JamesF's observatory build

[JamesF]

3 hours ago, Dr_Ju_ju said:

I'm allergic to the little blighters & blow up like a balloon, so hopefully you have fended them all off.....

I find that even if they bite, as long as I swat them as soon as they bite then I don't get any of the unpleasant after-effects.  I've no idea why that should be, but it seems to work.  The one that did get through today attacked my arm alongside my elbow.  I swatted it immediately I felt the bite, but even after it fell off I had a bit of blood running down my arm.  There are no visible effects now, however.  In fact I can't even see the wound.

James

[JamesF]

Photos of today's progress:

Whilst there's not a great deal visible, each block is about 70cm high (by 50cm square).  My father-in-law insisted on helping which was a bit of a mixed blessing (he's not supposed to do heavy lifting and suchlike), but did mean the entire job progressed much faster as he was in control of the mixer whilst I was shovelling out the previous mix.  So I was pretty much on repeats of "refill the mixer, push the barrow (with the previous load) to the pier, shovel out the concrete, take the barrow back" without a break for eleven mixer loads.

The short lengths of timber with the threaded rod are supported on 6mm steel bar that we happened to have lying about.  There's a nut on the underside of those pieces too, nipped up with the threaded rod in the holes in the concrete blocks so hopefully everything will fit nicely.  Because I'm, well, not paranoid exactly, but perhaps just more aware of all the potential ways things can go wrong, I've labelled the orientation of the rods relative to the blocks ("front" is the top of the block where the slits are) and numbered them, so every block should end up going onto a set of threaded rods that it was tested against before they went into the concrete.

It has been a really physically tough day's work, but I'm so pleased to have got it done.

[Astrokev]

Great progress James. And good idea to label the rods/blocks. There will almost certainly be minor variations and trying to figure out which goes where without labelling beforehand could be a real headache. I label stuff also - you can see some of my labelling on the wheel beams before they were lifted onto the roof to indicate which is which and orientation, and also numbered the wheels/holes they were matched to ? 

[JamesF]

Very much agree, Kev.  It may be possible to drill millimetre-accurate holes in concrete blocks, but frankly I can't do it with the kit I have at home so I have to accept that they may "wander" a little.  Not assuming that everything will be exactly the same will hopefully make life easier for me further down the line even if it does eat up a little more time now.

James

[Gina]

A great day's work James - well done ??

[JamesF]

After yesterday's marathon I had other stuff to get through today and didn't have much time left afterwards.  I did however manage to remove the jigs for the threaded rods and then finish screwing the outer rails for the floor together (I'd deliberately left that until all the concreting was finished).  At the same time I cut sections of DPC material that we had lying about to prevent any moisture getting into the timber from the concrete.  Had my floor not been so close to the ground at one end and if I'd been able to align the pads so rain won't be able to splash up off them then I probably wouldn't have bothered, but in this case it seems like a sensible precaution.

I need to finish off the corners next.  Then I can get on with putting all the floor joists in place.

James

[Astrokev]

Looking good James ??

[JamesF]

Just a little progress today, between finishing work and a visit from the builder...

Finished wrapping the timbers with the DPC.  I remembered why I hate wrapping presents

And I also cut most of the floor joists and carried them down to the observatory.

I'm going to have a little play with the measurements now and see if I can arrange the joists to avoid cutting any of them to go around the piers.  Or at least to minimise the number that have to be cut.

James

[Astrokev]

5 minutes ago, JamesF said:

 

I'm going to have a little play with the measurements now and see if I can arrange the joists to avoid cutting any of them to go around the piers.  Or at least to minimise the number that have to be cut.

James

Looks good James.

It may also be worth thinking about placing the joists and noggins to minimise the need to do too much cutting of whichever floor sheets you choose to use. My floor joists are positioned so that standard ply panels should (I say should!) have joists supporting all edges. Time will tell if I got this right or not ?

Edited June 25, 2018 by Astrokev

[JamesF]

Yes, my joists will be on 400mm centres (because I know the span is considered acceptable for the size of joist at that separation), so 2400x1200mm sheets should work ok for that.  I reckon I can shift one joist over 20mm and clear all the piers without any cutting.  If I need to support anything there I'll nail some roofing batten to the side of the joist, but I don't think I'll need to.

I'll also arrange for one joist to be under the warm room wall even if it messes up the spacing slightly.  I did consider doubling that one up, but haven't come to a conclusion yet.

James

[Gina]

I used regular floor boards on my floor. 

[JamesF]

24 minutes ago, Gina said:

I used regular floor boards on my floor. 

Was that because you happened to have them, or they were cheaper or something like that?

James

[Gina]

Can't remember now.   I think it might have been considered better.

[JamesF]

Was hoping to place the lower blocks for the piers (just to make sure the joists do in fact clear them) and get a few of the joists in place today, but sadly time got the better of me.  I shall try again tomorrow.

James

[JamesF]

A bit dark, this photo, but that's how it was when I finished about thirty minutes ago

I dropped the first set of pier blocks onto their threaded rods this evening and started laying out the joists.  The hangers are partially nailed on, but the bow in the left hand rail looks as though it has actually become worse so I need to pull that in before nailing the joists in their final positions.  Shouldn't be a problem.  I can do it with a couple of loops of rope and a chain hoist.

I've not bolted the blocks down yet.  I want to make sure they're level first.  I know it doesn't matter if the pier isn't level, but I don't want them leaning if I can avoid it.

James

[Dr_Ju_ju]

? well done

[Astrokev]

Disappointed you weren't trying to do more by candle light there James ? .

Yes, it would be good to sort out that left rail if you can; it may come back to bite you later on otherwise. Impressed with the progress you're making ? .

[JamesF]

Sadly it's been a bit breezy for candles

Actually, if I'm honest the breeze has been very pleasant.  Takes the edge off the humidity a bit.

James

[Davey-T]

Coming along nicely James, certainly got the weather for it, long ratchet straps are good for forcing incalcitrant joists into line.

Dave

[Gina]

Looking good ??

[JamesF]

9 hours ago, Davey-T said:

Coming along nicely James, certainly got the weather for it, long ratchet straps are good for forcing incalcitrant joists into line.

Dave

Ah, yes, good point.  I have a couple of hefty ratchet straps in the workshop.  They should do the job.

James

[JamesF]

Finished doing all the floor joists today, and pulled the sides together with a couple of hefty ratchet straps.  It now looks reasonably straight   In the end I did decide to put two joists together under the warm room wall.  I could only find 100mm joist hangers though, so I had to pack one side with a bit of scrap ply to make two of my my 47mm wide joists fit.  I'll take some photos later.

I also learned that a truly wise man does not tip a pile of nails into his front shorts pocket when they've been sitting in direct summer sunlight for a couple of hours.

I have started to wonder if perhaps the walls might be a bit high for the size of the piers and if I shouldn't lower the walls to nearer 1300mm from the planned 1500mm.  I shall ponder that over dinner as it did look ok from the design in Sketchup so I may be worrying unnecessarily, then perhaps I can get some of the studding for the walls cut this evening.

James

[Dr_Ju_ju]

Aren't you having diner in a cold bath, to ease the pain in your nether regions....

[JamesF]

1 hour ago, Dr_Ju_ju said:

Aren't you having diner in a cold bath, to ease the pain in your nether regions....

That rather depends on whether I am a truly wise man or not, doesn't it? :D

James

[JamesF]

Dinner is over however, and I think I'm coming to the conclusion that I shall drop the height of the walls.  I have realised that my initial calculations were based on the OTA being "above" the mount whereas it might actually be to the side, so I need to allow for that.  Other than the doorway it doesn't have an enormous impact elsewhere, so I think it's the right decision.

James

Edited June 30, 2018 by JamesF