Replating

[moggyjo]

Have you ever heard of a boat being replated from the inside? I would of thought that the steel you are trying to protect would rot away alot faster and not leave much for the new plate to adhere to. Any thoughts?

[1066]

It sounds very unusual .... has somebody offered to do this for you, or is it just a general question?

[moggyjo]

It sounds very unusual .... has somebody offered to do this for you, or is it just a general question?

A boat mechanic I know told me that a neighbour had had his Springer replated in the engine area ( not sure if its all the way through, although I have known the person for 20 years and hes never been out of the water) but he thought like you it was very unusual.

[Guest]

Sounds unlikely, but you never know.

[moggyjo]

Sounds unlikely, but you never know.

Would it protect the hull at all by putting it on the inside?

[Gnome K Gnome]

Would it protect the hull at all by putting it on the inside?

 

Overplating is a bodge repair. Whether its put on the inside or the outside its storing up issues to fester for another day.

 

Its used on say, a 30 year old boat to perhaps give it another 5 - 10 years, by which time it will be someone else's problem.....

[magnetman]

Just wondering if the 'replating from the inside' is actually referring to cutting out holes in the existing metal and welding the plating from inside as well as the outside. 'puddling, I think its called.

[Gnome K Gnome]

'puddling, I think its called.

 

Ah, puddle welding, plug welding, rosette welding....

 

Basically involves drilling a hole (or burning through with high amps) through the top layer and welding the two layers together through the hole...

[Dave45]

Overplating is a bodge repair. Whether its put on the inside or the outside its storing up issues to fester for another day.

 

Its used on say, a 30 year old boat to perhaps give it another 5 - 10 years, by which time it will be someone else's problem.....

dont agree with that.....where did you source your info....do u suggest throw aways oneday?

duh..

[John Orentas]

All repairs are a bodge if they aren't done correctly, over-plating carried out properly can add thirty years of life to a boat, done badly it can destroy it.. Beware the cowboys.

 

Over-plating on the inside ?, were did this come from it would be a near impossible task avoiding the knees and all the other framing.

[Guest]

Would it protect the hull at all by putting it on the inside?

Can' tsee it myself.

dont agree with that.....where did you source your info....do u suggest throw aways oneday?duh..

Me neither.

All repairs are a bodge if they aren't done correctly, over-plating carried out properly can add thirty years of life to a boat, done badly it can destroy it.. Beware the cowboys.Over-plating on the inside ?, were did this come from it would be a near impossible task avoiding the knees and all the other framing.

Agree.

[Gnome K Gnome]

All repairs are a bodge if they aren't done correctly, over-plating carried out properly can add thirty years of life to a boat, done badly it can destroy it.. Beware the cowboys.

 

dont agree with that.....where did you source your info....do u suggest throw aways oneday?

duh..

 

 

It is impossible to paint the sandwiched areas of steel once it is overplated and also impossible to prevent ingress of water to the gap. Pray tell me how you overplate properly........

 

The way this type of repair is done is to use steel thick enough to allow for the corrosion and not matter for 5, 10 or 30 years depending on the thickness of steel you choose. Basically its a total loss system that starts to decay from day one.

 

Its poor maintenance by owners that causes boats to rot out. Properly protected and regularly maintained they will last a lifetime.

 

PS. I am a welder and have been for 35 years.

Edited December 5, 2007 by Gnome K Gnome

[blackrose]

It is impossible to paint the sandwiched areas of steel once it is overplated and also impossible to prevent ingress of water to the gap. Pray tell me how you overplate properly........

 

The way this type of repair is done is to use steel thick enough to allow for the corrosion and not matter for 5, 10 or 30 years depending on the thickness of steel you choose. Basically its a total loss system that starts to decay from day one.

 

Its poor maintenance by owners that causes boats to rot out. Properly protected and regularly maintained they will last a lifetime.

 

PS. I am a welder and have been for 35 years.

 

I disagree. Overplating is a standard teqhnique for maintaining steel hulls and is carried out by boatyards worldwide. If overplating is properly done there will be no ingress of water between the sheets and the inside will not need painting. Yes, you can protect a hull by painting a boat but sometimes there's nothing you can do about hull wear - paint will wear off too. Are you a proper coded marine welder as recognised by marine insurance underwriters?

 

Sometimes worn sections of the original hull are cropped back before overplating so in this sense the boat is re-hulled rather than overplated, but as for overplating on the inside - as John said, apart from getting around all those knees and stringers which would be hell, leaving a worn hull on the outside is asking for trouble - once it wears or corrodes through then you've got water (and corrosion) between the sheets - and then you'll have to overplate from the outside again!

Edited December 5, 2007 by blackrose

[magnetman]

I heard that dot certified vessels aren't allowed to be overplated any more - full replacement of material is required.

[blackrose]

I heard that dot certified vessels aren't allowed to be overplated any more - full replacement of material is required.

 

Yes, so the worn sections of hull are cropped back and replaced. It's basically overplating but without anything behind apart from what's being welded onto.

[magnetman]

If the 're-hulling' involves insertion of material followed by welding from both sides it can't be called 'overplating'. There is a vagueness in terms which could cause problems.If the 're-hulling' involves insertion of material followed by welding from both sides it can't be called 'overplating'. There is a vagueness in terms which could cause problems.

[blackrose]

If the 're-hulling' involves insertion of material followed by welding from both sides it can't be called 'overplating'. There is a vagueness in terms which could cause problems.

 

So call it re-hulling then.

[Guest]

Re-plating.

[Teadaemon]

Yes, so the worn sections of hull are cropped back and replaced. It's basically overplating but without anything behind apart from what's being welded onto.

 

There's a big, big difference between overplating a hull and re-plating it. When a hull is overplated, the new plates can only be welded on one side, and can only be attached to the old hull plates, which are always suspect (else you wouldn't need to overplate/re-plate them). It also provides a space where water can get in and corrosion occur undetected (at least until the rust building up in the gap between the old and new plates gets thick enough to crack the welds holding the new plate on to the hull). When a hull is re-plated it's normally possible to weld both sides of the new plates, and to weld them on to the ribs/stringers inside the hull, which is necessary if those ribs/stringers are to function as designed.

 

The prevalence of overplating as a method of repairing narrowboats (and fat narrowboats) comes about because of the rather unusual design and construction sequence where the plates come first and the stiffeners are added later. Effectively the skin plates of a narrowboat are what holds it together, so removing significant sections of that skin plating is likely to lead to distortion of the hull. Compare that to a steel yacht, where the frames, stringers and bulkheads are fabricated first, and the skin plating is then welded to them, and has no function other than keeping the water on the outside of the boat.

[Timleech]

The prevalence of overplating as a method of repairing narrowboats (and fat narrowboats) comes about because of the rather unusual design and construction sequence where the plates come first and the stiffeners are added later.

 

While I agree with most of what you say, the real reason it's so prevalent is that it's so much cheaper to do and can make major repairs to a tired old hull a viable proposition. Proper replating of large areas of a typical UK canal pleasure boat just wouldn't make any sort of sense.

I don't like overplating except for 'little local difficulties' though that doesn't mean I have never done it

What does concern me is the common misconception that a boat which has had the bottom plate doubled has had a 'new bottom'. An old boat even after major doubling is still an old boat, though it may have been given a useful stay of execution.

 

Tim

[smileypete]

It is impossible to paint the sandwiched areas of steel once it is overplated and also impossible to prevent ingress of water to the gap. Pray tell me how you overplate properly........

It also provides a space where water can get in and corrosion occur undetected (at least until the rust building up in the gap between the old and new plates gets thick enough to crack the welds holding the new plate on to the hull).

 

Just a minor point gents, corrosion isn't caused by water alone, but by a supply of oxygen too - rust is ferrous/ferric oxide etc.

 

Even a sealed cavity with some water in it will only corrode until the oxygen in the air and water is used up.

 

cheers,

Pete.

[Teadaemon]

While I agree with most of what you say, the real reason it's so prevalent is that it's so much cheaper to do and can make major repairs to a tired old hull a viable proposition. Proper replating of large areas of a typical UK canal pleasure boat just wouldn't make any sort of sense.

I don't like overplating except for 'little local difficulties' though that doesn't mean I have never done it

What does concern me is the common misconception that a boat which has had the bottom plate doubled has had a 'new bottom'. An old boat even after major doubling is still an old boat, though it may have been given a useful stay of execution.

 

Tim

 

I accept that economic considerations are the main reason why nobody considers re-plating rather than overplating a narrowboat, but equally I'm pretty sure that none of the steel narrowboats I've seen would cope with significant portions of their hull plating being removed for replacement, at least not without some fairly sizeable temporary supports in the right place. It might well be possible to do it one or two plates at a time, but that's going to add even more to the cost (it generally being a lot slower to constantly swap from one job to another, as opposed to doing all the removal followed by all of the replacement).

[blackrose]

There's a big, big difference between overplating a hull and re-plating it. When a hull is overplated, the new plates can only be welded on one side, and can only be attached to the old hull plates, which are always suspect (else you wouldn't need to overplate/re-plate them). It also provides a space where water can get in and corrosion occur undetected (at least until the rust building up in the gap between the old and new plates gets thick enough to crack the welds holding the new plate on to the hull). When a hull is re-plated it's normally possible to weld both sides of the new plates, and to weld them on to the ribs/stringers inside the hull, which is necessary if those ribs/stringers are to function as designed.

 

Ah, I see.

[Gnome K Gnome]

I accept that economic considerations are the main reason why nobody considers re-plating rather than overplating a narrowboat, but equally I'm pretty sure that none of the steel narrowboats I've seen would cope with significant portions of their hull plating being removed for replacement, at least not without some fairly sizeable temporary supports in the right place. It might well be possible to do it one or two plates at a time, but that's going to add even more to the cost (it generally being a lot slower to constantly swap from one job to another, as opposed to doing all the removal followed by all of the replacement).

 

The other consideration is that boats are often overplated with a new bottom and footings without stripping and refitting the interior. A major saving on labour and materials, and like I said earlier, a bodge.

[Dyad]

I know nothing about metals and even less about boats so this is going to be a silly question but here goes... Why are boats still made of something that has to be repainted and replated? surely there are better materials now. Is it for the heritage aspect?

 

Kev