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On 30/10/2017 at 23:00, rbrtcrowther said:

Just wondering if anyone has any suck work done at north kilworth warf... We're trying to sort out costs and logistics of having a potential purchase repaired.

 

Is there a question you wanted to ask?

 

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oooops.... Auto correct strikes again...any such work done.. Such!....Has anybody had any overplating or fabrication work done there. And how was the experience? The communication during the work.. Was it done on time and did it Stay on budget? That sort of thing.. It seems like a nice little place and might enquire about some work.. And as our boat will be moored in the marina opposite it would be rather handy

I say marina opposite... Big muddy puddle with a digger in it might be more accurate.. We did enquire at the warf but alas they had no room..

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If your at Kilworth you could also try sister marina Debdale at the bottom of Foxton - Andycraft are based there and I have seen them  overplating can’t comment on quality. They cut out and replaced a base plate for us years ago and fabricated our cabin top when we started converting no problem.

think new marina is being connected to system in November

Edited by Tuscan
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Thankyou very much I shall get a quote off andycraft. It all depends on of the vendor accepts the very low offer I'm going to put to them.. Its a bit of strange situation.. A previous buyer had a survey started and halted it when the condition of hull was found to have issues... But there is no information as what those issues were or how bad... It could right on the insurable limit... It might only have areas of deep pitting, or it might be about to sink.. All it says on the bit of paper is a full overplate may be required.... But then the broker said "another surveyor might arrive at a different conclusion!...

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26 minutes ago, rbrtcrowther said:

Thankyou very much I shall get a quote off andycraft. It all depends on of the vendor accepts the very low offer I'm going to put to them.. Its a bit of strange situation.. A previous buyer had a survey started and halted it when the condition of hull was found to have issues... But there is no information as what those issues were or how bad... It could right on the insurable limit... It might only have areas of deep pitting, or it might be about to sink.. All it says on the bit of paper is a full overplate may be required.... But then the broker said "another surveyor might arrive at a different conclusion!...

That person posted about the boat somewhere,not sure if it was here or Facebook

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  • 1 month later...

I have a couple of questions about overplating.My boat is ok for the moment,but a survey for insurance did suggest that some corrosion pitting would need spot welding or even overplating in the next couple of years.

I have heard that overplating costs about £100 per foot does anyone know if this is about right?

Is the old metal cut off and new metal welded to the frames,or is new metal simply welded to the old rusty stuff?

If new metal is welded to the old,is there a problem with the weight of the boat? It appears to me that if a boat is re-bottomed and re-sided over the old metal then the overall weight of the boat may exceed it's design parameters.

If some knowledgeable could answer these questions,I would be grateful.

Happy Christmas to all.

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11 minutes ago, Furness said:

I have a couple of questions about overplating.My boat is ok for the moment,but a survey for insurance did suggest that some corrosion pitting would need spot welding or even overplating in the next couple of years.

I have heard that overplating costs about £100 per foot does anyone know if this is about right?

Is the old metal cut off and new metal welded to the frames,or is new metal simply welded to the old rusty stuff?

If new metal is welded to the old,is there a problem with the weight of the boat? It appears to me that if a boat is re-bottomed and re-sided over the old metal then the overall weight of the boat may exceed it's design parameters.

If some knowledgeable could answer these questions,I would be grateful.

Happy Christmas to all.

Overplating is a literal description; extra plates are added outside the existing. There is a good recent thread showing pictures of the process by a member here called KEDIAN who undertakes this work and who has a good reputation.

Weight is an issue and it's normal to remove ballast after overplating so the draught remains the same. This isn't normally a problem because boats are usually ballasted with far more mass than the additional plate adds.

JP

Edited by Captain Pegg
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6 hours ago, Captain Pegg said:

Weight is an issue and it's normal to remove ballast after overplating so the draught remains the same. This isn't normally a problem because boats are usually ballasted with far more mass than the additional plate adds.

Assuming, of course, you cam get the floors up to get enough existing ballast out to compensate for the new steel added.

Not as easy as it sounds if plywood floors have been laid first, and everything else in the boat constructed on top of it.

In our current boat removing ballast would be a relative doddle, (much of the floor can be removed without dismantling anything else), but in our previous one it would have been a major nightmare to get at most of it.  I suspect the latter is true of many boats that get over-plated, and in practice they probably end up deeper in the water because ballast cannot be removed without major upheaval and maybe destruction of some of the interior.

If you are making it deeper in the water, you must be sure none of the following occurs....

Insufficient lip on weed hatch hole when cover removed.
Any air vents for engine now too close to waterline.
Front deck drains to0 near waterline.

Gas locker drains too near waterline.

Sink / shower / basin / bilge pump outlets too near waterline

Etc, etc.

 

 

 

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Ours was over-plated last year. The cost you suggest is about right. Because we have no ballast the boat now sits about 1" lower in the water which I welcome (I always said it was a bit too shallow) but it did add an extra £650 to the cost to have the gas lockers raised slightly.

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Back in the day before the advent of "Jeccy gizmo's" & the need for anodes the majority of over plating was confined to small patches over the outside corresponding to the knee positions the plating not giving as much & wearing thin with contact with lock sides hard piling of towpaths & other banks etc. Odd places on/under the counter etc  Big in terms of renewal of plate usually consisted of the damaged/corroded plate cut out & replaced with new  metal  only since the advent of pitting over large area's has over plating become a sort of reconnised repair for unserviceable plating Another difference seemed to be that iron hull sides had a longer life span than even the steel used in the 30's & later could be the reason for the survival rate of a good #of "Josher's" still being around at twice the age of GU boats, the hull of my motor (Iron ) when the blacking got scraped off formed surface rust but then didn't appear to get any worse if the top coat of rust was left undisturbed but my GU H&W butty with steel hull sides the rust seemed to keep growing as per normal for steel plate

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On 25/12/2017 at 02:24, Keeping Up said:

Ours was over-plated last year. The cost you suggest is about right. Because we have no ballast the boat now sits about 1" lower in the water which I welcome (I always said it was a bit too shallow) but it did add an extra £650 to the cost to have the gas lockers raised slightly.

This is a timely thread for me. I discovered a lot of loose flaking rust on the inside of the bottom plate of my aged (1976!) 45' steel narrowboat this fall. I did a lot of scraping, rust treatment and paint, but am obviously considering whether overplating is in order, especially since the original steel was only 6mm thick. However, accessing ballast from the inside of the boat would be a total nightmare. (Aside: I think the rust was due to water collecting in the cabin bilge for a long time before I owned the boat. Since I got it dried out there's been very little accumulation, so I feel reasonably confident it's not an ongoing issue.)

I've got a few questions:

Keeping Up: How much overplating did you have done? I'm worried about the ballast issue so when you said your boat is 1" lower, that seemed less than I expected.

Anyone and Everyone: What else do I need to be aware of when considering overplating? Will it make the boat "like new"-ish? Or is this a silk purse/sow's ear situation?

Thanks,

Pam ("Lucky Nickel")

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I'm probably going to fall into some trap here - I seem to recall having done so with a similar argument in the past - but here goes.......

If you are going to over-plate a narrow boat, few people, I suggest,  would consider it worth doing in less than 6 mm steel.

If you over-plate just the whole of the base plate in 6mm steel, then I suggest that because steel is 8 times denser than water, it would increase the draught of the boat by 8 x 6mm (i.e. 48mm).

That alone to me would sound like the boat would sit more like 2" deeper in the water, assuming you take no ballast out, and make no other changes.

But generally you will not just over-plate the bottom, but part way up the sides as well, and if that plating is to come above water level, I suggest you will add at least 50% more extra plate than if you were just doing the bottom.

So to me that suggests the boat would typically be more like (at least) 3" lower in the water than 2".

I'm struggling to see how adding a complete 6mm over-plate to all the underwater bits of a typical narrow boat could possibly only add about 1" to the draft, but Allan's experiences seem to say otherwise.

So is there some massive flaw in my science/arithmetic/logic - and, if so, where have I gone wrong please?

(I accept the answer may well be that I should not have had a drink before posting!......)

 

 

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We only needed to have the sides over-plated because the bottom plate was originally built as a half inch (12.5mm) thick, which is why we don't have any ballast (because the bottom itself is so heavy) and also that is why the increase in draft was about 1"

The sides were originally 6 mm thick and the over-plating was also 6 mm, from the baseplate to just above the water line.

Despite the expense of the work I am sure that the repaired boat is still worth considerably less than it was before the problems started 2 years ago.

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5 hours ago, Prairiekid said:

Keeping Up: How much overplating did you have done? I'm worried about the ballast issue so when you said your boat is 1" lower, that seemed less than I expected.

Anyone and Everyone: What else do I need to be aware of when considering overplating? Will it make the boat "like new"-ish? Or is this a silk purse/sow's ear situation?

 

2 hours ago, Keeping Up said:

We only needed to have the sides over-plated because the bottom plate was originally built as a half inch (12.5mm) thick, which is why we don't have any ballast (because the bottom itself is so heavy) and also that is why the increase in draft was about 1"

The sides were originally 6 mm thick and the over-plating was also 6 mm, from the baseplate to just above the water line.

 

Ah thanks Allan - that explains your low number.............

"Prariekid" - so I reckon about 1" extra draught if you use 6mm plate, and only overplate the sides, (which is supported by Allan's figure).

But if it is the baseplate as well, reckon on more like 3" extra draught.

If you can't compensate by removing ballast, that is quite likely to bring you to a point where gas locker drains, weed hatch, and maybe pump and other waste outlets may be an issue, I think.

Obviously it will depend from boat to boat, but in 6mm over-plate, the 1" and 3" figures feel about right to me, based on the physics and arithmetic.

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There's a handy calculator for the weight of steel here: 

http://www.steelexpress.co.uk/steel-weight-calculator.html

As a back of fag packet way to calculate how much your boat will sink, when we load our large GU boat we reckon that once the boat is levelled off (i.e. the gunnels are parallel with the water) we will have loaded 18 tonnes, which added to the approx 20 tonnes displacement of the empty boat gives 38 tonnes. After that, every tonne we load puts the boat 1" lower in the water.

Our 57' leisure boat has a displacement of about 16 tonnes so I would reckon that adding a tonne of steel would put it about  38/16 = 2.4" lower.

For illustration, a base plate measuring 7' x 50' x 6mm weighs 1.5 tonnes.

I am working from memory regarding the displacement of the two boats, but the 1" per tonne on the big one is right, so I think the logic of the calculation holds.

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8 minutes ago, David Mack said:

Your 57 ft boat is about 80% of the length of your full length GU so will load at 1.25" per ton.

I suspect you're right David and the significant ratio is between the original displacements (16/20 = 80%). Until the big one's flat on there's no ready reckoner about inches per tonne, so I should have ignored the 18 tonnes of cargo. Much easier just to ring Brinklow and ask!

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My 40 foot boat has now been overplated twice (nine grand, but still cheaper than buying a new boat and I'm used to the old monster) as it wasn't done very well the first time, although I suppose it lasted nearly twenty years so I've no real complaints.  No need to warn of any yard, both that and the welders have disappeared since.  It certainly sat a couple of inches lower in the water this time round and I had to take out all the ballast I could get at, then put some of it back to get the trim right again.  I had to have a new weed hatch because the water was too near the top of it - this was before I took the ballast out.  It's still a little lower than it was, I don't think a new boat would have the gas locker and front deck drainage or the engine air holes so low.

The latest yard did consider cutting the previous bottom off because of the weight, but decided against it and just welded it back on, then welded the new on to it, plus a LOT of new steel on the sides.  It cost a couple of thou more than their estimate as the more they shotblasted, the worse it looked and the more they found they needed to do.  I understand that you're not supposed to be able to see daylight through the hull...

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I bought Goliath with a freshly overplated baseplate. I had to remove pretty much all the ballast in the rear half of the 48ft boat to get the counter sitting nice. Getting to the ballast elsewhere was too difficult. I raised the boat at least 2inches. 

But I never saw the boat sitting in the water prior to having the new plate, so can't  compare  

I did botice the boat became significantly more tender which of course it would but again can't compare to its original state.  

 

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On ‎25‎/‎12‎/‎2017 at 16:35, X Alan W said:

Back in the day before the advent of "Jeccy gizmo's" & the need for anodes the majority of over plating was confined to small patches over the outside corresponding to the knee positions the plating not giving as much & wearing thin with contact with lock sides hard piling of towpaths & other banks etc. Odd places on/under the counter etc  Big in terms of renewal of plate usually consisted of the damaged/corroded plate cut out & replaced with new  metal  only since the advent of pitting over large area's has over plating become a sort of reconnised repair for unserviceable plating Another difference seemed to be that iron hull sides had a longer life span than even the steel used in the 30's & later could be the reason for the survival rate of a good #of "Josher's" still being around at twice the age of GU boats, the hull of my motor (Iron ) when the blacking got scraped off formed surface rust but then didn't appear to get any worse if the top coat of rust was left undisturbed but my GU H&W butty with steel hull sides the rust seemed to keep growing as per normal for steel plate

You seem to be suggesting that it's the electrical appliances that are responsible for pitting? You can have as many electrical appliances on a steel boat as you wish and as long as the boat's DC system is correctly wired and the AC system has some form of earth isolation when plugged into shore power then the steel should not suffer any more pitting than a boat without any electrical gizmos. My old narrowboat was badly pitted all over and had to be overplated yet it had never been plugged into shore power as it has no AC system and only a basic DC system. In contrast, my "new" boat has loads of electrical gizmos and has spent a fair amount of its life on shore power. The hull below the waterline still looks new. I realise that there are other variables such as maintenance, but there is no direct correlation between electrical gizmos on board and the amount of hull pitting. That's a myth.

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4 hours ago, Balder said:

Balder,

I note that was your first post so welcome to the forum. Is this just an article you have searched and found or do you have relevant experience to share?

That particular article has been discussed on this forum previously.

JP

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