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sboogert

Metal dome interior lining

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I have a large (maybe 4 metres, 12 feet in diameter) metal dome which is in need of some refurbishment. Does anyone have any particular advice about what to cover the interior with? Previously there was some polystyrene panels  fixed up with wallpaper glue which over time have broken off and land on my optics and equipment, something I'm not very happy about. Take a look a the video or pictures in the instagram for what has happened over time (https://www.instagram.com/rhulobservatory)

Is there any particular need to cover the interior at all? 

Thanks,

Stewart 

 

 

 

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I'd cover the inside with high density black foam mat to prevent condensation.

You might get the same problem after 20 years though..

 

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You do need something or you'll get condensation dripping on the toys. There are people who spray van interiors with a thin coat of insulating foam. This would be good, but I don't know anything about it other than seeing the excellent result when a friend was converting a panel van into a camper.

You could use closed cell camping mat bonded to the metal. I did this when making my own camper van conversion. All my observatories are flat sided and roofed so I just use rigid domestic insulation panel.

Olly

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Personally I would prefer the condensation to form on some surface like the obsy roof rather than to form on my expensive and delicate toys.

You only get condensation when the water vapour in the obsy's air cools to such an extent that the air cannot contain it any more (the dew point). if there is a chance that your observing equipment temperature would fall below the local, interior, dewpoint that is a bad thing. Having the dome cooler than your equipment means the dew will form on that, preferentially.

 

Clearly you don't want the dew to drip onto your stuff, so as long as the inside of the dome won't get rusty (and there are preparations to stop that), the problem would seem to be one of managing the runoff to somewhere outside the dome.

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Try polystyrene wall paper veneer.  Cheap as chips and once painted over, no flaking off.

http://www.wickes.co.uk/Wickes-Polystyrene-Veneer-Lining-Paper-White-10m/p/105968

I stuck mine on with solvent-free No More Nails then painted it over with white paint.  Works a treat with no substantial loss in 7 years.

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17 hours ago, pete_l said:

Personally I would prefer the condensation to form on some surface like the obsy roof rather than to form on my expensive and delicate toys.

You only get condensation when the water vapour in the obsy's air cools to such an extent that the air cannot contain it any more (the dew point). if there is a chance that your observing equipment temperature would fall below the local, interior, dewpoint that is a bad thing. Having the dome cooler than your equipment means the dew will form on that, preferentially.

 

Clearly you don't want the dew to drip onto your stuff, so as long as the inside of the dome won't get rusty (and there are preparations to stop that), the problem would seem to be one of managing the runoff to somewhere outside the dome.

Fair point, so insulate the roof but not the walls? Drive it onto the walls.

25 minutes ago, michaelmorris said:

Try polystyrene wall paper veneer.  Cheap as chips and once painted over, no flaking off.

http://www.wickes.co.uk/Wickes-Polystyrene-Veneer-Lining-Paper-White-10m/p/105968

I stuck mine on with solvent-free No More Nails then painted it over with white paint.  Works a treat with no substantial loss in 7 years.

Another good idea.

Olly

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Thanks all for the tips, the currently exposed surfaces don't see to suffer to much. I am going to strip the existing material and use it for a winter. I have covers for the toys inside and see the extent of the problem over the winter and apply an insulating covering the following summer.

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Ever late to the ball but worth reviving: Any interior dome insulation wants to be "closed cell."

Even an inch of "ordinary" polystyrene board will become saturated in the presence of interior moisture. [Breathing!]

I lined a wooden T&G shed once with bare 1" polystyrene sheet and it soon turned brown in large patches from the coloured treatment on the T&G board cladding.

It was also apt to drip from the ceiling after being so treated. You need to add a vapour barrier to your side of the insulation.

I believe the correct term is interstitial condensation. A  dew point can be reached within the thickest insulation where it is slightly cooler than further in.

Buildings always need a vapour barrier on the warm side of "open" insulation materials like fiberglass and rock wool.

A vapour barrier is rather difficult to fit to a dome.

Telescope mounts usually have enough mass to lag well behind the constantly changing air temperature.

They will often become covered in dew simply because they are colder than the warmer air.

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