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Sir Percy

Roofing felt - why?

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On excavating down to the bottom of my boat - having taken up the floorboards and removed the ballast (concrete paving slabs), I then had to peel away a nasty, sticky mess of roofing felt. I can understand that it was there to protect the metal against water, but it hadn't - so also had to remove scale rust.

Why roofing felt? This isn't a load-bearing material.

Should the ballast have been laid differently?

Are there any alternatives - like Butyl pond liner?

 

Thanks for looking, appreciate any responses. Bear with me if I need explanation - newbie.

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It's to protect the baseplate from the slabs shuffling about

 

Richard

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On excavating down to the bottom of my boat - having taken up the floorboards and removed the ballast (concrete paving slabs), I then had to peel away a nasty, sticky mess of roofing felt. I can understand that it was there to protect the metal against water, but it hadn't - so also had to remove scale rust.

Why roofing felt? This isn't a load-bearing material.

Should the ballast have been laid differently?

Are there any alternatives - like Butyl pond liner?

 

Thanks for looking, appreciate any responses. Bear with me if I need explanation - newbie.

 

 

Yeah, ends up a right mess in most cases and if water does get to the bilges it will end up getting trapped between the felt and ballast.

 

When we ballasted all the 2 x 2 slabs were laid on strips of solid plastic, (offcut strips from double glazing) These keep the ballast off the base plate and a decent air gap between. Should any leakage occur, water will flow easily to the stern and dry out quickly between ballast & base plate. There's also good air flow.

 

We accessed our bilges just last week, first time for 6 years so didn't know what to expect.

 

Happy to see this though.

 

DSCF2879_zps50deb767.jpg

 

No damp or musty smells either. I always intended to put an accessible hatch in this area but prioritised other things. Might well do so now.

Edited by Julynian

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As Richard says it's supposed to stop the ballast scratching the protective paint off the baseplate, but the flip side is should any water get down there it is going to take an age to dry out, if it ever does.

 

I think I'm right in saying that in the days when boats were built with "wet" cabin bilges, the floors had longitudinal L section strips which held the concrete slab ballast clear of the baseplate. This method was still used, and probably is still used in some boats even though all boats now have dry bilges. It seems to me to make a lot of sense though it doesn't work if you are using brick ballast.

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Funny that,

When I built, I used roofing felt (as I didn't know any better) as an alternative to waxoil which seemed nasty and sticky. I didn't know it was a general practice.

'twas several years ago.

 

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Like Julynian my ballast is laid on spacers, I didn't have access to plastic spacers at the time and just used 1/2" batten.

The ballast itself is mixed steel block and pig iron and after about 15 years all is still fine there although I have had a couple of minor floods due to plumbing problems. The raised ballast allowed a good air flow (aided by a fan heater)to dry the bilges quickly and thoroughly boat.gif

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As Richard says it's supposed to stop the ballast scratching the protective paint off the baseplate, but the flip side is should any water get down there it is going to take an age to dry out, if it ever does.

 

I think I'm right in saying that in the days when boats were built with "wet" cabin bilges, the floors had longitudinal L section strips which held the concrete slab ballast clear of the baseplate. This method was still used, and probably is still used in some boats even though all boats now have dry bilges. It seems to me to make a lot of sense though it doesn't work if you are using brick ballast.

 

My first boat had a wet bilge and the slabs were just laid directly on the baseplate.

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From what you've all said, I reckon that my best bet is to go with using a protective layer of primer/paint, then plastic spacers on which to lay my ballast, as it's concrete slabs.

 

I'm thinking that time / movement probably caused the old felt layer to fail. Now that the metal is no longer smooth due to the corrosion, a new layer would be more of a potential water trap.

 

Thanks all.

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Hello All,

Me and my girlfriend are currently in the same position with our narrowboat that Sir Percy was in back in 2014. Just wandering if anyone could recommend anywhere that we could get some plastic spacers that would work to create this ventilation gap between the bilge and the ballast - have been scouring the interweb and can't really find what we want.

Many thanks.

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another option I have seen used is the pipe clips for 15mm pipe

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use an old hosepipe cut into about 3inch lengths, alternatively get hold of some old twin and earth cable and cut that up to use as spacers

  • Greenie 1

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use an old hosepipe cut into about 3inch lengths, alternatively get hold of some old twin and earth cable and cut that up to use as spacers

 

If there is any wet, won't the copper in the cable cause problems.... i.e. dissimilar metals

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If there is any wet, won't the copper in the cable cause problems.... i.e. dissimilar metals

 

No. It isn't in contact with the hull

 

Richard

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I used those big tile spacers too - cheap, quick and simple. In a few other spots used cut-off pieces of hose. That works too but a bit fiddly over large areas I'd say.

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If there is any wet, won't the copper in the cable cause problems.... i.e. dissimilar metals

Yes, it will become a copper/iron battery, but only if the water in the bilge is deep enough to cover the copper. If the two dissimilar metals are kept apart all will be ok, although personally I would use plastic as spacers.

 

See the bit about the statue of liberty in the attached.

 

https://en.m.wikipedia.org/wiki/Galvanic_corrosion

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Hello All,

Me and my girlfriend are currently in the same position with our narrowboat that Sir Percy was in back in 2014. Just wandering if anyone could recommend anywhere that we could get some plastic spacers that would work to create this ventilation gap between the bilge and the ballast - have been scouring the interweb and can't really find what we want.

Many thanks.

 

You might have timed this just right - I don't mean picking up on a thread two years old, I mean we're just now getting some hot, dry weather after a wet summer. I think it was like this when I was looking around for material to go underneath the ballast. What I found was quite a few garden hoses being chucked out by people needing to do a bit of a watering and finding that theirs was old and knackered.

Good luck!

Gav

Edited by Sir Percy

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Old fan belts cut into 1" pieces are excellent spacers. I think rubber is better than plastic, less chance of vibration. Also, waxoyl tends to dry out over time and becomes crusty, any water then gets trapped under the waxoyl and retains the dampness in the bilge. Undesirable.

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