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what to do with my rusty bilge?


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Good evening,

Here are some pics of my bilge after scraping and applying Kurust to turn the rust into something else? from bow to stern each section gets worse, the front 3 sections seem good to acceptable but the last section I lifted a good Kilogram of rusted debris, when I put the rust inhibitor down it poured into a hole never to be seen again! Which leads to me to the idea, can I put a plate over it? is that an acceptable fix?  is it necessary? and affordable? (will be done by welder) (it is already over plated on the outside) will it need a support strut or would a plate alone suffice? 

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Edited by firstboat
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Doesn't look too bad to be honest. I would just get rid of the loose scale, use kurust or similar, then paint it. Remember, you need gloss or waterproof paint to keep the water off the steel, I used bitumastic water tank paint which seems ok but many other paints are ok. Trying to plate that will end in tears.

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If the Kurust went down a hole but canal water did not come in then either the boat is out of the water or its been overplated. I see no reason not to weld a patch over it if it makes you feel better but if its been overplated properly its not needed.

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Contrary to popular opinion gloss and other paints are not waterproof! At least they are not designed for underwater applications and will soon peel off if you get water in your bilges. Bitumen might fare a bit better. On the other hand good prep and properly applied two part epoxy will be fine for many years. And if you're going to all the trouble of prepping the steel you may as well use proper paint.

As you'd be painting steel which is sitting in cold water I'd use winter grade hardener. 3 or 4 coats of that and you won't need any top coat. Remember to mix the entire can of paint before you take any out to mix with hardener in a separate container. And only mix what you can use in about an hour.

http://www.paintmarine.co.uk/jotun-jotamastic-87-aluminium-epoxy-mastic-primer-44ltr-71-p.asp?_=&variantid=72&gclid=CKO3mrfquNQCFQcQ0woda6wGMg

http://www.jotun.com/Datasheets/Download?url=%2FTDS%2FTDS__523__Jotamastic 87 Aluminium__Euk__GB.pdf

 

Edited by blackrose
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1 hour ago, Tony Brooks said:

If the Kurust went down a hole but canal water did not come in then either the boat is out of the water or its been overplated. I see no reason not to weld a patch over it if it makes you feel better but if its been overplated properly its not needed.

The OP said its plated on the outside

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The fact that the liquid "disappeared" down a hole is there any advice from the more knowledgeable regarding how the obvious cavity that I would certainly assume exists between the two "hulls" can be "dried" out otherwise I would assume like an exhaust pipe etc would decay from the inside out? Am I being pessimistic on behalf of the OP?

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Our 1966 cruiser stern was overplated in 2008 with 6mm stock then epoxied externally. We purchased it in 2010 and in stripping an refitting it we decided to scrape all the loose bilge rust from the original skin internally - wire brush, scrape, Vactan rust converter and then bitumin blacked the lot but probably only one coat.  It's in reasonable shape now last time I had the floorboards up. 

There is a hole  at the very bow which leads to the "Twilight Zone" that is the area between the old skin and the new external skin.  I remember being terrified when water came out when the ballast was all moved forward during refit. 

The the boatyard reassured that it was simply water trapped between the skins, and as the bow went down the water came out.  

Now - this is definitely not ideal.  But i was advised by the yard and subsequently by a surveyor that a) you won't ever dry it out - condensation will always form and gather.  b ) don't fret it: it'll outlive you as long as you look after the outside through good blacking. The theory being that the trapped water inside between the plates has very little oxygen.

We live aboard and there is then inevitable condensation that forms inside - on occasion in the winter I may be required to wet and dry Hoover a litre or so out. 

Basically, you won't beat it. It'll always be a bit damp but some basic prep on the internal skin won't hurt but I wouldn't kill yourself to do it. It's hardly necessary. 

Subsequent surveys after 10years or so inboard have shown no thinning of any note. 

Epoxy info the entire inner bilge is a real waste of money in my opinion. Although apologies if that is a misunderstanding as to the suggestion. Small areas I can see it may have a purpose (in fact, my eternally wet engine bilge is a strong candidate!) 

 

 

 

 

 

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The no oxygen thing would tend to indicate a patch would be a good idea. Seal the void so as the iron turns to iron oxide it uses up all the oxygen - hence no more rusting.

The OP could always ask the welder to use the hole to plug weld the two skins together before welding a patch it but I doubt its necessary. the plug weld may even seal the hole.

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