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JamesF

JamesF's observatory build

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Yesterday was a write-off thanks to the weather and I didn't have much time free today (a shame given that the weather was pretty much perfect for welding outdoors), but I've managed to get the rest of the bracing that I cut last week welded into position.

Sadly however I didn't get everything done that I want finished before I put the roof in place.  I'm planning on getting the remainder of the pieces of steel cut this week during the evenings, then having one more day of welding work on the ground to get as much done as I can before putting the roof structure in place at the end of the day.  Practice definitely seems to be helping as I'm getting noticeably quicker at the actual welding now.

A quick check of the weather forecast suggests that the tail end of the week could be a bit miserable and wet whilst Tuesday and Wednesday look as though they might be quite sunny, so I may have to bite the bullet and take a day off to get things done.

James

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Thank you, John :)  Much appreciated.

James

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But for a foggy start it has been a lovely day here today, allowing me to skip off work for a few hours and get some welding done.  So at long last, here we have it.  Pretty much all the welding work complete (anything else I'll do once the roof is in place).

obsy-build-40.jpg

obsy-build-41.jpg

@ollypenrice has long been a proponent of the welded frame rolling roof, though I'm not sure he ever had something quite this large in mind :)

It was my plan to lift the roof into place as soon as I'd finished, but I'm lacking "volunteers" to help lift it this afternoon, so that may have to wait until the weekend.

James

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Bribery and\or Extortion, I find usually works best, when help is needed....

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1 minute ago, Dr_Ju_ju said:

Bribery and\or Extortion, I find usually works best, when help is needed....

Oh, there'll be no problem when the time comes, but this afternoon only my in-laws are at home and they're in their 80s so I can't really ask them.

James

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Nicely done James, are you going to give it a coat of Hammerite first ?

Dave

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I can see why you've gone for welded steel tubing James.  I imagine that will be a lot lighter than a timber version.  Looks good :thumbsup:

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It's definitely going to get a coat of Hammerite -- I have some satin black that Screwfix were knocking out at half price (presumably because no-one wants it), but I may well do that with the frame in place as well.  Just having the roof on will allow me to move forward with other jobs like finishing the warm room roof, making up the flap on the south end, cutting the rails to length, making up the piers and so on.  As the evenings draw in it's useful to have a choice of things to do depending on the time available and the weather.

Things are looking pretty poor weather-wise from this evening until Saturday evening, but I can at least now think about ordering the OSB and EPDM for the roof.  Sunday and the first few days of next week are looking ok at the moment.  If I could get the painting done on Sunday morning then it should have time to harden off nicely and give me a chance to get the roof sorted by the end of October.

James

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5 minutes ago, Gina said:

I can see why you've gone for welded steel tubing James.  I imagine that will be a lot lighter than a timber version.  Looks good :thumbsup:

I've just had a quick check up on the left over steel.  I ordered 54m of tube altogether and I have about 5m left over.  I reckon the tube weighs a shade under 1.6kg per metre, so even with the wheels and plating I reckon it's still very close to 80kg so far.  Even if I used all of the usable remaining tube (about 4m worth) for bracing if I start to have doubts once the roof is in place, it will still be well under 90kg.  I think that's really quite light given the span involved and the 600mm wall height.

James

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What are you putting on top underneath the rubber roofing?  I used 6mm marine ply on mine to keep the weight down.  It was strong enough for me to walk on and I'm no lightweight!

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Are you set on OSB and EPDM for the roof james ?

Have you considered box profile rigid PVC coated sheeting, it comes in 1 meter by any length you want, guaranteed to last, easily fixed with self drill screws and a lot lighter than OSB, about  £30.00 for 2.5 meter sheet.

Dave

Edited by Davey-T

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40 minutes ago, Gina said:

What are you putting on top underneath the rubber roofing?  I used 6mm marine ply on mine to keep the weight down.  It was strong enough for me to walk on and I'm no lightweight!

I was planning to use OSB, but ply would work equally well.  I used OSB for the beer shack and that has worked fine.

James

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27 minutes ago, Davey-T said:

Are you set on OSB and EPDM for the roof james ?

Have you considered box profile rigid PVC sheeting, it comes in 1 meter by any length you want, guaranteed to last, easily fixed with self drill screws and a lot lighter than OSB, about  £30.00 for 2.5 meter sheet.

Dave

Do you mean the type of stuff that is sometimes used for conservatory roofing?

James

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OSB has a very high weight to strength ratio.  If you can avoid walking on it I guess 6mm OSB would suffice but marine play would be better.

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I'm not sure OSB comes thinner than 9mm.  I don't intend to be standing on it though.  I'm far too heavy to want to risk doing that.  I intended to use 6mm ply for the inner wall lining, so there would be benefits to using it on the roof as well in that there'd probably be less waste overall.

James

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You may be right about OSB - I guess it might fall apart if too thin.  I used 11mm OSB on my warm room roof where weight didn't matter.  I used 6mm marine ply on the walls and ceiling of my warm room with polystyrene foam slabs in walls and ceiling for insulation.  And under the floorboards.  No insulation for the scope room.

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8 minutes ago, JamesF said:

I'd be concerned about condensation with that I think.  Although it's plastic coated it is made of steel sheet.

James

You could bond 25mm Kingspan to the bottom.

Dave

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I wondered about the weight of that corrugated roofing but the website says it's lightweight.  Actually, rubber roofing is pretty heavy so that stuff could well be lighter than rubber on plywood.  Had I found something like that when I built my observatory, I might have used it.  Ordinary corrugated galvanised iron sheet was too heavy.

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6 minutes ago, Gina said:

I wondered about the weight of that corrugated roofing but the website says it's lightweight

Various suppliers on EB at various prices but no one lists the weight.

Dave

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EPDM certainly is heavy.  The beer shack has a single sheet measuring 7m by 4m and it was not pleasant lifting it up onto the roof.  I think it weighed close to 50kg.  I think what I want for the rolling section of the roof of the observatory would be considerably less though.  Probably nearer 20kg.

James

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13 minutes ago, Davey-T said:

Various suppliers on EB at various prices but no one lists the weight.

Dave

Shouldn't be too hard to estimate though.  The link you posted earlier uses sheets folded from 1250mm wide 0.7mm steel to give a 1m wide sheet.  I'd need about twelve square metres for the rolling roof, or 150,000 square cm allowing for the folds.  At 0.7mm that's 1050 cubic cm.  Plain mild steel has a density of about 7.85g/cc, so the total weight of steel would be close to 8.25kg.  The plastic coating surely can't add much to that.

In terms of weight that makes it quite appealing, but I'm just not sure about a metal roof.  Even if it is insulated on the underside, it still needs ventilating to allow moisture to get out where it forms in the ridges above the insulation.

James

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I used 11mm OSB for my warm room with EPDM on top. Easy to work with and well strong enough to stand on, although the ceiling rafters were on quite narrow spacings which helped. EPDM is certainly heavy though.

I'm hoping to put the roof on my scope room next week if the weather holds through the week, using the same materials. Knowing that my time estimates are always way off, I will no doubt therefore be doing it the week after next! It will be interesting to see how I get on. Not looking forward to sticking down the EPDM on such a big area as the working time is quite short, especially in warm weather.

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