understandably high price for their skills. Its not worth worrying too much about the odd millimetre, the hull is never going to get 10 tons of wet gravel shot into it from a lorry, it is seldom going to grind its way over a rocky bottom, all it has to do is not rust at a devastating rate and for that the owner has to keep the insides dry and protected as much as poss. and every inch of the outside painted properly. When it does eventually get thin or pitted weld a plate over it and start again. 

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43 minutes ago, PD1964 said:

With the overplating ins and outs. Did your boat sell?

I decreased the price to £40k when I found out 4mm was uncommon, but not sold for the moment. Almost all interested buyers are new to boating. They're first very interested and then they do some online research about 4mm plating and get scared. You often find online that all insurers require min. 4mm, which is simply not true. That's also why I want to put things right here. I'm confident about my price now though!

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2 hours ago, Alan de Enfield said:

 

I think you overstate the general* levels of expertise in NB building and repair work on the inland waterways.

 

* not 'all'. There are some with a good reputation but they are far outnumbered by those whose work would be questioned in any other environment.

Could that be a rash generalisation? How many have you had actual experience of?

 

Care to name some names? (Given your statement, i would expect it to be a long list  😀 ).

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It's important to recognise that the tolerances on hot rolled mild steel plates are significant. For a 4mm plate the tolerance band is 1.2mm and when ordering it's very important to understand the tolerance class required, because there is only one class - of four available - that guarantees a plate that will not be less than the nominal thickness. Given 4mm is sometimes applied as a minimum thickness criteria for insurance this is really important if 4mm plate is used.

 

If the buyer doesn't understand this and just buys an available 4mm plate it might only be 3.4mm thick as a minimum. If this is what the surveyor thinks constitutes "bad steel" then that's not really the case, it's perfectly good steel but incorrectly specified by the user.

 

It's also the case that a plate will not have a uniform thickness across it's overall area even when new if measured to the nearest 0.1mm.

 

These are reasons why quoting hull thickness loss or attempting to extrapolate the lifespan of a hull from ultrasonic test meter readings is impossible if you don't have a set of original reference readings and measure in the same places with a calibrated instrument using the same method every time.

 

Edited by Captain Pegg
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I don't know about other buyers but when I was looking for my third boat I turned down three because they had been overplated. I suppose it depends on how desparate a buyer is to have a boat.

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Just now, pete.i said:

I don't know about other buyers but when I was looking for my third boat I turned down three because they had been overplated. I suppose it depends on how desparate a buyer is to have a boat.

 

I have said on many occasions that the subject is discussed - I would never buy an overplated boat, you have no idea if it was done properly or just a 'bodge' to get it sold.

I would buy a boat needing overplating as I could then control who did it and how it was done.

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17 hours ago, Njiruk said:

Professional marine welders are used to weld boats together, which clearly are not leaking! So, there really is no higher likelihood that such professionally installed overplating would have faults. The space behind such plating is hermetically sealed.

 

You would like to think so wouldn't you? But I suspect professional marine welders don't often get involved in the gutty end of canal boat hull repairing, that being fixing up the old rusty ones, as they can earn far better money elsewhere do better quality work.

 

I'd also be amazed if all the over-plating on overplated boats really was hermetically sealed behind. How would the welder know and test? And why would he bother when he was selected to to the work because he was the cheapest quote and all the insurance co demands is an ultrasonic thickness test result of over 4mm?

 

I once spent a couple of hours closely looking at the overplating on a boat I really liked that was out on the hard standing. The standard of welding was horrifyingly bad. So was the standard of the cutting, shaping and fitting of each of the panels crassly welded on. I doubt it were anything like hermetically sealed behind the plating, so rough was the job. More likely full of water rather than air. I elected not to buy it. 

 

 

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