Over plating on an iron hull, is it ok?

[Phil.specialist.electrical]

Hi Guys. I’m just going through the sale this week of LMS station butty Ethel. She is getting a hull survey this week.  I’ve done lots of research and spoke to various builders including Brinklow who did extensive work to her in the 90’s. Replacing the footings and knees.  Recently she has had a 6mm parcial over plate on the base plate forward.

I had feed back from a boater over the weekend that they had heard Ethel had incorrect method of over plating the base plate and that it should of been cut out and replaced. Does anyone know if that opinion is just for historical particularity? Is it ok to over plate an iron hull like this? My surveyor seems to think so. Any advice would be very much appreciated. 

[agg221]

I suspect you are going to get a lot of different opinions, and maybe even the link to the article about the overplated boat sinking on the Thames. However, here is an opinion to kick things off.

 

When was the boat built? Was the bottom originally rivetted in and has the bottom been replaced before? Brinklow are likely to be able to answer these questions if you don't know. What this will establish is whether the bottom is likely to be rivetted wrought iron, rivetted mild steel or welded mild steel. This has a bearing on the way different repair processes will work. Welding to wrought iron is not impossible, but it is trickier than welding to mild steel. Wrought iron has laminations within it, with some fairly pure iron surrounded by silica slag. By modern standards it is a horribly unspecific material, but it lasts well and doesn't corrode very fast (the silica tends to protect the iron which, being pure, corrodes relatively slowly anyway). Trying to weld to it, you never quite know what you have got so getting something to stick well can be difficult, and it may pull off from within the iron structure. Spreading the load around by overplating and plug welding between the new steel and the old iron would generally be a good idea. Cutting out and butt-welding in around the edges is also a good idea but needs a wide V-prep on the iron side and a buttering technique to avoid melting too much of the iron into the weld which will tend to risk porosity. If it was built with mild steel or has already had the bottom replaced then the above issues do not apply and welding is much simpler.

 

In an ideal world you would always cut out and replace damaged areas, however overplating is much quicker and cheaper and, in some cases, the only practical option, for example in a fully fitted out boat or where there is something like a tank or an engine bearer the other side. Done properly with the old and new plates properly welded together as well as around the edges it doesn't cause problems except in a few very rare circumstances.

 

On a boat the age of yours, if the bottom is still original, to be honest I would expect to find some overplating due to wear rather than corrosion - the bottom is often rather closer to the top than is ideal!

 

Alec

Edited September 11, 2022 by agg221

[David Mack]

1 hour ago, agg221 said:

Welding to wrought iron is not impossible, but it is trickier than welding to mild steel. 

Whether you cut out and replace or just overplate, you will still be welding new steel to old iron. Unless you go for fully riveted repairs, which Brinklow can do for you.

[beerbeerbeerbeerbeer]

6 hours ago, Phil.specialist.electrical said:

Hi Guys. I’m just going through the sale this week of LMS station butty Ethel. She is getting a hull survey this week.  I’ve done lots of research and spoke to various builders including Brinklow who did extensive work to her in the 90’s. Replacing the footings and knees.  Recently she has had a 6mm parcial over plate on the base plate forward.

I had feed back from a boater over the weekend that they had heard Ethel had incorrect method of over plating the base plate and that it should of been cut out and replaced. Does anyone know if that opinion is just for historical particularity? Is it ok to over plate an iron hull like this? My surveyor seems to think so. Any advice would be very much appreciated. 

Don’t listen to ‘a boater’.

Get professional advise.
I recently had some over plating done on my iron hull and it wasn’t a complicated job. 
It’s not rocket science. New steel to old iron is fine.

 

 

[agg221]

11 hours ago, David Mack said:

Whether you cut out and replace or just overplate, you will still be welding new steel to old iron. Unless you go for fully riveted repairs, which Brinklow can do for you.

This is true, but if welded then the success of the outcome in terms of porosity, strength and durability, which lead to how long it will last and whether it will fail by corrosion through the weld, corrosion behind the weld, ripping off the whole repair piece or eventual general wear and tear depends on the technique used, and the technique to get the best out of it is different to that for mild steel.

 

7 hours ago, Goliath said:

Get professional advise.
I recently had some over plating done on my iron hull and it wasn’t a complicated job. 
It’s not rocket science. New steel to old iron is fine.

 

Agreed that it isn't complicated, but it is different to mild steel and not all welders are familiar with wrought iron since it hasn't really been used in new construction for over 50yrs and mild steel has been gradually replacing it for over 130yrs. That means you need to pick your source of advice carefully - not all 'professionals' are qualified to answer the question. New steel to old iron can be fine. It can also be awful to the point where you would have been better off using car body filler as it would be stronger and last longer - the difference is partly down to the knowledge and care of the person doing the work and partly down to the characteristics of the particular piece of iron you are trying to repair.

 

For reference, I work for TWI (formerly The Welding Institute) and a lot of my work is manufacturing engineering, so practical process selection. That means I quite often discuss process options with our welding engineers. They also do me the odd favour and write welding procedure schedules (WPS) for some of the things I take on myself. Wrought iron repair is a subject we talk about from time to time. The guidance on wrought iron can be found here:

 

https://www.twi-global.com/technical-knowledge/faqs/faq-can-wrought-iron-be-repaired-by-welding

 

My own boat was repaired mainly by letting in sections using the approach I described in the first post. It was done before I got it, but I could inspect the welds to see how it had been done. There are a couple of areas underneath the engine bed which could not be cut out so were overplated. I have no concerns that this repair technique was used but Monmoor Best was a high quality wrought iron so that did make the work easier.

 

Alec

Edited September 12, 2022 by agg221

[roland elsdon]

Go and talk to Brinklow. 
We discussed overplate versus cutting out with them, many times.

Handy hint they overplate boats of all ages.

We overplated our current  boat on the baseplate after grit blasting for 2 pack evidenced a likely poor long term benefit.

Full rebottom is a huge job there are lots of ‘ while I’m here I might as well do that and this.’ Before you know it you have new bottom repaired knees and sides up to the gunnels, and weld that rivet and this rivet. Then new gunnels.

Dont ask how I know.

 

And the boat especially a butty is worth little more. I know that too.

[MtB]

14 hours ago, Phil.specialist.electrical said:

I had feed back from a boater over the weekend that they had heard Ethel had incorrect method of over plating the base plate and that it should of been cut out and replaced.

 

Given that Brinklow did this supposedly suspect work, I'd be more inclined to delve into the experience and qualifications of the boater giving you this advice.

 

Brinklow cut out and replaced (most of) the baseplate and footings on my riveted iron boat and the welding to the (presumably) wrought iron looks superb. I know you can't tell by looking but if it looks good, it probably is whereas if it looks shyte, it probably is too. 

 

 

[Phil.specialist.electrical]

Everyone is giving such great advise here, I’m really getting a good idea of what’s needed and what to check.
Something I didn’t make clear was the over plate was not at Brinklow, the over plate was more recently at streethay. I wonder if anyone knows Streethays capabilities of welding to old iron? 

[beerbeerbeerbeerbeer]

1 hour ago, Phil.specialist.electrical said:

Everyone is giving such great advise here, I’m really getting a good idea of what’s needed and what to check.
Something I didn’t make clear was the over plate was not at Brinklow, the over plate was more recently at streethay. I wonder if anyone knows Streethays capabilities of welding to old iron? 

Streethay over plated my boat earlier this year. 
Did a great job welding to iron that’s about 150 yr old.
They were very understanding with what I wanted doing. 
It got a good survey report afterwards from Mike Carter who knows what he’s looking at. 
 

Just read through the thread properly and understand what you’re after now.

I think the advice given above by others is spot on. 
And as said, sometimes over plating is the only option. 

Who have you got surveying? Choose someone who has knowledge of historic boats.

I found some surveyors won’t deal with old boats.

I have a survey every 4 or 5 years for insurance reasons, the last survey was done by someone with knowledge and he picked up on stuff that the previous surveyor missed.

So choose your surveyor carefully. Might cost a bit more but it’s worth it and may actually save you money.

 

 

Edited September 12, 2022 by Goliath

[Stroudwater1]

Yes I think the boat has had repairs at two of the most respected operators around that deal with these specific issues. Things can go wrong in the best of hands I imagine but its probably much less likely.

 

I dont know either firm directly but I suspect that if they were asked to do a bodge they would direct you to other establishments, or more likely somewhere else to sling your hook or hang . 

 

Goliaths advise is wise.