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Gina's Observatory


Gina

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It stopped raining for a while this evening so feeling "stir crazy" I went out to the site and tried to level the remains of the soil heap outside the "shed" area but even with the rain we've had, it was still very hard and I made little impression.

However, having levelled off the underfloor area (thereby reducing the tripping hazard) I thought I'd try the mount on the adapter. So having uncovered the pier I lugged the mount outdoors and up onto the pier adapter. Once I'd undone the azimuth screws it sat down on the adapter with a nice close fit but still easily adjustable. But as soon as I'd taken a couple of photos, down came the rain again! So back on went the cover. But this time over the mount as well.

Here are the photos I took of the mount. Only had time for the two.

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I've now fixed the mount onto the adapter. I decided that since I'd already placed the mount in position, I'd try undoing the top to bottom plate bolts and lift up one side to put the centre bolt and washers in place. Slightly tricky but managed by using a piece of wood to prop the top plate up while I used the fingers of both hands to get the bolt and washers in place and screwed up finger tight. Then returned top plate and mount into normal position and tightened up the nuts and bolts.

The mount moves easily and smoothly when adjusted with the azimuth screws - better than it did on it's own tripod. So I'm pleased with the result :BangHead: Polar alignment should be no problem (any time we actually get a clear night!!). Once polar alignment is done I can easily tighten the centre bolt with a spanner to hold the mount solidly.

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Been looking at the shed part again and the timber requirements. I had it all worked out, but a month or two on (well it seems like it!) I'm going over things and seeing if I have any second thoughts on any aspect.

I find myself thinking about the 8x4 sheets of plywood for the floor and the weight involved in handling it. Even half inch plywood (12mm) is going to be very heavy. OTOH, PTG flooring boards are very much easier to handle as well as making a superior floor, I believe. Also, the ply would need cutting to size for the warm room (the obsy is 8x8 so takes 2 whole sheets with no cutting) - a lot more difficult than chopping up PTG which I can do on my sawbench. I'm going to ring the timber yard this afternoon and see what their price is for PTG.

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You could buy a circular saw for ~£30, might be valuable in lots of ways during your build?
I have one but not found it all that easy to keep to a straight line.
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For straight edges when cutting sheet materials I have always found a length 2x1 and a couple of g-clamps very useful...
Thanks for the tip :BangHead:
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Gina, You could use the smaller sheet material used for boarding out loft spaces. They would need some treatment and a layer (or two) of polythene under them to prevent moisture uptake from the ground below. They have T&G edges so they interlock with individual pieces being about 4ft x 2 ft in old money and 18 mm thick.

Whatever flooring you use make sure the load bearing joists under them do not come into contact with the pier slab.

These sheets are fairly hard wearing but would probably need a non moisture retentive covering. e.g. lino?

Francis

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Gina, You could use the smaller sheet material used for boarding out loft spaces. They would need some treatment and a layer (or two) of polythene under them to prevent moisture uptake from the ground below. They have T&G edges so they interlock with individual pieces being about 4ft x 2 ft in old money and 18 mm thick.
Chipboard is not really suitable for garden shed flooring though Wickes do a moisture resistant version :- Tongued and Grooved Chipboard Flooring - Chipboard Flooring - Sheet Materials -Building Materials - Wickes

Are you implying that this or plywood would be better that PTG floorboards? Smaller size plywood works out more expensive that PTG.

Whatever flooring you use make sure the load bearing joists under them do not come into contact with the pier slab.
Oh yes, I'm aware of that :BangHead:
These sheets are fairly hard wearing but would probably need a non moisture retentive covering. e.g. lino?
Sounds like a second best option to me.
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Hi Gina, I was concerned because I believe in an earlier part of the thread you were worried about handling large sheets of plywood - hence the suggestion of the smaller loft sheets. Although they are chipboard provided they are treated in some way or bought ready treated (your PTG will also need some form of treatment for moisture/insect damage) when installed over a vapour barrier they will last just the same as normal softwood flooring (which is all chipboard is). The suggestion of a covering for the upper surface was purely as a moisture preventative, because with the best will in the world UK observatory buildings are more prone to moist air because of their construction (roof opening, rolling etc)... unless you intend to run a good sized dehumidifier. I used to keep a tower PC and monitor in mine but damp air and electronics don't mix - I now take my laptop to and from the obs when needed.

I have to admit I have planed T&G in the 'office' area of my obs - plain concrete around the scope. But both areas are provided with moisture barriers due to the high water table in my area. My lawn sometimes has puddles but the floor of my obs which is below ground level remains dry.

The cut end grain, back face and T&G edges of any flooring should be treated whether PTG, chipboard or ply.

Francis

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Gina, Just seen you with the blue tractor on the webcam - you have my full admiration with this project:icon_salut:. Clear skies (day & night) to you. Wish I could help

Francis

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Hi Gina, I was concerned because I believe in an earlier part of the thread you were worried about handling large sheets of plywood - hence the suggestion of the smaller loft sheets. Although they are chipboard provided they are treated in some way or bought ready treated (your PTG will also need some form of treatment for moisture/insect damage) when installed over a vapour barrier they will last just the same as normal softwood flooring (which is all chipboard is).
Yes, I see. I was under the impression that solid wood was better but maybe only if it's a hardwood. Looks like there is little to choose between treated chipboard (to P5 standard) and treated solid softwood or treated softwood plywood. The floor will be protected from direct wet and will be well ventillated so maybe I'm being too cautious. Tongued and grooved panels would mean better joins (even if there are more of them). And of course, as you say, so much easier to handle.
The suggestion of a covering for the upper surface was purely as a moisture preventative, because with the best will in the world UK observatory buildings are more prone to moist air because of their construction (roof opening, rolling etc)... unless you intend to run a good sized dehumidifier. I used to keep a tower PC and monitor in mine but damp air and electronics don't mix - I now take my laptop to and from the obs when needed.
Yes, good point :BangHead:
I have to admit I have planed T&G in the 'office' area of my obs - plain concrete around the scope. But both areas are provided with moisture barriers due to the high water table in my area. My lawn sometimes has puddles but the floor of my obs which is below ground level remains dry.
We are on sloping ground and the drainage is good - the water runs off down the hill.
The cut end grain, back face and T&G edges of any flooring should be treated whether PTG, chipboard or ply.

Francis

Yes, we have plenty of creosote ;) It's the real stuff not the modern imitation.
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Gina, Just seen you with the blue tractor on the webcam - you have my full admiration with this project:icon_salut:. Clear skies (day & night) to you. Wish I could help

Francis

Thank you ;) It's a big job but I'm getting on top of it :( Well, I am when the weather allows :BangHead:
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Quote: "Yes, I see. I was under the impression that solid wood was better but maybe only if it's a hardwood. Looks like there is little to choose between treated chipboard (to P5 standard) and treated solid softwood or treated softwood plywood. The floor will be protected from direct wet and will be well ventillated so maybe I'm being too cautious. Tongued and grooved panels would mean better joins (even if there are more of them). And of course, as you say, so much easier to handle."

Remember all timber expands and contract with changes in it's moisture content. If you get kiln dried or install after a few days of 'dry weather' (only joking:D) make sure you leave room for expansion - more across the width of your PTG than the length. Otherwise if things get wet they could if installed too tightly push your walls out!

I remember at school (too many years ago) our woodwork workshop's roof leaked and on Monday morning the wood block floor had come up in a dome and all the work benches had slid to the side - and we still didn't get the day off!

Francis

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Remember all timber expands and contract with changes in it's moisture content. If you get kiln dried or install after a few days of 'dry weather' (only joking:D) make sure you leave room for expansion - more across the width of your PTG than the length. Otherwise if things get wet they could if installed too tightly push your walls out!
Yes, that's why we have tongues and grooves :( And yes, I know to leave a slight gap in dry weather.
I remember at school (too many years ago) our woodwork workshop's roof leaked and on Monday morning the wood block floor had come up in a dome and all the work benches had slid to the side - and we still didn't get the day off!

Francis

;):D Like it :BangHead:
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Moved the floor beams out to the site yesterday and today I've started laying the beams in place, on top of DPC.

Here are some enhanced images from the webcam :-

1. Cutting and laying the damp proof course.

2. Moving the first beam into position.

3. Laying the beam onto the DPC.

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Thank you Both :( I won't be putting my feet up much but I will be enjoying myself progressing my build :BangHead:

I've now placed all three floor beams onto DPC and onto the support pads. Next to fasten them down with wood screws through the S/S loops. Checked the clearance to the pier base - not as much as I'd planned, the top shuttering must have lifted up a bit on the RHS as seen from the webcam.

Regarding the flooring... I rang the timber yard for price of PTG floorboards. A little bit dearer than Wickes but much wider and thicker boards. 150mm x 25mm as opposed to 120mm x 18mm. Cost for the job using pressure treated wood works out at £180. That compares with about £100 for 12mm plywood. Twice as strong but not twice the cost. And I can't see that rotting in a hurry! :) It also means the joists could be further apart so a slight saving there. I'm looking at going for 150x47 joists say 500-600mm apart. So it looks like I'm going for the STRONG option! ;) Tim my OH, says "do the job properly, don't skimp it". Have to admit, he's often right :(

I'm hoping to order the timber today or tomorrow.

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Been looking up spans for joists and 47 x 122 mm will span 2.09 m @ 600mm spacing. So it looks like I can still use that size for my span of 2m.

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That's the profile at the bottom of the opening screen - NOT the displayed profile in the above photos... ;) Francis

hehehe, no, the profile in the pictures doesn't say "it's my birthday" :BangHead:

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Thank you Both :BangHead: ... Checked the clearance to the pier base - not as much as I'd planned, the top shuttering must have lifted up a bit on the RHS as seen from the webcam. .

Gina - you can always lay a piece of 2 x 1 (or similar) on top of your joists just to give a bit more clearance...

Francis

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