hole in baseplate but rusted from inside the shell

[Lee Crook]

Hi All, just looking for some advice/reassurance! Have bought a 1980 Hancock and Lane 32ft narrowboat and have been stripping it out over the past week or so. The entire inside of the baseplate had torch welded bitumen/roofing felt adhered to it, which was an absolute pig to remove but seems to have done a very good job of protecting the baseplate on the whole until today where I happened upon what I thought was a pit in the steel but actually turned out to be a very deep/wide hole. From my observations I'm certain that the corrosion has occurred from the inside of the boat, as there is clear evidence of extensive corrosion on the transom just in front of the hole and the flooring I removed was soaking wet and rotten. I've Identified where water was getting into the boat which was from just under the cill on the bow doors and have stopped the water ingress.

[Alan de Enfield]

It is probably of no help to you, but, you are correct, a boat that is holding water inside the hull will rust thru from the inside, more easily than from the outside.

 

Presumably you are now planning to get the stern overplated.

[Lee Crook]

Hi Alan, many thanks for your prompt response. It's actually at the front of the boat i.e. about 18 inches in from the bow doors. I was wondering how thick the baseplate is on this boat as the hole is at least 10mm deep. I didn't want to prod any further with my screwdriver as the boat is still afloat and I've cleaned things up around the hole and done an emergency repair with some metal epoxy filler. The boat is going onto hardstanding next week so I'll have a better impression on the extent of the damage then. Am I correct in thinking I only to do a patch overplate if the rest of the baseplate is in sound condition? Thank you in advance.

[Alan de Enfield]

42 minutes ago, Lee Crook said:

Hi Alan, many thanks for your prompt response. It's actually at the front of the boat i.e. about 18 inches in from the bow doors.

 

You fooled me when you said the water was geting in at the bow, but the hole was at the transom (at least that's what I read it as).

Transom being across the stern, (where, on an outboard powered boat the engine is attached)

Any water that comes in at the bow normally runs under the floor to the stern bilge where it is pumped out.

 

43 minutes ago, Lee Crook said:

Am I correct in thinking I only to do a patch overplate if the rest of the baseplate is in sound condition?

 

You can only put on an overplate if you have got sound steel to weld to - this is the problem, I know of several people who have had estimates for overplating a hole that eventually turns out to be a huge job as they chase the steel back until they find solid steel to weld to. One, which was for (originally) a 12" square 'patch' became 6 foot x 6 foot. 'patch'.

[alan_fincher]

11 hours ago, Lee Crook said:

I was wondering how thick the baseplate is on this boat as the hole is at least 10mm deep.

It is exceedingly unlikely that a 1980 Hancock & Lane build used steel anything like as 10mm thick for the baseplate.

 

I would have thought 1/4 inch tops (so about 6mm).

 

Hard to see how you can be seeing "at least 10mm", unless it has either already been re-bottomed or over-plated.

I don't think there is much advice anyone can give you until it has been pulled out, and the problem(s) can be viewed from both sides.  Clearly this requires that it ends up far enough off the ground to give ull access underneath.

[MtB]

17 minutes ago, alan_fincher said:

Hard to see how you can be seeing "at least 10mm", unless it has either already been re-bottomed or over-plated.

 

That is exactly my interpretation of the photo. A hole in the original baseplate through which the over-plating can be seen.

[David Mack]

1 hour ago, MtB said:

 

That is exactly my interpretation of the photo. A hole in the original baseplate through which the over-plating can be seen.

And if the hole is 10mm deep and the original baseplate was 6mm thick, that means there is a 4mm gap between the original bottom and the overplating. And you have no idea how much corrosion is going on in that void.

[___]

I’m struggling with what people are seeing here.

 

I see a hole beneath which is wet muddy ground/shallow water.

 

The plate thickness may be observed as being thicker than the original because it’s mostly layers of laminar rust rather than good steel.

 

I suspect too it would have been 6mm originally.

[David Mack]

15 minutes ago, Captain Pegg said:

I’m struggling with what people are seeing here.

 

I see a hole beneath which is wet muddy ground/shallow water

The photo is looking through a hole in the original baseplate, and you are seeing water sitting on the upper surface of the overplating.

[Alan de Enfield]

9 minutes ago, David Mack said:

The photo is looking through a hole in the original baseplate, and you are seeing water sitting on the upper surface of the overplating.

 

Which if correct suggests that the boat will need serious work doing to it - best to just cut your losses sell it for what you can and walk away.

[matty40s]

You can have a lot of water in that gap.....

 

[___]

52 minutes ago, David Mack said:

The photo is looking through a hole in the original baseplate, and you are seeing water sitting on the upper surface of the overplating.

 

Ah, so what looked like a stone on my iPhone is in fact the edge of some flaky rust.

 

That's a big void. In reality it's not possible to have the overplating absolutely flush with the original but if it was properly plug welded there shouldn't be any big voids. Given the original baseplate is porous it's possibly the case that the water has entered from the inside rather than the outside.

 

A couple of years ago I had an overflow of my sump pump into the rear cabin bilge and after drying it out, derusting it, and cleaning it up for painting I had a continual but very very slow (<10ml per week) leak through the intermittent weld line between the keelson and the baseplate in one spot. I was worried this was water finding its way in through the overplating so had the boat out at Braunston bottom lock and Roger Farrington said to me "if it's full of water we'll see it run out when we lift it". Thankfully it wasn't and being out of the water didn't stop it. In fact the change in shape of the baseplate squeezed more out. I refloored the area concerned over the past winter but built an in inspection hatch and checked it for the first time since spring last week. Thankfully it was totally dry but it's taken over a year to get that way, not helped by a water pump leak while I wasn't aboard in the interim.

 

 

Edited September 16, 2022 by Captain Pegg

[Lee Crook]

Hi all, well I plugged the hole with some metal filler which held until I got it lifted out. It's been out of the water for a couple of months now and I can confirm that the original baseplate is around 5mm. The boat had never been overplated and the only reason it didn't sink that day was the amount of crud built up on the baseplate. Once out of the water, as soon I touched it with a screwdriver, there was daylight.

Edited December 15, 2022 by Lee Crook

[Lee Crook]

I have a large collection of videos showing the work I've done since getting the boat out of the water. I'll try to get a YouTube channel setup over Xmas and update you ASAP. Many thanks and Happy Christmas!

[john.k]

At the sandblasters  a steel barge would come in for grit blasting and painting.........payment in advance for the handling and initial hammer whacking......  would look like a lace curtain from inside the hull with sunshine streaming in thru a thousand holes.,previously plugged with rust and coating.

[koukouvagia]

I don't want to be a Job's comforter, but I'd say you've got quite a problem.  The back end of my butty had rotted through from the inside just like yours.  My son poked a hole in the hull while de-rusting it while it was in the water :(.

This resulted in a large part of the stern being re-plated (not overplated). 

 

 

the original hole and the subsequent re-plating

 

 

[Lee Crook]

Nice job! I've decided to overplate rather than replate as I'm doing the entire boat to above the waterline. I'm also overplating the baseplate and counter.

 

Here are a few pics before the snow/ice stopped play. I've drilled a line of holes along the centre line of the plates and plug welded these from the inside. There will be an additional rubbing strake going just above the sheets which will disguise them quite well.

 

Edited December 16, 2022 by Lee Crook

[Alan de Enfield]

If you have not already considered it you should take the weight of the steel you are adding to the boat and then remove a similar amount of ballast, or, your boat may sit too low in the water and any hull fittings could be too low.

 

Having been overplated, a boat sank on the Thames as it hull openings were now actually below water with 5 people (and a dog) on board.

 

 

Edited December 16, 2022 by Alan de Enfield

[Jon57]

1 minute ago, Alan de Enfield said:

If you have not already considered it you should take the weight of the steel you are adding to the boat and then remove a similar amount of ballast, or, your boat may sit too low in the water and any hull fittings could be too low.

 

Having been overplated, a boat sank on the Thames as it hull openings were now actually below water with 5 people (and a dog) on board.

 

 

 

I would have thought he would be well aware or the extra weight and take the the appropriate action looking haw he’s approached the over plating . But if not I’m sure he would take your comments on board sort of speak.

[Lee Crook]

Hi Alan, I've removed around 350 engineering bricks which made up the ballast. I took 10 bricks home and they all weighed exactly 3.4kg each. I do have a spreadsheet somewhere but there was only a small difference between the calculated weight of steel vs ballast removed, so I won't be replacing the ballast and can now insulate under the floor.

[Alan de Enfield]

Just now, Jon57 said:

 

I would have thought he would be well aware or the extra weight and take the the appropriate action looking haw he’s approached the over plating . But if not I’m sure he would take your comments on board sort of speak.

 

I've found it better to never assume - if the suggestion offends then so be it, if it saves his boat from sinking then it was worth it.

 

The boat that sank on the Thames was overplated by a 'professional' yard with years of overolating experience and yet they must have 'forgotten' or never considered the potential problem. The boat was examined by a surveyor, who again never considered the potential problem of the extra weight and was "signed off" so they bought the boat.

 

ASSUME - makes at ASS out of U and ME

[Jon57]

3 hours ago, Alan de Enfield said:

 

I've found it better to never assume - if the suggestion offends then so be it, if it saves his boat from sinking then it was worth it.

 

The boat that sank on the Thames was overplated by a 'professional' yard with years of overolating experience and yet they must have 'forgotten' or never considered the potential problem. The boat was examined by a surveyor, who again never considered the potential problem of the extra weight and was "signed off" so they bought the boat.

 

ASSUME - makes at ASS out of U and ME

I never as Ass ume. 👍

[Alan de Enfield]

5 minutes ago, Jon57 said:

I never as Ass ume. 👍

 

Ok - but does not .............

 

3 hours ago, Jon57 said:

I would have thought ............

 

Mean pretty much the same as 'assume'.

[Jon57]

1 minute ago, Alan de Enfield said:

 

Ok - but does not .............

 

 

Mean pretty much the same as 'assume'.

😁

Just now, Jon57 said:

😁

Assume nothing 👍

[rusty69]

4 hours ago, Alan de Enfield said:

If you have not already considered it you should take the weight of the steel you are adding to the boat and then remove a similar amount of ballast, or, your boat may sit too low in the water and any hull fittings could be too low.

 

Having been overplated, a boat sank on the Thames as it hull openings were now actually below water with 5 people (and a dog) on board.

 

 

When our boat eventually needs plating I intend to remove ballast by chucking out Mrs R's shoe and handbag collection. That should just about do it.