Bitumen and mastic

[Moley]

I'm putting a 4ft x 2ft (fairly shallow) bath in our boat, as a kid-sized bath / big shower tray. Because of headroom I need to drop it through the floor and onto the base plate, which is Vactanned and well bitumened. I'm spreading the load with a 4ft x 1ft x 1 inch piece of nylon (which I picked up from somewhere and kept as it ‘might come in useful one day’).

 

I think I ought to lay this on a generous bed of mastic.

 

Is there anything I should either use or avoid?

 

Thanks,

Ade.

[John Orentas]

I'm putting a 4ft x 2ft (fairly shallow) bath in our boat, as a kid-sized bath / big shower tray. Because of headroom I need to drop it through the floor and onto the base plate, which is Vactanned and well bitumened. I'm spreading the load with a 4ft x 1ft x 1 inch piece of nylon (which I picked up from somewhere and kept as it ‘might come in useful one day’).

 

I think I ought to lay this on a generous bed of mastic.

 

Is there anything I should either use or avoid?

 

Thanks,

Ade.

 

 

I would be inclined to simply sit it onto the bitumen painted surface, presumably the floor will locate it.

[Moley]

Trouble is, the base plate ain't as flat as it could be, and I'm going across the ridge of a weld seam.

[bottle]

How about sitting it on a thick (1 inch/2.5 cms) piece of polystyrene (flameproof) this would compress slightly to take up any deviations.

[Bones]

How about sitting it on a thick (1 inch/2.5 cms) piece of polystyrene (flameproof) this would compress slightly to take up any deviations.

 

Moley - I think mine is installed on the baseplate, I will have a look at it and report back what the situation is. The baseplate is probably straight though... I am intrigued by yours!

[Moley]

Surprising how it helps, just ‘thinking out loud.’

 

How about carpet underlay? That would prevent slip and take up any minor deviation.

[bottle]

Surprising how it helps, just 'thinking out loud.'

 

How about carpet underlay? That would prevent slip and take up any minor deviation.

 

There you go only took you 1 hour and 29 minutes to come up with the answer.

[Alastair]

except that when the carpet underlay gets damp, it will really, really stink.

[bottle]

except that when the carpet underlay gets damp, it will really, really stink.

 

Ah! ........................back to the drawing board, perhaps my praise was to quick

[david and julie]

I don't follow.

 

Surely the bath legs will adjust to suit the base plate? or are you fitting it without the legs? what about the waste?

[Moley]

Surely the bath legs will adjust to suit the base plate? or are you fitting it without the legs? what about the waste?

What legs?

 

There's a chipboard plank glued to the bottom of the bath (as seems customary with all fibreglass baths, boat or domestic). To this are attached two wooden battens, about 35mm square. This gives sufficient clearance for the waste outlet (obviously there's no trap).

 

I've gone for the nylon ‘plank’, bedded down on a full cartridge worth of exterior grade frame sealant, with a groove routed or chiselled out of the underside to span the weld I mentioned. (Incidentally, damned difficult stuff to cut - I used my most vicious blade in a jigsaw, but the friction and heat from the blade means that the cut welds itself shut again as the blade passes).

 

Anyway Alastair, why should the underlay get damp? I'm going to use copious quantities of sealant and more bitumen to try to ensure that no splashes can get into the dry bilge, as we've got kids, and they will get water everywhere, irrespective of any requests or instructions they may receive.

[stuart]

Did you have fun with the plumbing fittings and connecting this to the gulper pump?

[Moley]

Gulper's not come yet Expected soon

 

Seller's had problems, wound up in hospital for a couple of weeks.

Contact re-established, I think I believe him

I used PayPal, so I'm covered.

[mr toad]

Just thought this might be usefull on here. When cutting plastics and nylons with a jigsaw it helps to put a strip of masking tape across then cut through. Masking tape stops the plastic welding itself back together. I know this works on 15mm thick plastic because I have tried it

[Moley]

Now he tells me

 

I just made a second pass across the same cut line and then smacked it

 

 

Useful for future reference though, thanks.

Edited March 29, 2006 by Moley

[ChrisPy]

I would bed the bath on polyurethane foam sprayed/injected underneath. Keeps out moisture, supports the bath and makes it sound solid. Just weight it down well as the foam expands. Start with a small amount of foam squirted under the centre. One hour later squirt around the perimeter.

[Moley]

Thanks Chris, that makes sense.

 

Ade.

[Alastair]

 

Anyway Alastair, why should the underlay get damp? I'm going to use copious quantities of sealant and more bitumen to try to ensure that no splashes can get into the dry bilge, as we've got kids, and they will get water everywhere, irrespective of any requests or instructions they may receive.

 

Condensation. All boats get a little bit, with good ventilation it isn't a problem. If you have something on the base plate that can absorb water, then it will retain the water and over time become sodden. This is bad because of the smell, and because it encourages corrosion.

[david and julie]

What legs?

 

There's a chipboard plank glued to the bottom of the bath (as seems customary with all fibreglass baths, boat or domestic). To this are attached two wooden battens, about 35mm square. This gives sufficient clearance for the waste outlet (obviously there's no trap).

 

 

I've also fitted several baths in houses and one in my boat and yes they have all had a chipboard bases, but they have all had legs too. When I say legs I mean the two tubular pieces of steel which attach under the top edge, each piece of steel then has two adjusting legs, one either side, at floor level.

 

I have never seen one that uses the chipboard directly mounted onto the floor. But fair enough if its got timber battens they must do it with some.

[Guest]

What legs?

 

There's a chipboard plank glued to the bottom of the bath (as seems customary with all fibreglass baths, boat or domestic). To this are attached two wooden battens, about 35mm square. This gives sufficient clearance for the waste outlet (obviously there's no trap).

 

I've gone for the nylon ‘plank’, bedded down on a full cartridge worth of exterior grade frame sealant, with a groove routed or chiselled out of the underside to span the weld I mentioned. (Incidentally, damned difficult stuff to cut - I used my most vicious blade in a jigsaw, but the friction and heat from the blade means that the cut welds itself shut again as the blade passes).

Anyway Alastair, why should the underlay get damp? I'm going to use copious quantities of sealant and more bitumen to try to ensure that no splashes can get into the dry bilge, as we've got kids, and they will get water everywhere, irrespective of any requests or instructions they may receive.

Put wide sellotape over the cut-it lubrictaes the blade.

Edit sorry didn't see Mr toads psot.

Edited March 29, 2006 by Guest