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Major leak and rust under floor


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Morning all! 

 

I havn't posted here in a long while but I'm hoping I can seek some advice.

 

I'm on a 70ft nb with a 10mm base plate and overplated 6mm sides.

 

I've recently removed a calorifier and upon doing so I discovered a rotten floor, below this I discovered about three inches of water resting under my bedroom.

 

there is a lotttttttt of rust and I'm a bit scared about it. Upon buying my three years ago the boat the survey said baseplate measured between 10.1 to 8.9 with widespread pitting at 2mm.

 

My question to the wise ones here is would you say this is safe to chip away at the rust or could I risk going right through my floor? And finding myself with a brand new swimming pool in my boat.

 

I've read every forum post I can find on this topic and it seems the best things for the job would be a scraper/ wire brush on drill. Followed by a rust neatruliser like vactan, followed by some kind of paint.

 

unfortunately this problem will mean I have to remove several walls and a massive chunck of the boats flooring, so any tips on how to make this as easy as possible would be greatly appreciated.

 

the suspected cause of the leak is the calorifier and the water pump, both were wet and the water pump often went off for small birsts every now and then.

 

This is the price you pay for the 'I'll fix it later' mentality... ?

 

here is a link of the damage (aftrr I've removed the water) 

 

 

Thanks a lot!

 

James

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I've seen worse and these sort of rust issues generally look a lot worse than they actually are.  If you're really scared of blowing a puncture, get it onto some hardstanding or a dry dock first.  Then get a hull survey before doing anything else.  It shouldn't be too hard to get it out of the water, surveyed and back in the same day.  My guess is that if you started with 10mm, you'l still have plenty left.  Then you can scrape it back and vactan it with confidence. 

 

All narrowboats should be built with large inspection hatches at the back of the cabin so you can easily look down into the bilge.  Most don't though.

 

  • Greenie 1
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Rust is about ten times the volume of the original metal loss.  So unless the scale is massively thick you will be fine.

 

Scrape, wire brush, rust treatment  and then paint as you suggest.

When you refit the floor leave some vent holes and some access panels in case of another leak.

 

N

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I had the same in my engine bay last year. Looked a lot worse, but scraped it, washed it out with gunk and water, sucking it all out, (rust remnants and all), with a wet and dry vac from wickes. Vactan, Primer, undercoat, bilge paint, (Craftmaster), and the job's a good 'un.

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I wouldn't panic - looks like the inside of my water tank before I treated it. Good thing about using Vactan is that you don't have to get back to clean steel before applying it which is difficult/impossible where it is inaccessible and you don't have to dry it out completely beforehand as it's water based anyway.

 

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Thanks for the replies.. heres a clip of i scraping off.. wierdly satisfying,

 

so can i apply vatcan as soon as I've got rid of all the cruddy bits?

 

 

cheers!

Edited by JCheetham
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It looks OK to do this, as others have said.

As a belt and braces approach, I'd have some epoxy putty handy just in case you hit a really thin spot.  This is a remarkable fix/bodge material. When I went through the hull  while descaling rust (on a surveyor's advice, I might add!) it set so hard that it had to be chipped off with a chisel.

 

 

  • Greenie 1
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It also looks likely that the rust has spread up behind the walls and i imagine thats why it was over-plated on the sides.

 

would the sensible thing to do to be rip down the walls/insulation and essentially start again.. or is that an over reaction?

 

thanks for all the help so far!

 

 

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Have you actually found the source of the leak and fixed it? It wasn't clear from your original post. 

 

If not, all your scraping and wire brushing will be a waste of time and effort.

 

Edit: Always switch your water pump off when you leave the boat, and if you're onboard and hear the pump activating regularly for no apparent reason then investigate.

Edited by blackrose
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On 15/07/2019 at 12:21, JCheetham said:

so can i apply vatcan as soon as I've got rid of all the cruddy bits?

I’d dry it out a bit first, it’s pretty wet. Paper towels or simply allow it to air dry for a couple of days. Then vacuum off the loose dust before applying Vactan. 

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I could see that the water pump and callorifier were both leaking, both have been removed, so hopefully there is nothing else... But I'll be keeping a close eye from now on after i install a new pump..

 

is Fertan good? It was the only thing my local chandelry had, but if not I can grab some vatcan.. still a while before I'll get to that stage anyway..

 

Cheers

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19 minutes ago, JCheetham said:

is Fertan good? It was the only thing my local chandelry had, but if not I can grab some vatcan.. still a while before I'll get to that stage anyway..

Fertan requires you to wash the treated surface down. Thereby introducing the one thing you don’t want on a rust-treated surface; moisture. Then it must be primed. Vactan doesn’t require washing off and also acts as a primer. 

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6 hours ago, JCheetham said:

is Fertan good? It was the only thing my local chandelry had, but if not I can grab some vatcan

I've used both - Fertan needs to be wiped down and immediately dried off again and is better for car bodies and shiny boats where you need to prime-sand-undercoat-sand etc. Vactan is easier to use and better suited to water tanks and bilges. I would consider using bitumen paint for the bilge as ordinary paint is not waterproof under standing water.

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