18.03.2021 Lifting the roof.

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Thursday 18th 32F, bright but cloudy. No wind.  Further thoughts on lifting the "roof" segment into place:
 

The chain hoist will be hung as high as possible in the eastern hedge. There are several thick tree trunks there. Or I can use a ladder as an anchor to spread the load across several trees.  

The height will help to ensure increased lift in the early stages rather than just a horizontal pull on the A-frame. I have six, new, 3.6m lengths of 2x4 as candidates for the A-frame.

The actual roof segment needs to be flopped face down first. [i.e. Convex upwards.] This means moving both roof segments. The "spare" [intended for shutter material] will get in the way if it is not moved. Using ground boards to lower friction should help to reduce the effort required. I may use the boat winch if I can find a suitable anchor point.

It would help if I could start the drag and lift process with the roof segment already lifted and propped. This would help to reduce the risk of the segment merely moving forwards rather than immediately rising. The A-frame geometry should ensure an early lift. However, this could severely stress the A-frame in the starting position. If it is not already sloping upwards at a fair angle.

I shall use ratchet strap as the links between the A-frame and roof segment. There is a risk that the sharp edges of the drilled holes in the GRP would cut through highly tensioned cord. The ratchet strap's steel hooks fit easily in the drilled holes and are immune to cutting.


The ratchets can also be adjusted to improve the level of the segment if needed. I shall use several straps to help spread the loads along the edge of the roof segment. The more straps I use the lower the direct load on each of them.

Fortunately the dome is very robustly built. They are intended to be used for decades in the rough and tumble of a farm environment. The price to be paid is in the sheer weight of all that thick fibreglass reinforced plastic. [GRP]

Farmers have the lifting machinery to hand. Which the lone amateur [like myself] lacks. An astro society or club can usually call on many hands to make light work. I must use ingenuity and enhanced, medieval technology to manage the loads.

It took nearly three hours to finally get the roof segment in place. Once there, it proved almost impossible to fit the clamping screws at the joints. I was using hex socket drivers to align the holes.  Only to find the next hole did not line up.

I managed to fit two rows of the mastic sealing tape to one joint and fix about a dozen bolts. The other joint is squashed too tight to reach inside the joint. I'll need to open up the joint again to fit the tape. I am too exhausted to process and share the images. That will happen later:

The text justification is a mess but the images show the general idea. I did not have the roof segment aligned with the base segments. So I had to be extremely careful not to tip the roof segment sideways. I couldn't tip the A-frame over the segment. Which greatly delayed the lift as I inched upwards on protective sheets of plywood using the ratchet straps.

The 360° laser, internal images show how dreadful the ground level is and [probably] why the bolt hole alignment was so poor. There is over 6" [15cm] difference in level from one side of the dome skirt to the other! 

Early tomorrow morning promises to be mostly about levelling the dome accurately on wood blocks. To see if that helps bolt hole alignment.

Google blogspot is messing about again. I can't drag images around the post without them vanishing. I'll have another go tomorrow.

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