felt it, or not!

[Still-waters]

in the next week or two will hope to start ballasting with concrete slabs. Already have applied 2-3 coats of bitumen paint. On reading previous posting am still not sure if I should or should not have roofing felt down 1st. What are your thoughts? Thanks

 

[Bee]

Personally I wouldn't, I think you would get permanent damp under the felt but I have only ever just laid broken paving stones straight onto steel, if you are using whole slabs perhaps lift them off the bottom with bits of wood.

[Bod]

I wouldn't put felt in for the above reasons.

But use lengths of old hose pipe rather than bits of wood to keep the air gaps under the ballast. (wood rots, plastic hose survives damp!)

 

Bod

[Odana]

PLEASE DON'T USE FELT!!! If you do, you and any future owners of the boat will have to live with a thin film (at best) of damp from condensation, and if you get a leak it will never dry out. I know this - my boat has felt under its slabs and it is just yuk to work around. Doubtless when it was shiny new it seemed like a good idea.

Search some other threads here about what to put under - thin rods of plastic or wood were suggested somewhere to allow water/air flow (preferably only ever air, but you have to be prepared)

[pete.i]

Yep cheap lengths of plastic hose to keep the slabs off the base plate and allow a gap so that air can circulate.

[Markinaboat]

If you use wood, get tanalised sawn timber. Not too expensive and won't rot unless left submerged for a couple of years. Make sure you lay them lengthwise so as not to prevent water from running astern.

[trackman]

I'd be worried about wet timber causing corrosion of the baseplate. I suspect Tanalised timber might be worse still because of the chemicals in it.

Use inert and non-absorbent material like the hose already suggested.

[Markinaboat]

Wouldn't know if the chemicals would interact with the primer/oxide/bilge paint that they'd be resting on. But wouldn't hose compress under the weight of the slabs over a short period of time. The smallest amount of crud would surely build up and close the gaps.

[luctor et emergo]

Use the little plastic crosses used to space tiles..

[alan_fincher]

But wouldn't hose compress under the weight of the slabs over a short period of time. The smallest amount of crud would surely build up and close the gaps.

 

We are talking, I think cheapo garden hosepipe. It will squash down, almost immediately, but still leave a very adequate gap, even so.

 

Use the little plastic crosses used to space tiles..

 

Far too thin to be much use, I would say

 

All that said in "Chalice" the broken paving slabs have proved to be laid straight on the painted baseplate, and under those I have lifted out when working on the boat there has been zero water and zero corrosion. This despite the original boat fitter deciding to leave large amounts of sawdust around the ballast, which I would have expected to exacerbate any problems, if there were likely to be any. In my experience, for a modern boat, designed with dry bilges, this potential issue is rather overstated.

 

I would certainly not put felt though!

[davey b]

Off cuts of 240v cable works well, the wood could be sealed with blacking or similar (as long as it is dry first... the bundle I got from Wickes on Wednesday appears to have been stored under water).

 

Don't felt it. It get damp, it sweats tar, it drops its mineral chips... just don't - its 'orrible. Been there, cleaned that!

Edited January 9, 2015 by davey b

[David Mack]

Yep cheap lengths of plastic hose to keep the slabs off the base plate and allow a gap so that air can circulate.

Or lengths of domestic twin and earth cable that you can't use for boat wiring.

[blackrose]

I've got bitumen soaked cloth. It doesn't get damp unless there's a water leak. Also there's no condensation down there. I've cut enough inspection hatches to know. If it does get wet it will dry out eventually - any concrete ballast placed directly onto a baseplate will take a long time to dry out if it gets wet.

So I agree with Alan that the issue is overstated. However, having said all that, I wouldn't use cloth or felt as I don't think there are any advantages. I'd create a gap under the ballast with hose or plastic spacers as others have advised.

Edited January 10, 2015 by blackrose

[cuthound]

You can put paving slabs on lengths off old toothed alternator drive belts. Waterproof and allows any water to run through the gaps between the teeth.

 

Edited to korrect spillung

Edited January 10, 2015 by cuthound

[Sir Percy]

Had to take up the ballast in my boat, under which was a nasty, sticky mess of old roofing felt. Up it came with a load of plate rust, caused by the moisture trapped under the felt.

 

I must have seen the suggestion of garden hose somewhere on these forum pages - anyway, I was scratching my head trying to think of what I could put down under the paving slabs. Biking around last Summer, I saw a hose which had been thrown out and thought, 'that'll do nicely'. Since then, I managed to collect three more from off the street. I guess that's when people discover their old one has got a leak. You'll often see one alongside with rubble and waste from house renovations (but make sure it has been dumped).

[Still-waters]

Thanks and I based on your help is defiantly no to felt and a possible maybe to cheep hosepipe to get squashed. Much appreciated as this is the potential 1st of many questions as our fit-out progresses.

[Neil Smith]

I waxoyled my base plate on top of the black two pack black the shell builder put on as it is self healing and if your ballast moves a bit if you ever hit a bank or lock gate it should not scrape off to leave bare metal, I was also told to lay it on breathable roofing membrane.

 

Neil

[Sabcat]

You can put paving slabs on lengths off old toothed alternator drive belts. Waterproof and allows any water to run through the gaps between the teeth.

 

Edited to korrect spillung

 

I used toothed cam belts under slabs in our boat.